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Sample records for bandpass butterworth filter

  1. Adaptive usage of the Butterworth digital filter.

    PubMed

    Erer, Koray S

    2007-01-01

    The Butterworth lowpass filter is a conventional tool that has been commonly used in gait analysis applications. Its operation mainly depends on the selection of the cut-off frequency, which must be done based on the condition of the raw signal assuming that it is stationary. This tool is unable to deal with nonstationary signals especially if impact is involved. In this paper, a modified version of the Butterworth filter that can handle nonstationary signals is presented. The new filter has a variable cut-off frequency distribution defined for each data point, which is determined by local signal characteristics. Because of its adaptive nature, it is possible for the filter to accommodate changes in the frequency content of the signal.

  2. Design and responses of Butterworth and critically damped digital filters.

    PubMed

    Robertson, D Gordon E; Dowling, James J

    2003-12-01

    For many years the Butterworth lowpass filter has been used to smooth many kinds of biomechanical data, despite the fact that it is underdamped and therefore overshoots and/or undershoots data during rapid transitions. A comparison of the conventional Butterworth filter with a critically damped filter shows that the critically damped filter not only removes the undershooting and overshooting, but has a superior rise time during rapid transitions. While analog filters always create phase distortion, both the critically damped and Butterworth filters can be modified to become zero-lag filters when the data are processed in both the forward and reverse directions. In such cases little improvement is realized by applying multiple passes. The Butterworth filter has superior 'roll-off' (attenuation of noise above the cutoff frequency) than the critically damped filter, but by increasing the number of passes of the critically damped filter the same 'roll-off' can be achieved. In summary, the critically damped filter was shown to have superior performance in the time domain than the Butterworth filter, but for data that need to be double differentiated (e.g. displacement data) the Butterworth filter may still be the better choice.

  3. Filter design of eight order butterworth infinite impulse response for earthquake sign

    NASA Astrophysics Data System (ADS)

    Perdana, Yusuf Hadi; Marsono, Agus

    2017-07-01

    Filtering is an important procedure in modern seismology analysis to obtain the best quality result in advanced process. There are many programs of signal processing consisting of signal filtering features, for example Seismic Analysis Code (SAC). Unfortunately, the basic mathematical equations in signal processing are not explained in detail. This research has purposes to design a Butterworth filter and to examine the influence of increasing order on the arrival time, polarity, and first motion amplitude of seismic wave. Filter design was done by computing eight order lowpass analog transfer functions and transforming them into lowpass, highpass, and bandpass digital using bilinear transformation so we have recursive and causal filters. The designed filter was then validated by the result of SAC. Based on the research we have found that the method and algorithm of designed filter are consistent with SAC. Increasing filter order can clarify the phases of seismic wave positions. On the other hand, it can influence the phase delay and impulse attenuation of seismic waves. The implication of this effects are error on computation of earthquake parameter and source mechanism. Filter instability due to increasing order will quickly occur if the cutoff frequency range is short or the sampling frequency is high. An appropriate passband frequency at low filter order can optimally generate earthquake filtered waves.

  4. Acoustic bandpass filters employing shaped resonators

    NASA Astrophysics Data System (ADS)

    Červenka, M.; Bednařík, M.

    2016-11-01

    This work deals with acoustic bandpass filters realized by shaped waveguide-elements inserted between two parts of an acoustic transmission line with generally different characteristic impedance. It is shown that the formation of a wide passband is connected with the eigenfrequency spectrum of the filter element which acts as an acoustic resonator and that the required filter shape substantially depends on whether the filter characteristic impedance is higher or lower than the characteristic impedance of the waveguide. It is further shown that this class of filters can be realized even without the need of different characteristic impedance. A heuristic technique is proposed to design filter shapes with required transmission properties; it is employed for optimization of low-frequency bandpass filters as well as for design of bandpass filters with wide passband surrounded by wide stopbands as it is typical for phononic crystals, however, in this case the arrangement is much simpler as it consists of only one simple-shaped homogeneous element.

  5. Graphical design of millimeter-wave finline bandpass filters

    NASA Astrophysics Data System (ADS)

    Nguyen, Cam

    1987-12-01

    A very simple yet accurate design procedure for the finline bandpass filters at millimeter wavelengths is presented. The technique enables the geometry of finline bandpass filters to be obtained accurately from simple closed-form equations and curves. Using this graphical approach, various millimeter-wave finline bandpass filters have been designed. Results in V-band (50 to 75 GHz) and W-band (75 to 110 GHz) are presented and indicate a good agreement between the calculated and measured performances.

  6. Narrow bandpass cryogenic filter for microwave measurements

    NASA Astrophysics Data System (ADS)

    Ivanov, B. I.; Klimenko, D. N.; Sultanov, A. N.; Il'ichev, E.; Meyer, H.-G.

    2013-05-01

    An ultra-wide stopband hairpin bandpass filter with integrated nonuniform transmission lines was designed and fabricated for highly sensitive measurements at cryogenic temperatures down to millikelvin and a frequency range of 10 Hz-10 GHz. The scattering matrices of the filter were characterized at T = 4.2 K. The filter provides a stopband from 10 Hz to 2.2 GHz and from 2.3 GHz to 10 GHz with more than 50 dB and 40 dB of amplitude suppression, respectively. The center frequency of the passband is f0 = 2.25 GHz with a bandwidth Δf = 80 MHz. The maximum insertion loss in the passband is 4 dB. The filter has a 50 Ω input and output impedance, SubMiniature version A connector termination, and significantly reduced form factor. The wide stopband frequency range and narrow passband in conjunction with small dimensions make the filter suitable to use it as a part of a high sensitive readout for superconducting quantum circuits, such as superconducting quantum bits and cryogenic parametric amplifiers.

  7. The design of digital filters for biomedical signal processing. Part 3: The design of Butterworth and Chebychev filters.

    PubMed

    Challis, R E; Kitney, R I

    1983-04-01

    The first two papers in this series reviewed the basic concepts which apply to digital filter theory and presented design techniques based on the z plane pole-zero plot. In this paper these methods are used to develop digital versions of Butterworth and Chebychev filters. The basic theory of both filter types is reviewed and the bilinear transformation is used to derive the z-transforms of the filters from their s-plane continuous time descriptions. Recurrence relationships which may be used to implement filters of various orders are developed. The impulse and frequency responses of the elements are illustrated and examples are given of their application to ECG data.

  8. Microwave Bandpass Filter Based on Mie-Resonance Extraordinary Transmission

    PubMed Central

    Pan, Xiaolong; Wang, Haiyan; Zhang, Dezhao; Xun, Shuang; Ouyang, Mengzhu; Fan, Wentao; Guo, Yunsheng; Wu, Ye; Huang, Shanguo; Bi, Ke; Lei, Ming

    2016-01-01

    Microwave bandpass filter structure has been designed and fabricated by filling the periodically metallic apertures with dielectric particles. The microwave cannot transmit through the metallic subwavelength apertures. By filling the metallic apertures with dielectric particles, a transmission passband with insertion loss 2 dB appears at the frequency of 10–12 GHz. Both simulated and experimental results show that the passband is induced by the Mie resonance of the dielectric particles. In addition, the passband frequency can be tuned by the size and the permittivity of the dielectric particles. This approach is suitable to fabricate the microwave bandpass filters. PMID:27992440

  9. Tunable multimode-interference bandpass fiber filter.

    PubMed

    Antonio-Lopez, J E; Castillo-Guzman, A; May-Arrioja, D A; Selvas-Aguilar, R; Likamwa, P

    2010-02-01

    We report on a wavelength-tunable filter based on multimode interference (MMI) effects. A typical MMI filter consists of a multimode fiber (MMF) spliced between two single-mode fibers (SMF). The peak wavelength response of the filter exhibits a linear dependence when the length of the MMF is modified. Therefore a capillary tube filled with refractive-index-matching liquid is used to effectively increase the length of the MMF, and thus wavelength tuning is achieved. Using this filter a ring-based tunable erbium-doped fiber laser is demonstrated with a tunability of 30 nm, covering the full C-band.

  10. Thermoluminescence dosimeters with narrow bandpass filters

    DOEpatents

    Walker, Scottie W.

    2004-07-20

    A dosimetry method exposes more than one thermoluminescence crystals to radiation without using conventional filters, and reads the energy stored in the crystals by converting the energy to light in a conventional manner, and then filters each crystal output in a different portion of the spectrum generated by the crystals.

  11. Compact Micromachined Infrared Bandpass Filters for Planetary Spectroscopy

    NASA Technical Reports Server (NTRS)

    Merrell, Willie C., II; Aslam, Shahid; Brown, Ari D.; Chervenak, James A.; Huang, Wei-Chung; Quijada, Manuel; Wollack, Edward

    2011-01-01

    The future needs of space based observational planetary and astronomy missions include low mass and small volume radiometric instruments that can operate in high radiation and low temperature environments. Here we focus on a central spectroscopic component, the bandpass filter. We model the bandpass response of the filters to target the wavelength of the resonance peaks at 20, 40, and 60 micrometers and report good agreement between the modeled and measured response. We present a technique of using common micromachining processes for semiconductor fabrication to make compact, free standing resonant metal mesh filter arrays with silicon support frames. The process can accommodate multiple detector array architectures and the silicon frame provides lightweight mechanical support with low form factor. We also present a conceptual hybridization of the filters with a detector array.

  12. ACSL (Advanced Continuous Simulation Language) Simulation of a Third Order Butterworth Filter Using Implementations Derived From Both Z and S Domain Representations.

    DTIC Science & Technology

    1984-02-01

    proerm witi three ina added to it for geeration of the mueamdn of tho the em tem doadom Wee. CCI’ % ud he dowo Z domsan veruloms, CWVUN sad CIILL The m...THIRD ORDER BUTTERWORTH FILTER USING IMPLEMENTATIONS DERIVED FROM BOTH Z AND S DOMAIN REPRESENTATIONS get Edvard E. L. Mitchell Mitchell and Gauthier...S. TYPE OF REPORT & PERIOD COVERED ACSL SIMULATION OF A THIRD ORDER BUTTERWORTH FILTER USING IMPLEMENTATIONS DERIVED FROM BOTH Z AND S DOMAIN

  13. Raman imaging using fixed bandpass filter

    NASA Astrophysics Data System (ADS)

    Landström, L.; Kullander, F.; Lundén, H.; Wästerby, P.

    2017-05-01

    By using fixed narrow band pass optical filtering and scanning the laser excitation wavelength, hyperspectral Raman imaging could be achieved. Experimental, proof-of-principle results from the Chemical Warfare Agent (CWA) tabun (GA) as well as the common CWA simulant tributyl phosphate (TBP) on different surfaces/substrates are presented and discussed.

  14. Compact micromachined infrared bandpass filters for planetary spectroscopy.

    PubMed

    Merrell, Willie C; Aslam, Shahid; Brown, Ari D; Chervenak, James A; Huang, Wei-Chung; Quijada, Manuel; Wollack, Edward J

    2012-05-20

    The future needs of space-based, observational planetary and astronomy missions include low mass and small volume radiometric instruments that can operate in high-radiation and low-temperature environments. Here, we focus on a central spectroscopic component, the bandpass filter. We model the bandpass response of the filters to target the wavelength of the resonance peaks at 20, 40, and 60 µm and report good agreement between the modeled and measured response. We present a technique of using standard micromachining processes for semiconductor fabrication to make compact, free-standing, resonant, metal mesh filter arrays with silicon support frames. The process can be customized to include multiple detector array architectures, and the silicon frame provides lightweight mechanical support with low form factor.

  15. Switched Band-Pass Filters for Adaptive Transceivers

    NASA Technical Reports Server (NTRS)

    Wang, Ray

    2007-01-01

    Switched band-pass filters are key components of proposed adaptive, software- defined radio transceivers that would be parts of envisioned digital-data-communication networks that would enable real-time acquisition and monitoring of data from geographically distributed sensors. Examples of sensors to be connected to such networks include security cameras, radio-frequency identification units, and geolocation units based on the Global Positioning System. Through suitable software configuration and without changing hardware, these transceivers could be made to operate according to any of a number of complex wireless-communication standards that could be characterized by diverse modulation schemes, bandwidths, and data-handling protocols. The adaptive transceivers would include field-programmable gate arrays (FPGAs) and digital signal-processing hardware. In the receiving path of a transceiver, the incoming signal would be amplified by a low-noise amplifier (LNA). The output spectrum of the LNA would be processed by a band-pass filter operating in the frequency range between 900 MHz and 2.4 GHz. Then a down-converter would translate the signal to a lower frequency range to facilitate analog-to-digital conversion, which would be followed by baseband processing by one or more FPGAs. In the transmitting path, a digital stream would first be converted to an analog signal, which would then be up-converted to a selected frequency band before being applied to a transmitting power amplifier. The aforementioned band-pass filter in the receiving path would be a combination of resonant inductor-and-capacitor filters and switched band-pass filters. The overall combination would implement a switch function designed mathematically to exhibit desired frequency responses and to switch the signal in each frequency band to an analog-to-digital converter appropriate for that band to produce a digital intermediate-frequency signal for digital signal processing.

  16. Annular-slot arrays as far-infrared bandpass filters.

    PubMed

    Krug, P A; Dawes, D H; McPhedran, R C; Wright, W; Macfarlane, J C; Whitbourn, L B

    1989-09-01

    Arrays of both annular and square annular slots in a conducting sheet on a dielectric substrate have been fabricated photolithographically. The structures are shown to behave as bandpass filters in the far infrared, with a resonant wavelength slightly larger than the average circumference or perimeter of the slot. The measured far-infrared transmittance of the annular array is approximately 76% of that predicted by theory, while its resonant frequency agrees with theory to within 5%.

  17. Polarization-insensitive, stacked, liquid crystal polarization grating bandpass filters

    NASA Astrophysics Data System (ADS)

    Nicolescu, Elena; Escuti, Michael J.

    2011-03-01

    We introduce a polarization-insensitive tunable bandpass filter design having the following unique properties: (i) high peak transmittance (~ 80 - 90%) that is independent of input polarization, (ii) non-mechanical tuning over a potentially large wavelength range (> 100 nm) with a narrow passband (< 10 nm possible), (iii) low-cost, simple, and compact (thin-film) construction with a large clear aperture suitable for many simple camera systems. This is a stacked birefringent filter approach similar to Lyot and Solc fiters but with significantly less loss due to the removal of polarizers from the system. The filter is based on a stacked configuration of polymer polarization gratings (PGs) and either fixed or tunable wave plates. PGs are a class of thin film anisotropic diffraction gratings, which exhibit unique properties including zero-order transmittance that is independent of incident polarization, and practically all diffracted light appears within the zero- and first-diffraction orders with efficiency ranging from nearly 100% to 0%. In this work we explore a variety of filter stack configurations and analyze them theoretically using Jones Calculus and Poincare Sphere reasoning. Both fixed and tunable filter configurations are presented and analyzed in terms of finesse, full width at half maximum, free spectral range, and tuning range. We then present preliminary experimental data for a three stage fixed bandpass filter.

  18. Reconstructing tethered satellite skiprope motion by bandpass filtering magnetometer measurements

    NASA Technical Reports Server (NTRS)

    Polites, M. E.

    1992-01-01

    This paper presents a unique scheme for reconstructing tethered satellite skiprope motion by ground processing satellite magnetometer measurements. The measurements are modified based on ground knowledge of the earth's magnetic field and passed through bandpass filters tuned to the skiprope frequency. Skiprope motion is then deduced from the steady-state outputs of the filters. Simulation results are presented which verify the scheme and show it to be robust. The concept is not just limited to tethered satellites. Indeed, it can be applied whenever there is a need to reconstruct the coning motion of a body about a known axis, given measurements of a known vector in body-fixed axes.

  19. 3D Display Using Conjugated Multiband Bandpass Filters

    NASA Technical Reports Server (NTRS)

    Bae, Youngsam; White, Victor E.; Shcheglov, Kirill

    2012-01-01

    Stereoscopic display techniques are based on the principle of displaying two views, with a slightly different perspective, in such a way that the left eye views only by the left eye, and the right eye views only by the right eye. However, one of the major challenges in optical devices is crosstalk between the two channels. Crosstalk is due to the optical devices not completely blocking the wrong-side image, so the left eye sees a little bit of the right image and the right eye sees a little bit of the left image. This results in eyestrain and headaches. A pair of interference filters worn as an optical device can solve the problem. The device consists of a pair of multiband bandpass filters that are conjugated. The term "conjugated" describes the passband regions of one filter not overlapping with those of the other, but the regions are interdigitated. Along with the glasses, a 3D display produces colors composed of primary colors (basis for producing colors) having the spectral bands the same as the passbands of the filters. More specifically, the primary colors producing one viewpoint will be made up of the passbands of one filter, and those of the other viewpoint will be made up of the passbands of the conjugated filter. Thus, the primary colors of one filter would be seen by the eye that has the matching multiband filter. The inherent characteristic of the interference filter will allow little or no transmission of the wrong side of the stereoscopic images.

  20. Broadband microstrip antenna with a hairpin bandpass filter

    NASA Astrophysics Data System (ADS)

    Belyaev, B. A.; Voloshin, A. S.; Morozov, N. V.; Galeev, R. G.

    2015-03-01

    A new design for a broadband microstrip antenna is proposed, the working band of which is broadened using a bandpass filter based on two hairpin resonators electromagnetically coupled with a half-wave radiating resonator with a rectangular strip conductor. It is shown that the operating frequency range of this antenna is significantly extended as compared with that of analogous antennas, while its directivity and polarization diagrams remain highly stable within this range, which makes this design promising for applications. Operability of the antenna is demonstrated using its operating prototype. The measured characteristics of the antenna prototype agree well with the calculated data.

  1. Air gap resonant tunneling bandpass filter and polarizer.

    PubMed

    Melnyk, A; Bitarafan, M H; Allen, T W; DeCorby, R G

    2016-04-15

    We describe a bandpass filter based on resonant tunneling through an air layer in the frustrated total internal reflection regime, and show that the concept of induced transmission can be applied to the design of thin film matching stacks. Experimental results are reported for Si/SiO2-based devices exhibiting a polarization-dependent passband, with bandwidth on the order of 10 nm in the 1550 nm wavelength range, peak transmittance on the order of 80%, and optical density greater than 5 over most of the near infrared region.

  2. Rational engineering of nanoporous anodic alumina optical bandpass filters

    NASA Astrophysics Data System (ADS)

    Santos, Abel; Pereira, Taj; Law, Cheryl Suwen; Losic, Dusan

    2016-08-01

    Herein, we present a rationally designed advanced nanofabrication approach aiming at producing a new type of optical bandpass filters based on nanoporous anodic alumina photonic crystals. The photonic stop band of nanoporous anodic alumina (NAA) is engineered in depth by means of a pseudo-stepwise pulse anodisation (PSPA) approach consisting of pseudo-stepwise asymmetric current density pulses. This nanofabrication method makes it possible to tune the transmission bands of NAA at specific wavelengths and bandwidths, which can be broadly modified across the UV-visible-NIR spectrum through the anodisation period (i.e. time between consecutive pulses). First, we establish the effect of the anodisation period as a means of tuning the position and width of the transmission bands of NAA across the UV-visible-NIR spectrum. To this end, a set of nanoporous anodic alumina bandpass filters (NAA-BPFs) are produced with different anodisation periods, ranging from 500 to 1200 s, and their optical properties (i.e. characteristic transmission bands and interferometric colours) are systematically assessed. Then, we demonstrate that the rational combination of stacked NAA-BPFs consisting of layers of NAA produced with different PSPA periods can be readily used to create a set of unique and highly selective optical bandpass filters with characteristic transmission bands, the position, width and number of which can be precisely engineered by this rational anodisation approach. Finally, as a proof-of-concept, we demonstrate that the superposition of stacked NAA-BPFs produced with slight modifications of the anodisation period enables the fabrication of NAA-BPFs with unprecedented broad transmission bands across the UV-visible-NIR spectrum. The results obtained from our study constitute the first comprehensive rationale towards advanced NAA-BPFs with fully controllable photonic properties. These photonic crystal structures could become a promising alternative to traditional optical

  3. Bandpass filter arrays patterned by photolithography for multispectral remote sensing

    NASA Astrophysics Data System (ADS)

    Bauer, T.; Thome, Heidi; Eisenhammer, Thomas

    2014-10-01

    Optical remote sensing of the earth from air and space typically utilizes several channels from visible (VIS), near infrared (NIR) up to the short wave infrared (SWIR) spectral region. Thin-film optical filters are applied to select these channels. Filter wheels and arrays of discrete stripe filters are standard configurations. To achieve compact and light weight camera designs multi-channel filter plates or assemblies can be mounted close to the electronic detectors. Optics Balzers has implemented a micro-structuring process based on a sequence of multiple coatings and photolithography on the same substrate. High-performance band pass filters are applied by plasma assisted evaporation (plasma IAD) with advance plasma source (APS) technology and optical broad-band monitoring (BBM). This technology has already proven for various multi spectral imager (MSI) configurations on fused silica, sapphire and other substrates for remote sensing application. The optical filter design and performance is limited by the maximum coating thickness micro-structurable by photolithographic lift-off processes and by thermal and radiation load on the photoresist mask during the process Recent progress in image resolution and sensor selectivity requires improvements of optical filter performance. Blocking in the UV and NIR and in between the spectral cannels, in-band transmission and filter edge steepness are subject of current development. Technological limits of the IAD coating accuracy can be overcome by more precise coating technologies like plasma assisted reactive magnetron sputtering (PARMS) and combination with optical broadband monitoring (BBM). We present an overview about concepts and technologies for band-pass filter arrays for multi-spectral imaging at Optics Balzers. Recent performance improvements of filter arrays made by micro-structuring will be presented.

  4. Numerical study of tunable band-pass filter made of one dimensional composite periodic structure

    NASA Astrophysics Data System (ADS)

    Anusha N., P.; Sharan, Alok

    2017-06-01

    Band-pass filters are used to allow transmission of certain range of frequencies and attenuate the rest. In this report we propose a 1-D periodic structure made of alternate layer of single negative index medium and zero index medium which works as band-pass filter. We have numerically simulated the band-pass filter using Finite Difference Time Domain (FDTD) method in Matlab. Entire range of frequency is reflected back when the light is incident on a single negative index medium slab. We were able to create a tunable narrow band-pass filter using the proposed periodic structure by choosing the appropriate values of permittivity and permeability.

  5. Optically tunable acoustic wave band-pass filter

    SciTech Connect

    Swinteck, N.; Lucas, P.; Deymier, P. A.

    2014-12-15

    The acoustic properties of a hybrid composite that exhibits both photonic and phononic behavior are investigated numerically with finite-element and finite-difference time-domain simulations. The structure is constituted of a periodic array of photonic resonant cavities embedded in a background superlattice. The resonant cavities contain a photo-elastic chalcogenide glass that undergoes atomic-scale structural reorganization when irradiated with light having energy close to its band-gap. Photo-excitation of the chalcogenide glass changes its elastic properties and, consequently, augments the acoustic transmission spectrum of the composite. By modulating the intensity of light irradiating the hybrid photonic/phononic structure, the position and spectral width of phonon passing-bands can be controlled. This demonstration offers the technological platform for optically-tunable acoustic wave band-pass filters.

  6. Optically tunable acoustic wave band-pass filter

    NASA Astrophysics Data System (ADS)

    Swinteck, N.; Lucas, P.; Deymier, P. A.

    2014-12-01

    The acoustic properties of a hybrid composite that exhibits both photonic and phononic behavior are investigated numerically with finite-element and finite-difference time-domain simulations. The structure is constituted of a periodic array of photonic resonant cavities embedded in a background superlattice. The resonant cavities contain a photo-elastic chalcogenide glass that undergoes atomic-scale structural reorganization when irradiated with light having energy close to its band-gap. Photo-excitation of the chalcogenide glass changes its elastic properties and, consequently, augments the acoustic transmission spectrum of the composite. By modulating the intensity of light irradiating the hybrid photonic/phononic structure, the position and spectral width of phonon passing-bands can be controlled. This demonstration offers the technological platform for optically-tunable acoustic wave band-pass filters.

  7. An OTA-based CMOS bandpass filter for NMR applications

    NASA Astrophysics Data System (ADS)

    Shesharaman, K. N.; Kittur, Harish M.

    2012-12-01

    One of the very popular medical imaging techniques used in present-day radiology is the magnetic resonance imaging (MRI) which is based on the phenomenon of nuclear magnetic resonance (NMR) in the hydrogen atoms present in the body. There is ever-increasing research in electronic circuit design for biomedical applications using NMR. Earlier magnetic resonance imagers operated at a magnetic field strength of 0.3 T. The present imagers operate at a magnetic field of 1.5 T, the resonance frequency of the nuclei being 64 MHz. This article presents a CMOS bandpass filter (BPF) design for NMR applications. The overall BPF design is realised in 180 nm CMOS technology which occupies an active area of 24.23 × 33.125 µm2 and consumes 0.165 mW of power from a 1.5 V supply.

  8. On the difference between single- and double-sided bandpass filtering of spatial frequencies

    NASA Astrophysics Data System (ADS)

    Yang, Xin; Jia, Wei; Wu, Di; Poon, Ting-Chung

    2017-02-01

    It is well-known that bandpass filtering will lead to edge extraction in image processing. However, the difference between single- and double-sided bandpass filtering has never been compared and investigated in the literature. We investigate the difference between single- and double-sided bandpass spatial filtering in a 4-f coherent optical image processing system. We find that single-sided filtering can approximate the operation of a first-order derivative, while double-sided filtering gives a second-order derivative. Simulations and optical experiments confirm our findings.

  9. Human localisation of band-pass filtered noise.

    PubMed

    van Schaik, A; Jin, C; Carlile, S

    1999-10-01

    In this work we study the influence and relationship of five different acoustical cues to the human sound localisation process. These cues are: interaural time delay, interaural level difference, interaural spectrum, monaural spectrum, and band-edge spectral contrast. Of particular interest was the synthesis and integration of the different cues to produce a coherent and robust percept of spatial location. The relative weighting and role of the different cues was investigated using band-pass filtered white noise with a frequency range (in kHz) of: 0.3-5, 0.3-7, 0.3-10, 0.3-14, 3-8, 4-9, and 7-14. These stimuli provided varying amounts of spectral information and physiologically detectable temporal information, thus probing the localisation process under varying sound conditions. Three subjects with normal hearing in both ears have performed five trials of 76 test positions for each of these stimuli in an anechoic room. All subjects showed systematic mislocalisation on most of these stimuli. The location to which they are mislocalised varies among subjects but in a systematic manner related to the five different acoustical cues. These cues have been correlated with the subject's localisation responses on an individual basis with the results suggesting that the internal weighting of the spectral cues may vary with the sound condition.

  10. High Selectivity Wideband Bandpass Filter Using Stub Loaded Resonator

    NASA Astrophysics Data System (ADS)

    Ma, Xing-Bing; Jiang, Ting

    2017-07-01

    This article presents a high selectivity wideband bandpass filter (BPF) adopting stub loaded resonator. Hereinto, aim passband is determined by BPF without stub embedded, which is only composed of four half-wavelength open-loop resonators. Based on typical tapped-line coupling, two same stubs are located at physical middle points of two resonators connected with I/O feed lines, respectively. Due to embedded point at middle of loaded resonator, the stub with two open-end branches has no influence on original half-wavelength resonant frequency, and aim passband keeps unchanged. Because of different even-mode resonant frequencies between loaded and unloaded resonators, no new passband is constructed. With the help of embedded stubs, original transmission zero (TZ) near low-edge of aim passband is shifted towards passband, and a new TZ is introduced near high-edge. High selectivity and good passband characteristics are obtained optimizing sizes of stubs, I/O tapped position and top open-end length of loaded resonator.

  11. Enabling tunable micromechanical bandpass filters through phase-change materials

    NASA Astrophysics Data System (ADS)

    Cao, Yunqi; Torres, David; Wang, Tongyu; Tan, Xiaobo; Sepúlveda, Nelson

    2017-08-01

    Vanadium dioxide (VO2), one of the most promising phase-change smart materials, has shown strong frequency tuning capabilities in MEMS resonators. In this paper, we demonstrate the potential use of VO2-based MEMS devices as second-order kilohertz (kHz) bandpass filters with tunable band selectivity and adjustable bandwidth (BW). Two identical on-chip micro resonators are actuated using mechanical excitation and measured using optical detection. One of the resonators is not actuated while the other is tuned by applying electric currents across an integrated resistive heater, which induces the phase transition of the VO2, and consequently a large stress to the mechanical structure. The responses of both MEMS resonators are combined, resulting in a resonant peak of tunable BW controlled by the input current. The BW can be extended to 2.62 times by using two bridges or 2.39 times by implementing one pair of cantilevers. The results for both devices are discussed.

  12. Notes on the Design of Microstrip and Stripline Bandpass Filters

    DTIC Science & Technology

    1974-08-01

    9177 gold ink on 0.635mm, Coors ADS 945, alumina substrates. The conductor patteins were printed through 325 mesh, stainless steel screens. A firing...I4. ITI 0𔃺 0 Sf14 FIg.4 Frequency f f a ’Cf o 0 £ L 0 U c - Afa L Fm Fig. 4 Typical Butterworth maximally - flat response Flg.S5 I Frequency

  13. Postfabrication exposure of gap-type bandpass filters in broadly chirped fiber gratings.

    PubMed

    Zhang, L; Sugden, K; Williams, J A; Bennion, I; Reid, D C; Ragdale, C M

    1995-09-15

    High efficiency in-fiber bandpass filters with arbitrary passband/stop-band combinations have been produced successfully with an UV postfabrication exposure technique in broadly chirped fiber gratings. By further concatenating such a bandpass filter with two additional chirped gratings we achieved a finesse as high as 220 for a 36-nm stop band. This new approach exhibits great advantages in controlling precisely the profiles of bandpass filters in terms of stop-band width, transmission wavelength and linewidth, and spacing of passbands.

  14. A Novel Broadband Band-pass Filter Based on Spoof Surface Plasmon Polaritons

    PubMed Central

    Zhao, Lei; Zhang, Xin; Wang, Jun; Yu, Wenhua; Li, Jiandong; Su, Hai; Shen, Xiaopeng

    2016-01-01

    In this paper, we present a novel broadband bandpass filter based on spoof surface plasmon polaritons (SSPPs) in the microwave frequency band. The proposed bandpass filter includes three parts: (1) coplanar waveguide (CPW); (2) matching transition; and (3) coupled structure that is an asymmetric coupled filter constructed by five grooved strips. The proposed bandpass filter realizes excellent low loss performance from 7 to 10 GHz, in which its insertion loss is around 1.5 dB in the same frequency band. Meanwhile, this filter has a good band stop characteristic from 3 to 7 GHz. A simple but accurate transmission line model was proposed to evaluate the proposed broadband SSPPs filter. The measured data, simulated results and the results obtained from the transmission line model have shown a very good agreement. The proposed planar broadband filter plays an important role for filtering surface plasmon polaritons (SPPs) waves in plasmonic circuits and systems. PMID:27796313

  15. A Novel Broadband Band-pass Filter Based on Spoof Surface Plasmon Polaritons

    NASA Astrophysics Data System (ADS)

    Zhao, Lei; Zhang, Xin; Wang, Jun; Yu, Wenhua; Li, Jiandong; Su, Hai; Shen, Xiaopeng

    2016-10-01

    In this paper, we present a novel broadband bandpass filter based on spoof surface plasmon polaritons (SSPPs) in the microwave frequency band. The proposed bandpass filter includes three parts: (1) coplanar waveguide (CPW); (2) matching transition; and (3) coupled structure that is an asymmetric coupled filter constructed by five grooved strips. The proposed bandpass filter realizes excellent low loss performance from 7 to 10 GHz, in which its insertion loss is around 1.5 dB in the same frequency band. Meanwhile, this filter has a good band stop characteristic from 3 to 7 GHz. A simple but accurate transmission line model was proposed to evaluate the proposed broadband SSPPs filter. The measured data, simulated results and the results obtained from the transmission line model have shown a very good agreement. The proposed planar broadband filter plays an important role for filtering surface plasmon polaritons (SPPs) waves in plasmonic circuits and systems.

  16. Spectral design of temperature-invariant narrow bandpass filters for the mid-infrared.

    PubMed

    Stolberg-Rohr, Thomine; Hawkins, Gary J

    2015-01-12

    The ability of narrow bandpass filters to discriminate wavelengths between closely-separated gas absorption lines is crucial in many areas of infrared spectroscopy. As improvements to the sensitivity of infrared detectors enables operation in uncontrolled high-temperature environments, this imposes demands on the explicit bandpass design to provide temperature-invariant behavior. The unique negative temperature coefficient (dn/dT<0) of Lead-based (Pb) salts, in combination with dielectric materials enable bandpass filters with exclusive immunity to shifts in wavelength with temperature. This paper presents the results of an investigation into the interdependence between multilayer bandpass design and optical materials together with a review on invariance at elevated temperatures.

  17. Dual and tri-band bandpass filters based on novel Π-shaped resonator

    NASA Astrophysics Data System (ADS)

    Xiao, Jian-Kang; Zhu, Wen-Jun; Zhao, Wei

    2014-05-01

    A novel Π-shaped resonator is proposed, and compact dual-band and tri-band bandpass filters that meet IEEE 802.11 application requirements by using the new resonator are designed. The dual-band bandpass filter centres at 2.45 and 5.6 GHz with a simulated passband insertion loss of no more than 0.8 dB, and the tri-band bandpass filter which is got by two-path coupling achieves simulated passband insertion loss of no more than 1.1 dB. The new designs are demonstrated by experiment. The new filters have advantages of simple and compact structures, low passband insertion losses, good frequency selectivity and miniature circuit sizes. All these have prospect to be applied in future wireless communication systems.

  18. A Quasi-Elliptic Bandpass Filter-Integrated Single-Pole Double-Throw Switch

    NASA Astrophysics Data System (ADS)

    Ji, Yu-Xue; Xu, Jin; Li, Zhao-Zhao; Wang, Huan; Huang, Jin-Jie

    2017-09-01

    This paper proposes a quasi-elliptic bandpass filter-integrated single-pole double-throw (SPDT) switch. The series-parallel configuration of p-i-n diodes embedded into the impedance matching circuit is proposed to combine two quasi-elliptic response bandpass filters to constitute the proposed SPDT switch. To validate our design approach, a proposed quasi-elliptic bandpass filter-integrated SPDT switch is designed and fabricated with a central frequency of 1.25 GHz and a 3 dB fractional bandwidth of 16 %. Low insertion loss in the on state and good isolation in the off state are achieved. The switch size including bias circuits but excluding feeding lines is 0.447λg×0.134λg.

  19. Light trimming of a narrow bandpass filter based on a photosensitive chalcogenide spacer.

    PubMed

    Shen, W D; Cathelinaud, M; Lequime, M D; Charpentier, F; Nazabal, V

    2008-01-07

    We present an experimental study of the photosensitive properties of a narrow bandpass filter based on a Ge(15)Sb(20)S(65) spacer fabricated by electron beam deposition. For a single layer, near the optical bandgap of this chalcogenide material, the efficiency of the photo-bleaching increases as the central wavelength of the light source for exposure decreases. The maximum relative photo-induced change of the optical thickness reaches about 1%. By using controlled light exposure around 480 nm of a photosensitive narrow bandpass filter centered at 1550 nm, we obtained a spatially localized shift of its peak wavelength up to 5.4 nm. This property is used to perform, for the first time at our knowledge, the post trimming of a narrow bandpass filter with a light beam. A 5 x 5 mm(2) ultra uniform area in which the relative spatial variation of its peak wavelength remains below 0.004% is demonstrated.

  20. A novel 2nd-order bandpass MFSS filter with miniaturized structure

    NASA Astrophysics Data System (ADS)

    Fang, C. Y.; Gao, J. S.; Feng, X. G.

    2015-08-01

    In order to effectively obtain a miniaturized structure and good filtering properties, we propose a novel 2nd-order bandpass metamaterial frequency selective surface (MFSS) filter which contains two capacitive layers and one inductive layer, where there are multi-loop metallic patches as shunt capacitor C and planar wire grids as series inductor L respectively. Unlike the traditional operation way—the tuned elements used in resonant surface approximately equal to one wavelength in circumference and the structure thickness with a spacing of a quarter wavelength apart, by changing the value of L and C and matching multilayer dielectric to adjust the LC coupling resonance and the resonance impedance respectively, the proposed MFSS filter can achieves a miniatured structure with ideal bandpass properties. Measurement results of the fabricated prototype of the bandpass filter (BPF) indicate that the dimension of the tuned element on resonant surface is approximately 0.025 wavelength, i.e., 0.025λ. At the same time, the filter has the stable center frequency of f0 = 1.53GHz and the transmittance of T ⩾ 96.3% and high Q-value for the TE/TM wave polarization at various incidence angles. The novel 2nd-order bandpass MFSS filter with miniaturized structure not only can decrease structure dimension, but also has a wide range of applications to microwave and infrared band.

  1. Miniaturized sharp band-pass filter based on complementary electric-LC resonator

    NASA Astrophysics Data System (ADS)

    Torabi, Yalda; Dadashzadeh, Golamreza; Oraizi, Homayoon

    2016-04-01

    In this paper, a novel application of complementary electric-LC (CELC) resonator as a basic element to synthesize miniaturized sharp band-pass filters is introduced. The proposed metamaterial band-pass filter is a three-stage CELC-based device, where two shunt short-circuited stubs are employed in the input and output stages and a series gap is etched in the middle stage. By these means, a high-selectivity prototype band-pass filter with 2 % fractional bandwidth in S band is designed and fabricated. The out-of-band attenuation is better than 40 dB, and the upper and lower transition bands are also quite sharp due to the presence of two transmission zeros (nearly 60 and 30 dB fall in 0.2 GHz at lower and upper edges, respectively). Moreover, the filter is substantially miniaturized with a size of effective region of 1.3 cm × 1 cm at 2.9 GHz, which is quite smaller relative to conventional designs with the same performance. The fabrication and measurement of the proposed filter configuration attest to its expected desirable features. Therefore, the application of CELC resonator is proposed for super-compact sharp band-pass filters.

  2. Design of optical bandpass filters based on a two-material multilayer structure.

    PubMed

    Belyaev, B A; Tyurnev, V V; Shabanov, V F

    2014-06-15

    An easy method for designing filters with equalized passband ripples of a given magnitude is proposed. The filter, which is made of two dielectric materials, comprises coupled half-wavelength resonators and multilayer mirrors. The filter design begins with the synthesis of the multimaterial filter prototype whose mirrors consist of quarter-wavelength layers. Optimal refractive indices of the layers in the prototype are obtained by a special optimization based on universal rules. The thicknesses of the mirrors' layers in the final filter are computed using derived formulas. A design procedure example for silicon-air bandpass filters with a fractional bandwidth of 1% is described.

  3. Alkali metal for ultraviolet band-pass filter

    NASA Technical Reports Server (NTRS)

    Mardesich, Nick (Inventor); Fraschetti, George A. (Inventor); Mccann, Timothy A. (Inventor); Mayall, Sherwood D. (Inventor); Dunn, Donald E. (Inventor); Trauger, John T. (Inventor)

    1993-01-01

    An alkali metal filter having a layer of metallic bismuth deposited onto the alkali metal is provided. The metallic bismuth acts to stabilize the surface of the alkali metal to prevent substantial surface migration from occurring on the alkali metal, which may degrade optical characteristics of the filter. To this end, a layer of metallic bismuth is deposited by vapor deposition over the alkali metal to a depth of approximately 5 to 10 A. A complete alkali metal filter is described along with a method for fabricating the alkali metal filter.

  4. Design of bandpass filters composed of dielectric layers separated by gratings of strip conductors.

    PubMed

    Belyaev, B A; Tyurnev, V V

    2016-02-01

    We derive the design formulas for novel multilayer bandpass filters in which every dielectric layer (resonator) is separated from the adjacent layer or external medium by a grating of strip conductors. Every grating acts as a semi-reflecting mirror. Such novel filters have wide stop bands compared to conventional filters with multilayer dielectric mirrors between resonators at the same passband width. The parameters of the lowpass, lumped-element prototype filter, as well as the theory of resonator-coupling coefficients, are considered in our approach. The computed frequency response of the fifth-order Chebyshev filter that was synthesized using the proposed formulas is also presented.

  5. Fabric defect detection based on annular Gaussian band-pass filters

    NASA Astrophysics Data System (ADS)

    Han, Runping; Su, Jianxia

    2013-07-01

    A new method for fabric defect detection is proposed. It is based on the filter group containing four annular Gaussian band-pass filters and aimed at detecting defects in fabrics with plain and twill structures. A fabric sample image is processed by using this filter group and the filtered images are obtained. These filtered images are binarized and fused in order to reconstruct the defect binary image that distinguishes defects from texture background. In the performance evaluation and comparison experiments, this method is applied to a variety of fabrics with various defects. Experiment results have confirmed this method has good real time performance and is effective in fabric defect detection.

  6. A robust SEM auto-focus algorithm using multiple band-pass filters

    NASA Astrophysics Data System (ADS)

    Harada, Minoru; Obara, Kenji; Nakamae, Koji

    2017-01-01

    An auto-focus algorithm using multiple band-pass filters for a scanning electron microscope (SEM) is proposed. To acquire sharp images of various kinds of defects by SEM defect observation in semiconductor manufacturing, the auto-focus process must be robust. A method for designing a band-pass filter for calculating the ‘focus measure’ (a key parameter of the auto-focus process) is proposed. To achieve an optimal specific frequency response for various images, multiple band-pass filters are introduced. As for the proposed method, two series of focus measures are calculated by using multiple band-pass filters independently, and it is selected according to reliability of the series of focus measures. The signal-to-noise ratio of an image for acceptable auto-focus precision is determined by simulation using pseudo images. In an experiment using the proposed method with real images, the success rate of auto focus is improved from 79.4% to 95.6%.

  7. Spectral and Wavefront Error Performance of WFIRST-AFTA Bandpass Filter Coating Prototypes

    NASA Technical Reports Server (NTRS)

    Quijada, Manuel A.; Seide, Laurie; Pasquale, Bert A.; McMann, Joseph C.; Hagopian, John G.; Dominguez, Margaret Z.; Gong, Quian; Marx, Catherine T.

    2016-01-01

    The Cycle 5 design baseline for the Wide-Field Infrared Survey Telescope Astrophysics Focused Telescope Assets (WFIRST/AFTA) instrument includes a single wide-field channel (WFC) instrument for both imaging and slit-less spectroscopy. The only routinely moving part during scientific observations for this wide-field channel is the element wheel (EW) assembly. This filter-wheel assembly will have 8 positions that will be populated with 6 bandpass filters, a blank position, and a Grism that will consist of a three-element assembly to disperse the full field with an undeviated central wavelength for galaxy redshift surveys. All filter elements in the EW assembly will be made out of fused silica substrates (110 mm diameter) that will have the appropriate bandpass coatings according to the filter designations (Z087, Y106, J129, H158, F184, W149 and Grism). This paper presents and discusses the performance (including spectral transmission and reflected/transmitted wavefront error measurements) of a subset of bandpass filter coating prototypes that are based on the WFC instrument filter compliment. The bandpass coating prototypes that are tested in this effort correspond to the Z087, W149, and Grism filter elements. These filter coatings have been procured from three different vendors to assess the most challenging aspects in terms of the in-band throughput, out of band rejection (including the cut-on and cutoff slopes), and the impact the wavefront error distortions of these filter coatings will have on the imaging performance of the wide-field channel in the WFIRST/AFTA observatory.

  8. An optically tunable wideband optoelectronic oscillator based on a bandpass microwave photonic filter.

    PubMed

    Jiang, Fan; Wong, Jia Haur; Lam, Huy Quoc; Zhou, Junqiang; Aditya, Sheel; Lim, Peng Huei; Lee, Kenneth Eng Kian; Shum, Perry Ping; Zhang, Xinliang

    2013-07-15

    An optoelectronic oscillator (OEO) with wideband frequency tunability and stable output based on a bandpass microwave photonic filter (MPF) has been proposed and experimentally demonstrated. Realized by cascading a finite impulse response (FIR) filter and an infinite impulse response (IIR) filter together, the tunable bandpass MPF successfully replaces the narrowband electrical bandpass filter in a conventional single-loop OEO and serves as the oscillating frequency selector. The FIR filter is based on a tunable multi-wavelength laser and dispersion compensation fiber (DCF) while the IIR filter is simply based on an optical loop. Utilizing a long length of DCF as the dispersion medium for the FIR filter also provides a long delay line for the OEO feedback cavity and as a result, optical tuning over a wide frequency range can be achieved without sacrificing the quality of the generated signal. By tuning the wavelength spacing of the multi-wavelength laser, the oscillation frequency can be tuned from 6.88 GHz to 12.79 GHz with an average step-size of 0.128 GHz. The maximum frequency drift of the generated 10 GHz signal is observed to be 1.923 kHz over 1 hour and its phase noise reaches the -112 dBc/Hz limit of our measuring equipment at 10 kHz offset frequency.

  9. Compact Micromachined Bandpass Filters for Infrared Planetary Spectroscopy

    NASA Technical Reports Server (NTRS)

    Brown, Ari D.; Aslam, Shahid; Chervenak, James A.; Huang, Wei-Chung; Merrell, Willie; Quijada, Manuel

    2011-01-01

    The thermal instrument strawman payload of the Jupiter Europa Orbiter on the Europa Jupiter Science Mission will map out thermal anomalies, the structure, and atmospheric conditions of Europa and Jupiter within the 7-100 micron spectral range. One key requirement for the payload is that the mass cannot exceed 3.7 kg. Consequently, a new generation of light-weight miniaturized spectrometers needs to be developed. On the path toward developing these spectrometers is development of ancillary miniaturized spectroscopic components. In this paper, we present a strategy for making radiation hard and low mass FIR band pass metal mesh filters. Our strategy involves using MEMS-based fabrication techniques, which will permit the quasi-optical filter structures to be made with micron-scale precision. This will enable us to achieve tight control over both the pass band of the filter and the micromachined silicon support structure architecture, which will facilitate integration of the filters for a variety of applications.

  10. Optical Interference Coatings Design Contest 2007: triple bandpass filter and nonpolarizing beam splitter.

    PubMed

    Tilsch, Markus; Hendrix, Karen

    2008-05-01

    A triple bandpass filter (28 solutions received) and a nonpolarizing beam splitter (23 solutions received) were the subjects of the design contest held in conjunction with the 2007 Optical Interference Coatings topical meeting of the Optical Society of America. Fifteen designers participated using a wide spectrum of design approaches and optimization strategies to create the submissions. The results differ significantly, but all meet the contest requirements. Fabien Lemarchand wins both contests by submitting the thinnest (6254 nm) triple bandpass design and the widest (61.7 nm) nonpolarizing beam-splitter design. Michael Trubetskov is in second place, followed by Vladimir Pervak in both contests. The submitted designs are described and evaluated.

  11. Reconfigurable UWB Bandpass Filter with Flexible Notch Characteristics

    NASA Astrophysics Data System (ADS)

    Dhwaj, Kirti

    The thesis reports a compact tunable ultra-wideband (UWB) notch filter using hybrid microstrip and coplanar waveguide (CPW) structure. The tunable notch is implemented to filter out the wireless local area network (WLAN) channels from 5GHz to 6GHz. The proposed structure utilizes the resonance of open ended stubs to achieve transmission zeroes in the filter passband. Varactors and by-pass capacitors are then introduced for dynamic tunability of notch. Further, the electromagnetic decoupling of the two resonators leads to tunable bandwidth of notch. DC bias circuitry is implemented to control the varactor capacitances. Rejection levels up to 25 dB are attained using this technique while maintaining insertion loss levels below 2.5 dB in the passband. The reconfigurability of bandwidth is shown by maintaining a constant bandwidth of 150 MHz across the WLAN band for the notch. The filter achieves an excellent wide bandwidth (from 2.5 GHz to 8.5 GHz) using multimode-resonator (MMR) based topology which makes the filter one wavelength long at the central frequency.

  12. Frequency Selective Surface Based Bandpass Filter for THz Communication System

    NASA Astrophysics Data System (ADS)

    Das, Subrata; Reza, Khan Mamun; Habib, Md. Ahsan

    2012-11-01

    In this work, a band pass filter based on frequency selective surface (FSS) is presented. The resonance of the FSS is achieved by perforating slot type ring structure on an Aluminum layer. To ensure adequate mechanical strength, this structure is again supported by a dielectric layer. The physical dimensions of the FSS, i.e. ring radius, slot width, cell dimension and width of the layers all are responsible for the resonance behavior. In its electrical equivalent circuit, these dimensions act as inductor and capacitor. The center frequency of the designed filter is at 0.16 THz with a -3 dB bandwidth of 18 GHz. This filter can be utilized as a part of any THz communication system to achieve application specific frequency discrimination. The simulation has been carried by using commercial software-CST Microwave Studio. The performance of the fabricated FSS is evaluated by Microwave Vector Network Analyzer.

  13. Composite thin-foil bandpass filter for EUV astronomy Titanium-antimony-titanium

    NASA Technical Reports Server (NTRS)

    Jelinsky, P.; Martin, C.; Kimble, R.; Bowyer, S.; Steele, G.

    1983-01-01

    Thin metallic foils of antimony and titanium have been investigated in an attempt to develop an EUV filter with a bandpass from 350 to 550 A. A composite filter has been developed composed of antimony sandwiched between two titanium foils. The transmissions of sample composite foils and of pure titanium foils from 130 to 1216 A are presented. The absorption coefficients of anatimony and titanium and the effect of titanium oxide on the transmission are derived. The composite filter has been found to be quite stable and mechanically rugged. Among other uses, the filter shows substantial promise for EUV astronomy.

  14. Composite thin-foil bandpass filter for EUV astronomy Titanium-antimony-titanium

    NASA Technical Reports Server (NTRS)

    Jelinsky, P.; Martin, C.; Kimble, R.; Bowyer, S.; Steele, G.

    1983-01-01

    Thin metallic foils of antimony and titanium have been investigated in an attempt to develop an EUV filter with a bandpass from 350 to 550 A. A composite filter has been developed composed of antimony sandwiched between two titanium foils. The transmissions of sample composite foils and of pure titanium foils from 130 to 1216 A are presented. The absorption coefficients of anatimony and titanium and the effect of titanium oxide on the transmission are derived. The composite filter has been found to be quite stable and mechanically rugged. Among other uses, the filter shows substantial promise for EUV astronomy.

  15. Effect of bandpass filtering on melodic contour identification by cochlear implant users

    PubMed Central

    Galvin, John J.; Fu, Qian-Jie

    2011-01-01

    Melodic contour identification was measured in cochlear implant (CI) and normal-hearing (NH) subjects for piano samples processed by four bandpass filters: low (310–620 Hz), middle (620–2480 Hz), high (2480–4960 Hz), and full (310–4960 Hz). NH performance was near-perfect for all filter ranges and much higher than CI performance. The best mean CI performance was with the middle frequency range; performance was much better for some CI subjects with the middle rather than the full filter. These results suggest that acoustic filtering may reduce potential mismatches between fundamental frequencies and harmonic components thereby improving CI users’ melodic pitch perception. PMID:21361410

  16. Compact Q-value enhanced bandpass filter based on the EIT-like effect accompanying application in downconversion APL.

    PubMed

    Yu, Hongchen; Chen, Minghua; Li, Pengxiao; Yang, Sigang; Chen, Hongwei; Xie, Shizhong

    2013-10-01

    A compact quality factor (Q)-enhanced bandpass filter based on the electromagnetically induced transparency (EIT)-like effect between two-ring resonators was proposed and experimental demonstrated. The enhancement in Q can be 2-3 orders of magnitude compared to the single ring bandpass filter, and a 27 times enhanced bandpass filter with a bandwidth of approximately 4.8 GHz was successfully realized. A downconversion analog photonic link (APL) based on the proposed filter has been presented and the spurious free dynamic range of the link was as high as 103.9 dB-Hz(2/3).

  17. Ultra-narrow bandpass filters for infrared applications with improved angle of incidence performance

    NASA Astrophysics Data System (ADS)

    Rahmlow, Thomas D.; Fredell, Markus; Chanda, Sheetal; Johnson, Robert

    2016-05-01

    Narrow band-pass optical interference filters are used for a variety of applications to improve signal quality in laser based systems. Applications include LIDAR, sensor processing and free space communications. A narrow band width optical filter allows for passage of the laser signal while rejecting ambient light. The more narrow the bandwidth, the better the signal to noise. However, the bandwidth of a design for a particular application is typically limited by a number of factors including spectral shift over the operational angles of incidence, thermal shift over the range of operating temperature and, in the case of laser communication, rejection of adjacent laser channels. The trade-off of these parameters can significantly impact system design and performance. This paper presents design and material approaches to maximize the performance of narrow bandpass filters in the infrared.

  18. Radiation Hard Bandpass Filters for Mid- to Far-IR Planetary Instruments

    NASA Technical Reports Server (NTRS)

    Brown, Ari D.; Aslam, Shahid; Chervenack, James A.; Huang, Wei-Chung; Merrell, Willie C.; Quijada, Manuel; Steptoe-Jackson, Rosalind; Wollack, Edward J.

    2012-01-01

    We present a novel method to fabricate compact metal mesh bandpass filters for use in mid- to far-infrared planetary instruments operating in the 20-600 micron wavelength spectral regime. Our target applications include thermal mapping instruments on ESA's JUICE as well as on a de-scoped JEO. These filters are novel because they are compact, customizable, free-standing copper mesh resonant bandpass filters with micromachined silicon support frames. The filters are well suited for thermal mapping mission to the outer planets and their moons because the filter material is radiation hard. Furthermore, the silicon support frame allows for effective hybridization with sensors made on silicon substrates. Using a Fourier Transform Spectrometer, we have demonstrated high transmittance within the passband as well as good out-of-band rejection [1]. In addition, we have developed a unique method of filter stacking in order to increase the bandwidth and sharpen the roll-off of the filters. This method allows one to reliably control the spacing between filters to within 2 microns. Furthermore, our method allows for reliable control over the relative position and orienta-tion between the shared faces of the filters.

  19. Retinal blood vessel extraction using tunable bandpass filter and fuzzy conditional entropy.

    PubMed

    Sil Kar, Sudeshna; Maity, Santi P

    2016-09-01

    Extraction of blood vessels on retinal images plays a significant role for screening of different opthalmologic diseases. However, accurate extraction of the entire and individual type of vessel silhouette from the noisy images with poorly illuminated background is a complicated task. To this aim, an integrated system design platform is suggested in this work for vessel extraction using a sequential bandpass filter followed by fuzzy conditional entropy maximization on matched filter response. At first noise is eliminated from the image under consideration through curvelet based denoising. To include the fine details and the relatively less thick vessel structures, the image is passed through a bank of sequential bandpass filter structure optimized for contrast enhancement. Fuzzy conditional entropy on matched filter response is then maximized to find the set of multiple optimal thresholds to extract the different types of vessel silhouettes from the background. Differential Evolution algorithm is used to determine the optimal gain in bandpass filter and the combination of the fuzzy parameters. Using the multiple thresholds, retinal image is classified as the thick, the medium and the thin vessels including neovascularization. Performance evaluated on different publicly available retinal image databases shows that the proposed method is very efficient in identifying the diverse types of vessels. Proposed method is also efficient in extracting the abnormal and the thin blood vessels in pathological retinal images. The average values of true positive rate, false positive rate and accuracy offered by the method is 76.32%, 1.99% and 96.28%, respectively for the DRIVE database and 72.82%, 2.6% and 96.16%, respectively for the STARE database. Simulation results demonstrate that the proposed method outperforms the existing methods in detecting the various types of vessels and the neovascularization structures. The combination of curvelet transform and tunable bandpass

  20. The Dual Carrier ABSK System Based on a FIR Bandpass Filter

    PubMed Central

    Chen, Zhimin; Wu, Lenan; Wang, Jiwu

    2014-01-01

    The special impacting filter (SIF) with IIR structure has been used to demodulate ABSK signals. The key points of SIF, including the resonance circuit's high Q value and the “slope-phase discrimination” character of the filter sideband, are demonstrated in the paper. The FIR narrow-band bandpass filtering system, which can also provide the impact-filtering effect, is proposed. A dual carrier system of ABSK signals is designed with the proposed FIR filter as its receiver. The simulation results show that the FIR filter can work well. Moreover, compared to the traditional SIF, the proposed FIR filter can not only achieve higher spectral efficiency, but also give better demodulation performance. PMID:24658625

  1. Investigation of Dual-Mode Microstrip Bandpass Filter Based on SIR Technique

    PubMed Central

    Mezaal, Yaqeen S.; Ali, Jawad K.

    2016-01-01

    In this paper, a new bandpass filter design has been presented using simple topology of stepped impedance square loop resonator. The proposed bandpass filter has been simulated and fabricated using a substrate with an insulation constant of 10.8, thickness of 1.27mm and loss tangent of 0.0023 at center frequency of 5.8 GHz. The simulation results have been evaluated using Sonnet simulator that is extensively adopted in microwave analysis and implementation. The output frequency results demonstrated that the proposed filter has high-quality frequency responses in addition to isolated second harmonic frequency. Besides, this filter has very small surface area and perceptible narrow band response features that represent the conditions of recent wireless communication systems. Various filter specifications have been compared with different magnitudes of perturbation element dimension. Furthermore, phase scattering response and current intensity distribution of the proposed filter have been discussed. The simulated and experimental results are well-matched. Lastly, the features of the proposed filter have been compared with other designed microstrip filters in the literature. PMID:27798675

  2. Investigation of Dual-Mode Microstrip Bandpass Filter Based on SIR Technique.

    PubMed

    Mezaal, Yaqeen S; Ali, Jawad K

    2016-01-01

    In this paper, a new bandpass filter design has been presented using simple topology of stepped impedance square loop resonator. The proposed bandpass filter has been simulated and fabricated using a substrate with an insulation constant of 10.8, thickness of 1.27mm and loss tangent of 0.0023 at center frequency of 5.8 GHz. The simulation results have been evaluated using Sonnet simulator that is extensively adopted in microwave analysis and implementation. The output frequency results demonstrated that the proposed filter has high-quality frequency responses in addition to isolated second harmonic frequency. Besides, this filter has very small surface area and perceptible narrow band response features that represent the conditions of recent wireless communication systems. Various filter specifications have been compared with different magnitudes of perturbation element dimension. Furthermore, phase scattering response and current intensity distribution of the proposed filter have been discussed. The simulated and experimental results are well-matched. Lastly, the features of the proposed filter have been compared with other designed microstrip filters in the literature.

  3. Wideband bandpass filters employing broadside-coupled microstrip lines for MIC and MMIC applications

    NASA Technical Reports Server (NTRS)

    Tran, M.; Nguyen, C.

    1994-01-01

    Wideband bandpass filters employing half-wavelength broadside-coupled microstrip lines suitable for microwave and mm-wave integrated monolithic integrated circuits (MIC and MMIC) are presented. Several filters have been developed at X-band (8 to 12 GHz) with 1 dB insertion loss. Fair agreement between the measured and calculated results has been observed. The analysis of the broadside-coupled microstrip lines used in the filters, based on the quasi-static spectral domain technique, is also described.

  4. A band-pass plasmonic filter with dual-square ring resonator

    NASA Astrophysics Data System (ADS)

    Duan, Gaoyan; Lang, Peilin; Wang, Lulu; Yu, Li; Xiao, Jinghua

    2014-09-01

    In this paper, we show the simulation of a plasmonic band-pass filter which consists of two surface plasmon polaritons (SPPs) waveguides and a resonator in metal-insulator-metal (MIM) structure. The resonator is formed by two square rings and a patch between them. The patch is a tiny rectangle cavity in order to transfer the SPPs from one ring to the other. The finite element method (FEM) method is employed in simulation. The results show that the dual-ring resonator performs better than a single ring does. The 3 dB bandwidth near the peak wavelength λ = 1054 nm is merely 31.7 nm. The resonant wavelength can be shifted by changing the side length of the square ring. This narrow band-pass filter is easy to fabricate and has potential applications in future integrated optical circuits.

  5. Design and manufacture of a bandpass filter with high transmittance and steep edge on both sides

    NASA Astrophysics Data System (ADS)

    Wang, Ruisheng; Lü, Shaobo; Yin, Xiaojun; Zhao, Shuaifeng; Sun, Yan

    2016-01-01

    By using Nb2O5 and SiO2 as the coating material, a 152 layers (12 cavities) bandpass film stack with steep edge on both sides was designed. Multiple thickness control methods, including direct optical monitoring control and time control were used in coating strategy. To confirm the feasibility of this coating strategy, a process simulation was performed using Simulator software, and the simulation result indicated that relative thickness errors for all layers were less than ±0.1%. A bandpass filter with this film stack on one side was manufactured by using a plasma assisted reactive magnetic sputtering coating machine. The measuring result shows that the peak transmittance of the filter (without AR on backside) is up to 95.4%, and the steepness of both blocking slope are less than λ/100.

  6. Project Report: Reducing Color Rivalry in Imagery for Conjugated Multiple Bandpass Filter Based Stereo Endoscopy

    NASA Technical Reports Server (NTRS)

    Ream, Allen

    2011-01-01

    A pair of conjugated multiple bandpass filters (CMBF) can be used to create spatially separated pupils in a traditional lens and imaging sensor system allowing for the passive capture of stereo video. This method is especially useful for surgical endoscopy where smaller cameras are needed to provide ample room for manipulating tools while also granting improved visualizations of scene depth. The significant issue in this process is that, due to the complimentary nature of the filters, the colors seen through each filter do not match each other, and also differ from colors as seen under a white illumination source. A color correction model was implemented that included optimized filter selection, such that the degree of necessary post-processing correction was minimized, and a chromatic adaptation transformation that attempted to fix the imaged colors tristimulus indices based on the principle of color constancy. Due to fabrication constraints, only dual bandpass filters were feasible. The theoretical average color error after correction between these filters was still above the fusion limit meaning that rivalry conditions are possible during viewing. This error can be minimized further by designing the filters for a subset of colors corresponding to specific working environments.

  7. Project Report: Reducing Color Rivalry in Imagery for Conjugated Multiple Bandpass Filter Based Stereo Endoscopy

    NASA Technical Reports Server (NTRS)

    Ream, Allen

    2011-01-01

    A pair of conjugated multiple bandpass filters (CMBF) can be used to create spatially separated pupils in a traditional lens and imaging sensor system allowing for the passive capture of stereo video. This method is especially useful for surgical endoscopy where smaller cameras are needed to provide ample room for manipulating tools while also granting improved visualizations of scene depth. The significant issue in this process is that, due to the complimentary nature of the filters, the colors seen through each filter do not match each other, and also differ from colors as seen under a white illumination source. A color correction model was implemented that included optimized filter selection, such that the degree of necessary post-processing correction was minimized, and a chromatic adaptation transformation that attempted to fix the imaged colors tristimulus indices based on the principle of color constancy. Due to fabrication constraints, only dual bandpass filters were feasible. The theoretical average color error after correction between these filters was still above the fusion limit meaning that rivalry conditions are possible during viewing. This error can be minimized further by designing the filters for a subset of colors corresponding to specific working environments.

  8. All-optical OFDM demultiplexing by spectral magnification and band-pass filtering.

    PubMed

    Palushani, E; Mulvad, H C Hansen; Kong, D; Guan, P; Galili, M; Oxenløwe, L K

    2014-01-13

    We propose a simple OFDM receiver allowing for the use of standard WDM receivers to receive spectrally advanced OFDM signals. We propose to spectrally magnify the optical-OFDM super-channels using a spectral telescope consisting of two time-lenses, which enables reduced inter-carrier-interference in subcarrier detection by simple band-pass filtering. A demonstration on an emulated 100 Gbit/s DPSK optical-OFDM channel shows improved sensitivities after 4-times spectral magnification.

  9. Guided mode resonance in subwavelength metallodielectric free-standing grating for bandpass filtering.

    PubMed

    Sakat, Emilie; Vincent, Grégory; Ghenuche, Petru; Bardou, Nathalie; Collin, Stéphane; Pardo, Fabrice; Pelouard, Jean-Luc; Haïdar, Riad

    2011-08-15

    We present the experimental study of a free-standing metallic guided-mode resonant structure, for bandpass filtering applications in the mid-IR wavelength range. Structure consists of a subwavelength gold grating with narrow slits deposited on a silicon nitride membrane. High optical transmission is measured with up to 78% transmission at resonance. Angularly resolved spectra are presented revealing Fano-type resonance. © 2011 Optical Society of America

  10. Stepped Impedance Resonators in Triple Band Bandpass Filter Design for Wireless Communication Systems

    SciTech Connect

    Eroglu, Abdullah

    2010-01-01

    Triple band microstrip tri-section bandpass filter using stepped impedance resonators (SIRs) is designed, simulated, built, and measured using hair pin structure. The complete design procedure is given from analytical stage to implementation stage with details The coupling between SIRs is investigated for the first time in detail by studying their effect on the filter characteristics including bandwidth, and attenuation to optimize the filter perfomance. The simulation of the filler is performed using method of moment based 2.5D planar electromagnetic simulator The filter is then implemented on RO4003 material and measured The simulation, and measured results are compared and found to be my close. The effect of coupling on the filter performance is then investigated using electromagnetic simulator It is shown that the coupling effect between SIRs can be used as a design knob to obtain a bandpass Idler with a better performance jar the desired frequency band using the proposed filter topology The results of this work can used in wireless communication systems where multiple frequency bandy are needed

  11. A narrow band-pass filter type Wilkinson power divider for I-Q demodulator in microwave interferometer system

    NASA Astrophysics Data System (ADS)

    Wang, X.; Yoshikawa, M.; Kohagura, J.; Shima, Y.; Ikezoe, R.; Sakamoto, M.; Imai, T.; Nakashima, Y.; Ma, Z.; Sakagami, I.; Mase, A.

    2015-11-01

    I-Q (In-phase Quadrature) demodulator is one of key components in microwave interferometer system application. Normally, I-Q demodulator consists of amplifiers, mixers, 90 degree phase shifter, power divider and band-pass filters, and it is widely used in various microwave communication systems and measurement systems. In this paper, power divider and band-pass filters are newly designed as one single passive component, therefore, I-Q demodulator topology becomes simplified. The novel narrow band-pass filter type Wilkinson power divider not only provides extremely miniaturized circuit size, but also maintains the band-pass filter performance and power division function as well. One experimental circuit shows good agreement with the theoretical simulation.

  12. Bandpass filter with adjustable bandwidth based on a press-induced long-period twisted holey-fiber grating.

    PubMed

    Torres-Gómez, I; Martínez-Ríos, A; Ceballos-Herrera, D E; Mejía-Beltrán, E; Selvas-Aguilar, R

    2007-12-01

    A bandpass filter with adjustable bandwidth based on a press-induced long-period grating in a twisted holey fiber is presented. By twisting the holey fiber prior to the application of periodic pressure, each rejection band of the nontwisted induced long-period grating is split into two shifted rejection bands that move further apart as the twist ratio increases. This feature results in a wide bandpass filter with controllable bandwidth. A bandpass filter at 1523 nm with adjustable bandwidth from 15 to 65 nm with near-linear response and insertion loss lower than 0.7 dB is demonstrated. Additionally, the bandpass filter can be tuned over 100 nm.

  13. Bandpass transmission filters based on phase shifted fiber Bragg gratings in microstructured polymer optical fibers

    NASA Astrophysics Data System (ADS)

    Ortega, Beatriz; Min, Rui; Sáez-Rodríguez, David; Mi, Yang; Nielsen, Kristian; Bang, Ole

    2017-05-01

    In this contribution we report on the fabrication of novel bandpass transmission filters based on PS-FBGs in microstructured polymer fibers at telecom wavelengths. The phase mask technique is employed to fabricate several superimposed gratings with slight different periods in order to form Moiré structures with a single or various π phase shifts along the device. Simulations and experimental results are included in order to demonstrate very narrowband transmission filters. Experimental characterization under strain and temperature variations is provided in a non-annealed fiber and time stability of the fabricated devices has been also measured under different pre-strain conditions.

  14. System design for a million channel digital spectrum analyzer /MCSA/. [of bandpass filtering in SETI receivers

    NASA Technical Reports Server (NTRS)

    Peterson, A.; Narasimha, M.; Narayan, S.

    1980-01-01

    The system design of a wideband (8 MHz) million-channel digital spectrum analyzer for use with a SETI receiver is presented. The analyzer makes use of a digital bandpass filter bank for transforming the wideband input signal into a specified number (120) of uniform narrowband output channels by the use of a Fourier transform digital processor combined with a prototype digital weighting network (finite impulse response filter). The output is then processed separately by 120 microprocessor-based discrete Fourier transform computers, each producing 8190 output channels of approximately 8 Hz bandwidth by the use of an 8190-point prime factor algorithm.

  15. An algorithm used for quality criterion automatic measurement of band-pass filters and its device implementation

    NASA Astrophysics Data System (ADS)

    Liu, Qianshun; Liu, Yan; Yu, Feihong

    2013-08-01

    As a kind of film device, band-pass filter is widely used in pattern recognition, infrared detection, optical fiber communication, etc. In this paper, an algorithm for automatic measurement of band-pass filter quality criterion is proposed based on the proven theory calculation of derivate spectral transmittance of filter formula. Firstly, wavelet transform to reduce spectrum data noises is used. Secondly, combining with the Gaussian curve fitting and least squares method, the algorithm fits spectrum curve and searches the peak. Finally, some parameters for judging band-pass filter quality are figure out. Based on the algorithm, a pipeline for band-pass filters automatic measurement system has been designed that can scan the filter array automatically and display spectral transmittance of each filter. At the same time, the system compares the measuring result with the user defined standards to determine if the filter is qualified or not. The qualified product will be market with green color, and the unqualified product will be marked with red color. With the experiments verification, the automatic measurement system basically realized comprehensive, accurate and rapid measurement of band-pass filter quality and achieved the expected results.

  16. Miniaturized Dual-Band Bandpass Filter Using Embedded Dual-Mode Resonator with Controllable Bandwidths

    NASA Astrophysics Data System (ADS)

    Zhu, Chuanming; Xu, Jin; Kang, Wei; Hu, Zhenxin; Wu, Wen

    2016-09-01

    In this paper, a miniaturized dual-band bandpass filter (DB-BPF) using embedded dual-mode resonator (DMR) with controllable bandwidths is proposed. Two passbands are generated by two sets of resonators operating at two different frequencies. One set of resonators is utilized not only as the resonant elements that yield the lower passband, but also as the feeding structures with source-load coupling to excite the other to produce the upper passband. Sufficient degrees of freedom are achieved to control the center frequencies and bandwidths of two passbands. Moreover, multiple transmission zeros (TZs) are created to improve the passband selectivity of the filter. The design of the filter has been demonstrated by the measurement. The filter features not only miniaturized circuit sizes, low insertion loss, independently controllable central frequencies, but also controllable bandwidths and TZs.

  17. Lumped-equivalent circuit model for multi-stage cascaded magnetoelectric dual-tunable bandpass filter

    NASA Astrophysics Data System (ADS)

    Zhang, Qiu-Shi; Zhu, Feng-Jie; Zhou, Hao-Miao

    2015-10-01

    A lumped-equivalent circuit model of a novel magnetoelectric tunable bandpass filter, which is realized in the form of multi-stage cascading between a plurality of magnetoelectric laminates, is established in this paper for convenient analysis. The multi-stage cascaded filter is degraded to the coupling microstrip filter with only one magnetoelectric laminate and then compared with the existing experiment results. The comparison reveals that the insertion loss curves predicted by the degraded circuit model are in good agreement with the experiment results and the predicted results of the electromagnetic field simulation, thus the validity of the model is verified. The model is then degraded to the two-stage cascaded magnetoelectric filter with two magnetoelectric laminates. It is revealed that if the applied external bias magnetic or electric fields on the two magnetoelectric laminates are identical, then the passband of the filter will drift under the changed external field; that is to say, the filter has the characteristics of external magnetic field tunability and electric field tunability. If the applied external bias magnetic or electric fields on two magnetoelectric laminates are different, then the passband will disappear so that the switching characteristic is achieved. When the same magnetic fields are applied to the laminates, the passband bandwidth of the two-stage cascaded magnetoelectric filter with two magnetoelectric laminates becomes nearly doubled in comparison with the passband filter which contains only one magnetoelectric laminate. The bandpass effect is also improved obviously. This research will provide a theoretical basis for the design, preparation, and application of a new high performance magnetoelectric tunable microwave device. Project supported by the National Natural Science Foundation of China (Grant Nos. 11172285 and 11472259) and the Natural Science Foundation of Zhejiang Province, China (Grant No. LR13A020002).

  18. Metamaterial composite bandpass filter with an ultra-broadband rejection bandwidth of up to 240 terahertz

    NASA Astrophysics Data System (ADS)

    Strikwerda, Andrew C.; Zalkovskij, Maksim; Lund Lorenzen, Dennis; Krabbe, Alexander; Lavrinenko, Andrei V.; Uhd Jepsen, Peter

    2014-05-01

    We present a metamaterial, consisting of a cross structure and a metal mesh filter, that forms a composite with greater functional bandwidth than any terahertz (THz) metamaterial to date. Metamaterials traditionally have a narrow usable bandwidth that is much smaller than common THz sources, such as photoconductive antennas and difference frequency generation. The composite structure shown here expands the usable bandwidth to exceed that of current THz sources. To highlight the applicability of this combination, we demonstrate a series of bandpass filters with only a single pass band, with a central frequency (f0) that is scalable from 0.86-8.51 THz, that highly extinguishes other frequencies up to >240 THz. The performance of these filters is demonstrated in experiment, using both air biased coherent detection and a Fourier transform infrared spectrometer (FTIR), as well as in simulation. We present equations—and discuss their scaling laws—which detail the f0 and full width at half max (Δf) of the pass band, as well as the required geometric dimensions for their fabrication using standard UV photolithography and easily achievable fabrication linewidths. With these equations, the geometric parameters and Δf for a desired frequency can be quickly calculated. Using these bandpass filters as a proof of principle, we believe that this metamaterial composite provides the key for ultra-broadband metamaterial design.

  19. Broadband Interferometer for Measuring Transmitted Wavefronts of Optical Bandpass Filters for HST (ACS)

    NASA Technical Reports Server (NTRS)

    Boucarut, R. A.; Leviton, D. B.

    1998-01-01

    The transmitted wavefronts of optical filters for the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) are characterized using the Wildly and Openly Modified Broadband Achromatic Twyman Green (WOMBAT) Interferometer developed in the NASA/GSFC Optics Branch's Diffraction Grating Evaluation Facility (DGEF). Because only four of thirty-three of ACS's optical bandpass filters transmit the 633 nm light of most commercial interferometers, a broadband interferometer is required to verify specified transmitted wavefront of ACS filters. WOMBAT's design is a hybrid of the BAT interferometer developed by JPL used for HST Wide Field and Planetary Camera 2 (WFPC-2) filters and a WYKO 400 phase shifting interferometer. It includes a broadband light source, monochromator, off-axis, parabolic collimating and camera mirrors, an aluminum-coated fused silica beam splitter, flat retroreflecting mirrors for the test and reference arms, and a LTV-sensitive CCD camera. An outboarded, piezo-electric phase shifter holds the flat mirror in the interferometer's reference arm. The interferometer is calibrated through interaction between the WYKO system's software and WONMAT hardware for the test wavelength of light entering the beam splitter. Phase-shifted interferograms of the filter mounted in the test arm are analyzed using WYKO's Vision' software. Filters as large as 90 mm in diameter have been measured over a wavelength range from 200 to 1100 nm with a sensitivity of lambda/200 rms at lambda = 633 nm. Results of transmitted wavefront measurements are shown for ACS fixed band pass and spatially-variable bandpass filters for a variety of wavelengths.

  20. Investigation of New Microstrip Bandpass Filter Based on Patch Resonator with Geometrical Fractal Slot.

    PubMed

    Mezaal, Yaqeen S; Eyyuboglu, Halil T

    2016-01-01

    A compact dual-mode microstrip bandpass filter using geometrical slot is presented in this paper. The adopted geometrical slot is based on first iteration of Cantor square fractal curve. This filter has the benefits of possessing narrower and sharper frequency responses as compared to microstrip filters that use single mode resonators and traditional dual-mode square patch resonators. The filter has been modeled and demonstrated by Microwave Office EM simulator designed at a resonant frequency of 2 GHz using a substrate of εr = 10.8 and thickness of h = 1.27 mm. The output simulated results of the proposed filter exhibit 22 dB return loss, 0.1678 dB insertion loss and 12 MHz bandwidth in the passband region. In addition to the narrow band gained, miniaturization properties as well as weakened spurious frequency responses and blocked second harmonic frequency in out of band regions have been acquired. Filter parameters including insertion loss, return loss, bandwidth, coupling coefficient and external quality factor have been compared with different values of perturbation dimension (d). Also, a full comparative study of this filter as compared with traditional square patch filter has been considered.

  1. Use of band-pass filter analysis to evaluate outcomes in an antidepressant trial for treatment resistant patients.

    PubMed

    Targum, Steven D; Burch, Daniel J; Asgharnejad, Mahnaz; Petersen, Timothy; Gomeni, Roberto; Fava, Maurizio

    2014-08-01

    Band-pass filtering is a novel statistical methodology that proposes that filtering out data from trial sites generating non-plausible high or low levels of placebo response can yield a more accurate effect size and greater separation of active drug (when efficacious) from placebo. We applied band-pass filters to re-analyze data from a negative antidepressant trial (NCT00739908) evaluating CX157 (a reversible and selective monoamine oxidase inhibitor-A) versus placebo. 360 patients from 29 trial sites were randomized to either CX157 treatment (n=182) or placebo (n=178). We applied two filters of<3 or>7 points (filter #1) or<3 and>9 points (filter #2) mean change of the total MADRS placebo scores for each site. Trial sites that had mean placebo MADRS score changes exceeding the boundaries of these band-pass filter thresholds were considered non-informative and all of the data from these sites were excluded from the post-hoc re-analysis. The two band-pass filters reduced the sample of informative patients from 353 patients in the mITT population to 62 in filter #1 and 152 in the filter #2 group. The placebo response was reduced from 31.1% in the mITT population to 9.4% with filter #1 and 20.8% with filter #2. MMRM analysis revealed a non-statistically significant trend of p=0.13 and 0.16 for the two filters in contrast to the mITT population (p= 0.58). Our findings support the band-pass filter hypothesis and highlight issues related to site-based scoring variability and inappropriate subject selection that may contribute to trial failure.

  2. Tunable Plasmonic Band-Pass Filter with Dual Side-Coupled Circular Ring Resonators

    PubMed Central

    Liu, Dongdong; Wang, Jicheng; Zhang, Feng; Pan, Yuewu; Lu, Jian; Ni, Xiaowu

    2017-01-01

    A wavelength band-pass filter with asymmetric dual circular ring resonators in a metal-insulator-metal (MIM) structure is proposed and numerically simulated. For the interaction of the local discrete state and the continuous spectrum caused by the side-coupled resonators and the baffle, respectively, the transmission spectrum exhibits a sharp and asymmetric profile. By adjusting the radius and material imbedded in one ring cavity, the off-to-on plasmon-induced absorption (PIA) optical response can be tunable achieved. In addition, the structure can be easily extended to other similar compact structures to realize the filtering task. Our structures have important potential applications for filters and sensors at visible and near-infrared regions. PMID:28335398

  3. Demodulation of an optical fiber MEMS pressure sensor based on single bandpass microwave photonic filter.

    PubMed

    Wang, Yiping; Ni, Xiaoqi; Wang, Ming; Cui, Yifeng; Shi, Qingyun

    2017-01-23

    In this paper, a demodulation method for optic fiber micro-electromechanical systems (MEMS) extrinsic Fabry-Perot interferometer (EFPI) pressure sensor exploiting microwave photonics filter technique is firstly proposed and experimentally demonstrated. A single bandpass microwave photonic filter (MPF) which mainly consists of a spectrum-sliced light source, a pressurized optical fiber MEMS EFPI, a phase modulator (PM) and a length of dispersion compensating fiber (DCF) is demonstrated. The frequency response of the filter with respect to the pressure is studied. By detecting the resonance frequency shifts of the MPF, the pressure can be determined. The theoretical and experimental results show that the proposed EFPI pressure demodulation method has a higher resolution and higher speed than traditional methods based on optical spectrum analysis. The sensitivity of the sensor is measured to be as high as 86 MHz/MPa in the range of 0-4Mpa. Moreover, the sensitivity can be easily adjusted.

  4. Polarization insensitive wide-angle triple-band metamaterial bandpass filter

    NASA Astrophysics Data System (ADS)

    Fu, Wenyue; Han, Yuchen; Li, Jiandong; Wang, Haoshen; Li, Haipeng; Han, Kui; Shen, Xiaopeng; Cui, Tiejun

    2016-07-01

    In this letter, we report the design, fabrication and measurement of a polarization insensitive wide-angle triple-band metamaterial bandpass filter (BPF) in the microwave frequency. The proposed BPF consists of two identical metal resonant units which have three concentric square slots separated by a dielectric layer. Experimental results show that the BPF has three distinctive transmission bands centered at frequencies 6.22 GHz, 9.46 GHz and 12.14 GHz with transmission rates of  -0.40 dB, -0.71 dB and  -1.40 dB, respectively, agreeing well with simulation results. By introducing the substrate integrated waveguide, the filter is valid to a wide range of incident angles for both transverse electric and transverse magnetic polarizations. The triple-band metamaterial BPF can be used as multiband filters and radomes owing to its multiband transmissions, polarizations insensitive and wide-angle responses.

  5. Programmable Spectral Source and Design Tool for 3D Imaging Using Complementary Bandpass Filters

    NASA Technical Reports Server (NTRS)

    Shahinian, Hrayr Karnig (Inventor); Shearn, Michael J. (Inventor); Bae, Youngsam (Inventor); Korniski, Ronald J. (Inventor); Fritz, Eric W. (Inventor); Ream, Allen (Inventor)

    2017-01-01

    An endoscopic illumination system for illuminating a subject for stereoscopic image capture, includes a light source which outputs light; a first complementary multiband bandpass filter (CMBF) and a second CMBF, the first and second CMBFs being situated in first and second light paths, respectively, where the first CMBF and the second CMBF filter the light incident thereupon to output filtered light; and a camera which captures video images of the subject and generates corresponding video information, the camera receiving light reflected from the subject and passing through a pupil CMBF pair and a detection lens. The pupil CMBF includes a first pupil CMBF and a second pupil CMBF, the first pupil CMBF being identical to the first CMBF and the second pupil CMBF being identical to the second CMBF, and the detection lens includes one unpartitioned section that covers both the first pupil CMBF and the second pupil CMBF.

  6. Band-pass filters for THz spectral range fabricated by laser ablation

    NASA Astrophysics Data System (ADS)

    Voisiat, B.; Bičiūnas, A.; Kašalynas, I.; Račiukaitis, G.

    2011-09-01

    The terahertz resonant metal-mesh filters were fabricated using the laser direct writing technique. UV picosecond laser was employed to cut matrixes of cross-shaped holes in stainless steel foil and molybdenum layer deposited on polyimide substrate. Different laser processing strategies were developed: holes were cut through in the metal foil and the molybdenum film was removed from the polyimide by laser ablation. Band-pass filters with a different center frequency were designed and fabricated. The regular shape, smoothness of edges and sharpness of corners of the cross-shaped holes in the metal were the main attributes for quality assessment for the laser ablation process. Spectral characteristics of the filters, determined by the mesh period, cross-arm length, and its width, were investigated by terahertz time-domain spectroscopy and conventional space-domain Fourier transform spectroscopy. Experimental data were supported by three-dimensional finite-difference time-domain simulations.

  7. Technology optimization techniques for multicomponent optical band-pass filter manufacturing

    NASA Astrophysics Data System (ADS)

    Baranov, Yuri P.; Gryaznov, Georgiy M.; Rodionov, Andrey Y.; Obrezkov, Andrey V.; Medvedev, Roman V.; Chivanov, Alexey N.

    2016-04-01

    Narrowband optical devices (like IR-sensing devices, celestial navigation systems, solar-blind UV-systems and many others) are one of the most fast-growing areas in optical manufacturing. However, signal strength in this type of applications is quite low and performance of devices depends on attenuation level of wavelengths out of operating range. Modern detectors (photodiodes, matrix detectors, photomultiplier tubes and others) usually do not have required selectivity or have higher sensitivity to background spectrum at worst. Manufacturing of a single component band-pass filter with high attenuation level of wavelength is resource-intensive task. Sometimes it's not possible to find solution for this problem using existing technologies. Different types of filters have technology variations of transmittance profile shape due to various production factors. At the same time there are multiple tasks with strict requirements for background spectrum attenuation in narrowband optical devices. For example, in solar-blind UV-system wavelengths above 290-300 nm must be attenuated by 180dB. In this paper techniques of multi-component optical band-pass filters assembly from multiple single elements with technology variations of transmittance profile shape for optimal signal-tonoise ratio (SNR) were proposed. Relationships between signal-to-noise ratio and different characteristics of transmittance profile shape were shown. Obtained practical results were in rather good agreement with our calculations.

  8. A scheme for bandpass filtering magnetometer measurements to reconstruct tethered satellite skiprope motion

    NASA Technical Reports Server (NTRS)

    Polites, M. E.

    1991-01-01

    A scheme is presented for reconstructing tethered satellite skiprope motion by ground processing of satellite magnetometer measurements. The measurements are modified based on ground knowledge of the earth's magnetic field and passed through bandpass filters tuned to the skiprope frequency. Simulation results are presented which verify the scheme and show it to be quite robust. The concept is not just limited to tethered satellites. Indeed, it can be applied wherever there is a need to reconstruct the coning motion of a body about a known axis, given measurements of a known vector in body-fixed axes.

  9. Experimental study on narrow spectral width FP lasers with a wavelength detuned band-pass filter

    NASA Astrophysics Data System (ADS)

    Fu, Junwei; Xi, Yanping; Li, Xun; Hong, Wei; Huang, Weiping

    2017-08-01

    In this paper, a 1310 nm InAlGaAs/InP multiple quantum well ridge waveguide FP laser with a built-in wavelength detuned band-pass filter has been fabricated and investigated in experiments. When compared to the reference FP laser fabricated in the same wafer, it is observed that the root-mean-square spectral width can be approximately reduced to half; and moreover, significant improvements on the transmission performances in terms of the power penalty at given transmission distance and the longest transmission distance at given bit error rate, have been achieved for the proposed laser at the same fabrication cost.

  10. Design of cross-coupled planar microstrip band-pass filters using a novel adjustment method

    NASA Astrophysics Data System (ADS)

    Alkafaji, Muhammed S. S.

    2015-02-01

    In this paper the design of a cross-coupled planar microwave band-pass filter using open-loop square microstrip resonators, with two symmetrically placed attenuation poles, is presented. The design starts from the following specifications: central frequency 3GHz, 150MHz bandwidth, 1dB ripple in the pass-band corresponding to return loss of 6.8dB.The adjustment method using additional ports placed on each resonator of the filter is used, allowing the interconnection of the filter structure with external lumped elements. Connecting a reactive element (capacitor) from such an additional port to ground allows a fine tuning of the resonator. Connecting a reactive element between two such additional ports allows a fine change in the coupling coefficient between these resonators. After adding four extra ports and connecting the external elements (capacitors), it is possible to use fast circuit simulation software to optimize the filter's response. Then all these capacitors have to be gradually eliminated, by compensating their effects through fine changes back in the layouts. If some specific issues are properly handled, this procedure improves considerably the quality of the final design of the filter. After a thorough optimization of the layout, the filter was fabricated and measured. The results of measurements are in good agreement with the specifications of the filter, showing this way the efficiency of the applied optimization method.

  11. Design and Specification of Optical Bandpass Filters for Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS)

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B.; Tsevetanov, Zlatan; Woodruff, Bob; Mooney, Thomas A.

    1998-01-01

    Advanced optical bandpass filters for the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) have been developed on a filter-by-filter basis through detailed studies which take into account the instrument's science goals, available optical filter fabrication technology, and developments in ACS's charge-coupled-device (CCD) detector technology. These filters include a subset of filters for the Sloan Digital Sky Survey (SDSS) which are optimized for astronomical photometry using today's charge-coupled-devices (CCD's). In order for ACS to be truly advanced, these filters must push the state-of-the-art in performance in a number of key areas at the same time. Important requirements for these filters include outstanding transmitted wavefront, high transmittance, uniform transmittance across each filter, spectrally structure-free bandpasses, exceptionally high out of band rejection, a high degree of parfocality, and immunity to environmental degradation. These constitute a very stringent set of requirements indeed, especially for filters which are up to 90 mm in diameter. The highly successful paradigm in which final specifications for flight filters were derived through interaction amongst the ACS Science Team, the instrument designer, the lead optical engineer, and the filter designer and vendor is described. Examples of iterative design trade studies carried out in the context of science needs and budgetary and schedule constraints are presented. An overview of the final design specifications for the ACS bandpass and ramp filters is also presented.

  12. Design and Specification of Optical Bandpass Filters for Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS)

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B.; Tsevetanov, Zlatan; Woodruff, Bob; Mooney, Thomas A.

    1998-01-01

    Advanced optical bandpass filters for the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) have been developed on a filter-by-filter basis through detailed studies which take into account the instrument's science goals, available optical filter fabrication technology, and developments in ACS's charge-coupled-device (CCD) detector technology. These filters include a subset of filters for the Sloan Digital Sky Survey (SDSS) which are optimized for astronomical photometry using today's charge-coupled-devices (CCD's). In order for ACS to be truly advanced, these filters must push the state-of-the-art in performance in a number of key areas at the same time. Important requirements for these filters include outstanding transmitted wavefront, high transmittance, uniform transmittance across each filter, spectrally structure-free bandpasses, exceptionally high out of band rejection, a high degree of parfocality, and immunity to environmental degradation. These constitute a very stringent set of requirements indeed, especially for filters which are up to 90 mm in diameter. The highly successful paradigm in which final specifications for flight filters were derived through interaction amongst the ACS Science Team, the instrument designer, the lead optical engineer, and the filter designer and vendor is described. Examples of iterative design trade studies carried out in the context of science needs and budgetary and schedule constraints are presented. An overview of the final design specifications for the ACS bandpass and ramp filters is also presented.

  13. A thermally tunable terahertz bandpass filter with insulator-metal phase transition of VO2 thin film

    NASA Astrophysics Data System (ADS)

    Li, Wei; Chang, Sheng-jiang; Wang, Xiang-hui; Lin, Lie; Bai, Jin-jun

    2014-05-01

    A terahertz bandpass filter with the sandwich structure consisting of thermally tunable vanadium dioxide (VO2) thin film, silica substrate and subwavelength rectangular Cu hole arrays is designed and theoretically analyzed. The results show that the transmittance of the filter can be actively tuned by controlling the temperature of VO2, the narrow band terahertz (THz) waves with the transmittance from 85.2% to 10.5% can be well selected at the frequency of 1.25 THz when the temperature changes from 50 °C to 80 °C, and the maximum modulation depth of this terahertz bandpass filter can achieve 74.7%.

  14. Investigation of utilizing a VCSEL diode to work as a tunable optical bandpass filter

    NASA Astrophysics Data System (ADS)

    Chang, Ching-Hung; Huang, Yi-Syuan; Li, Chung-Yi

    2017-04-01

    Tunable optical band-pass filter (TOBPF) composed of a vertical-cavity surface-emitting laser (VCSEL) is proposed for multi-wavelength optical fiber transport systems. Experimental results prove that through properly adjusting VCSEL driving current, one of multiple injected lightwaves can properly flow through the proposed optical filter and others will be attenuated roughly 12 dB. Furthermore, by changing the VCSEL driving current, the pass-band window of the VCSEL-based TOBPF can be shifted to align with different designated injected lightwave and to block the others. By employing the TOBPF in multi-wavelength optical fiber transport systems, proper eye diagrams are experimentally observed for each dedicated optical signal. The proposed scheme is shown to be a practical and flexible component for multi-wavelength optical fiber transport systems.

  15. Compact dual-band bandpass filter based on signal-interference techniques

    NASA Astrophysics Data System (ADS)

    Ma, Xingbing; Jiang, Ting

    2017-08-01

    To realize good isolation between two signal passbands, a dual-band bandpass filter (BPF) in this article was presented using signal-interference techniques, in which five open loop resonators are adopted. The proposed filter topology is made up of two signal transmission paths in parallel, under signal-interference principles, overlap section of two original passbands, decided respectively by two different transmission paths, is selectively removed from the combined passband, as a result, two aim passbands are realized. In addition, good isolation between two aim passbands is established due to two new transmission zeros, produced by adopted signal-interference techniques. At last, good agreement can be observed between simulation and measurement.

  16. Note: characterization of CaF2/acetone bandpass photon detector with Kr filter gas.

    PubMed

    Maniraj, M; Raja Sekhar, B N; Barman, S R

    2012-04-01

    A modified design of a CaF(2)/acetone bandpass photon detector that uses Kr as a filter gas to tune the energy resolution is presented. Our design combines two standard single window detector tubes to build the Kr filter gas chamber. Synchrotron radiation has been used to determine the energy resolution of the detector, as a function of Kr pressure. The improvement in the detector energy resolution by 250 meV compared to the CaF(2)/acetone detector is better than that reported earlier. Substantial variation in the shape of the CaF(2)/acetone detector response functions is observed for different acetone pressure (≤3 mbar), and anode voltage (≤800 V). Our analysis reveals that the changes in the shape of the detector response function are associated to different regions of the detector operation. © 2012 American Institute of Physics

  17. Plasmonic band-pass filter device using coupled asymmetric cross-shaped cavity

    NASA Astrophysics Data System (ADS)

    Geng, Xiao-Meng; Mi, Si-Chen; Wang, Tie-Jun; He, Lin-Yan; Wang, Chuan

    2017-01-01

    In this paper, a novel plasmonic band-pass filter by using the system consisting four waveguides and an asymmetric cross-shaped resonator is proposed. The plasmonic system is based on the metal-insulator-metal (MIM) structure which could overcome the diffraction limit and exhibit various promising applications. Here, we investigate the transmission spectra of the cross-shaped resonator by using finite-different-time-domain (FDTD) method and we find that the peak-wavelength on different ports show redshift or blueshift behaviors which are linearly changed with the length of cavity or the coupling distance. Moreover, the wavelength filter could be achieved and further applied in optical signal integrated circuits.

  18. Continued Development of an Ultra-Narrow Bandpass Filter for Solar Research

    NASA Technical Reports Server (NTRS)

    Rust, David M.

    1993-01-01

    The objective of work under this task was to develop ultranarrow optical bandpass filters and related technology necessary for construction of a compact solar telescope capable of operating unattended in space. The scientific problems to which such a telescope could be applied include solar seismology, solar activity monitoring, solar irradiance variations, solar magnetic field evolution, and the location of targets for narrow-field specialized telescopes. We have demonstrated a Y-cut lithium-niobate Fabry-Perot etalon. This filter will be used on the Flare Genesis Experiment. We also obtained solar images with a Z-cut etalon. The technical report on etalon filters is attached to this final report. We believe that work under this grant will lead to the commercial availability of a universal optical filter with approximately 0.1 A bandwidth. Progress was made toward making a suitable 1-2 A tunable blocker filter, but it now appears that the best approach is to make a double-cavity etalon that will not require such a narrow blocker. Broader band blockers are commercially available.

  19. Wide Bandpass and Narrow Bandstop Microstrip Filters Based on Hilbert Fractal Geometry: Design and Simulation Results

    PubMed Central

    Mezaal, Yaqeen S.; Eyyuboglu, Halil T.; Ali, Jawad K.

    2014-01-01

    This paper presents new Wide Bandpass Filter (WBPF) and Narrow Bandstop Filter (NBSF) incorporating two microstrip resonators, each resonator is based on 2nd iteration of Hilbert fractal geometry. The type of filter as pass or reject band has been adjusted by coupling gap parameter (d) between Hilbert resonators using a substrate with a dielectric constant of 10.8 and a thickness of 1.27 mm. Numerical simulation results as well as a parametric study of d parameter on filter type and frequency responses are presented and studied. WBPF has designed at resonant frequencies of 2 and 2.2 GHz with a bandwidth of 0.52 GHz, −28 dB return loss and −0.125 dB insertion loss while NBSF has designed for electrical specifications of 2.37 GHz center frequency, 20 MHz rejection bandwidth, −0.1873 dB return loss and 13.746 dB insertion loss. The proposed technique offers a new alternative to construct low-cost high-performance filter devices, suitable for a wide range of wireless communication systems. PMID:25536436

  20. GaN-based metamaterial terahertz bandpass filter design: tunability and ultra-broad passband attainment.

    PubMed

    Khodaee, M; Banakermani, M; Baghban, H

    2015-10-10

    Engineering metamaterial-based devices such as terahertz bandpass filters (BPFs) play a definitive role in advancement of terahertz technology. In this article, we propose a design procedure to obtain a considerably broadband terahertz BPF at a normal incidence; it shows promising filtering characteristics, including a wide passband of ∼1.34  THz at a central frequency of 1.17 THz, a flat top in a broad band, and high transmission, compared to previous reports. Then, exploiting the voltage-dependent carrier density control in an AlGaN/GaN heterostructure with a Schottky gate configuration, we investigate the tuning of the transmission properties in a narrow-band terahertz filter. A combination of the ultra-wide, flat-top BPF in series with the tunable, narrow band filter designed in the current study offers the ability to tune the desired resonance frequency along with high out-of-band rejection and the suppression of unwanted resonances in a large spectral range. The proposed structure exhibits a frequency tunability of 103 GHz for a voltage change between -8 and 2 V, and a transmission amplitude change of ∼0.51. This scheme may open up a route for the improved design of terahertz filters and modulators.

  1. Wide Bandpass and Narrow Bandstop Microstrip Filters based on Hilbert fractal geometry: design and simulation results.

    PubMed

    Mezaal, Yaqeen S; Eyyuboglu, Halil T; Ali, Jawad K

    2014-01-01

    This paper presents new Wide Bandpass Filter (WBPF) and Narrow Bandstop Filter (NBSF) incorporating two microstrip resonators, each resonator is based on 2nd iteration of Hilbert fractal geometry. The type of filter as pass or reject band has been adjusted by coupling gap parameter (d) between Hilbert resonators using a substrate with a dielectric constant of 10.8 and a thickness of 1.27 mm. Numerical simulation results as well as a parametric study of d parameter on filter type and frequency responses are presented and studied. WBPF has designed at resonant frequencies of 2 and 2.2 GHz with a bandwidth of 0.52 GHz, -28 dB return loss and -0.125 dB insertion loss while NBSF has designed for electrical specifications of 2.37 GHz center frequency, 20 MHz rejection bandwidth, -0.1873 dB return loss and 13.746 dB insertion loss. The proposed technique offers a new alternative to construct low-cost high-performance filter devices, suitable for a wide range of wireless communication systems.

  2. Lumped modeling with circuit elements for nonreciprocal magnetoelectric tunable band-pass filter

    NASA Astrophysics Data System (ADS)

    Li, Xiao-Hong; Zhou, Hao-Miao; Zhang, Qiu-shi; Hu, Wen-Wen

    2016-11-01

    This paper presents a lumped equivalent circuit model of the nonreciprocal magnetoelectric tunable microwave band-pass filter. The reciprocal coupled-line circuit is based on the converse magnetoelectric effect of magnetoelectric composites, includes the electrical tunable equivalent factor of the piezoelectric layer, and is established by the introduced lumped elements, such as radiation capacitance, radiation inductance, and coupling inductance, according to the transmission characteristics of the electromagnetic wave and magnetostatic wave in an inverted-L-shaped microstrip line and ferrite slab. The nonreciprocal transmission property of the filter is described by the introduced T-shaped circuit containing controlled sources. Finally, the lumped equivalent circuit of a nonreciprocal magnetoelectric tunable microwave band-pass filter is given and the lumped parameters are also expressed. When the deviation angles of the ferrite slab are respectively 0° and 45°, the corresponding magnetoelectric devices are respectively a reciprocal device and a nonreciprocal device. The curves of S parameter obtained by the lumped equivalent circuit model and electromagnetic simulation are in good agreement with the experimental results. When the deviation angle is between 0° and 45°, the maximum value of the S parameter predicted by the lumped equivalent circuit model is in good agreement with the experimental result. The comparison results of the paper show that the lumped equivalent circuit model is valid. Further, the effect of some key material parameters on the performance of devices is predicted by the lumped equivalent circuit model. The research can provide the theoretical basis for the design and application of nonreciprocal magnetoelectric tunable devices. Project supported by the National Natural Science Foundation of China (Grant Nos. 11172285, 11472259, and 11302217) and the Natural Science Foundation of Zhejiang Province, China (Grant No. LR13A020002).

  3. Optimisation of SIW bandpass filter with wide and sharp stopband using space mapping

    NASA Astrophysics Data System (ADS)

    Xu, Juan; Bi, Jun Jian; Li, Zhao Long; Chen, Ru shan

    2016-12-01

    This work presents a substrate integrated waveguide (SIW) bandpass filter with wide and precipitous stopband, which is different from filters with a direct input/output coupling structure. Higher modes in the SIW cavities are used to generate the finite transmission zeros for improved stopband performance. The design of SIW filters requires full wave electromagnetic simulation and extensive optimisation. If a full wave solver is used for optimisation, the design process is very time consuming. The space mapping (SM) approach has been called upon to alleviate this problem. In this case, the coarse model is optimised using an equivalent circuit model-based representation of the structure for fast computations. On the other hand, the verification of the design is completed with an accurate fine model full wave simulation. A fourth-order filter with a passband of 12.0-12.5 GHz is fabricated on a single layer Rogers RT/Duroid 5880 substrate. The return loss is better than 17.4 dB in the passband and the rejection is more than 40 dB in the stopband. The stopband is from 2 to 11 GHz and 13.5 to 17.3 GHz, demonstrating a wide bandwidth performance.

  4. Segmentation and tracking of the electro-encephalogram signal using an adaptive recursive bandpass filter.

    PubMed

    Gharieb, R R; Cichocki, A

    2001-03-01

    An adaptive filtering approach for the segmentation and tracking of electro-encephalogram (EEG) signal waves is described. In this approach, an adaptive recursive bandpass filter is employed for estimating and tracking the centre frequency associated with each EEG wave. The main advantage inherent in the approach is that the employed adaptive filter has only one unknown coefficient to be updated. This coefficient, having an absolute value less than 1, represents an efficient distinct feature for each EEG specific wave, and its time function reflects the non-stationarity behaviour of the EEG signal. Therefore the proposed approach is simple and accurate in comparison with existing multivariate adaptive approaches. The approach is examined using extensive computer simulations. It is applied to computer-generated EEG signals composed of different waves. The adaptive filter coefficient (i.e. the segmentation parameter) is -0.492 for the delta wave, -0.360 for the theta wave, -0.191 for the alpha wave, -0.027 for the sigma wave, 0.138 for the beta wave and 0.605 for the gamma wave. This implies that the segmentation parameter increases with the increase in the centre frequency of the EEG waves, which provides fast on-line information about the behaviour of the EEG signal. The approach is also applied to real-world EEG data for the detection of sleep spindles.

  5. Learning Multiple Band-Pass Filters for Sleep Stage Estimation: Towards Care Support for Aged Persons

    NASA Astrophysics Data System (ADS)

    Takadama, Keiki; Hirose, Kazuyuki; Matsushima, Hiroyasu; Hattori, Kiyohiko; Nakajima, Nobuo

    This paper proposes the sleep stage estimation method that can provide an accurate estimation for each person without connecting any devices to human's body. In particular, our method learns the appropriate multiple band-pass filters to extract the specific wave pattern of heartbeat, which is required to estimate the sleep stage. For an accurate estimation, this paper employs Learning Classifier System (LCS) as the data-mining techniques and extends it to estimate the sleep stage. Extensive experiments on five subjects in mixed health confirm the following implications: (1) the proposed method can provide more accurate sleep stage estimation than the conventional method, and (2) the sleep stage estimation calculated by the proposed method is robust regardless of the physical condition of the subject.

  6. The Ring of Fire - an internal illimination system for detector sensitivity and filter bandpass characterization

    SciTech Connect

    Scarpine, Victor E.; Kent, Stephen M.; Deustua, Susana E.; Sholl, Michael J.; Mufson, Stuart L.; Ott, Melanie N.; Wiesner, Matthew P.; Baptitst, Brian J.; /Indiana U.

    2010-07-01

    We describe a prototype of an illumination system, the Ring of Fire (ROF), which is used as part of an internal calibration system for large focal plane detector arrays in TMA (Three Mirror Anastigmat) telescope designs. Such designs have been proposed for the SNAP (SuperNova Acceleration Probe) version of a Joint Dark Energy Mission (JDEM). The ROF system illuminates the focal plane with a light beam the closely matches that of the telescope and is used for creating high spatial frequency flat fields and monitoring filter bandpasses for experiments that demand a highly accurate characterization of the detectors. We present measurements of a mockup of this prototype ROF design including studies in variations in illumination across a large focal plane.

  7. Compact Dual-band Bandpass Filter Based on HMSIW and DS-CSRR

    NASA Astrophysics Data System (ADS)

    Kang, Hong Yi; Song, Jing Pan; Li, Jiao; Wei, Feng

    2017-07-01

    A compact dual-band bandpass filter (BPF) based on a half-mode substrate integrated waveguide (HMSIW) and double-side complementary split-ring resonators (DS-CSRR) is investigated in this paper. The proposed DS-CSRR consists of two complementary split-ring resonators (CSRRs) with different sizes. One is etched on the top surface of HMSIW, the other is on the ground. By changing the parameters of DS-CSRR, both the center frequencies and the bandwidths can be controlled independently, respectively. In order to validate its practicability, a dual-band BPF centered at 3.5 GHz/5.2 GHz is designed and demonstrated. The simulated and measured results are in good agreement with each other.

  8. Optimal design of bandpass filters to reduce emission from photovoltaic cells under monochromatic illumination

    NASA Astrophysics Data System (ADS)

    Takeda, Yasuhiko; Iizuka, Hideo; Ito, Tadashi; Mizuno, Shintaro; Hasegawa, Kazuo; Ichikawa, Tadashi; Ito, Hiroshi; Kajino, Tsutomu; Higuchi, Kazuo; Ichiki, Akihisa; Motohiro, Tomoyoshi

    2015-08-01

    We have theoretically investigated photovoltaic cells used under the illumination condition of monochromatic light incident from a particular direction, which is very different from that for solar cells under natural sunlight, using detailed balance modeling. A multilayer bandpass filter formed on the surface of the cell has been found to trap the light generated by radiative recombination inside the cell, reduce emission from the cell, and consequently improve conversion efficiency. The light trapping mechanism is interpreted in terms of a one-dimensional photonic crystal, and the design guide to optimize the multilayer structure has been clarified. For obliquely incident illumination, as well as normal incidence, a significant light trapping effect has been achieved, although the emission patterns are extremely different from each other depending on the incident directions.

  9. Symmetrical band-pass loudspeaker systems

    NASA Astrophysics Data System (ADS)

    Matusiak, Grzegorz Piotr

    2001-12-01

    Loudspeaker systems are analyzed in a doctoral dissertation. The dissertation concerns loudspeaker systems, which are known as subwoofers or band-pass loudspeaker systems. Their advantages include: high- quality sound reproduction in the low-frequency range, small dimensions, small nonlinear distortions and the fact that they can be placed anywhere in a room or car. Band-pass loudspeaker systems are used widely in the so- called Home Theatre as well as to provide sound in cinema, theatre, concert, discotheque, opera, operetta, philharmonic and amphitheater halls, at open-air concerts, and so on. Various designs are mass-produced by a large number of manufacturers. The study covers an analysis of band-pass loudspeaker systems to which the frequency transformation, i.e. the reactance transformation, has been applied. Since this is a symmetrical transformation, amplitude frequency responses of the studied band-pass systems are also symmetrical (logarithmic scale of a frequency). As a result, the high-pass loudspeaker system design method, known as the Thiele-Small, Benson analysis, can be employed. The investigations include the formulation of band-pass system equations (fourth, sixth and eighth-order polynomials) and the subsequent derivation of relations for the calculation of system parameters. The obtained results enable the calculation of optimum designs for prescribed alignments, e.g. (Chebyshev) equal-ripple, (Butterworth) maximally flat, or quasi-maximally flat (QB). The analysis covers fourth, sixth and eighth-order symmetrical systems. Eighth-order systems have been divided into three kinds according to three ways of physical realization. The doctoral dissertation includes band-pass loudspeaker systems, which can be designed with active or passive filters or without the filter. Designed systems consist of a loudspeaker whose front of a diaphragm is loaded with a Helmholtz resonator, i.e. an enclosure with a vent, which radiates sound outwards. The back is

  10. Electrically Conductive Photopatternable Silver Paste for High-Frequency Ring Resonator and Band-Pass Filter

    NASA Astrophysics Data System (ADS)

    Umarji, Govind; Qureshi, Nilam; Gosavi, Suresh; Mulik, Uttam; Kulkarni, Atul; Kim, Taesung; Amalnerkar, Dinesh

    2017-02-01

    In conventional thick-film technology, there are often problems associated with poor edges, rough surfaces, and reproducibility due to process limitations, especially for high-frequency applications. These difficulties can be circumvented by using thin-film technology, but process cost and complexity remain major concerns. In this context, photopatternable thick-film technology can offer a viable alternative due to its Newtonian rheology, which can facilitate formation of the required sharp edges. We present herein a unique attempt to formulate a photopatternable silver paste with organic (photosensitive polymer) to inorganic (silver and glass) ratio of 30:70, developed in-house by us for fabrication of thick-film-based ring resonator and band-pass filter components. The ring resonator and band-pass component structures were realized by exposing screen-printed film to ultraviolet light at wavelength of 315 nm to 400 nm for 30 s to crosslink the photosensitive polymer. The pattern was subsequently developed using 1% sodium carbonate aqueous solution. For comparison, conventional silver and silver-palladium thick films were produced using in-house formulations. The surface topology and microstructural features were examined by stereomicroscopy and scanning electron microscopy. The smoothness and edge definition of the film were assessed by profilometry. The resistivity of the samples was observed and remained in the range from 3.4 μΩ cm to 3.6 μΩ cm. The electrical properties were compared by measuring the insertion loss characteristics. The results revealed that the ring resonator fabricated using the photopatternable silver paste exhibited better high-frequency properties compared with components based on conventional silver or silver-palladium paste, especially in terms of the resonant frequency of 10.1 GHz (versus 10 GHz designed) with bandwidth of 80 MHz. Additionally, the band-pass filter fabricated using the photopatternable silver paste displayed better

  11. Spin-wave band-pass filters based on yttrium iron garnet films for tunable microwave photonic oscillators

    NASA Astrophysics Data System (ADS)

    Ustinov, A. B.; Drozdovskii, A. V.; Nikitin, A. A.; Kalinikos, B. A.

    2015-12-01

    The paper reports on development of tunable band-pass microwave filters for microwave photonic generators. The filters were fabricated with the use of epitaxial yttrium iron garnet films. Principle of operation of the filters was based on excitation, propagation, and reception of spin waves. In order to obtain narrow pass band, the filtering properties of excitation and reception antennas were exploited. The filters demonstrated insertion losses of 2-3 dB, bandwidth of 25-35 MHz, and tuning range of up to 1.5 GHz in the range 3-7 GHz.

  12. Performance Enhancement of Tunable Bandpass Filters Using Selective Etched Ferroelectric Thin Films

    NASA Technical Reports Server (NTRS)

    Miranda, Felix A.; Mueller, Carl H.; VanKeuls, Fred W.; Subramanyam, Guru; Vignesparamoorthy, Sivaruban

    2003-01-01

    The inclusion of voltage-tunable barium strontium titanate (BSTO) thin films into planar band pass filters offers tremendous potential to increase their versatility. The ability to tune the passband so as to correct for minor deviations in manufacturing tolerances, or to completely reconfigure the operating frequencies of a microwave communication system, are highly sought-after goals. However, use of ferroelectric films in these devices results in higher dielectric losses, which in turn increase the insertion loss and decrease the quality factors of the filters. This study explores the use of patterned ferroelectric layers to minimize dielectric losses without degrading tunability. Patterning the ferroelectric layers enables us to constrict the width of the ferroelectric layers between the coupled microstrip lines, and minimize losses due to ferroelectric layers. Coupled one-pole microstrip bandpass filters with fundamental resonances at approx. 7.2 GHz and well defined harmonic resonances at approx. 14.4 and approx. 21.6 GHz, were designed, simulated and tested. For one of the filters, experimental results verified that its center frequency was tunable by 528 MHz at a center frequency of 21.957 GHz, with insertion losses varying from 4.3 to 2.5 dB, at 0 and 3.5 V/micron, respectively. These data demonstrate that the tuning-to-loss figure of merit of tunable microstrip filters can be greatly improved using patterned ferroelectric thin films as the tuning element, and tuning can be controlled by engineering the ferroelectric constriction in the coupled sections.

  13. Tunable microwave bandpass filter integrated power divider based on the high anisotropy electro-optic nematic liquid crystal.

    PubMed

    Liu, Yupeng; Liu, Yang; Li, Haiyan; Jiang, Di; Cao, Weiping; Chen, Hui; Xia, Lei; Xu, Ruimin

    2016-07-01

    A novel, compact microwave tunable bandpass filter integrated power divider, based on the high anisotropy electro-optic nematic liquid crystal, is proposed in this letter. Liquid crystal, as the electro-optic material, is placed between top inverted microstrip line and the metal plate. The proposed structure can realize continuous tunable bandpass response and miniaturization. The proposed design concept is validated by the good performance of simulation results and experimental results. The electro-optic material has shown great potential for microwave application.

  14. Tunable microwave bandpass filter integrated power divider based on the high anisotropy electro-optic nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Liu, Yupeng; Liu, Yang; Li, Haiyan; Jiang, Di; Cao, Weiping; Chen, Hui; Xia, Lei; Xu, Ruimin

    2016-07-01

    A novel, compact microwave tunable bandpass filter integrated power divider, based on the high anisotropy electro-optic nematic liquid crystal, is proposed in this letter. Liquid crystal, as the electro-optic material, is placed between top inverted microstrip line and the metal plate. The proposed structure can realize continuous tunable bandpass response and miniaturization. The proposed design concept is validated by the good performance of simulation results and experimental results. The electro-optic material has shown great potential for microwave application.

  15. Improved color coordinates of green monochromatic pc-LED capped with a band-pass filter.

    PubMed

    Oh, Ji Hye; Yang, Su Ji; Sung, Yeon-Goog; Do, Young Rag

    2013-02-25

    This study introduces a "greener" green monochromatic phosphor-converted light-emitting diode (pc-LED) using a band-pass filter (BPF) combined with a long-pass dichroic filter (LPDF) and a short-pass dichroic filter (SPDF) to improve the color quality of our previously developed LPDF-capped green pc-LED. This can also address the drawbacks of III-V semiconductor-type green LEDs, which show a low luminous efficacy and a poor current dependence of the efficacy and color coordinates compared to blue semiconductor-type LEDs. The optical properties of green monochromatic pc-LEDs using a BPF are compared with those of LPDF-capped green pc-LEDs, which have a broad band spectrum, and III-V semiconductor-type green LEDs by changing the transmittance wavelength range of the BPF and the peak wavelength of the green phosphors. BPF-capped green monochromatic pc-LEDs provide a high luminous efficacy (134 lm/W at 60 mA), and "greener" 1931 Commission Internationale d'Eclairage (CIE; CIEx, CIEy) color coordinates (0.24, 0.66) owing to the narrowed emission spectrum. We also propose a two-dimensional (2D) polystyrene (PS) microbead (2-μm diameter) monolayer as a scattering layer to overcome the poor angular dependence of the color coordinates of the transmitted light through a nano-multilayered dichroic filter such as an LPDF or BPF. The 2D PS scattering layer improves the angular dependence of the green color emitted from a BPF-capped green pc-LED with only 3% loss of luminous efficacy.

  16. Application of Cu2O-doped phosphate glasses for bandpass filter

    NASA Astrophysics Data System (ADS)

    Elhaes, H.; Attallah, M.; Elbashar, Y.; El-Okr, M.; Ibrahim, M.

    2014-09-01

    Phosphate glasses doped with copper ions having general composition 42P2O5-39ZnO-(18-x) Na2O-1CaO-xCu2O [x=2, 4, 6, 8, 10 mol%] were prepared using a conventional melt-quench technique. Physical and chemical properties of the glasses were investigated using X-ray diffraction technique and UV-visible optical absorption. The density was measured by Archimedes' method, and molar volume (VM) was calculated. It is found that density and molar volume show opposite trend by increasing Cu2O content. Absorbance and transmittance at the normal incidence are measured by a spectrophotometer in the spectral range of 190-1100 nm. Analyses of the obtained results were considered in the frame of current theories. Absorption data were used for absorption coefficient, the optical band gap (Eopt), the cutoff in UV and IR bands to the bandpass filter, which confirmed the optical properties of this type of filter. Eopt values for different glass samples are found to decrease with increasing Cu2O content.

  17. Realisation and optical engineering of linear variable bandpass filters in nanoporous anodic alumina photonic crystals.

    PubMed

    Sukarno; Law, Cheryl Suwen; Santos, Abel

    2017-06-08

    We present the first realisation of linear variable bandpass filters in nanoporous anodic alumina (NAA-LVBPFs) photonic crystal structures. NAA gradient-index filters (NAA-GIFs) are produced by sinusoidal pulse anodisation and used as photonic crystal platforms to generate NAA-LVBPFs. The anodisation period of NAA-GIFs is modified from 650 to 850 s to systematically tune the characteristic photonic stopband of these photonic crystals across the UV-visible-NIR spectrum. Then, the nanoporous structure of NAA-GIFs is gradually widened along the surface under controlled conditions by wet chemical etching using a dip coating approach aiming to create NAA-LVBPFs with finely engineered optical properties. We demonstrate that the characteristic photonic stopband and the iridescent interferometric colour displayed by these photonic crystals can be tuned with precision across the surface of NAA-LVBPFs by adjusting the fabrication and etching conditions. Here, we envisage for the first time the combination of the anodisation period and etching conditions as a cost-competitive, facile, and versatile nanofabrication approach that enables the generation of a broad range of unique LVBPFs covering the spectral regions. These photonic crystal structures open new opportunities for multiple applications, including adaptive optics, hyperspectral imaging, fluorescence diagnostics, spectroscopy, and sensing.

  18. First results on narrow bandpass steep edge optical filters for the JST/T250 telescope instrumentation

    NASA Astrophysics Data System (ADS)

    Reichel, S.; Brauneck, U.; Bourquin, S.; Marín-Franch, A.

    2016-07-01

    The Observatorio Astrofisico de Javalambre in Spain will conduct an all-sky astronomical surveys using multi-bands, where optical filters are needed. 54 narrow bandpass (FWHM = 14.5 nm) filters will continuously populate the spectrum between 370 to 920 nm with 10.0 nm steps. Here results on 2 filters with center wavelength of 460 nm and 470 nm and blocking from 250 to 1050 nm with OD5 will be shown. The filters have a maximum transmission of larger than 85% and a transmitted wavefront error of better than λ/2 over an aperture > 100mm.

  19. A K-band Frequency Agile Microstrip Bandpass Filter using a Thin Film HTS/Ferroelectric/dielectric Multilayer Configuration

    NASA Technical Reports Server (NTRS)

    Subramanyam, Guru; VanKeuls, Fred; Miranda, Felix A.

    1998-01-01

    We report on YBa2Cu3O(7-delta) (YBCO) thin film/SrTiO3 (STO) thin film K-band tunable bandpass filters on LaAlO3 (LAO) dielectric substrates. The 2 pole filter has a center frequency of 19 GHz and a 4% bandwidth. Tunability is achieved through the non-linear dc electric field dependence of the relative dielectric constant of STO(epsilon(sub rSTO). A large tunability ((Delta)f/f(sub 0) = (f(sub Vmax) - f(sub 0)/f(sub 0), where f(sub 0) is the center frequency of the filter at no bias and f(sub Vmax) is the center frequency of the filter at the maximum applied bias) of greater than 10% was obtained in YBCO/STO/LAO microstrip bandpass filters operating below 77 K. A center frequency shift of 2.3 GHz (i.e., a tunability factor of approximately 15%) was obtained at a 400 V bipolar dc bias, and 30 K, with minimal degradation in the insertion loss of the filter. This paper addresses design, fabrication and testing of tunable filters based on STO ferroelectric thin films. The performance of the YBCO/STO/LAO filters is compared to that of gold/STO/LAO counterparts.

  20. Mode Coupling and Nonlinear Resonances of MEMS Arch Resonators for Bandpass Filters

    PubMed Central

    Hajjaj, Amal Z.; Hafiz, Md Abdullah; Younis, Mohammad I.

    2017-01-01

    We experimentally demonstrate an exploitation of the nonlinear softening, hardening, and veering phenomena (near crossing), where the frequencies of two vibration modes get close to each other, to realize a bandpass filter of sharp roll off from the passband to the stopband. The concept is demonstrated based on an electrothermally tuned and electrostatically driven MEMS arch resonator operated in air. The in-plane resonator is fabricated from a silicon-on-insulator wafer with a deliberate curvature to form an arch shape. A DC current is applied through the resonator to induce heat and modulate its stiffness, and hence its resonance frequencies. We show that the first resonance frequency increases up to twice of the initial value while the third resonance frequency decreases until getting very close to the first resonance frequency. This leads to the phenomenon of veering, where both modes get coupled and exchange energy. We demonstrate that by driving both modes nonlinearly and electrostatically near the veering regime, such that the first and third modes exhibit softening and hardening behavior, respectively, sharp roll off from the passband to the stopband is achievable. We show a flat, wide, and tunable bandwidth and center frequency by controlling the electrothermal actuation voltage. PMID:28134329

  1. Mode Coupling and Nonlinear Resonances of MEMS Arch Resonators for Bandpass Filters

    NASA Astrophysics Data System (ADS)

    Hajjaj, Amal Z.; Hafiz, Md Abdullah; Younis, Mohammad I.

    2017-01-01

    We experimentally demonstrate an exploitation of the nonlinear softening, hardening, and veering phenomena (near crossing), where the frequencies of two vibration modes get close to each other, to realize a bandpass filter of sharp roll off from the passband to the stopband. The concept is demonstrated based on an electrothermally tuned and electrostatically driven MEMS arch resonator operated in air. The in-plane resonator is fabricated from a silicon-on-insulator wafer with a deliberate curvature to form an arch shape. A DC current is applied through the resonator to induce heat and modulate its stiffness, and hence its resonance frequencies. We show that the first resonance frequency increases up to twice of the initial value while the third resonance frequency decreases until getting very close to the first resonance frequency. This leads to the phenomenon of veering, where both modes get coupled and exchange energy. We demonstrate that by driving both modes nonlinearly and electrostatically near the veering regime, such that the first and third modes exhibit softening and hardening behavior, respectively, sharp roll off from the passband to the stopband is achievable. We show a flat, wide, and tunable bandwidth and center frequency by controlling the electrothermal actuation voltage.

  2. A Novel K-Band Tunable Microstrip Bandpass Filter Using a Thin Film HTS/Ferroelectric/ Dielectric Configuration

    NASA Technical Reports Server (NTRS)

    Subramanyam, G.; VanKeuls, F.; Miranda, F. A.

    1998-01-01

    We report on YBCO/strontium titanate (STO) thin film K-band tunable bandpass filters on lanthanum aluminate substrates. The 2 pole filters were designed for a center frequency of 19 GHz and 4% bandwidth. Tunability is achieved through the non-linear dc electric field dependence of the relative dielectric constant of STO (epsilon-rSTO). Center frequency shifts greater than 2 GHz were obtained at a 400V bipolar dc bias at temperatures below 77K, with minimum degradation in the insertion loss of the filters.

  3. Terahertz band-pass filters based on fishnet metamaterials fabricated on free-standing SiNx membrane

    NASA Astrophysics Data System (ADS)

    Ao, Tianhong; Xu, Xiangdong; Gu, Yu; Chen, Zhegeng; Jiang, Yadong; Li, Xinrong; Lian, Yuxiang; Wang, Fu; He, Qiong; Chen, Zexiang; Zhou, Jun

    2017-12-01

    Terahertz (THz) band-pass filters constructed by metal-SiNx-metal hollow fishnet metamaterials were designed and fabricated. Results reveal that the as-fabricated single-layer filter responds at 3.75 THz with a high transmission of 88.1% and broad full width at half maximum of 2.79 THz. For such filters, a free-standing SiNx membrane is utilized specially as both dielectric and supporting materials, by which the insertion loss widely existed in those filters fabricated on rigid substrates can be efficiently avoided. Moreover, the critical parameters for determining the responses of the filters were systematically investigated. In our approach, multi-layer filters can be easily fabricated just by stacking the metamaterials layer by layer, and thus the spectral transmission, bandwidth, and out-of-band rejection can be rationally adjusted. This work describes a promising approach to design and fabricate THz band-pass filters based on substrate-free fishnet metamaterials.

  4. Development of simple band-spectral pyranometer and quantum meter using photovoltaic cells and bandpass filters

    SciTech Connect

    Bilguun, Amarsaikhan Nakaso, Tetsushi; Harigai, Toru; Suda, Yoshiyuki; Takikawa, Hirofumi; Tanoue, Hideto

    2016-02-01

    In recent years, greenhouse automatic-control, based on the measurement of solar irradiance, has been attracting attention. This control is an effective method for improving crop production. In the agricultural field, it is necessary to measure Photon Flux Density (PFD), which is an important parameter in the promotion of plant growth. In particular, the PFD of Photosynthetically Active Radiation (PAR, 400-700 nm) and Plant Biologically Active Radiation (PBAR, 300-800 nm) have been discussed in agricultural plant science. The commercial quantum meter (QM, PAR meter) can only measure Photosynthetically Photon Flux Density (PPFD) which is the integrated PFD quantity on the PAR wavelength. In this research, a band-spectral pyranometer or quantum meter using PVs with optical bandpass filters for dividing the PBAR wavelength into 100 nm bands (five independent channels) was developed. Before field testing, calibration of the instruments was carried out using a solar simulator. Next, a field test was conducted in three differing weather conditions such as clear, partly cloudy and cloudy skies. As a result, it was found that the response rate of the developed pyranometer was faster by four seconds compared with the response rate of the commercial pyranometer. Moreover, the outputs of each channel in the developed pyranometer were very similar to the integrated outputs of the commercial spectroradiometer. It was confirmed that the solar irradiance could be measured in each band separately using the developed band-spectral pyranometer. It was indicated that the developed band-spectral pyranometer could also be used as a PV band-spectral quantum meter which is obtained by converting the band irradiance into band PFD.

  5. Development of simple band-spectral pyranometer and quantum meter using photovoltaic cells and bandpass filters

    NASA Astrophysics Data System (ADS)

    Bilguun, Amarsaikhan; Nakaso, Tetsushi; Harigai, Toru; Suda, Yoshiyuki; Takikawa, Hirofumi; Tanoue, Hideto

    2016-02-01

    In recent years, greenhouse automatic-control, based on the measurement of solar irradiance, has been attracting attention. This control is an effective method for improving crop production. In the agricultural field, it is necessary to measure Photon Flux Density (PFD), which is an important parameter in the promotion of plant growth. In particular, the PFD of Photosynthetically Active Radiation (PAR, 400-700 nm) and Plant Biologically Active Radiation (PBAR, 300-800 nm) have been discussed in agricultural plant science. The commercial quantum meter (QM, PAR meter) can only measure Photosynthetically Photon Flux Density (PPFD) which is the integrated PFD quantity on the PAR wavelength. In this research, a band-spectral pyranometer or quantum meter using PVs with optical bandpass filters for dividing the PBAR wavelength into 100 nm bands (five independent channels) was developed. Before field testing, calibration of the instruments was carried out using a solar simulator. Next, a field test was conducted in three differing weather conditions such as clear, partly cloudy and cloudy skies. As a result, it was found that the response rate of the developed pyranometer was faster by four seconds compared with the response rate of the commercial pyranometer. Moreover, the outputs of each channel in the developed pyranometer were very similar to the integrated outputs of the commercial spectroradiometer. It was confirmed that the solar irradiance could be measured in each band separately using the developed band-spectral pyranometer. It was indicated that the developed band-spectral pyranometer could also be used as a PV band-spectral quantum meter which is obtained by converting the band irradiance into band PFD.

  6. Tin-polyimide and indium-polyimide thin-film composites as soft X-ray bandpass filters

    NASA Technical Reports Server (NTRS)

    Powell, Stephen F.; Allen, Maxwell J.; Willis, Thomas D.

    1993-01-01

    A tin-polyimide and an indium-polyimide soft X-ray bandpass filter were fabricated with thicknesses of 1400 and 1750 A for the metal and polyimide components, respectively. The transmission of each filter was measured at the Stanford Synchrotron Radiation Laboratory. The transmission of the tin-polyimide filter was found to be about 40 percent for radiation with wavelengths between 60 and 80 A. The transmission of the indium-polyimide filter was greater than 40 percent between 70 and 90 A. The indium was about 5 percent more transmissive than the tin and attained a maximum transmission of about 48 percent at 76 A. Such filters have potential applications to soft X-ray telescopes that operate in this region. They might also be of interest to investigators who work with X-ray microscopes that image live biological specimens in the 23-44-A water window.

  7. Tin-polyimide and indium-polyimide thin-film composites as soft X-ray bandpass filters

    NASA Technical Reports Server (NTRS)

    Powell, Stephen F.; Allen, Maxwell J.; Willis, Thomas D.

    1993-01-01

    A tin-polyimide and an indium-polyimide soft X-ray bandpass filter were fabricated with thicknesses of 1400 and 1750 A for the metal and polyimide components, respectively. The transmission of each filter was measured at the Stanford Synchrotron Radiation Laboratory. The transmission of the tin-polyimide filter was found to be about 40 percent for radiation with wavelengths between 60 and 80 A. The transmission of the indium-polyimide filter was greater than 40 percent between 70 and 90 A. The indium was about 5 percent more transmissive than the tin and attained a maximum transmission of about 48 percent at 76 A. Such filters have potential applications to soft X-ray telescopes that operate in this region. They might also be of interest to investigators who work with X-ray microscopes that image live biological specimens in the 23-44-A water window.

  8. Improving the Pass-Band Return Loss in Liquid Crystal Dual-Mode Bandpass Filters by Microstrip Patch Reshaping

    PubMed Central

    Torrecilla, Javier; Urruchi, Virginia; Sánchez-Pena, José Manuel; Bennis, Noureddine; García, Alejandro; Segovia, Daniel

    2014-01-01

    In this paper, the design and experimental characterization of a tunable microstrip bandpass filter based on liquid crystal technology are presented. A reshaped microstrip dual-mode filter structure has been used in order to improve the device performance. Specifically, the aim is to increase the pass-band return loss of the filter by narrowing the filter bandwidth. Simulations confirm the improvement of using this new structure, achieving a pass-band return loss increase of 1.5 dB at least. Because of the anisotropic properties of LC molecules, a filter central frequency shift from 4.688 GHz to 5.045 GHz, which means a relative tuning range of 7.3%, is measured when an external AC voltage from 0 Vrms to 15 Vrms is applied to the device. PMID:28788690

  9. Design of a Broadband Band-Pass Filter with Notch-Band Using New Models of Coupled Transmission Lines

    PubMed Central

    Daryasafar, Navid; Baghbani, Somaye; Naser Moghaddasi, Mohammad; Sadeghzade, Ramezanali

    2014-01-01

    We intend to design a broadband band-pass filter with notch-band, which uses coupled transmission lines in the structure, using new models of coupled transmission lines. In order to realize and present the new model, first, previous models will be simulated in the ADS program. Then, according to the change of their equations and consequently change of basic parameters of these models, optimization and dependency among these parameters and also their frequency response are attended and results of these changes in order to design a new filter are converged. PMID:25243202

  10. Reconfigurable and frequency-agile on-chip microwave photonic bandpass and bandstop filters using stimulated Brillouin scattering

    NASA Astrophysics Data System (ADS)

    Choudhary, Amol; Aryanfar, Iman; Shahnia, Shayan; Morrison, Blair; Pagani, Mattia; Liu, Yang; Vu, Khu; Madden, Stephen; Luther-Davies, Barry; Marpaung, David; Eggleton, Benjamin J.

    2016-09-01

    In this paper, we present our recent results in the area of microwave photonics. Integrated microwave photonic bandpass and bandstop filters were realized using stimulated Brillouin scattering (SBS). Our recent breakthrough in the fabrication of chalcogenide waveguides has allowed us to achieve an on-chip SBS gain of >40 dB, enabling for the first time the tailoring of the SBS response well beyond the intrinsic linewidth ( 30 MHz). An electrical comb generated by an arbitrary waveform generator was modulated onto an optical carrier to generate a broadened pump which via the SBS effect created a flat and rectangular bandpass filter response in the RF domain. Controlling the number of pump lines allowed bandwidth reconfigurability from 30 MHz to 440 MHz. The measured selectivity and the passband ripple were >20 dB and <1.9 dB, respectively and the center frequency of the filter was tuned up to 30 GHz. A bandstop filter response was realized by using a novel RF interferometry technique via accurate control of the amplitude and phase of the sidebands of the modulated probe. The bandwidth was reconfigurable from 75 MHz-300 MHz and the central frequency of the filter was tunable up to 30 GHz.

  11. Free-standing guided-mode resonance band-pass filters: from 1D to 2D structures.

    PubMed

    Sakat, Emilie; Vincent, Grégory; Ghenuche, Petru; Bardou, Nathalie; Dupuis, Christophe; Collin, Stéphane; Pardo, Fabrice; Haïdar, Riad; Pelouard, Jean-Luc

    2012-06-04

    We study experimentally and theoretically band-pass filters based on guided-mode resonances in free-standing metal-dielectric structures with subwavelength gratings. A variety of filters are obtained: polarizing filters with 1D gratings, and unpolarized or selective filters with 2D gratings, which are shown to behave as two crossed-1D structures. In either case, a high transmission (up to ≈ 79 %) is demonstrated, which represents an eight-fold enhancement compared to the geometrical transmission of the grating. We also show that the angular sensitivity strongly depends on the rotation axis of the sample. This behavior is explained with a detailed description of the guided-mode transmission mechanism.

  12. A bandpass filter for the enhancement of an X-ray reconstruction of the tissue in the spinal canal

    NASA Technical Reports Server (NTRS)

    Reed, I. S.; Glenn, W. V.; Kwoh, Y. S.; Truong, T. K.

    1980-01-01

    In this communication, a new bandpass reconstruction filter is developed to partially remove the low spatial frequencies of the bone and the soft tissue in an X-ray reconstruction of a lumbar spine. This partial removal of the low frequencies suppresses the bony vertebral body and the soft tissue components within the projections of actual clinical data. It also has the effect of enhancing the sharp edges of the fatty tissue surrounding the spinal cord region. The intent of this effort is to directly visualize the spinal cord without the need for water-soluble contrast (e.g., metrizamide) to be installed through lumbar punctures.

  13. A bandpass filter for the enhancement of an X-ray reconstruction of the tissue in the spinal canal

    NASA Technical Reports Server (NTRS)

    Reed, I. S.; Glenn, W. V.; Kwoh, Y. S.; Truong, T. K.

    1980-01-01

    In this communication, a new bandpass reconstruction filter is developed to partially remove the low spatial frequencies of the bone and the soft tissue in an X-ray reconstruction of a lumbar spine. This partial removal of the low frequencies suppresses the bony vertebral body and the soft tissue components within the projections of actual clinical data. It also has the effect of enhancing the sharp edges of the fatty tissue surrounding the spinal cord region. The intent of this effort is to directly visualize the spinal cord without the need for water-soluble contrast (e.g., metrizamide) to be installed through lumbar punctures.

  14. Optical contrast of 2D InSe on SiO2/Si and transparent substrates using bandpass filters.

    PubMed

    Brotons-Gisbert, M; Andres-Penares, D; Martínez-Pastor, J P; Cros, A; Sánchez-Royo, J F

    2017-03-17

    The particular optical and electronic properties recently reported for 2D InSe depict this 2D material as being very versatile for future electronic and optoelectronic devices with tunable and optimized functionalities. For its fundamental study and the development of practical applications, rapid and accurate identification methods of atomically thin InSe are essential. Here, we demonstrate an enhancement of the optical contrast between InSe nanosheets and the underlying SiO2/Si substrate by illuminating with a 40 nm wide bandpass filter centered at 500 nm. Moreover, we study the optical contrast of 2D InSe on transparent substrates. Our results suggest that a good optical contrast is achieved for transparent substrates with low real refractive indices such as LiF or a viscoelastic polydimethylsiloxane stamp. In this case, an optimum optical contrast would be achieved by using a bandpass filter centered at 450 nm. These results can be very useful for speeding up the continuously growing research on 2D InSe and its applications.

  15. Optical contrast of 2D InSe on SiO2/Si and transparent substrates using bandpass filters

    NASA Astrophysics Data System (ADS)

    Brotons-Gisbert, M.; Andres-Penares, D.; Martínez-Pastor, J. P.; Cros, A.; Sánchez-Royo, J. F.

    2017-03-01

    The particular optical and electronic properties recently reported for 2D InSe depict this 2D material as being very versatile for future electronic and optoelectronic devices with tunable and optimized functionalities. For its fundamental study and the development of practical applications, rapid and accurate identification methods of atomically thin InSe are essential. Here, we demonstrate an enhancement of the optical contrast between InSe nanosheets and the underlying SiO2/Si substrate by illuminating with a 40 nm wide bandpass filter centered at 500 nm. Moreover, we study the optical contrast of 2D InSe on transparent substrates. Our results suggest that a good optical contrast is achieved for transparent substrates with low real refractive indices such as LiF or a viscoelastic polydimethylsiloxane stamp. In this case, an optimum optical contrast would be achieved by using a bandpass filter centered at 450 nm. These results can be very useful for speeding up the continuously growing research on 2D InSe and its applications.

  16. A dual-mode bandpass filter with multiple controllable transmission-zeros using T-shaped stub-loaded resonators.

    PubMed

    Yao, Zh; Wang, C; Kim, N Y

    2014-01-01

    A dual-mode broadband bandpass filter (BPF) with multiple controllable transmission-zeros using T-shaped stub-loaded resonators (TSSLRs) is presented. Due to the symmetrical plane, the odd-even-mode theory can be adopted to characterize the BPF. The proposed filter consists of a dual-mode TSSLR and two modified feed-lines, which introduce two capacitive and inductive source-load (S-L) couplings. Five controllable transmission zeros (TZs) can be achieved for the high selectivity and the wide stopband because of the tunable amount of coupling capacitance and inductance. The center frequency of the proposed BPF is 5.8 GHz, with a 3 dB fraction bandwidth of 8.9%. The measured insertion and return losses are 1.75 and 28.18 dB, respectively. A compact size and second harmonic frequency suppression can be obtained by the proposed BPF with S-L couplings.

  17. Bandwidth-variable tunable optical filter unit for illumination and spectral imaging systems using thin-film optical band-pass filters.

    PubMed

    Hennig, Georg; Brittenham, Gary M; Sroka, Ronald; Kniebühler, Gesa; Vogeser, Michael; Stepp, Herbert

    2013-04-01

    An optical filter unit is demonstrated, which uses two successively arranged tunable thin-film optical band-pass filters and allows for simultaneous adjustment of the central wavelength in the spectral range 522-555 nm and of the spectral bandwidth in the range 3-16 nm with a wavelength switching time of 8 ms∕nm. Different spectral filter combinations can cover the complete visible spectral range. The transmitted intensity was found to decrease only linearly with the spectral bandwidth for bandwidths >6 nm, allowing a high maximum transmission efficiency of >75%. The image of a fiber bundle was spectrally filtered and analyzed in terms of position-dependency of the transmitted bandwidth and central wavelength.

  18. Linear variable narrow bandpass optical filters in the far infrared (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Rahmlow, Thomas D.

    2017-06-01

    We are currently developing linear variable filters (LVF) with very high wavelength gradients. In the visible, these filters have a wavelength gradient of 50 to 100 nm/mm. In the infrared, the wavelength gradient covers the range of 500 to 900 microns/mm. Filter designs include band pass, long pass and ulta-high performance anti-reflection coatings. The active area of the filters is on the order of 5 to 30 mm along the wavelength gradient and up to 30 mm in the orthogonal, constant wavelength direction. Variation in performance along the constant direction is less than 1%. Repeatable performance from filter to filter, absolute placement of the filter relative to a substrate fiducial and, high in-band transmission across the full spectral band is demonstrated. Applications include order sorting filters, direct replacement of the spectrometer and hyper-spectral imaging. Off-band rejection with an optical density of greater than 3 allows use of the filter as an order sorting filter. The linear variable order sorting filters replaces other filter types such as block filters. The disadvantage of block filters is the loss of pixels due to the transition between filter blocks. The LVF is a continuous gradient without a discrete transition between filter wavelength regions. If the LVF is designed as a narrow band pass filter, it can be used in place of a spectrometer thus reducing overall sensor weight and cost while improving the robustness of the sensor. By controlling the orthogonal performance (smile) the LVF can be sized to the dimensions of the detector. When imaging on to a 2 dimensional array and operating the sensor in a push broom configuration, the LVF spectrometer performs as a hyper-spectral imager. This paper presents performance of LVF fabricated in the far infrared on substrates sized to available detectors. The impact of spot size, F-number and filter characterization are presented. Results are also compared to extended visible LVF filters.

  19. Semiquantitative analysis of SPECT images using 99Tc(m) -HMPAO in the treatment of brain perfusion after the attenuation correction by the Chang method and the application of the Butterworth filter.

    PubMed

    Stelter, P; Junik, R; Krzyminiewski, R; Gembicki, M; Sowiński, J

    2001-08-01

    The aim of this work was to optimize the parameters for semiquantitative analysis with regard to the average number of counts per pixel in tomographic projections. The analysed studies were divided into three groups, proportionally, to average the counts per pixel. The analysis of results proved the dependence (P<0.05) between the average geometric contrast of images with the maximum counts per pixel higher than 500, reconstructed with the cut-off frequency fc=0.50fn, and the standard image. Also, the same dependence was found between the group with an average of 200 counts per pixel and the standard image at the cut-off frequency fc=0.40fn. The analysis of the attenuation coefficient, c, showed significant differences. The attenuation coefficient c=0.12 cm-1 as accepted for further studies. Optimization of the matrix order of interpolation filter proved increasing of contrast with decreasing size of the matrix. In conclusion, according to the average number of counts per pixel in a projection the parameters of image reconstruction, particularly the cut-off frequency fc of the Butterworth filter, should be changed. Additionally, an attenuation correction with coefficient c=0.12 cm-1 and interpolation with matrix size equal 7x7 should be applied.

  20. A Hybrid Circuit for Spoof Surface Plasmons and Spatial Waveguide Modes to Reach Controllable Band-Pass Filters

    PubMed Central

    Zhang, Qian; Zhang, Hao Chi; Wu, Han; Cui, Tie Jun

    2015-01-01

    We propose a hybrid circuit for spoof surface plasmon polaritons (SPPs) and spatial waveguide modes to develop new microwave devices. The hybrid circuit includes a spoof SPP waveguide made of two anti-symmetric corrugated metallic strips and a traditional substrate integrated waveguide (SIW). From dispersion relations, we show that the electromagnetic waves only can propagate through the hybrid circuit when the operating frequency is less than the cut-off frequency of the SPP waveguide and greater than the cut-off frequency of SIW, generating efficient band-pass filters. We demonstrate that the pass band is controllable in a large range by designing the geometrical parameters of SPP waveguide and SIW. Full-wave simulations are provided to show the large adjustability of filters, including ultra wideband and narrowband filters. We fabricate a sample of the new hybrid device in the microwave frequencies, and measurement results have excellent agreements to numerical simulations, demonstrating excellent filtering characteristics such as low loss, high efficiency, and good square ratio. The proposed hybrid circuit gives important potential to accelerate the development of plasmonic integrated functional devices and circuits in both microwave and terahertz frequencies. PMID:26552584

  1. A Hybrid Circuit for Spoof Surface Plasmons and Spatial Waveguide Modes to Reach Controllable Band-Pass Filters.

    PubMed

    Zhang, Qian; Zhang, Hao Chi; Wu, Han; Cui, Tie Jun

    2015-11-10

    We propose a hybrid circuit for spoof surface plasmon polaritons (SPPs) and spatial waveguide modes to develop new microwave devices. The hybrid circuit includes a spoof SPP waveguide made of two anti-symmetric corrugated metallic strips and a traditional substrate integrated waveguide (SIW). From dispersion relations, we show that the electromagnetic waves only can propagate through the hybrid circuit when the operating frequency is less than the cut-off frequency of the SPP waveguide and greater than the cut-off frequency of SIW, generating efficient band-pass filters. We demonstrate that the pass band is controllable in a large range by designing the geometrical parameters of SPP waveguide and SIW. Full-wave simulations are provided to show the large adjustability of filters, including ultra wideband and narrowband filters. We fabricate a sample of the new hybrid device in the microwave frequencies, and measurement results have excellent agreements to numerical simulations, demonstrating excellent filtering characteristics such as low loss, high efficiency, and good square ratio. The proposed hybrid circuit gives important potential to accelerate the development of plasmonic integrated functional devices and circuits in both microwave and terahertz frequencies.

  2. Fully integrated high quality factor GmC bandpass filter stage with highly linear operational transconductance amplifier

    NASA Astrophysics Data System (ADS)

    Briem, Jochen; Mader, Marco; Reiter, Daniel; Amirpour, Raul; Grözing, Markus; Berroth, Manfred

    2017-09-01

    This paper presents an electrical, fully integrated, high quality (Q) factor GmC bandpass filter (BPF) stage for a wireless 27 MHz direct conversion receiver for a bendable sensor system-in-foil (Briem et al., 2016). The core of the BPF with a Q factor of more than 200 is an operational transconductance amplifier (OTA) with a high linearity at an input range of up to 300 mVpp, diff. The OTA's signal-to-noise-and-distortion-ratio (SNDR) of more than 80 dB in the mentioned range is achieved by stabilizing its transconductance Gm with a respective feedback loop and a source degeneration resistors RDG. The filter stage can be tuned and is tolerant to global and local process variations due to offset and common-mode feedback (CMFB) control circuits. The results are determined by periodic steady state (PSS) simulations at more than 200 global and local process variation parameter and temperature points and corner simulations. It is expected, that the parasitic elements of the layout have no significant influence on the filter behaviour. The current consumption of the whole filter stage is less than 600 µA.

  3. A Multispectral Image Creating Method for a New Airborne Four-Camera System with Different Bandpass Filters

    PubMed Central

    Li, Hanlun; Zhang, Aiwu; Hu, Shaoxing

    2015-01-01

    This paper describes an airborne high resolution four-camera multispectral system which mainly consists of four identical monochrome cameras equipped with four interchangeable bandpass filters. For this multispectral system, an automatic multispectral data composing method was proposed. The homography registration model was chosen, and the scale-invariant feature transform (SIFT) and random sample consensus (RANSAC) were used to generate matching points. For the difficult registration problem between visible band images and near-infrared band images in cases lacking manmade objects, we presented an effective method based on the structural characteristics of the system. Experiments show that our method can acquire high quality multispectral images and the band-to-band alignment error of the composed multiple spectral images is less than 2.5 pixels. PMID:26205264

  4. A compact dual-band bandpass filter based on porous silicon dual-microcavity of one-dimensional photonic crystal

    NASA Astrophysics Data System (ADS)

    Ma, Hui; Zhang, Hong-yan

    2015-03-01

    We propose a compact dual-band bandpass filter (BPF) based on one-dimensional porous silicon (PS) photonic crystal by electrochemical etching. By inserting three periods of high and low reflective index layers in the center of porous silicon microcavity (PSM), two sharp resonant peaks appear in the high reflectivity stop band on both sides of the resonance wavelength. Through simulation and experiment, the physical mechanisms of the two resonance peaks and the resonance wavelength are also studied. It is found that the resonance wavelength can be tuned only by adjusting the effective optical thickness (EOT) of each PS layer, in which different resonance wavelengths have different widths between the two sharp resonance peaks. Besides, the analysis indicates that oxidization makes the blue shift become larger for high wavelength than that for low wavelength. Such a fabricated BPF based on PS dual-microcavity is easy to be fabricated and low cost, which benefits the application of integrated optical devices.

  5. A Multispectral Image Creating Method for a New Airborne Four-Camera System with Different Bandpass Filters.

    PubMed

    Li, Hanlun; Zhang, Aiwu; Hu, Shaoxing

    2015-07-20

    This paper describes an airborne high resolution four-camera multispectral system which mainly consists of four identical monochrome cameras equipped with four interchangeable bandpass filters. For this multispectral system, an automatic multispectral data composing method was proposed. The homography registration model was chosen, and the scale-invariant feature transform (SIFT) and random sample consensus (RANSAC) were used to generate matching points. For the difficult registration problem between visible band images and near-infrared band images in cases lacking manmade objects, we presented an effective method based on the structural characteristics of the system. Experiments show that our method can acquire high quality multispectral images and the band-to-band alignment error of the composed multiple spectral images is less than 2.5 pixels.

  6. Miniaturized bandpass filter using a meandered stepped-impedance resonator with a meandered-line stub-load on a GaAs substrate.

    PubMed

    Chuluunbaatar, Z; Wang, C; Kim, N Y

    2014-01-01

    This paper reports a compact bandpass filter with improved skirt selectivity using integrated passive device fabrication technology on a GaAs substrate. The structure of the filter consists of electromagnetically coupled meandered-line symmetric stepped-impedance resonators. The strength of the coupling between the resonators is enhanced by using a meandered-line stub-load inside the resonators to improve the selectivity and miniaturize the size of the filter. In addition, the center frequency of the filter can be flexibly controlled by varying degrees of the capacitive coupling between resonator and stub-load. To verify the proposed concept, a protocol bandpass filter with center frequency of 6.53 GHz was designed, fabricated, and measured, with a return loss and insertion loss of 39.1 dB and 1.63 dB.

  7. Approximate bandpass and frequency response models of the difference of Gaussian filter

    NASA Astrophysics Data System (ADS)

    Birch, Philip; Mitra, Bhargav; Bangalore, Nagachetan M.; Rehman, Saad; Young, Rupert; Chatwin, Chris

    2010-12-01

    The Difference of Gaussian (DOG) filter is widely used in optics and image processing as, among other things, an edge detection and correlation filter. It has important biological applications and appears to be part of the mammalian vision system. In this paper we analyse the filter and provide details of the full width half maximum, bandwidth and frequency response in order to aid the full characterisation of its performance.

  8. Generation of red color and near infrared bandpass filters using nano-scale plasmonic structures

    NASA Astrophysics Data System (ADS)

    Sokar, Ahmed A. Z.; Hutter, Franz X.; Burghartz, Joachim N.

    2015-05-01

    Extraordinary/Enhanced optical transmission (EOT) is studied in the realization of plasmonic based filters in the visible range and near infrared spectrum for the purpose of substituting the Bayer-pattern filter with a new CMOS-compatible filter which can be easily tuned to provide different filter spectra. The filters studied in this paper are based on nano-structured 150nm thick Aluminum (Al) layer sandwiched between silicon dioxide (SiO2) layers. The resonance wavelengths achieved by the filters are at 700nm and 950 nm. Three parameters are used for tuning the two filters, i.e., aperture area, the period, and the holes arrangement (square or rhombic lattice). The filter is based on the principle of surface plasmon polaritons (SPPs), where the electromagnetic waves of the incident light couples with the free charges of the metal at the metal-dielectric interface. EOT is observed when the metal is structured with apertures such as rectangular, circular, cross, bowtie, etc. The resonance frequency in that case depends on the shape of the aperture, material used, the size of the apertures, the period of the array, and the surrounding material. The fabricated two filters show EOT at wavelengths as designed and simulated with blueshift in the peak location.

  9. Spoof surface plasmon-based bandpass filter with extremely wide upper stopband

    NASA Astrophysics Data System (ADS)

    Xiaoyong, Liu; Lei, Zhu; Yijun, Feng

    2016-03-01

    We investigate the guiding modes of spoof surface plasmon polaritons (SPPs) on a symmetric ultra-thin plasmonic structure. From the analysis, we deduce the operating frequency region of the single-mode propagation. Based on this property, a spoof SPPs lowpass filter is then constituted in the microwave frequency. By introducing a transmission zero at the lower frequency band using a pair of stepped-impedance stubs, a wide passband filter is further realized. The proposed filter is fed by a transducer composed of a microstrip line with a flaring ground. The simulated results show that the presented filter has an extremely wide upper stopband in addition to excellent passband filtering characteristics such as low loss, wide band, and high square ratio. A prototype passband filter is also fabricated to validate the predicted performances. The proposed spoof-SPPs filter is believed to be very promising for other surface waveguide components in microwave and terahertz bands. Project supported by the Key Grant Project of Ministry of Education of China (Grant No. 313029), the FDCT Research Grant from Macao Science and Technology Development Fund, China (Grant No. 051/2014/A1), and the Multi-Year Research Grant from University of Macau, Macau SAR, China (Grant No. MYRG2014-00079-FST).

  10. "The Design of a Compact, Wide Spurious-Suppression Bandwidth Bandpass Filter Using Stepped Impedance Resonators"

    NASA Technical Reports Server (NTRS)

    U-Yen, Kongpop; Wollack, Edward J.; Doiron, Terence; Papapolymerou, John; Laskar, Joy

    2005-01-01

    We propose an analytical design for a microstrip broadband spurious-suppression filter. The proposed design uses every section of the transmission lines as both a coupling and a spurious suppression element, which creates a very compact, planar filter. While a traditional filter length is greater than the multiple of the quarter wavelength at the center passband frequency (lambda(sub g)/4), the proposed filter length is less than (order n(Ssup th) + l)center dot lambda(sub g)/8. The filter s spurious response and physical dimension are controlled by the step impedance ratio (R) between two transmission line sections as a lambda(sub g)/4 resonator. The experimental result shows that, with R of 0.2, the out-of-band attenuation is greater than 40 dB; and the first spurious mode is shifted to more than 5 times the fundamental frequency. Moreover, it is the most compact planar filter design to date. The results also indicate a low in-band insertion loss.

  11. Active tuning of a microstrip hairpin-line microwave bandpass filter on a polycrystalline yttrium iron garnet substrate using small magnetic fields

    NASA Astrophysics Data System (ADS)

    Gillette, S. M.; Geiler, A. L.; Chen, Z.; Chen, Y.; Arruda, T.; Xie, C.; Wang, L.; Zhu, X.; Liu, M.; Mukerjee, S.; Vittoria, C.; Harris, V. G.

    2011-04-01

    Active magnetic tuning of a microstrip hairpin-line coupled resonator bandpass filter fabricated on a polycrystalline yttrium iron garnet substrate has been demonstrated. The filter exhibits a five-pole Chebyshev response with passband center frequency tunability from 8.3 to 9 GHz under low applied H fields of 50-200 Oe. The instantaneous bandwidth was measured to be approximately 1 GHz. During tuning, passband center frequency insertion loss varies between 1 and 1.4 dB. Good agreement between simulated and measured device performance was demonstrated. Advantages of the proposed filter design include planar geometry, compact size, low insertion loss, and low field tunability. The proposed design approach lends itself to the implementation of a wide range of filter responses, including low pass, high pass, bandpass, and band stop, as well as passband characteristics, including center frequency, fractional bandwidth, passband ripple, out-of-band rejection, etc.

  12. Tunable photonic filters: a digital signal processing design approach.

    PubMed

    Binh, Le Nguyen

    2009-05-20

    Digital signal processing techniques are used for synthesizing tunable optical filters with variable bandwidth and centered reference frequency including the tunability of the low-pass, high-pass, bandpass, and bandstop optical filters. Potential applications of such filters are discussed, and the design techniques and properties of recursive digital filters are outlined. The basic filter structures, namely, the first-order all-pole optical filter (FOAPOF) and the first-order all-zero optical filter (FOAZOF), are described, and finally the design process of tunable optical filters and the designs of the second-order Butterworth low-pass, high-pass, bandpass, and bandstop tunable optical filters are presented. Indeed, we identify that the all-zero and all-pole networks are equivalent with well known principles of optics of interference and resonance, respectively. It is thus very straightforward to implement tunable optical filters, which is a unique feature.

  13. Silicon on-chip bandpass filters for the multiplexing of high sensitivity photonic crystal microcavity biosensors

    SciTech Connect

    Yan, Hai Zou, Yi; Yang, Chun-Ju; Chakravarty, Swapnajit; Wang, Zheng; Tang, Naimei; Chen, Ray T.; Fan, Donglei

    2015-03-23

    A method for the dense integration of high sensitivity photonic crystal (PC) waveguide based biosensors is proposed and experimentally demonstrated on a silicon platform. By connecting an additional PC waveguide filter to a PC microcavity sensor in series, a transmission passband is created, containing the resonances of the PC microcavity for sensing purpose. With proper engineering of the passband, multiple high sensitivity PC microcavity sensors can be integrated into microarrays and be interrogated simultaneously between a single input and a single output port. The concept was demonstrated with a 2-channel L55 PC biosensor array containing PC waveguide filters. The experiment showed that the sensors on both channels can be monitored simultaneously from a single output spectrum. Less than 3 dB extra loss for the additional PC waveguide filter is observed.

  14. Silicon on-chip bandpass filters for the multiplexing of high sensitivity photonic crystal microcavity biosensors

    NASA Astrophysics Data System (ADS)

    Yan, Hai; Zou, Yi; Chakravarty, Swapnajit; Yang, Chun-Ju; Wang, Zheng; Tang, Naimei; Fan, Donglei; Chen, Ray T.

    2015-03-01

    A method for the dense integration of high sensitivity photonic crystal (PC) waveguide based biosensors is proposed and experimentally demonstrated on a silicon platform. By connecting an additional PC waveguide filter to a PC microcavity sensor in series, a transmission passband is created, containing the resonances of the PC microcavity for sensing purpose. With proper engineering of the passband, multiple high sensitivity PC microcavity sensors can be integrated into microarrays and be interrogated simultaneously between a single input and a single output port. The concept was demonstrated with a 2-channel L55 PC biosensor array containing PC waveguide filters. The experiment showed that the sensors on both channels can be monitored simultaneously from a single output spectrum. Less than 3 dB extra loss for the additional PC waveguide filter is observed.

  15. A Dual-Mode Bandpass Filter with Multiple Controllable Transmission-Zeros Using T-Shaped Stub-Loaded Resonators

    PubMed Central

    Yao, Zh.; Wang, C.; Kim, N. Y.

    2014-01-01

    A dual-mode broadband bandpass filter (BPF) with multiple controllable transmission-zeros using T-shaped stub-loaded resonators (TSSLRs) is presented. Due to the symmetrical plane, the odd-even-mode theory can be adopted to characterize the BPF. The proposed filter consists of a dual-mode TSSLR and two modified feed-lines, which introduce two capacitive and inductive source-load (S-L) couplings. Five controllable transmission zeros (TZs) can be achieved for the high selectivity and the wide stopband because of the tunable amount of coupling capacitance and inductance. The center frequency of the proposed BPF is 5.8 GHz, with a 3 dB fraction bandwidth of 8.9%. The measured insertion and return losses are 1.75 and 28.18 dB, respectively. A compact size and second harmonic frequency suppression can be obtained by the proposed BPF with S-L couplings. PMID:24688406

  16. Design of high-order HTS dual-band bandpass filters with receiver subsystem for future mobile communication systems

    NASA Astrophysics Data System (ADS)

    Sekiya, N.

    2016-08-01

    We have developed two high-order high-temperature superconducting (HTS) dual-band bandpass filters (BPFs) with a receiver subsystem for future mobile communication systems. They feature stub-loaded hair-pin resonators with two types of microstrip lines between them. One has a six-pole design, and the other has an eight-pole design. Both were designed to operate at 2.15 GHz with a 43-MHz (2%) bandwidth for the lower passband and at 3.50 GHz with a 70-MHz (2%) bandwidth for the upper one. They were fabricated using YBa2Cu3Oy thin film on a CeO2-bufferd r-Al2O3 substrate. The measured results for both filters agree well with the simulated ones. The HTS dual-band BPF receiver subsystem uses a pulse tube cryocooler and a wideband low noise amplifier (LNA). We measured the frequency response of the six-pole dual-band BPF with and without a wideband LNA with a gain of 10 dB. The measured return losses were close.

  17. A novel pulse compression algorithm for frequency modulated active thermography using band-pass filter

    NASA Astrophysics Data System (ADS)

    Chatterjee, Krishnendu; Roy, Deboshree; Tuli, Suneet

    2017-05-01

    This paper proposes a novel pulse compression algorithm, in the context of frequency modulated thermal wave imaging. The compression filter is derived from a predefined reference pixel in a recorded video, which contains direct measurement of the excitation signal alongside the thermal image of a test piece. The filter causes all the phases of the constituent frequencies to be adjusted to nearly zero value, so that on reconstruction a pulse is obtained. Further, due to band-limited nature of the excitation, signal-to-noise ratio is improved by suppressing out-of-band noise. The result is similar to that of a pulsed thermography experiment, although the peak power is drastically reduced. The algorithm is successfully demonstrated on mild steel and carbon fibre reference samples. Objective comparisons of the proposed pulse compression algorithm with the existing techniques are presented.

  18. High Temperature Superconductivity Space Experiment (HTSSE). Hybrid HTS/Dielectric Resonator Bandpass Filter

    DTIC Science & Technology

    1992-04-02

    enlarged ( limited by waveguide moding) or the metal walls replaced by HTS material . HTS walls are particularly attractive since they can be placed...an order of magnitude the resistive losses of filters, waveguide feeds, and transmission lines. Significant reduction in size and weight of these...suspending a dielectric resonator inside a waveguide cavity below cutoff. One of the basic advantages of a dielectric resonator as compared to a

  19. Improvised design of THz spectrophotometer using LT-GaAs photoconductive antennas, pyroelectric detector and band-pass filters

    NASA Astrophysics Data System (ADS)

    Mottamchetty, V.; Chaudhary, A. K.

    2016-01-01

    We report the improvised design of LT-GaAs photoconductive antenna and pyroelectric detector-based terahertz (THz) spectrophotometer by introducing band-pass filters. The spectrophotometer provides direct optical/absorption information of materials in THz domain without using any signal processing devices (such as lock-in amplifier) and delay arrangement, etc., which are required in conventional THz spectrometer. Moreover, obtained absorption results from spectrometer are less affected by laser fluctuations and inherent noises of the detector. The laser pulses of duration 15 fs at 80 MHz repetition rate are utilized in this spectrometer to generate THz radiation with good conversion efficiency ( η) of the order 3 × 10-3. In addition, emphasis is also given to understand the effect of single- and two-photon absorption on generated THz power with respect to incident laser power density. Absorption properties of packing materials such as paper, Teflon, transparency and rubber (eraser) sheets are investigated in terms of their attenuation coefficients and absorbance at 0.5 and 1.5 THz region in our newly designed THz spectrophotometer. Our study demonstrates the significant information about their attenuation coefficients lying between 300 and 5000 dB/m. The attenuation in THz power has been measured as a function of the paper thickness (0.3-1.5 mm). The obtained results show the exponential growth in absorption with respect to paper thickness.

  20. U and Pu Gamma-Ray Measurements of Spent Fuel Using a Gamma-Ray Mirror Band-Pass Filter

    SciTech Connect

    Ziock, Klaus-Peter; Alameda, J.B.; Brejnholt, N.F.; Decker, T.A.; Descalle, M.A.; Fernandez-Perea, M.; Hill, R.M.; Kisner, R.A.; Melin, A.M.; Patton, B.W.; Ruz, J.; Soufli, R.; Pivovaroff, M.J.

    2014-01-01

    Abstract. We report on the use of grazing incidence gamma-ray mirrors to serve as a narrow band-pass filter for advanced non-destructive analysis (NDA) of spent nuclear fuel. The purpose of the mirrors is to limit the radiation reaching a HPGe detector to narrow spectral bands around characteristic emission lines from fissile isotopes in the fuel. This overcomes the normal rate issues when performing gamma-ray NDA measurements. In a proof-of-concept experiment, a set of simple flat gamma-ray mirrors were used to directly observe the atomic florescence lines from U and Pu from spent fuel pins with the detector located in a shirt-sleeve environment. The mirrors, consisting of highly polished silicon substrates deposited with WC/SiC multilayer coatings, successfully deflected the lines of interest while the intense primary radiation beam from the fuel was blocked by a lead beam stop. The gamma-ray multilayer coatings that make the mirrors work at the gamma-ray energies used here (~ 100 keV) have been experimentally tested at energies as high as 645 keV, indicating that direct observation of nuclear emission lines from 239Pu should be possible with an appropriately designed optic and shielding configuration.

  1. The role of excitation-pattern cues in the detection of frequency shifts in bandpass-filtered complex tones

    PubMed Central

    Marmel, Frederic; Plack, Christopher J.; Hopkins, Kathryn; Carlyon, Robert P.; Gockel, Hedwig E.; Moore, Brian C. J.

    2016-01-01

    One task intended to measure sensitivity to temporal fine structure (TFS) involves the discrimination of a harmonic complex tone from a tone in which all harmonics are shifted upwards by the same amount in hertz. Both tones are passed through a fixed bandpass filter centered on the high harmonics to reduce the availability of excitation-pattern cues and a background noise is used to mask combination tones. The role of frequency selectivity in this “TFS1” task was investigated by varying level. Experiment 1 showed that listeners performed more poorly at a high level than at a low level. Experiment 2 included intermediate levels and showed that performance deteriorated for levels above about 57 dB sound pressure level. Experiment 3 estimated the magnitude of excitation-pattern cues from the variation in forward masking of a pure tone as a function of frequency shift in the complex tones. There was negligible variation, except for the lowest level used. The results indicate that the changes in excitation level at threshold for the TFS1 task would be too small to be usable. The results are consistent with the TFS1 task being performed using TFS cues, and with frequency selectivity having an indirect effect on performance via its influence on TFS cues. PMID:25994700

  2. Performance of two-pole bandpass filters photodefined on double-sided Y-Ba-Cu-O and Tl-Ba-Ca-Cu-O thin films

    NASA Technical Reports Server (NTRS)

    Miranda, F. A.; Toncich, S. S.; Bhasin, K. B.

    1993-01-01

    The performance of 7.3-GHz two-pole bandpass filters (5% bandwidth) fabricated on double-sided Y-Ba-Cu-O and Tl-Ba-Ca-Cu-O thin films deposited on LaAlO3 is discussed. At 77 K, the Tl-Ba-Ca-Cu-O and Y-Ba-Cu-O superconducting filters exhibited minimum passband insertion losses of 0.3 and 1.2 dB, respectively. An insertion loss of 3.4 dB was measured for an all-gold filter at 77 K.

  3. Reduction of timing jitter and intensity noise in normal-dispersion passively mode-locked fiber lasers by narrow band-pass filtering.

    PubMed

    Qin, Peng; Song, Youjian; Kim, Hyoji; Shin, Junho; Kwon, Dohyeon; Hu, Minglie; Wang, Chingyue; Kim, Jungwon

    2014-11-17

    Fiber lasers mode-locked with normal cavity dispersion have recently attracted great attention due to large output pulse energy and femtosecond pulse duration. Here we accurately characterized the timing jitter of normal-dispersion fiber lasers using a balanced cross-correlation method. The timing jitter characterization experiments show that the timing jitter of normal-dispersion mode-locked fiber lasers can be significantly reduced by using narrow band-pass filtering (e.g., 7-nm bandwidth filtering in this work). We further identify that the timing jitter of the fiber laser is confined in a limited range, which is almost independent of cavity dispersion map due to the amplifier-similariton formation by insertion of the narrow bandpass filter. The lowest observed timing jitter reaches 0.57 fs (rms) integrated from 10 kHz to 10 MHz Fourier frequency. The rms relative intensity noise (RIN) is also reduced from 0.37% to 0.02% (integrated from 1 kHz to 5 MHz Fourier frequency) by the insertion of narrow band-pass filter.

  4. Robust detection of heart beats in multimodal records using slope- and peak-sensitive band-pass filters.

    PubMed

    Pangerc, Urška; Jager, Franc

    2015-08-01

    In this work, we present the development, architecture and evaluation of a new and robust heart beat detector in multimodal records. The detector uses electrocardiogram (ECG) signals, and/or pulsatile (P) signals, such as: blood pressure, artery blood pressure and pulmonary artery pressure, if present. The base approach behind the architecture of the detector is collecting signal energy (differentiating and low-pass filtering, squaring, integrating). To calculate the detection and noise functions, simple and fast slope- and peak-sensitive band-pass digital filters were designed. By using morphological smoothing, the detection functions were further improved and noise intervals were estimated. The detector looks for possible pacemaker heart rate patterns and repairs the ECG signals and detection functions. Heart beats are detected in each of the ECG and P signals in two steps: a repetitive learning phase and a follow-up detecting phase. The detected heart beat positions from the ECG signals are merged into a single stream of detected ECG heart beat positions. The merged ECG heart beat positions and detected heart beat positions from the P signals are verified for their regularity regarding the expected heart rate. The detected heart beat positions of a P signal with the best match to the merged ECG heart beat positions are selected for mapping into the noise and no-signal intervals of the record. The overall evaluation scores in terms of average sensitivity and positive predictive values obtained on databases that are freely available on the Physionet website were as follows: the MIT-BIH Arrhythmia database (99.91%), the MGH/MF Waveform database (95.14%), the augmented training set of the follow-up phase of the PhysioNet/Computing in Cardiology Challenge 2014 (97.67%), and the Challenge test set (93.64%).

  5. Terahertz modulation using a bandpass filter combined with a graphene supercapacitor

    NASA Astrophysics Data System (ADS)

    Takan, Taylan; Nebioglu, Mehmet A.; Kakenov, Nurbek; Balci, Osman; Kocabas, Coskun; Altan, Hakan

    2015-10-01

    Graphene is proving to be an efficient medium for the control of mm-wave/THz radiation. Its electrical and dielectric properties allows it to be incorporated into various existing device architectures. One such application is in the modulation of the amplitude of the propagating THz radiation. Due to its electrical properties this interaction is typically broadband in nature. To make this frequency selective we propose the use of metamaterials or frequency selective surfaces. Generally, these structures perform the frequency filtering by modifying the propagation of the input wave with respect to changing structural parameters of the device itself. By fabricating a frequency selective surface based on a periodic circular hole array on an aluminum sheet we show that the transmission of a narrow band of THz radiation can be modulated when the sheet is combined with a highly efficient graphene based supercapacitor device. The modulation depth of the device was 15% in the frequency region of interest. The simple structure of the device coupled with the obtained performance shows that graphene based devices have great potential for the development of THz technologies.

  6. Insertion loss and noise-temperature contribution of high-temperature superconducting bandpass filters centered at 2.3 and 8.45 GHz

    NASA Technical Reports Server (NTRS)

    Prater, J. L.; Bautista, J. J.

    1993-01-01

    Two superconducting Tl-Ca-Cu-Ba-O bandpass filters were fabricated for JPL by Superconductor Technologies Incorporated, Santa Barbara, California. The filters were designed to operate at 2.3 GHz (S-band) with a 0.5-dB bandwidth of 60 MHz and at 8.45 GHz (X-band) with a 0.5-dB bandwidth of 150 MHz. The structure selected for both filters incorporates half-wavelength thin-film resonators in a stripline configuration. The S-band filter uses an edge-coupled interdigital design and the X-band filter uses an end-coupled design. The insertion loss and the noise-temperature contribution were measured at 12 K for both filters.

  7. SEMICONDUCTOR INTEGRATED CIRCUITS: An asymmetric MOSFET-C band-pass filter with on-chip charge pump auto-tuning

    NASA Astrophysics Data System (ADS)

    Fangxiong, Chen; Min, Lin; Heping, Ma; Hailong, Jia; Yin, Shi; Forster, Dai

    2009-08-01

    An asymmetric MOSFET-C band-pass filter (BPF) with on chip charge pump auto-tuning is presented. It is implemented in UMC (United Manufacturing Corporation) 0.18 μm CMOS process technology. The filter system with auto-tuning uses a master-slave technique for continuous tuning in which the charge pump outputs 2.663 V, much higher than the power supply voltage, to improve the linearity of the filter. The main filter with third order low-pass and second order high-pass properties is an asymmetric band-pass filter with bandwidth of 2.730-5.340 MHz. The in-band third order harmonic input intercept point (IIP3) is 16.621 dBm, with 50 Ω as the source impedance. The input referred noise is about 47.455 μVrms. The main filter dissipates 3.528 mW while the auto-tuning system dissipates 2.412 mW from a 1.8 V power supply. The filter with the auto-tuning system occupies 0.592 mm2 and it can be utilized in GPS (global positioning system) and Bluetooth systems.

  8. A Triple-band Bandpass Filter using Tri-section Step-impedance and Capacitively Loaded Step-impedance Resonators for GSM, WiMAX, and WLAN systems

    NASA Astrophysics Data System (ADS)

    Chomtong, P.; Akkaraekthalin, P.

    2014-05-01

    This paper presents a triple-band bandpass filter for applications of GSM, WiMAX, and WLAN systems. The proposed filter comprises of the tri-section step-impedance and capacitively loaded step-impedance resonators, which are combined using the cross coupling technique. Additionally, tapered lines are used to connect at both ports of the filter in order to enhance matching for the tri-band resonant frequencies. The filter can operate at the resonant frequencies of 1.8 GHz, 3.7 GHz, and 5.5 GHz. At resonant frequencies, the measured values of S11 are -17.2 dB, -33.6 dB, and -17.9 dB, while the measured values of S21 are -2.23 dB, -2.98 dB, and -3.31 dB, respectively. Moreover, the presented filter has compact size compared with the conventional open-loop cross coupling triple band bandpass filters

  9. Biomedical bandpass filter for fluorescence microscopy imaging based on TiO2/SiO2 and TiO2/MgF2 dielectric multilayers

    NASA Astrophysics Data System (ADS)

    Butt, M. A.; Fomchenkov, S. A.; Ullah, A.; Verma, P.; Khonina, S. N.

    2016-08-01

    We report a design for creating a multilayer dielectric optical filters based on TiO2 and SiO2/MgF2 alternating layers. We have selected Titanium dioxide (TiO2) for high refractive index (2.5), Silicon dioxide (SiO2) and Magnesium fluoride (MgF2) as a low refractive index layer (1.45 & 1.37) respectively. Miniaturized visible spectrometers are useful for quick and mobile characterization of biological samples. Such devices can be fabricated by using Fabry-Perot (FP) filters consisting of two highly reflecting mirrors with a central cavity in between. Distributed Bragg Reflectors (DBRs) consisting of alternating high and low refractive index material pairs are the most commonly used mirrors in FP filters, due to their high reflectivity. However, DBRs have high reflectivity for a selected range of wavelengths known as the stopband of the DBR. This range is usually much smaller than the sensitivity range of the spectrometer range. Therefore a bandpass filters are required to restrict wavelength outside the stopband of the FP DBRs. The proposed filter shows a high quality with average transmission of 97.4% within the passbands and the transmission outside the passband is around 4%. Special attention has been given to keep the thickness of the filters within the economic limits. It can be suggested that these filters are exceptional choice for florescence imaging and Endoscope narrow band imaging.

  10. Group delay and chromatic dispersion of thin-film-based, narrow bandpass filters used in dense wavelength-division-multiplexed systems.

    PubMed

    Zhang, Keqi; Wang, Jue; Schwendeman, Erik; Dawson-Elli, David; Faber, Ralf; Sharps, Robert

    2002-06-01

    Theoretical analysis is made for thin-film-based, 200- and 100-GHz narrow bandpass filters with respect to the intensity response as well as to the chromatic dispersion. The results indicate that the narrower the passband, the higher the chromatic dispersion. The maximum chromatic dispersion appears at the edges of the 0.5-dB passband, owing to the fast change of the group delay in the region. The deviation of chromatic dispersion induced by manufacturing error is simulated. Effective-medium approximation layers are added to simulate the contribution of surface roughness and the mixture interfaces to the passband ripple as well as the chromatic dispersion. The simulations are compared with the experimental results. The measured chromatic dispersion matches the general trend of the theoretical calculation. The imperfect surface and layer mismatch induce additional ripples across the 0.5-dB passband. The maximum chromatic dispersion within a 0.5-dB passband is 20.7 and 54.9 ps/nm for 200- and 100-GHZ narrow bandpass filters, respectively.

  11. Improved flatness and tunable bandwidth of the supercontinuum generation in all-normal dispersion-flattened PCF using Littman-Metcalf optical bandpass filter

    NASA Astrophysics Data System (ADS)

    Jing, Qi; zhang, Xia; Ma, Huifang; Huang, Yongqing; Ren, Xiaomin

    2012-09-01

    We have proved that in an all-normal dispersion-flattened photonic crystal fiber (PCF), the four-wave mixing (FWM) process dominantly affects the flatness of the generated supercontinuum (SC). The numerical results show that pulses with steepened edges can enhance the FWM conversion efficiency during the SC's generation and the minima of the spectral oscillatory structure will be smoothed. A double-pass Littman-Metcalf optical bandpass filter is used to make the 1.60 ps hyperbolic-Secant shaped pulses obtain steepened edges. The experimental results show that the flatness of the SC generated from the 4 nm filtered pulses is improved by 0.21 dB. The SC with 10-65 nm tunable bandwidths is obtained by adjusting the filter bandwidth from 1 nm to 7 nm. Further numerical results show that the filter induced SC's flatness improvement is more effective for pulses with 2.0-4.0 ps FWHM. The improved SC can be used for applications which require stable modulation carriers and flexible bandwidth.

  12. Reactanceless synthesized impedance bandpass amplifier

    NASA Technical Reports Server (NTRS)

    Kleinberg, L. L. (Inventor)

    1985-01-01

    An active R bandpass filter network is formed by four operational amplifier stages interconnected by discrete resistances. One pair of stages synthesize an equivalent input impedance of an inductance (L sub eq) in parallel with a discrete resistance (R sub o) while the second pair of stages synthesizes an equivalent input impedance of a capacitance (C sub eq) serially coupled to another discrete resistance (R sub i) coupled in parallel with the first two stages. The equivalent input impedances aggregately define a tuned resonant bandpass filter in the roll-off regions of the operational amplifiers.

  13. Ultra-Compact Broadband High-Spurious Suppression Bandpass Filter Using Double Split-end Stepped Impedance Resonators

    NASA Technical Reports Server (NTRS)

    U-Yen, Kongpop; Wollack, Ed; Papapolymerou, John; Laskar, Joy

    2005-01-01

    We propose an ultra compact single-layer spurious suppression band pass filter design which has the following benefit: 1) Effective coupling area can be increased with no fabrication limitation and no effect on the spurious response; 2) Two fundamental poles are introduced to suppress spurs; 3) Filter can be designed with up to 30% bandwidth; 4) The Filter length is reduced by at least 100% when compared to the conventional filter; 5) Spurious modes are suppressed up to at the seven times the fundamental frequency; and 6) It uses only one layer of metallization which minimize the fabrication cost.

  14. Fibre coupled micro-light emitting diode array light source with integrated band-pass filter for fluorescence detection in miniaturised analytical systems.

    PubMed

    Vaculovičová, Markéta; Akther, Mahbub; Maaskant, Pleun; Brabazon, Dermot; Macka, Mirek

    2015-04-29

    In this work, a new type of miniaturized fibre-coupled solid-state light source is demonstrated as an excitation source for fluorescence detection in capillary electrophoresis. It is based on a parabolically shaped micro-light emitting diode (μ-LED) array with a custom band-pass optical interference filter (IF) deposited at the back of the LED substrate. The GaN μ-LED array consisted of 270 individual μ-LED elements with a peak emission at 470 nm, each about 14 μm in diameter and operated as a single unit. Light was extracted through the transparent substrate material, and coupled to an optical fibre (OF, 400 μm in diameter, numerical aperture NA=0.37), to form an integrated μ-LED-IF-OF light source component. This packaged μ-LED-IF-OF light source emitted approximately 225 μW of optical power at a bias current of 20 mA. The bandpass IF filter was designed to reduce undesirable LED light emissions in the wavelength range above 490 nm. Devices with and without IF were compared in terms of the optical power output, spectral characteristics as well as LOD values. While the IF consisted of only 7.5 pairs (15 layers) of SiO2/HfO2 layers, it resulted in an improvement of the baseline noise as well as the detection limit measured using fluorescein as test analyte, both by approximately one order of magnitude, with a LOD of 1×10(-8) mol L(-1) obtained under optimised conditions. The μ-LED-IF-OF light source was then demonstrated for use in capillary electrophoresis with fluorimetric detection. The limits of detection obtained by this device were compared to those obtained with a commercial fibre coupled LED device.

  15. Effect of Selectively Etched Ferroelectric Thin-Film Layer on the Performance of a Tunable Bandpass Filter

    NASA Technical Reports Server (NTRS)

    Subramanyam, Guru; Vignesparamoorthy, Sivaruban; Mueller, Carl; VanKeuls, Fred; Warner, Joseph; Miranda, Felix A.

    2001-01-01

    The main purpose of this work is to study the effect of a selectively etched ferroelectric thin film layer on the performance of an electrically tunable filter. An X-band tunable filter was designed, fabricated and tested on a selectively etched Barium Strontium Titanate (BSTO) ferroelectric thin film layer. Tunable filters with varying lengths of BSTO thin-film in the input and output coupling gaps were modeled, as well as experimentally tested. Experimental results showed that filters with coupling gaps partially filled with BSTO maintained frequency tunability and improved the insertion loss by approx. 2dB. To the best of our knowledge, these results represent the first experimental demonstration of the advantages of selective etching in the performance of thin film ferroelectric-based tunable microwave components.

  16. A 4th-order band-pass filter using differential readout of two in-phase actuated contour-mode resonators

    NASA Astrophysics Data System (ADS)

    Yagubizade, Hadi; Darvishi, Milad; Elwenspoek, Miko C.; Tas, Niels R.

    2013-10-01

    A 4th-order band-pass filter (BPF) based on the subtraction of two 2nd-order contour-mode Lamb-wave resonators is presented. The resonators have slightly different resonance frequencies around 380 MHz. Each resonator consists of a 500 nm pulsed-laser deposited lead zirconate titanate (PZT) thin-film on top of a 3 μm silicon (PZT-on-Si). The resonators are actuated in-phase, and their outputs are subtracted. Utilizing this technique, the feed-through signals are eliminated while the outputs of the resonators are added up constructively, due to the phase difference between the two output signals. The BPF is presented using 50 Ω termination with a bandwidth of approximately 3.9 MHz and 43 dB stopband rejection. This technique provides further opportunities for MEMS filter design in addition to existing methods, i.e., mechanical and/or electrical coupling. It also resolves the design issue associated with high feed-through when exploiting piezoelectric materials with high-dielectric constant like PZT.

  17. Compact Ultra Wide Band Microstrip Bandpass Filter Based on Multiple-Mode Resonator and Modified Complementary Split Ring Resonator

    PubMed Central

    Marcotegui, J. Antonio; Illescas, Jesús Miguel; Estevez, Aritz

    2013-01-01

    A new class of broadband microstrip filters for Ultra Wide Band (UWB) applications is proposed. In the design, different stages of parallel-coupled microstrip line and other stages with a Modified Complementary Split Ring Resonator (MCSRR)—a concept proposed here for the first time—are adjusted to obtain the desired response with broadband, sharp rejection, low insertion loss, and low return loss. Full wave simulation results as well as measurement results from fabricated prototypes are presented, showing good agreement. The proposed technique offers a new alternative to implement low-cost high-performance filter devices, applicable to a wide range of communication systems. PMID:24319366

  18. Compact ultra wide band microstrip bandpass filter based on multiple-mode resonator and modified complementary split ring resonator.

    PubMed

    Marcotegui, J Antonio; Illescas, Jesús Miguel; Estevez, Aritz; Falcone, Francisco

    2013-01-01

    A new class of broadband microstrip filters for Ultra Wide Band (UWB) applications is proposed. In the design, different stages of parallel-coupled microstrip line and other stages with a Modified Complementary Split Ring Resonator (MCSRR)-a concept proposed here for the first time-are adjusted to obtain the desired response with broadband, sharp rejection, low insertion loss, and low return loss. Full wave simulation results as well as measurement results from fabricated prototypes are presented, showing good agreement. The proposed technique offers a new alternative to implement low-cost high-performance filter devices, applicable to a wide range of communication systems.

  19. Linear absorption coefficient of beryllium in the 50-300-A wavelength range. [bandpass filter materials for ultraviolet astronomy instrumentation

    NASA Technical Reports Server (NTRS)

    Barstow, M. A.; Lewis, M.; Petre, R.

    1983-01-01

    Transmittances of thin-film filters fabricated for an extreme-UV astronomy sounding-rocket experiment yield values for the linear absorption coefficient of beryllium in the 50-300-A wavelength range, in which previous measurements are sparse. The inferred values are consistent with the lowest data previously published and may have important consequences for extreme-UV astronomers.

  20. Chromatic dispersion and polarization mode dispersion insensitive optical signal to noise ratio monitoring based on electronic variable optical attenuators and optical bandpass filter

    NASA Astrophysics Data System (ADS)

    Chang, Junde; Liu, Bo; Zhang, Lijia; Xin, Xiangjun; Zhang, Qi; Tian, Qinghua; Tian, Feng; Yin, Xiaoli; Rao, Lan; Wang, Yongjun

    2016-10-01

    In this paper, an optical signal to noise ratio (OSNR) monitoring method based on radio frequency (RF) power of two signals in parallel connection. The test optical signal was split equally into two signals in parallel connection. One removed out-of-band noise by optical bandpass filter, the other kept output power constant by electronic variable optical attenuators (EVOA) with power-locking control loop. One radio frequency power of the two signals treated by different ways increased with the increase of OSNR when the two signals are at the same place. The other decreased. The difference of radio frequency power of the two signals at the same place was used to monitor OSNR. The simulation results showed that the proposed technique can implement OSNR monitoring between 2dB and 30dB for 40Gb/s NRZDQPSK optical signal. Monitoring error was within 1.5dB and the proposed technique was insensitive to chromatic dispersion (CD) and polarization mode dispersion (PMD).

  1. Intensive Plasmonic Flash Light Sintering of Copper Nanoinks Using a Band-Pass Light Filter for Highly Electrically Conductive Electrodes in Printed Electronics.

    PubMed

    Hwang, Yeon-Taek; Chung, Wan-Ho; Jang, Yong-Rae; Kim, Hak-Sung

    2016-04-06

    In this work, an intensive plasmonic flash light sintering technique was developed by using a band-pass light filter matching the plasmonic wavelength of the copper nanoparticles. The sintering characteristics, such as resistivity and microstructure, of the copper nanoink films were studied as a function of the range of the wavelength employed in the flash white light sintering. The flash white light irradiation conditions (e.g., wavelength range, irradiation energy, pulse number, on-time, and off-time) were optimized to obtain a high conductivity of the copper nanoink films without causing damage to the polyimide substrate. The wavelength range corresponding to the plasmonic wavelength of the copper nanoparticles could efficiently sinter the copper nanoink and enhance its conductivity. Ultimately, the sintered copper nanoink films under optimal light sintering conditions showed the lowest resistivity (6.97 μΩ·cm), which was only 4.1 times higher than that of bulk copper films (1.68 μΩ·cm).

  2. NOVEL MICROWAVE FILTER DESIGN TECHNIQUES.

    DTIC Science & Technology

    ELECTROMAGNETIC WAVE FILTERS, MICROWAVE FREQUENCY, PHASE SHIFT CIRCUITS, BANDPASS FILTERS, TUNED CIRCUITS, NETWORKS, IMPEDANCE MATCHING , LOW PASS FILTERS, MULTIPLEXING, MICROWAVE EQUIPMENT, WAVEGUIDE FILTERS, WAVEGUIDE COUPLERS.

  3. Effect of RF Filtering on the Performance of Uncoded PCM/PM Telemetry Channels

    NASA Technical Reports Server (NTRS)

    Koerner, M. A.

    1984-01-01

    A method for calculating the increase in received telemetry signal power required to compensate for the use of a radio frequency interference (RFI) filter in front of the DSN receiving system low-noise amplifier is described. The telemetry system for which the degradation is calculated is an uncoded PCM/PM system in which the NRZ data directly modulates the carrier at a modulation level which leaves a discrete carrier. A phase-locked loop in the RF receiver tracks the discrete carrier and coherently demodulates the PCM data. The RFI filter may be a series of Butterworth, Tchebychev, or Bessel low-pass, high-pass, band-pass, or band-reject filters, each with arbitrary bandwidth, number of poles, and, for band-pass or band-reject filters, resonant frequency. The only restriction is that the RFI filter must have only simple poles. Numerical results are presented for the RFI filters the DSN plans to place in front of the S-band FET, S-band maser, and X-band maser low noise amplifiers. The main conclusion is that the filters will produce negligible degradation at data rates below 4 Mbps.

  4. The effect of spatial-frequency filtering on the visual processing of global structure.

    PubMed

    Sierra-Vázquez, Vicente; Serrano-Pedraza, Ignacio; Luna, Dolores

    2006-01-01

    In three experiments we measured reaction times (RTs) and error rates in identifying the global structure of spatially filtered stimuli whose spatial-frequency content was selected by means of three types of 2-D isotropic filters (Butterworth of order 2, Butterworth of order 10, and a filters with total or partial Gaussian spectral profile). In each experiment, low-pass (LP), bandpass (BP), and high-pass (HP) filtered stimuli, with nine centre or cut-off spatial frequencies, were used. Irrespective of the type of filter, the experimental results showed that: (a) RTs to stimuli with low spatial frequencies were shorter than those to stimuli with medium or high spatial frequencies, (b) RTs to LP filtered stimuli were nearly constant, but they increased in a nonmonotonic way with the filter centre spatial frequency in BP filtered stimuli and with the filter cut-off frequency in HP filtered stimuli, and (c) the identification of the global pattern occurred with all visible stimuli used, including BP and HP images without low spatial frequencies. To remove the possible influence of the energy, a fourth experiment was conducted with Gaussian filtered stimuli of equal contrast power (c(rms) = 0.065). Similar results to those described above were found for stimuli with spatial-frequency content higher than 2 cycles deg(-1). A model of isotropic first-order visual channels collecting the stimulus spectral energy in all orientations explains the RT data. A subsequent second-order nonlinear amplitude demodulation process, applied to the output of the most energetic first-order channel, could explain the perception of global structure of each spatially filtered stimulus, including images lacking low spatial frequencies.

  5. Study of a mode-locked erbium-doped frequency-shifted-feedback fiber laser incorporating a broad bandpass filter: Experimental results

    NASA Astrophysics Data System (ADS)

    Vazquez-Zuniga, Luis Alonso; Jeong, Yoonchan

    2013-10-01

    We present rigorous experimental studies on the spectral and temporal behaviors of an erbium-doped frequency-shifted-feedback fiber laser (FSFL), with respect to various parameters of the laser cavity, including the direction of the frequency-shift mechanism, the quantity of frequency-shift, and the output coupling ratio (OCR) of the cavity. We show that if the filter bandwidth is much broader than the laser linewidth, the laser spectrum tends to split and form a secondary spectral band (SSB) on the shorter or longer wavelength side of the primary spectrum, depending on whether the direction of the frequency-shift mechanism is upward or downward, respectively. We found that the SSB forms a parasitic pulse with much lower peak power traveling on the leading or trailing edge of the primary pulse, which leads to a significant asymmetry in the whole pulse formation in the time domain.

  6. Measurements of SO2 Degassing from Popocatépetl Volcano by an Ultraviolet Camera and a Set of Different Bandpass Filters.

    NASA Astrophysics Data System (ADS)

    Schiavo, B.; Stremme, W.; Grutter, M.; Campion, R.; Rivera, C. I.; Inguaggiato, S.

    2016-12-01

    The importance of monitoring and the time series of volcanic gas emissions is described and proven by many scientific studies. A time series of the Popocatépetl volcano will allow us to detect the volcanic gas as well as anomalies in volcanic processes and help to estimate the total emission flux of SO2 to improve our understanding of the atmospheric composition and balance. Monitoring of the activity of the Popocatépetl volcano is even more important because of the population in the closest proximity around the volcano and due its location of only 50 km south east of Mexico City and its airport. The images captured with the camera require a correction for different optical and environmental effects. In the contribution we present an SO2 camera system based on a Quantum Scientific Imaging (QSI) UV camara with automatic filterwheel, and describe how the main instrumental properties of the optical system can be characterized. Dark current, vignetting and filter characterization represent the instrumental part of a proper image correction, which is fairly constant and independent of the ambient conditions. However, other effects like "flattening" and the simplification of the radiative transfer dependence on environmental conditions need to be corrected as well to reduce the errors in the results. Images of volcanic SO2 plumes from the active Popocatépetl volcano in Mexico are presented, showing persistent passive degassing. The measurment are taken from the Altzomoni Atmospheric Observatory (19.12N, -98.65W, 3,985 m.a.s.l.), which forms part of the RUOA (www.ruoa.unam.mx) and NDACC (https://www2.acom.ucar.edu/irwg) networks. It is located north of the crater at 11 km distance. The data to calculate SO2 slant column densities (molec/cm2 or ppm*m) were recorded with the QSI UV camera and processed using Python scripts.

  7. Ideal bandpasses for type Ia supernova cosmology

    SciTech Connect

    Davis, Tamara M.; Schmidt, Brian P.; Kim, Alex G.

    2005-10-24

    To use type Ia supernovae as standard candles for cosmologywe need accurate broadband magnitudes. In practice the observed magnitudemay differ from the ideal magnitude-redshift relationship either throughintrinsic inhomogeneities in the type Ia supernova population or throughobservational error. Here we investigate how we can choose filterbandpasses to reduce the error caused by both these effects. We find thatbandpasses with large integral fluxes and sloping wings are best able tominimise several sources of observational error, and are also leastsensitive to intrinsic differences in type Ia supernovae. The mostimportant feature of a complete filter set for type Ia supernovacosmology is that each bandpass be a redshifted copy of the first. Wedesign practical sets of redshifted bandpasses that are matched totypical high resistivity CCD and HgCdTe infra-red detector sensitivities.These are designed to minimise systematic error in well observedsupernovae, final designs for specific missions should also considersignal-to-noise requirements and observing strategy. In addition wecalculate how accurately filters need to be calibrated in order toachieve the required photometric accuracy of future supernova cosmologyexperiments such as the SuperNova-Acceleration-Probe (SNAP), which is onepossible realisation of the Joint Dark-Energy mission (JDEM). We considerthe effect of possible periodic miscalibrations that may arise from theconstruction of an interference filter.

  8. 46 CFR 35.30-10 - Cargo tank hatches, ullage holes, and Butterworth plates-TB/ALL.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 1 2010-10-01 2010-10-01 false Cargo tank hatches, ullage holes, and Butterworth plates... OPERATIONS General Safety Rules § 35.30-10 Cargo tank hatches, ullage holes, and Butterworth plates—TB/ALL. No cargo tank hatches, ullage holes, or Butterworth plates shall be opened or shall remain open...

  9. 46 CFR 35.30-10 - Cargo tank hatches, ullage holes, and Butterworth plates-TB/ALL.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 1 2013-10-01 2013-10-01 false Cargo tank hatches, ullage holes, and Butterworth plates... OPERATIONS General Safety Rules § 35.30-10 Cargo tank hatches, ullage holes, and Butterworth plates—TB/ALL. No cargo tank hatches, ullage holes, or Butterworth plates shall be opened or shall remain open...

  10. 46 CFR 35.30-10 - Cargo tank hatches, ullage holes, and Butterworth plates-TB/ALL.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 1 2012-10-01 2012-10-01 false Cargo tank hatches, ullage holes, and Butterworth plates... OPERATIONS General Safety Rules § 35.30-10 Cargo tank hatches, ullage holes, and Butterworth plates—TB/ALL. No cargo tank hatches, ullage holes, or Butterworth plates shall be opened or shall remain open...

  11. 46 CFR 35.30-10 - Cargo tank hatches, ullage holes, and Butterworth plates-TB/ALL.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 1 2014-10-01 2014-10-01 false Cargo tank hatches, ullage holes, and Butterworth plates... OPERATIONS General Safety Rules § 35.30-10 Cargo tank hatches, ullage holes, and Butterworth plates—TB/ALL. No cargo tank hatches, ullage holes, or Butterworth plates shall be opened or shall remain open...

  12. 46 CFR 35.30-10 - Cargo tank hatches, ullage holes, and Butterworth plates-TB/ALL.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 1 2011-10-01 2011-10-01 false Cargo tank hatches, ullage holes, and Butterworth plates... OPERATIONS General Safety Rules § 35.30-10 Cargo tank hatches, ullage holes, and Butterworth plates—TB/ALL. No cargo tank hatches, ullage holes, or Butterworth plates shall be opened or shall remain open...

  13. Filter Design and Performance Evaluation for Fingerprint Image Segmentation.

    PubMed

    Thai, Duy Hoang; Huckemann, Stephan; Gottschlich, Carsten

    2016-01-01

    Fingerprint recognition plays an important role in many commercial applications and is used by millions of people every day, e.g. for unlocking mobile phones. Fingerprint image segmentation is typically the first processing step of most fingerprint algorithms and it divides an image into foreground, the region of interest, and background. Two types of error can occur during this step which both have a negative impact on the recognition performance: 'true' foreground can be labeled as background and features like minutiae can be lost, or conversely 'true' background can be misclassified as foreground and spurious features can be introduced. The contribution of this paper is threefold: firstly, we propose a novel factorized directional bandpass (FDB) segmentation method for texture extraction based on the directional Hilbert transform of a Butterworth bandpass (DHBB) filter interwoven with soft-thresholding. Secondly, we provide a manually marked ground truth segmentation for 10560 images as an evaluation benchmark. Thirdly, we conduct a systematic performance comparison between the FDB method and four of the most often cited fingerprint segmentation algorithms showing that the FDB segmentation method clearly outperforms these four widely used methods. The benchmark and the implementation of the FDB method are made publicly available.

  14. Filter Design and Performance Evaluation for Fingerprint Image Segmentation

    PubMed Central

    Thai, Duy Hoang; Huckemann, Stephan; Gottschlich, Carsten

    2016-01-01

    Fingerprint recognition plays an important role in many commercial applications and is used by millions of people every day, e.g. for unlocking mobile phones. Fingerprint image segmentation is typically the first processing step of most fingerprint algorithms and it divides an image into foreground, the region of interest, and background. Two types of error can occur during this step which both have a negative impact on the recognition performance: ‘true’ foreground can be labeled as background and features like minutiae can be lost, or conversely ‘true’ background can be misclassified as foreground and spurious features can be introduced. The contribution of this paper is threefold: firstly, we propose a novel factorized directional bandpass (FDB) segmentation method for texture extraction based on the directional Hilbert transform of a Butterworth bandpass (DHBB) filter interwoven with soft-thresholding. Secondly, we provide a manually marked ground truth segmentation for 10560 images as an evaluation benchmark. Thirdly, we conduct a systematic performance comparison between the FDB method and four of the most often cited fingerprint segmentation algorithms showing that the FDB segmentation method clearly outperforms these four widely used methods. The benchmark and the implementation of the FDB method are made publicly available. PMID:27171150

  15. Design and experimental characterization of a bandpass sampling receiver

    NASA Astrophysics Data System (ADS)

    Singh, Avantika; Kumar, Devika S.; Venkateswaran, Gomathy; Manjukrishna, S.; Singh, Amrendra Kumar; Kurup, Dhanesh G.

    2016-03-01

    In this paper, we present a robust and efficient approach for deigning reconfigurable Radio receivers based on Bandpass sampling. The direct sampled RF frontend is followed by signal processing blocks implemented on an FPGA and consists of a PLL based on second order Costas technique and a Kaiser windowing based lowpass filtering. The proposed method can be used for implementing a cost effective multi-channel receiver for data, audio, video etc. over various channels.

  16. Bandpass x-ray diode and x-ray multiplier detector

    DOEpatents

    Wang, C.L.

    1982-09-27

    An absorption-edge of an x-ray absorption filter and a quantum jump of a photocathode determine the bandpass characteristics of an x-ray diode detector. An anode, which collects the photoelectrons emitted by the photocathode, has enhanced amplification provided by photoelectron-multiplying means which include dynodes or a microchannel-plate electron-multiplier. Suppression of undesired high frequency response for a bandpass x-ray diode is provided by subtracting a signal representative of energies above the passband from a signal representative of the overall response of the bandpass diode.

  17. Band-pass processing in a GPCR signaling pathway selects for NFAT transcription factor activation.

    PubMed

    Sumit, M; Neubig, R R; Takayama, S; Linderman, J J

    2015-11-01

    Many biological processes are rhythmic and proper timing is increasingly appreciated as being critical for development and maintenance of physiological functions. To understand how temporal modulation of an input signal influences downstream responses, we employ microfluidic pulsatile stimulation of a G-protein coupled receptor, the muscarinic M3 receptor, in single cells with simultaneous real-time imaging of both intracellular calcium and NFAT nuclear localization. Interestingly, we find that reduced stimulation with pulses of ligand can give more efficient transcription factor activation, if stimuli are timed appropriately. Our experiments and computational analyses show that M3 receptor-induced calcium oscillations form a low pass filter while calcium-induced NFAT translocation forms a high pass filter. The combination acts as a band-pass filter optimized for intermediate frequencies of stimulation. We demonstrate that receptor desensitization and NFAT translocation rates determine critical features of the band-pass filter and that the band-pass may be shifted for different receptors or NFAT dynamics. As an example, we show that the two NFAT isoforms (NFAT4 and NFAT1) have shifted band-pass windows for the same receptor. While we focus specifically on the M3 muscarinic receptor and NFAT translocation, band-pass processing is expected to be a general theme that applies to multiple signaling pathways.

  18. On sampling band-pass signals

    NASA Technical Reports Server (NTRS)

    Sadr, R.; Shahshahani, M.

    1989-01-01

    Four techniques for uniform sampling of band-bass signals are examined. The in-phase and quadrature components of the band-pass signal are computed in terms of the samples of the original band-pass signal. The relative implementation merits of these techniques are discussed with reference to the Deep Space Network (DSN).

  19. Local fringe density determination by adaptive filtering.

    PubMed

    Vargas, J; Quiroga, J Antonio; Belenguer, T

    2011-01-01

    We demonstrate a method to easily and quickly determine the local fringe density map of a fringe pattern. The method is based on an isotropic adaptive bandpass filter that is tuned at different frequencies. The modulation map after applying a specific bandpass frequencies filter presents a maximum response in the regions where the bandpass filter and fringe frequencies coincide. We show a set of simulations and experimental results that prove the effectiveness of the proposed method.

  20. Michelson interferometer based interleaver design using classic IIR filter decomposition.

    PubMed

    Cheng, Chi-Hao; Tang, Shasha

    2013-12-16

    An elegant method to design a Michelson interferometer based interleaver using a classic infinite impulse response (IIR) filter such as Butterworth, Chebyshev, and elliptic filters as a starting point are presented. The proposed design method allows engineers to design a Michelson interferometer based interleaver from specifications seamlessly. Simulation results are presented to demonstrate the validity of the proposed design method.

  1. Photonic crystal fiber π-phase-shifted long-period gratings with wide bandpass and temperature insensitivity

    NASA Astrophysics Data System (ADS)

    Zheng, Shijie; Zhu, Yinian

    2015-11-01

    In order to solve for the mode intensity distributions in a photonic crystal fiber (PCF) cross section and the propagation constant for the design of fiber bandpass filters, we numerically analyze the modal distributions of the fundamental core mode and different cladding modes. Based on the simulation results, we also experimentally demonstrate a simple fabrication of bandpass filters inscribed on the PCF by inserting a π-phase shift in a 12-period long-period grating (LPG). Two rejection bands with greater than 18 dB isolation and an ultra-wide band of 85.3 nm are achieved. The phase-shifted PCF-LPGs are fabricated using a CO2 laser with point-by-point focused pulses. The proposed fiber bandpass filter is compact and is not influenced by temperature effects.

  2. Science of Test Measurement Accuracy - Data Sampling and Filter Selection during Data Acquisition

    DTIC Science & Technology

    2015-06-01

    sampling rate, aliasing, filtering, butterworth, chebyshev, Bessel, PSD and Bode plots 16. SECURITY CLASSIFICATION OF: Unclassified 17. LIMITATION...and PSD plots . SCIENCE OF TEST Measurement Accuracy - Data Sampling and Filter Selection during Data Acquisition David Kidman Air...Use both Bode and PSD plots to evaluate filter and sample rate effects prior to implementation Summary Reference: The Scientist and Engineer’s

  3. DFB fiber laser hydrophone with band-pass response.

    PubMed

    Zhang, Faxiang; Zhang, Wentao; Li, Fang; Liu, Yuliang

    2011-11-15

    A distributed-feedback fiber laser hydrophone with band-pass response is presented. The design of the hydrophone aims to equalize static pressure and eliminate signal aliasing of high-frequency acoustic components. Theoretical analysis is presented based on electro-acoustic theory. The experimental results agree well with the theory. The measured underwater responses show that the hydrophone has a pressure sensitivity of -170 dB re:pm/μPa over a bandwidth between 100 Hz and 500 Hz. A sensitivity reduction exceeding -35 dB is observed at 2500 Hz. The tested static pressure sensitivity of the hydrophone is -226 dB. The proposed fiber laser hydrophone of this kind is expected to have important application in deep water fiber-optic sonar systems with anti-aliasing, and the understanding gained through this work can be extended to a guide of hydrophone design for required filtering bandwidth.

  4. Global sensitivity analysis of bandpass and antireflection coating manufacturing by numerical space filling designs.

    PubMed

    Vasseur, Olivier; Cathelinaud, Michel; Claeys-Bruno, Magalie; Sergent, Michelle

    2011-03-20

    We present the effectiveness of global sensitivity analyses of optical coatings manufacturing to assess the robustness of filters by computer experiments. The most critical interactions of layers are determined for a 29 quarter-wave layer bandpass filter and for an antireflection coating with eight non-quarter-wave layers. Two monitoring techniques with the associated production performances are considered, and their influence on the interactions classification is discussed. Global sensitivity analyses by numerical space filling designs give clues to improve filter manufacturing against error effects and to assess the potential robustness of the coatings.

  5. Multiple Band-Pass Autoregressive Demodulation for Rolling-Element Bearing Fault Diagnosis

    NASA Astrophysics Data System (ADS)

    Altmann, J.; Mathew, J.

    2001-09-01

    This paper presents a novel method to enhance the detection and diagnosis of low-speed rolling-element bearing faults based on discrete wavelet packet analysis (DWPA). The method involves the automatic extraction of wavelet packets containing bearing fault-related features from the discrete wavelet packet analysis representation of machine vibrations. Automated selection of the wavelet packets of interest is achieved via an adaptive network-based fuzzy inference system (ANFIS), which can be implemented on-line. The resultant signal extracted by this technique is essentially an optimal multiple band-pass filter of the high-frequency bearing impact transients. Used in conjunction with the autoregressive (AR) spectrum of the envelope signal, a sensitive diagnosis of the bearing condition can be made. The discrete wavelet packet analysis multiple band-pass filtering of the signal results in a significantly improved signal-to-noise ratio compared to its high-pass counterpart, with an exceptional capacity to exclude contaminating sources of vibration. A more modest increase in the signal-to-noise ratio is achieved when compared to digital band-pass filtering, with the filter range adjusted to obtain the best possible isolation of the bearing transients.

  6. Generalized Sampling Theorem for Bandpass Signals

    NASA Astrophysics Data System (ADS)

    Prokes, Ales

    2006-12-01

    The reconstruction of an unknown continuously defined function[InlineEquation not available: see fulltext.] from the samples of the responses of[InlineEquation not available: see fulltext.] linear time-invariant (LTI) systems sampled by the[InlineEquation not available: see fulltext.]th Nyquist rate is the aim of the generalized sampling. Papoulis (1977) provided an elegant solution for the case where[InlineEquation not available: see fulltext.] is a band-limited function with finite energy and the sampling rate is equal to[InlineEquation not available: see fulltext.] times cutoff frequency. In this paper, the scope of the Papoulis theory is extended to the case of bandpass signals. In the first part, a generalized sampling theorem (GST) for bandpass signals is presented. The second part deals with utilizing this theorem for signal recovery from nonuniform samples, and an efficient way of computing images of reconstructing functions for signal recovery is discussed.

  7. Tunable Filter Made From Three Coupled WGM Resonators

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy; Iltchenko, Vladimir; Maleki, Lute; Matsko, Andrey

    2006-01-01

    A tunable third-order band-pass optical filter has been constructed as an assembly of three coupled, tunable, whispering-gallery-mode resonators similar to the one described in Whispering-Gallery-Mode Tunable Narrow-Band-Pass Filter (NPO-30896), NASA Tech Briefs, Vol. 28, No. 4 (April 2004), page 5a. This filter offers a combination of four characteristics that are desirable for potential applications in photonics: (1) wide real-time tunability accompanied by a high-order filter function, (2) narrowness of the passband, (3) relatively low loss between input and output coupling optical fibers, and (4) a sparse spectrum. In contrast, prior tunable band-pass optical filters have exhibited, at most, two of these four characteristics. As described in several prior NASA Tech Briefs articles, a whispering-gallery-mode (WGM) resonator is a spheroidal, disklike, or toroidal body made of a highly transparent material. It is so named because it is designed to exploit whispering-gallery electromagnetic modes, which are waveguide modes that propagate circumferentially and are concentrated in a narrow toroidal region centered on the equatorial plane and located near the outermost edge. Figure 1 depicts the optical layout of the present filter comprising an assembly of three coupled, tunable WGM resonators. Each WGM resonator is made from a disk of Z-cut LiNbO3 of 3.3-mm diameter and 50-m thickness. The perimeter of the disk is polished and rounded to a radius of curvature of 40 microns. The free spectral range of each WGM resonator is about 13.3 GHz. Gold coats on the flat faces of the disk serve as electrodes for exploiting the electro-optical effect in LiNbO3 for tuning. There is no metal coat on the rounded perimeter region, where the whispering-gallery modes propagate. Light is coupled from an input optical fiber into the whispering-gallery-modes of the first WGM resonator by means of a diamond prism. Another diamond prism is used to couple light from the whispering

  8. FORTRAN IV Digital Filter Design Programs. Digital Systems Education Project.

    ERIC Educational Resources Information Center

    Reuss, E.; And Others

    The goals of the Digital Systems Education Project (DISE) include the development and distribution of educational/instructional materials in the digital systems area. Toward that end, this document contains three reports: (1) A FORTRAN IV Design Program for Low-Pass Butterworth and Chebychev Digital Filters; (2) A FORTRAN IV Design Program for…

  9. Superconducting bandpass delta-sigma modulator

    NASA Astrophysics Data System (ADS)

    Bulzacchelli, J. F.; Lee, H.-S.; Misewich, J. A.; Ketchen, M. B.

    1999-11-01

    Bandpass delta-sigma modulators digitize narrowband signals with high dynamic range and linearity. The required sampling rate is only a few times higher than the centre frequency of the input. This paper presents a superconducting bandpass delta-sigma modulator for direct analogue-to-digital conversion of RF signals in the GHz range. The input signal is capacitively coupled to one end of a microstrip transmission line, and a single flux quantum balanced comparator quantizes the current flowing out of the other end. Quantization noise is suppressed at the quarter-wave resonance of the transmission line (about 2 GHz in our design). Circuit performance at a 20 GHz sampling rate has been studied with several long JSIM simulations. Full-scale (FS) input sensitivity is 20 mV (rms), and in-band noise is -53 dBFS and -57 dBFS over bandwidths of 39 MHz and 19.5 MHz, respectively. In-band intermodulation distortion is better than -69 dBFS.

  10. OQPSK and MSK systems with bandlimiting filters in transmitter and receiver and various detector filters

    NASA Astrophysics Data System (ADS)

    Korn, I.

    1980-12-01

    Formulas are presented for the computation of error probability of OQPSK (Offset Quadrature Phase Shift Keying) and MSK (Minimum Shift Keying) with narrow band filters in transmitter and receiver and various detector filters (matched filter, sampling detector, rectangular filter and half-rectangular filter). Numerical results are computed for the case when the filters in transmitter and receiver are identical Butterworth filters. The error probability is presented as a function of signal/noise ratio or normalized filter bandwidth with the filter order as a parameter. It is concluded that with narrowband filters, MSK with a sampling detector or half-rectangular detector filter and OQPSK with a samping detector are the best systems.

  11. CMOS Bit-Stream Band-Pass Beamforming

    DTIC Science & Technology

    2016-03-31

    CMOS Bit-Stream Band-Pass Beamforming1 Michael P. Flynn and Jaehun Jeong Electrical Engineering and Computer Science University of Michigan Ann...M. P. Flynn , “An IF 8- Element 2-Beam Bit-Stream Band-Pass Beamformer," IEEE Radio Frequency Integrated Circuits Symposium (RFIC), June 2015. 2. M

  12. Subjective Well-Being In Later Life: 20 years after the Butterworths monograph series on individual and population aging.

    PubMed

    Stones, Michael; Kozma, Albert; McNeil, Kevin; Worobetz, Sarah

    2011-09-01

    This article discusses developments in theory and research on happiness two decades after publication of Psychological Well-Being in Later Life (Butterworths, 1991) by Albert Kozma, Michael Stones, and Kevin McNeil. Major empirical advances include new knowledge about contributions to happiness resulting from genetically related effects and personality. Personality traits have stronger relationships with happiness than was apparent 20 years ago and contribute to covariance between happiness and some of its predictors. Evolving emphases in research include the ways in which genetically related effects influence how people shape, and react to, their environment.

  13. Temperature Tunable Air-Gap Etalon Filter

    NASA Technical Reports Server (NTRS)

    Krainak, Michael A.; Stephen, Mark A.; Lunt, David L.

    1998-01-01

    We report on experimental measurements of a temperature tuned air-gap etalon filter. The filter exhibits temperature dependent wavelength tuning of 54 pm/C. It has a nominal center wavelength of 532 nm. The etalon filter has a 27 pm optical bandpass and 600 pm free spectral range (finesse approximately 22). The experimental results are in close agreement with etalon theory.

  14. Optimizing the performance of bandpass photon detectors for inverse photoemission: Transmission of alkaline earth fluoride window crystals

    SciTech Connect

    Thiede, Christian Schmidt, Anke B.; Donath, Markus

    2015-08-15

    Bandpass photon detectors are widely used in inverse photoemission in the isochromat mode at energies in the vacuum-ultraviolet spectral range. The energy bandpass of gas-filled counters is usually formed by the ionization threshold of the counting gas as high-pass filter and the transmission cutoff of an alkaline earth fluoride window as low-pass filter. The transmission characteristics of the window have, therefore, a crucial impact on the detector performance. We present transmission measurements in the vacuum-ultraviolet spectral range for alkaline earth fluoride window crystals in the vicinity of the transmission cutoff as a function of crystal purity, surface finish, surface contamination, temperature, and thickness. Our findings reveal that the transmission characteristics of the window crystal and, thus, the detector performance depend critically on these window parameters.

  15. Wide-angle narrow-bandpass optical detection system optimally designed to have a large signal-to-noise ratio

    NASA Astrophysics Data System (ADS)

    Schweitzer, Naftali; Arieli, Yoel

    2000-02-01

    A method for achieving optimal design of a wide-angle narrow-bandpass optical detection system composed of a spherical interference filter and a circular photodetector is introduced. It was found that there is an optimal photodetector diameter that maximizes the signal-to-noise ratio (SNR) for a given filter configuration. We show how to optimize optical detection systems based on spherical interference filters for all the important parameters simultaneously. The SNR values of these systems are compared with the SNR values of spherical-step-filter-based detection systems. When large silicon photodetectors are used, the two systems have equal SNR values so that the more economical step-filter systems are preferable. The results given here in the near-infrared region can be used for the optimization of any configuration of a detection system based on a spherical interference filter and a silicon photodetector working at the same wavelength range, without further calculations.

  16. Research on spectroscopic imaging. Volume 1: Technical discussion. [birefringent filters

    NASA Technical Reports Server (NTRS)

    Title, A.; Rosenberg, W.

    1979-01-01

    The principals of operation and the capabilities of birefringent filters systems are examined. Topics covered include: Lyot, Solc, and partial polarizer filters; transmission profile management; tuning birefringent filters; field of view; bandpass control; engineering considerations; and recommendations. Improvements for field of view effects, and the development of birefringent filters for spaceflight are discussed in appendices.

  17. Boron and silicon - Filters for the extreme ultraviolet

    NASA Technical Reports Server (NTRS)

    Labov, S.; Bowyer, S.; Steele, G.

    1985-01-01

    Thin films of boron and silicon have been developed using electron beam deposition. The transmissions of these filters were measured from soft X-ray wavelengths to the far ultraviolet and at optical wavelengths. The boron filter transmission peaks near 66 A and the silicon filter peaks near 136 A as expected on theoretical grounds, but the extreme ultraviolet bandpass is narrower than expected. The peak transmission of these filters does not change with time, but the width of the silicon filter bandpass is reduced slightly as the filter ages.

  18. Remote high temperature sensing with a reflective bandpass long-period fiber grating and a fiber ring laser

    NASA Astrophysics Data System (ADS)

    Hou, Yusong; Zhu, Tao; Shi, Leilei; Zhang, Qiang; Chiang, Kin Sing

    2013-09-01

    We demonstrate a remote high temperature fiber sensing system, where the sensing element is a long-period fiber grating (LPFG) fusion-spliced to a short section of a hollow-core fiber (HCF) and sensor interrogation is achieved with a fiber ring laser. The HCF turns the LPFG from a band-rejection filter into a reflective bandpass filter, while the ring laser selects the reflected wavelength from the LPFG sensor. Our experimental sensor shows a sensitivity of 0.095 nm °C-1 over the temperature range from 150 to 600 °C and the sensing distance is about 1 km.

  19. Active imaging system with Faraday filter

    DOEpatents

    Snyder, James J.

    1993-01-01

    An active imaging system has a low to medium powered laser transmitter and receiver wherein the receiver includes a Faraday filter with an ultranarrow optical bandpass and a bare (nonintensified) CCD camera. The laser is locked in the vicinity of the passband of the Faraday filter. The system has high sensitivity to the laser illumination while eliminating solar background.

  20. Active imaging system with Faraday filter

    DOEpatents

    Snyder, J.J.

    1993-04-13

    An active imaging system has a low to medium powered laser transmitter and receiver wherein the receiver includes a Faraday filter with an ultranarrow optical bandpass and a bare (nonintensified) CCD camera. The laser is locked in the vicinity of the passband of the Faraday filter. The system has high sensitivity to the laser illumination while eliminating solar background.

  1. The legacy of filter design and how that has extended into current choices for advanced astronomical filter

    NASA Astrophysics Data System (ADS)

    Hull, T.; Reichel, S.; Brauneck, U.; Naulin, V.; Marín-Franch, A.

    2016-07-01

    SCHOTT was one of the interference filters inventors starting around 1935. Based on this legacy optical bandpass filters were design, manufactured, and integrated into optical instruments in satellites. In addition a special blocking coating was developed reducing cross talk and ghost. For ground based telescopes steep-edge narrow bandpass filters with low transmitted wavefront error and about 100 mm x 100 mm size were manufactured pushing the filter design and the technology to its limits. The reached results for design and measurements will be shown on an H-alpha filter.

  2. Reliability of Three-Dimensional Linear Kinematics and Kinetics of Swimming Derived from Digitized Video at 25 and 50 Hz with 10 and 5 Frame Extensions to the 4th Order Butterworth Smoothing Window

    PubMed Central

    Sanders, Ross H.; Gonjo, Tomohiro; McCabe, Carla B.

    2015-01-01

    The purpose of this study was to explore the reliability of estimating three-dimensional (3D) linear kinematics and kinetics of a swimmer derived from digitized video and to assess the effect of framing rate and smoothing window size. A stroke cycle of two high-level front crawl swimmers and one high level backstroke swimmer was recorded by four underwater and two above water video cameras. One of the front crawl swimmers was recorded and digitized at 50 Hz with a window for smoothing by 4th order Butterworth digital filter extending 10 frames beyond the start and finish of the stroke cycle, while the other front crawl and backstroke swimmer were recorded and digitized at 25 Hz with the window extending five frames beyond the start and finish of the stroke cycle. Each camera view of the stroke cycle was digitized five times yielding five independent 3D data sets from which whole body centre of mass (CM) component velocities and accelerations were derived together with wrist and ankle linear velocities. Coefficients of reliability ranging from r = 0.942 to r = 0.999 indicated that both methods are sufficiently reliable to identify real differences in net force production during the pulls of the right and left hands. Reliability of digitizing was better for front crawl when digitizing at 50Hz with 10 frames extension than at 25 Hz with 5 frames extension (p < 0.01) and better for backstroke than front crawl (p < 0.01). However, despite the extension and reflection of data, errors were larger in the first 15% of the stroke cycle than the period between 15 and 85% of the stroke cycle for CM velocity and acceleration and for foot speed (p < 0.01). Key points An inverse dynamics based on 3D position data digitized from multiple camera views above and below the water surface is sufficiently reliable to yield insights regarding force production in swimming additional to those of other approaches. The ability to link the force profiles to swimming actions and technique is

  3. Multilayers and Crystal for a Multi-bandpass Monochromator

    SciTech Connect

    Feng, Renfei; Platonov, Yuriy; Broadway, David; Ice, Gene E; Gerson, Andrea; McIntyre, Stewart

    2008-01-01

    VESPERS beamline is a hard X-ray microprobe beamline dedicated to micro-diffraction and micro-fluorescence analysis at the Canadian Light Source; it requires multi-bandpass X-ray beams for different types of samples and experiments. A specially designed double crystal/multilayer monochromator was built for this purpose with three different bandpasses: 0.01%, 1.6% and 10%. The diffraction elements used for the monochromator have a triple-stripe design using Si(111) crystal as a single substrate with two differing stripes of Mo/B4C multilayers deposited thereon. The uncovered Si(111) section provides a 0.01% bandpass, while the periodic and depth-graded Mo/B4C multilayers provide 1.6% and 10% bandpasses, respectively. This paper outlines the requirements and specifications of the diffracting elements as well as the design, deposition and optimization of the multilayers. The performance of the deposited multilayer structures has been tested using Cu-Ka radiation line with a Huber diffractometer.

  4. National Program for Inspection of Non-Federal Dams. Butterworth Dam (CT 00122), Connecticut Coastal Basin, Hamden, Connecticut. Phase I Inspection Report.

    DTIC Science & Technology

    1981-06-01

    acid, alkali, salts , or organic matter ( drinkable water ). - IV. Sand. Sand for concrete shall be clean, hard, strong, and durable 4" and shall be well...1963 to impound water for recreational use, is an ekrth embankment measuring approx. 215 ft. in length and 15 ft. high, with a maximum impoundment...Inspection Team: PETER M. HEYNEN, P.E. JAY A. COSTELLO MURALI ATLURU, P.E. The Butterworth Dam, built in 1963 to impound water for recrea- tional use

  5. Compact tunable microwave filter using retroreflective acousto-optic filtering and delay controls.

    PubMed

    Riza, Nabeel A; Ghauri, Farzan N

    2007-03-01

    Programmable broadband rf filters are demonstrated using a compact retroreflective optical design with an acousto-optic tunable filter and a chirped fiber Bragg grating. This design enables fast 34 micros domain analog-mode control of rf filter time delays and weights. Two proof-of-concept filters are demonstrated including a two-tap notch filter with >35 dB notch depth and a four-tap bandpass filter. Both filters have 2-8 GHz tunability and a 34 micros reset time.

  6. Multiband filters for near-infrared astronomical applications

    NASA Astrophysics Data System (ADS)

    Rhoads, James E.; Malhotra, Sangeeta; Scowen, Paul; Probst, Ron; McCarthy, Don

    2010-07-01

    Filters for astronomical imaging traditionally have a simple bandpass that admits (more or less equally) all the photons within some bandwith ▵λ around some central wavelength λ0. However, there are situations where not all photons are equally desirable. We plan to develop and apply multiband filters for practical astronomical application. A multiband filter is a bandpass filter whose transmission dips to zero at select, undesired wavelength ranges. Anticipated applications include (i) OH-suppressing filters, especially in the J band (λc ~ 1.2μm) (ii) economy of filter slots through multi-band filters used in series with broad blocking filters; and (iii) efficient searches for object classes with highly structured spectra. We present the design and anticipated photometric properties of a prototype reduced-background JR filter, which we plan to buy and test in 2010.

  7. Generation of a sub-Poissonian state with quantum high- and low-pass filters

    SciTech Connect

    Wang Haibo; Li Yongmin; Odate, Satoru; Kobayashi, Takayoshi

    2005-07-15

    We introduce a quantum component, the quantum high- and low-pass filter, and analyze its output characteristic. It is shown that a quantum bandpass filter can be achieved by using passive linear optics and projection measurements. Furthermore, we show that the sub-Poissonian state can be generated by using a cascaded quantum low-pass filter and high-pass filter.

  8. Bandpass calibration of a wideband spectrometer using coherent pulse injection

    NASA Astrophysics Data System (ADS)

    Patra, Nipanjana; Bray, Justin D.; Roberts, Paul; Ekers, Ron D.

    2017-04-01

    We present a relatively simple time domain method for determining the bandpass response of a system by injecting a nanosecond pulse and capturing the system voltage output. A pulse of sub-nanosecond duration contains all frequency components with nearly constant amplitude up to 1 GHz. Hence, this method can accurately determine the system bandpass response to a broadband signal. In a novel variation on this impulse response method, a train of pulses is coherently accumulated providing precision calibration with a simple system. The basic concept is demonstrated using a pulse generator-accumulator setup realised in a Bedlam board which is a high speed digital signal processing unit. The same system was used at the Parkes radio telescope between 2-13 October 2013 and we demonstrate its powerful diagnostic capability. We also present some initial test data from this experiment.

  9. Bandpass calibration of a wideband spectrometer using coherent pulse injection

    NASA Astrophysics Data System (ADS)

    Patra, Nipanjana; Bray, Justin D.; Roberts, Paul; Ekers, Ron D.

    2017-03-01

    We present a relatively simple time domain method for determining the bandpass response of a system by injecting a nanosecond pulse and capturing the system voltage output. A pulse of sub-nanosecond duration contains all frequency components with nearly constant amplitude up to 1 GHz. Hence, this method can accurately determine the system bandpass response to a broadband signal. In a novel variation on this impulse response method, a train of pulses is coherently accumulated providing precision calibration with a simple system. The basic concept is demonstrated using a pulse generator-accumulator setup realised in a Bedlam board which is a high speed digital signal processing unit. The same system was used at the Parkes radio telescope between 2-13 October 2013 and we demonstrate its powerful diagnostic capability. We also present some initial test data from this experiment.

  10. Optimization by Smoothed Bandpass Calibration in Radio Spectroscopy

    NASA Astrophysics Data System (ADS)

    Kameno, S.; Yamaki, H.; Mizuno, I.; Beppu, H.; Imai, H.; Kuno, N.; Akashi, T.

    2013-10-01

    We have developed the Smoothed Bandpass Calibration (SBC) method and the best suitable scan pattern to optimize radio spectroscopic observations. Adequate spectral smoothing is applied to the spectrum toward OFF-source blank sky adjacent to a target source direction for the purpose of bandpass correction. Because the smoothing process reduces noise, the integration time for OFF-source scans can be reduced keeping the signal-to-noise ratio. Since the smoothing is not applied to ON-source scans, the spectral resolution for line features is kept. An optimal smoothing window is determined by bandpass flatness evaluated by Spectral Allan Variance (SAV). An efficient scan pattern is designed to the OFF-source scans within the bandpass stability timescale estimated by Time-based Allan Variance (TAV). We have tested the SBC using the digital spectrometer, SAM45, on the Nobeyama 45-m telescope. The optimal smoothing windows were determined as 501, 28, 18, and 4 ch for bandwidths of 2000, 500, 125, and 15.6 MHz, respectively. The optimal scan pattern was designed as sequences of [60-s ON + 10-s OFF] and [48-s ON + 16-s OFF] scan pairs for narrow and wide bandwidth, respectively. The noise level with the SBC was reduced by factors of 1.8 and 1.3 compared with the conventional method. We also found sporadic instability (bursts) in the total power and spectra in IF during the test observations. Although the bursts significantly distorts the resultant spectra, we found a solution to cancel the spectral variation by decomposing them into static and burst components. This solution can be a hint to ease spectral flagging processes and to bring better efficiency in integration time.

  11. Optimization by Smoothed Bandpass Calibration in Radio Spectroscopy

    NASA Astrophysics Data System (ADS)

    Yamaki, Haruka; Kameno, Seiji; Beppu, Hirohisa; Mizuno, Izumi; Imai, Hiroshi

    2012-10-01

    We have developed the Smoothed Bandpass Calibration (SBC) method and the best suitable scan pattern to optimize radio spectroscopic observations. Adequate spectral smoothing is applied to the spectrum toward OFF-source blank sky adjacent to a target source for the purpose of bandpass correction. Because the smoothing process reduces noise, we can reduce the integration time for OFF-source scans while keeping the signal-to-noise ratio. Since smoothing is not applied to ON-source scans, the spectral resolution for line features is maintained. An optimal smoothing window is determined by the bandpass flatness evaluated by the spectral Allan variance (SAV). An efficient scan pattern is designed for OFF-source scans within the bandpass-stability time scale estimated by the time-based Allan variance (TAV). We tested the SBC using a digital spectrometer, VESPA, at the VERA Iriki station. For a targeted noise level of 5 × 10-4 as its ratio to the system noise, the optimal smoothing window was 32-60 channels (ch) over the whole bandwidth of 1024 ch, and the optimal scan pattern was designed as a sequence of 70 s ON + 10 s OFF scan pairs. The noise level by the SBC has been improved by a factor of 1.74, compared with that by the conventional method. The total telescope-time to reach our target with the SBC was 400 s, which is 1/3 of 1200 s required in the conventional way. Improvements in the telescope-time efficiency with the SBC were calculated to be 3× (for single-beam scans), 2× (dual-beam), and 1.3× (on-the-fly). The SBC is useful for optimizing scan patterns for observations from now on, and also for improving the signal-to-noise ratios of archival data if ON- and OFF-source spectra are separately recorded, though the efficiency depends on the spectral stability of the receiving system.

  12. Introducing passive acoustic filter in acoustic based condition monitoring: Motor bike piston-bore fault identification

    NASA Astrophysics Data System (ADS)

    Jena, D. P.; Panigrahi, S. N.

    2016-03-01

    Requirement of designing a sophisticated digital band-pass filter in acoustic based condition monitoring has been eliminated by introducing a passive acoustic filter in the present work. So far, no one has attempted to explore the possibility of implementing passive acoustic filters in acoustic based condition monitoring as a pre-conditioner. In order to enhance the acoustic based condition monitoring, a passive acoustic band-pass filter has been designed and deployed. Towards achieving an efficient band-pass acoustic filter, a generalized design methodology has been proposed to design and optimize the desired acoustic filter using multiple filter components in series. An appropriate objective function has been identified for genetic algorithm (GA) based optimization technique with multiple design constraints. In addition, the sturdiness of the proposed method has been demonstrated in designing a band-pass filter by using an n-branch Quincke tube, a high pass filter and multiple Helmholtz resonators. The performance of the designed acoustic band-pass filter has been shown by investigating the piston-bore defect of a motor-bike using engine noise signature. On the introducing a passive acoustic filter in acoustic based condition monitoring reveals the enhancement in machine learning based fault identification practice significantly. This is also a first attempt of its own kind.

  13. Hone filter bandwidth with computer ease

    NASA Astrophysics Data System (ADS)

    Crawford, J.

    1986-01-01

    It is pointed out that programmable calculators and computers address a variety of difficult problems which were too small for the large mainframe computer. An example for such problems represents the selection of the optimum bandwidth for a bandpass filter. It is now possible to evaluate filter performance quickly and accurately by making use of simple computer procedures which replace time-consuming filter nomographs and other estimation techniques. The computerized technique for evaluating filters permits optimum selection of a passband which concurrently satisfies specified stopband requirements. Attention is given to results of sample filter calculation, the passband maximizer, and tracking losses.

  14. A Study of Microstrip Line Balanced Filters with Attenuation Poles Based on Tapped Resonators

    NASA Astrophysics Data System (ADS)

    Kubo, Yoshiyuki; Wada, Kouji

    We propose microstrip-line balanced filters with controllable attenuation poles by using tapped resonators. These filters are basically composed of a coupled-line and tapped resonators. The coupled-line provides bandpass responses with attenuation poles and balanced filter operation. Also, the tappd resonators provide bandpass responses and attenuation poles. The position and number of the attenuation pole are controlled by the choice of the kind of the tapped resonator. In this paper, we examine a filter with an unbalanced port and a balanced port as well as a filter with a balanced port and a balanced port. The presented filters are simulated with commercial simulators and are measured with a vector network analyzer. We have confirmed that the bandpass characteristics with controllable attenuation poles and balanced characteristics(amplitude and phase balance performances) are obtained. The measured results of the fabricated filters agree well with the simulated results.

  15. Gas sensors using single layer patterned interference optical filters

    NASA Astrophysics Data System (ADS)

    Rahmlow, Thomas D.; Gallagher, Kieran; Johnson, Robert L.

    2016-03-01

    A method for fabricating filters for fiber optic sensors is presented. The interference filter's construction is laid on it's side to allow for the use of air as the low refractive index material. Bandpass filters tuned to the absorption line of a trace gas can then be used as a sensitive means of detecting gas concentration. Complex filter designs can be fabricated in a single patterned layer. A CO2/CH4 gas sensor is presented as a design example.

  16. Image quality, space-qualified UV interference filters

    NASA Technical Reports Server (NTRS)

    Mooney, Thomas A.

    1992-01-01

    The progress during the contract period is described. The project involved fabrication of image quality, space-qualified bandpass filters in the 200-350 nm spectral region. Ion-assisted deposition (IAD) was applied to produce stable, reasonably durable filter coatings on space compatible UV substrates. Thin film materials and UV transmitting substrates were tested for resistance to simulated space effects.

  17. Optical image segmentation using wavelet filtering techniques

    NASA Astrophysics Data System (ADS)

    Veronin, Christopher P.

    1990-12-01

    This research effort successfully implemented an automatic, optically based image segmentation scheme for locating potential targets in a cluttered FLIR image. Such a design is critical to achieve real-time segmentation and classification for machine vision applications. The segmentation scheme used in this research was based on texture discrimination and employs orientation specific, bandpass spatial filters as its main component. The orientation specific, bandpass spatial filters designed during this research include symmetrically located circular apertures implemented on heavy, black aluminum foil; cosine and sine Gabor filters implemented with detour-phase computer generated holography photoreduced onto glass slides; and symmetrically located circular apertures implemented on a liquid crystal television (LCTV) for real-time filter selection. The most successful design was the circular aperture pairs implemented on the aluminum foil. Segmentation was illustrated for simple and complex texture slides, glass template slides, and static and real-time FLIR imagery displayed on an LCTV.

  18. Microwave active filters based on coupled negative resistance method

    NASA Astrophysics Data System (ADS)

    Chang, Chi-Yang; Itoh, Tatsuo

    1990-12-01

    A novel coupled negative resistance method for building a microwave active bandpass filter is introduced. Based on this method, four microstrip line end-coupled filters were built. Two are fixed-frequency one-pole and two-pole filters, and two are tunable one-pole and two-pole filters. In order to broaden the bandwidth of the end-coupled filter, a modified end-coupled structure is proposed. Using the modified structure, an active filter with a bandwidth up to 7.5 percent was built. All of the filters show significant passband performance improvement. Specifically, the passband bandwidth was broadened by a factor of 5 to 20.

  19. Active imaging system with Faraday filter

    SciTech Connect

    Snyder, J.J.

    1992-12-31

    This invention is comprised of an active imaging system which has a low to medium powered laser transmitter and a receiver wherein the receiver includes a Faraday filter with an ultranarrow optical bandpass and a bare (nonintensified) CCD camera. The laser is locked in the vicinity of the passband of the Faraday filter. The system has high sensitivity to the laser illumination wile eliminating solar background.

  20. Image pre-filtering for measurement error reduction in digital image correlation

    NASA Astrophysics Data System (ADS)

    Zhou, Yihao; Sun, Chen; Song, Yuntao; Chen, Jubing

    2015-02-01

    In digital image correlation, the sub-pixel intensity interpolation causes a systematic error in the measured displacements. The error increases toward high-frequency component of the speckle pattern. In practice, a captured image is usually corrupted by additive white noise. The noise introduces additional energy in the high frequencies and therefore raises the systematic error. Meanwhile, the noise also elevates the random error which increases with the noise power. In order to reduce the systematic error and the random error of the measurements, we apply a pre-filtering to the images prior to the correlation so that the high-frequency contents are suppressed. Two spatial-domain filters (binomial and Gaussian) and two frequency-domain filters (Butterworth and Wiener) are tested on speckle images undergoing both simulated and real-world translations. By evaluating the errors of the various combinations of speckle patterns, interpolators, noise levels, and filter configurations, we come to the following conclusions. All the four filters are able to reduce the systematic error. Meanwhile, the random error can also be reduced if the signal power is mainly distributed around DC. For high-frequency speckle patterns, the low-pass filters (binomial, Gaussian and Butterworth) slightly increase the random error and Butterworth filter produces the lowest random error among them. By using Wiener filter with over-estimated noise power, the random error can be reduced but the resultant systematic error is higher than that of low-pass filters. In general, Butterworth filter is recommended for error reduction due to its flexibility of passband selection and maximal preservation of the allowed frequencies. Binomial filter enables efficient implementation and thus becomes a good option if computational cost is a critical issue. While used together with pre-filtering, B-spline interpolator produces lower systematic error than bicubic interpolator and similar level of the random

  1. Advanced astronomical interference filters from SCHOTT technology

    NASA Astrophysics Data System (ADS)

    Hull, Anthony B.; Reichel, Steffen; Brauneck, Ulf; Bourquin, Sebastien; Marin-Franch, Antoni

    2016-01-01

    Developing precision interference filters for astronomical radiometry often requires simultaneous solutions to very difficult requirements. SCHOTT's 80-year legacy methods with interference filters and 9,200-m2 facility dedicated to filters and optical fabrication bring multiple disciplines together to simultaneously solve requirements that include: narrow-band high-transmission, steep-edge bandpasses, extremely high out-of-band rejection across Si response, sizes accommodating large fields-of-view, precision mechanical filter assemblies and both spectral uniformity and excellent transmitted wavefront across the field. We discuss solutions as satisfied for Spain's state-of-the-art new fast LOCAL UNIVERSE 3° wide-field survey telescope.

  2. Detecting and Characterizing Exoplanets with the WFIRST Coronagraph: Colors of Planets in Standard and Designer Bandpasses-SETI

    NASA Astrophysics Data System (ADS)

    Turnbull, Margaret

    The WFIRST mission is now envisioned to include a coronagraph for the purpose of direct detection of nearby exoplanets, including planets known to exist via radial velocity detection and new discoveries. Assuming that starlight rejection sufficient for planet detection (~1e-9) can be achieved, what can be learned about these planets given a realistic spectral resolution and signal-to-noise ratio? We propose to investigate the potential for WFIRST to efficiently discriminate planets from background sources, and to characterize planets in terms of important diagnostic atmospheric features, using broad- and intermediate band color data. We will map out this capability as a function of signal-to-noise ratio, bandpass location, and bandpass width. Our investigation will place emphasis on gas giants, ice giants, and mini-Neptunes (compatible with current AFTA-C baseline performance specifications), as well as a variety of super-Earths (an AFTA-C "stretch" goal). We will explore a variety of compositions, cloud types, phase angles, and (in the case of super-Earths with semi-transparent atmospheres) surface types. Noiseless spectra generated for these model planets will be passed through (a) standard bandpasses for comparison to prior work and (b) filter transmission curves corresponding to bandpasses of 5-20% over the full range of WFIRST's expected bandpass (400 - 1,000 nm). From this, filter combinations will be used to generate planet colors and find filter sets that most efficiently discriminate between planets and background sources, and between planets of different type. We will then repeat this exercise for S/N levels of 1-1,000 in order to (1) explore the true efficacy of broadband measurements in exoplanet studies, and (2) provide an estimate of total required integration time for a compelling WFIRST exoplanet program. To accomplish this, we will use model spectra for mini-Neptunes, and ice and gas giants of varying composition (Hu et al. 2013), and observed

  3. Bandpass Delta Sigma A/D convertor using two-path multibit structure

    NASA Astrophysics Data System (ADS)

    Zhang, Z. X.; Temes, G. C.; Czarnul, Z.

    1991-10-01

    The concept of an N-path bandpass Delta Sigma A/D convertor is introduced. A multibit sixth-order SC implementation is described. The new scheme appears to be very effective for the realization of the narrowband bandpass delta-sigma modulators needed for communication applications.

  4. Spectral analysis and filtering techniques in digital spatial data processing

    USGS Publications Warehouse

    Pan, Jeng-Jong

    1989-01-01

    A filter toolbox has been developed at the EROS Data Center, US Geological Survey, for retrieving or removing specified frequency information from two-dimensional digital spatial data. This filter toolbox provides capabilities to compute the power spectrum of a given data and to design various filters in the frequency domain. Three types of filters are available in the toolbox: point filter, line filter, and area filter. Both the point and line filters employ Gaussian-type notch filters, and the area filter includes the capabilities to perform high-pass, band-pass, low-pass, and wedge filtering techniques. These filters are applied for analyzing satellite multispectral scanner data, airborne visible and infrared imaging spectrometer (AVIRIS) data, gravity data, and the digital elevation models (DEM) data. -from Author

  5. Magnetically tunable wideband microwave filter using ferrite-based metamaterials

    NASA Astrophysics Data System (ADS)

    Bi, Ke; Zhu, Wenting; Lei, Ming; Zhou, Ji

    2015-04-01

    Magnetically tunable wideband microwave filters have been designed and prepared by using ferrite-based metamaterial structures. The microwave properties of the filters have been investigated by experiments and simulations. The negative permeability appears around the ferromagnetic resonance frequency, which leads to a remarkable stopband for the bandstop filter. The bandpass filter is composed of two kinds of ferrite rods with different saturation magnetization. The bandwidth of the passband can be tuned by adjusting the saturation magnetization of the ferrite rods. Both the experimental and the simulated results show that those filters possess magnetically tunable property. This approach opens a way for designing tunable wideband microwave filters.

  6. IR Interference Filters Made Of Al Patterns On Si Substrates

    NASA Technical Reports Server (NTRS)

    Ksendzov, Alexander; Fathauer, Robert; Maker, Paul M.; Muller, Richard

    1996-01-01

    Filters relatively thin and better accommodate convergent infrared beams. Infrared (IR) interference filters with pass bands centered at wavelength of about 70 micrometer made in form of aluminum patterns 1,000 Angstrom thick on both sides of silicon substrates 12 to 15 micrometer thick. Substrates, in turn, mounted on silicon frames 0.2 millimeter thick. Prototypes of class of miniature band-pass infrared filters small enough to be bonded to, and cooled with, infrared detectors.

  7. Design of angularly tolerant zero-contrast grating filters for pixelated filtering in the mid-IR range.

    PubMed

    Macé, Léopold; Gauthier-Lafaye, Olivier; Monmayrant, Antoine; Camon, Henri

    2017-04-01

    Zero-contrast gratings (ZCG) can be used to implement narrow bandpass transmission filters. However, they suffer from poor angular tolerance, which hinders their use in pixelated applications. Combining ZCG with double-corrugation grating, we increase the resonance width and angular tolerance of the filter by more than 1 order of magnitude. Filters tunable around 4.6 μm with more than 90% transmission and compatibility with 140 μm pixel size are demonstrated.

  8. A linear-to-circular polarization converter based on a second-order band-pass frequency selective surface

    NASA Astrophysics Data System (ADS)

    Lin, Baoqin; Wu, Jia-liang; Da, Xin-yu; Li, Wei; Ma, Jia-jun

    2017-01-01

    In this work, we propose a linear-to-circular transmission polarization converter based on a second-order band-pass frequency selective surface (FSS). The FSS is composed of a three-layer aperture-coupled-patch structure, it can be interpreted as an array of antenna-filter-antenna modules, wherein the antenna is just a circularly polarized corner-truncated square microstrip antenna. A prototype of the proposed polarization converter is analyzed, fabricated and tested. Both simulation and experimental results show that the 3-dB axial ratio relative bandwidth of the polarization converter is over 30%, and the maximum insertion loss is only 1.87 dB; in addition, it can maintain good performance over a wide angular bandwidth at TE incidence.

  9. Wideband Tunable Frequency-Doubling Optoelectronic Oscillator Using a Polarization Modulator and an Optical Bandpass Filter

    NASA Astrophysics Data System (ADS)

    Huang, Qing-Chao; Wang, Qi; Yang, Cheng-Wu; Chen, Wei; Liu, Jian-Guo; Zhu, Ning-Hua

    2017-08-01

    Not Available Supported by the National Natural Science Foundation of China under Grant No 61675196, the National Basic Research Program of China under Grant No 2014CB340102, the National High-Tech Research and Development Program of China under Grant No 2015AA016903, and the Open Research of Beijing University of Posts and Telecommunications under Grant No IOOC2013A002.

  10. Bandpass filtering of moving-object laser heterodyne-signals by finite apertures.

    PubMed

    Leader, J C

    1978-04-15

    Expressions for the frequency power spectral density and power spectral density SNR of a heterodyne detection system are derived assuming the signal radiation field results from a laser illuminated, moving rough object. The calculated spectral density is attenuated at large spectral spread frequencies (resulting from target rotation) by averaging of the high spatial frequency speckle pattern by the finite extent (aperture) of the local oscillator field. Optimum signal detection is obtained only at the Doppler shifted frequency. Spatial anisotropy of the radiation field mutual coherence function precludes exact calculations for arbitrary local oscillator field distributions.

  11. Dynamic, Infrared Bandpass Filters Prepared from Polymer-Stabilized Cholesteric Liquid Crystals (Postprint)

    DTIC Science & Technology

    2016-04-04

    sapphire slides were spun-coated with an alignment layer from a polyimide (PI- 2555, HD Microsystem) or a nylon (Elvamide, DuPont), which was rubbed...transparent electrodes (graphene or silver nano- wires ), and filled with a cholesteric liquid crystal mixture. (b) Transmission spectra of substrates and

  12. Isotropically sensitive optical filter employing atomic resonance transitions

    DOEpatents

    Marling, John B.

    1981-01-01

    An ultra-high Q isotropically sensitive optical filter or optical detector employing atomic resonance transitions. More specifically, atomic resonance transitions utilized in conjunction with two optical bandpass filters provide an optical detector having a wide field of view (.about.2.pi. steradians) and very narrow acceptance bandwidth approaching 0.01 A. A light signal to be detected is transmitted through an outer bandpass filter into a resonantly absorbing atomic vapor, the excited atomic vapor then providing a fluorescence signal at a different wavelength which is transmitted through an inner bandpass filter. The outer and inner bandpass filters have no common transmission band, thereby resulting in complete blockage of all optical signals that are not resonantly shifted in wavelength by the intervening atomic vapor. Two embodiments are disclosed, one in which the light signal raises atoms contained in the atomic vapor from the ground state to an excited state from which fluorescence occurs, and the other in which a pump laser is used to raise the atoms in the ground state to a first excited state from which the light signal then is resonantly absorbed, thereby raising the atoms to a second excited state from which fluorescence occurs. A specific application is described in which an optical detector according to the present invention can be used as an underwater detector for light from an optical transmitter which could be located in an orbiting satellite.

  13. Rough surface scattering results based on bandpass autocorrelation forms

    NASA Technical Reports Server (NTRS)

    Miller, Lee S.; Parsons, Chester L.

    1990-01-01

    Surface-height autocorrelation forms such as Gaussian and exponential are often used in studies of near-normal incidence rough-surface scattering. Such models require the existence of a constant, or DC, value in the spectrum. The consequences of autocorrelation forms that correspond to spectral processes that are essentially bandpass in nature are examined. One such process is that of ocean wind waves. In this case, the spectral components do not extend down to zero frequency. The physical optics backscatter theory is reexamined relative to such autocorrelation functions. Experimental results obtained from a wavetank are compared to the autocorrelation model used in the analysis. The analysis indicates that Gaussian correlation length or mean-square slope is not an appropriate parameter for narrowband conditions and that significant slope is a more relevant parameter. Inherent in the deep-phase assumption is some form of slope dependency. The analysis given (and variants thereof) can be used to provide insight into the physical effects of separate spectral components and of spectral directionality.

  14. High energy resolution bandpass photon detector for inverse photoemission spectroscopy.

    PubMed

    Maniraj, M; D'Souza, S W; Nayak, J; Rai, Abhishek; Singh, Sanjay; Sekhar, B N Raja; Barman, S R

    2011-09-01

    We report a bandpass ultraviolet photon detector for inverse photoemission spectroscopy with energy resolution of 82 ± 2 meV. The detector (Sr(0.7)Ca(0.3)F(2)/acetone) consists of Sr(0.7)Ca(0.3)F(2) entrance window with energy transmission cutoff of 9.85 eV and acetone as detection gas with 9.7 eV photoionization threshold. The response function of the detector, measured using synchrotron radiation, has a nearly Gaussian shape. The n = 1 image potential state of Cu(100) and the Fermi edge of silver have been measured to demonstrate the improvement in resolution compared to the CaF(2)/acetone detector. To show the advantage of improved resolution of the Sr(0.7)Ca(0.3)F(2)/acetone detector, the metal to semiconductor transition in Sn has been studied. The pseudogap in the semiconducting phase of Sn could be identified, which is not possible with the CaF(2)/acetone detector because of its worse resolution. © 2011 American Institute of Physics

  15. Realization of High-Order Filters for 1-bit Signal Processing Based on Delta-Sigma Modulation

    NASA Astrophysics Data System (ADS)

    Murahashi, Yoshimitsu; Doki, Shinji; Okuma, Shigeru

    We discuss a realization method of basic 1-bit signal processing based on Delta-Sigma modulation in this paper. Additionally, we show the characteristics of basic 1-bit processor and an effective design method from the view point of SNR. As the application of the 1-bit signal processing, we proposed a realization method of high-order filters based on Delta-Sigma modulation. We applied the effective design method to decide coefficients of a 4th-order butterworth low pass filter. We show that the filter designed by using the proposed method achieves the highest SNR.

  16. Equivalent-nanocircuit-theory-based design to infrared broad band-stop filters.

    PubMed

    Zhang, Qing; Bai, Lihua; Bai, Zhengyuan; Hu, Pidong; Liu, Chengpu

    2015-04-06

    We theoretically introduced a design paradigm and tool by extending the circuit functionalities from radio frequency to near infrared domain, and a broad band-stop filter, is successfully demonstrated by cascading triple layers of nano-square arrays. The feasibility is confirmed by its consistency with the rigorous FDTD calculation. Moreover, such a third-order Butterworth filter is not only insensitive to the incident angle and but also to input light's polarization. The new paradigm forms a theoretical foundation for designing optical devices and also enriches the classic circuit operations at the optical frequency region.

  17. Filters in 2D and 3D Cardiac SPECT Image Processing.

    PubMed

    Lyra, Maria; Ploussi, Agapi; Rouchota, Maritina; Synefia, Stella

    2014-01-01

    Nuclear cardiac imaging is a noninvasive, sensitive method providing information on cardiac structure and physiology. Single photon emission tomography (SPECT) evaluates myocardial perfusion, viability, and function and is widely used in clinical routine. The quality of the tomographic image is a key for accurate diagnosis. Image filtering, a mathematical processing, compensates for loss of detail in an image while reducing image noise, and it can improve the image resolution and limit the degradation of the image. SPECT images are then reconstructed, either by filter back projection (FBP) analytical technique or iteratively, by algebraic methods. The aim of this study is to review filters in cardiac 2D, 3D, and 4D SPECT applications and how these affect the image quality mirroring the diagnostic accuracy of SPECT images. Several filters, including the Hanning, Butterworth, and Parzen filters, were evaluated in combination with the two reconstruction methods as well as with a specified MatLab program. Results showed that for both 3D and 4D cardiac SPECT the Butterworth filter, for different critical frequencies and orders, produced the best results. Between the two reconstruction methods, the iterative one might be more appropriate for cardiac SPECT, since it improves lesion detectability due to the significant improvement of image contrast.

  18. Filters in 2D and 3D Cardiac SPECT Image Processing

    PubMed Central

    Ploussi, Agapi; Synefia, Stella

    2014-01-01

    Nuclear cardiac imaging is a noninvasive, sensitive method providing information on cardiac structure and physiology. Single photon emission tomography (SPECT) evaluates myocardial perfusion, viability, and function and is widely used in clinical routine. The quality of the tomographic image is a key for accurate diagnosis. Image filtering, a mathematical processing, compensates for loss of detail in an image while reducing image noise, and it can improve the image resolution and limit the degradation of the image. SPECT images are then reconstructed, either by filter back projection (FBP) analytical technique or iteratively, by algebraic methods. The aim of this study is to review filters in cardiac 2D, 3D, and 4D SPECT applications and how these affect the image quality mirroring the diagnostic accuracy of SPECT images. Several filters, including the Hanning, Butterworth, and Parzen filters, were evaluated in combination with the two reconstruction methods as well as with a specified MatLab program. Results showed that for both 3D and 4D cardiac SPECT the Butterworth filter, for different critical frequencies and orders, produced the best results. Between the two reconstruction methods, the iterative one might be more appropriate for cardiac SPECT, since it improves lesion detectability due to the significant improvement of image contrast. PMID:24804144

  19. Auditory stream segregation using amplitude modulated bandpass noise

    PubMed Central

    Nie, Yingjiu; Nelson, Peggy B.

    2015-01-01

    The purpose of this study was to investigate the roles of spectral overlap and amplitude modulation (AM) rate for stream segregation for noise signals, as well as to test the build-up effect based on these two cues. Segregation ability was evaluated using an objective paradigm with listeners' attention focused on stream segregation. Stimulus sequences consisted of two interleaved sets of bandpass noise bursts (A and B bursts). The A and B bursts differed in spectrum, AM-rate, or both. The amount of the difference between the two sets of noise bursts was varied. Long and short sequences were studied to investigate the build-up effect for segregation based on spectral and AM-rate differences. Results showed the following: (1). Stream segregation ability increased with greater spectral separation. (2). Larger AM-rate separations were associated with stronger segregation abilities. (3). Spectral separation was found to elicit the build-up effect for the range of spectral differences assessed in the current study. (4). AM-rate separation interacted with spectral separation suggesting an additive effect of spectral separation and AM-rate separation on segregation build-up. The findings suggest that, when normal-hearing listeners direct their attention towards segregation, they are able to segregate auditory streams based on reduced spectral contrast cues that vary by the amount of spectral overlap. Further, regardless of the spectral separation they are able to use AM-rate difference as a secondary/weaker cue. Based on the spectral differences, listeners can segregate auditory streams better as the listening duration is prolonged—i.e., sparse spectral cues elicit build-up segregation; however, AM-rate differences only appear to elicit build-up when in combination with spectral difference cues. PMID:26300831

  20. Filtering Applications on Seismogram Analysis

    NASA Astrophysics Data System (ADS)

    Djordjevic, M.

    2004-12-01

    Useful data extraction from registered signals is an everyday problem. Seismogram filtering can be used to enhance the earthquake signal, especially, knowing that period range is strongly amplified by the seismograph itself. The goal of this project was to estimate tradeoffs between noise reduction and the sharpness of the filtered earthquake signal. The different filter bands were applied on the seismograms from different epicentral distances, including both local and regional earthquakes, in order to see the quality of the data. During the seismogram analysis we had two approaches: reading the wave phase (arrival time, amplitude, period) and spectral analysis, since frequency filtering is essential. The well-known set of Fourier orthogonal basis functions was used for spectral analysis. The main purpose of filtering was to remove the noise from the seismograms and to get as much possible information from the record. Practical application was obtained using custom made "Analysis" software. We processed 5 earthquake signals; four local and one distant earthquake. The data came from Djerdap Seismological Station, Serbia. Filtering was based on a band-pass filter with frequency cut-offs from 0.2Hz to 10Hz. Every record was filtered with five filters (10-1Hz,10-2.5Hz, 2.5-1Hz, 1-0.2Hz). The manipulation with different filter bands allowed us to define precisely the beginning of the earthquakes and first arrivals of different wave phases. The best result for the 45km epicentral distance earthquake was obtained using window 0.1-0.5sec, where very clear Pg and Sg arrivals could be distinguished. The distant earthquake showed the advantages of filtering seismograms to enhance the long period energy. The lowest frequency band-pass filter (1-0.2Hz) was the most successful. The results of the experiment were with very clear Pg and Sg arrivals when the right bands were used for filtering. This improved the quality of the original signals by emphasizing the temporal and

  1. Flexible RF filter using a nonuniform SCISSOR.

    PubMed

    Zhuang, Leimeng

    2016-03-15

    This work presents a flexible radiofrequency (RF) filter using an integrated microwave photonic circuit that comprises a nonuniform side-coupled integrated spaced sequence of resonators (N-SCISSOR). The filter passband can be reconfigured by varying the N-SCISSOR parameters. When employing a dual-parallel Mach-Zechnder modulator, the filter is also able to perform frequency down-conversion. In the experiment, various filter response shapes are shown, ranging from a flat-top band-pass filter to a total opposite high-rejection (>40  dB) notch filter, with a frequency coverage of greater than two octaves. The frequency down-conversion function is also demonstrated.

  2. Adaptive Spatial Filtering with Principal Component Analysis for Biomedical Photoacoustic Imaging

    NASA Astrophysics Data System (ADS)

    Nagaoka, Ryo; Yamazaki, Rena; Saijo, Yoshifumi

    Photoacoustic (PA) signal is very sensitive to noise generated by peripheral equipment such as power supply, stepping motor or semiconductor laser. Band-pass filter is not effective because the frequency bandwidth of the PA signal also covers the noise frequency. The objective of the present study is to reduce the noise by using an adaptive spatial filter with principal component analysis (PCA).

  3. A study of the effects of interference-rejection filters on feedback radiometer sensitivity

    NASA Technical Reports Server (NTRS)

    Stanley, W. D.; Hearn, C. P.

    1985-01-01

    The trade-offs between sensitivity and interference immunity resulting from input bandpass filter losses in a noise-injection feedback radiometer are examined. Data are provided to permit the selection of an optimum filter configuration based on the independent variables of percentage bandwidth, q-factors, and desired band-edge rejection.

  4. Auditory stream segregation using bandpass noises: evidence from event-related potentials

    PubMed Central

    Nie, Yingjiu; Zhang, Yang; Nelson, Peggy B.

    2014-01-01

    The current study measured neural responses to investigate auditory stream segregation of noise stimuli with or without clear spectral contrast. Sequences of alternating A and B noise bursts were presented to elicit stream segregation in normal-hearing listeners. The successive B bursts in each sequence maintained an equal amount of temporal separation with manipulations introduced on the last stimulus. The last B burst was either delayed for 50% of the sequences or not delayed for the other 50%. The A bursts were jittered in between every two adjacent B bursts. To study the effects of spectral separation on streaming, the A and B bursts were further manipulated by using either bandpass-filtered noises widely spaced in center frequency or broadband noises. Event-related potentials (ERPs) to the last B bursts were analyzed to compare the neural responses to the delay vs. no-delay trials in both passive and attentive listening conditions. In the passive listening condition, a trend for a possible late mismatch negativity (MMN) or late discriminative negativity (LDN) response was observed only when the A and B bursts were spectrally separate, suggesting that spectral separation in the A and B burst sequences could be conducive to stream segregation at the pre-attentive level. In the attentive condition, a P300 response was consistently elicited regardless of whether there was spectral separation between the A and B bursts, indicating the facilitative role of voluntary attention in stream segregation. The results suggest that reliable ERP measures can be used as indirect indicators for auditory stream segregation in conditions of weak spectral contrast. These findings have important implications for cochlear implant (CI) studies—as spectral information available through a CI device or simulation is substantially degraded, it may require more attention to achieve stream segregation. PMID:25309306

  5. Adaptive Mallow's optimization for weighted median filters

    NASA Astrophysics Data System (ADS)

    Rachuri, Raghu; Rao, Sathyanarayana S.

    2002-05-01

    This work extends the idea of spectral optimization for the design of Weighted Median filters and employ adaptive filtering that updates the coefficients of the FIR filter from which the weights of the median filters are derived. Mallows' theory of non-linear smoothers [1] has proven to be of great theoretical significance providing simple design guidelines for non-linear smoothers. It allows us to find a set of positive weights for a WM filter whose sample selection probabilities (SSP's) are as close as possible to a SSP set predetermined by Mallow's. Sample selection probabilities have been used as a basis for designing stack smoothers as they give a measure of the filter's detail preserving ability and give non-negative filter weights. We will extend this idea to design weighted median filters admitting negative weights. The new method first finds the linear FIR filter coefficients adaptively, which are then used to determine the weights of the median filter. WM filters can be designed to have band-pass, high-pass as well as low-pass frequency characteristics. Unlike the linear filters, however, the weighted median filters are robust in the presence of impulsive noise, as shown by the simulation results.

  6. Fractional-step Tow-Thomas biquad filters

    NASA Astrophysics Data System (ADS)

    Freeborn, Todd J.; Maundy, Brent; Elwakil, Ahmed

    In this paper we propose the use of fractional capacitors in the Tow-Thomas biquad to realize both fractional lowpass and asymmetric bandpass filters of order 0<α1+α2≤2, where α1 and α2 are the orders of the fractional capacitors and 0<α1,2≤1. We show how these filters can be designed using an integer-order transfer function approximation of the fractional capacitors. MATLAB and PSPICE simulations of first order fractional-step low and bandpass filters of order 1.1, 1.5, and 1.9 are given as examples. Experimental results of fractional low pass filters of order 1.5 implemented with silicon-fabricated fractional capacitors verify the operation of the fractional Tow-Thomas biquad.

  7. Development and applications of an interactive digital filter design program.

    PubMed

    Woo, H W; Kim, Y M; Tompkins, W J

    1985-10-01

    We have implemented an interactive digital filter design program in the HP 1000 computer at the Department of Electrical Engineering of the University of Washington. This program allows users to design different types of filters interactively with both amplitude and phase responses displayed on graphic devices. The performance of each designed filter can be evaluated conveniently before the best one is chosen and implemented for any particular application. This program can design recursive filters, e.g. Butterworth, Chebyshev and elliptic, or nonrecursive filters with one out of six different windows, i.e. rectangular, triangular, Hann, Hamming, Blackman and Kaiser. The main outputs from this program are coefficients of a transfer function of an analog filter, a digital filter, or both. Therefore, the design of both analog and digital filters is facilitated by using this program. The program is very simple to use and does not require background in analog or digital filter principles in order to run it. The program is written in standard FORTRAN and is about 30 kbytes in size excluding the graphics display routines. Since it uses standard FORTRAN, it can be easily transported to minicomputer and microcomputer systems that have a FORTRAN compiler and minimal graphics capabilities. This program is available for distribution to interested institutions and laboratories.

  8. Thermal control design of the Lightning Mapper Sensor narrow-band spectral filter

    NASA Technical Reports Server (NTRS)

    Flannery, Martin R.; Potter, John; Raab, Jeff R.; Manlief, Scott K.

    1992-01-01

    The performance of the Lightning Mapper Sensor is dependent on the temperature shifts of its narrowband spectral filter. To perform over a 10 degree FOV with an 0.8 nm bandwidth, the filter must be 15 cm in diameter and mounted externally to the telescope optics. The filter thermal control required a filter design optimized for minimum bandpass shift with temperature, a thermal analysis of substrate materials for maximum temperature uniformity, and a thermal radiation analysis to determine the parameter sensitivity of the radiation shield for the filter, the filter thermal recovery time after occultation, and heater power to maintain filter performance in the earth-staring geosynchronous environment.

  9. Note: Modified π-type Butterworth-Van Dyke model for dual-mode Lamb-wave resonator with precise two-port Y-parameter characterizations

    NASA Astrophysics Data System (ADS)

    Wang, Yong; Hong, Yan; Goh, Wang Ling; Mu, Xiaojing

    2016-10-01

    Dual-mode Lamb-wave resonator has become a powerful component for clock reference and sensing applications, enabling efficient compensations of temperature effects, concurrent measurements of multiple environmental parameters, etc. An equivalent circuit model for the dual-mode Lamb-wave resonator is indispensable as it provides a means as well as being an effective tool for evaluating device characteristics and to aid the designing of circuitry for the resonators. This could be the first time ever that an efficient equivalent-circuit model, i.e., modified π-type Butterworth-Van Dyke model for dual-mode Lamb-wave resonators is reported. Evaluated by experiments, this model attains noteworthy agreements on both the magnitudes and phases of Y11 and Y21 of the measurement results. Compared to literature, the proposed model is capable of modeling the dual resonances efficiently. Moreover, this work also proves more accurate when viewing the Y-parameters across a wide frequency range. The gained features of this model are most beneficial for the analysis of the dual-mode Lamb-wave resonator and also for the designing of circuits.

  10. Note: Modified π-type Butterworth-Van Dyke model for dual-mode Lamb-wave resonator with precise two-port Y-parameter characterizations.

    PubMed

    Wang, Yong; Hong, Yan; Goh, Wang Ling; Mu, Xiaojing

    2016-10-01

    Dual-mode Lamb-wave resonator has become a powerful component for clock reference and sensing applications, enabling efficient compensations of temperature effects, concurrent measurements of multiple environmental parameters, etc. An equivalent circuit model for the dual-mode Lamb-wave resonator is indispensable as it provides a means as well as being an effective tool for evaluating device characteristics and to aid the designing of circuitry for the resonators. This could be the first time ever that an efficient equivalent-circuit model, i.e., modified π-type Butterworth-Van Dyke model for dual-mode Lamb-wave resonators is reported. Evaluated by experiments, this model attains noteworthy agreements on both the magnitudes and phases of Y11 and Y21 of the measurement results. Compared to literature, the proposed model is capable of modeling the dual resonances efficiently. Moreover, this work also proves more accurate when viewing the Y-parameters across a wide frequency range. The gained features of this model are most beneficial for the analysis of the dual-mode Lamb-wave resonator and also for the designing of circuits.

  11. A novel filter bank for biotelemetry.

    PubMed

    Karagözoglu, B

    2001-03-01

    In a multichannel biotelemetry system, signals taken from a patient are distributed along the available frequency range (bandwidth) of the system through frequency-division-multiplexing, and combined into a single composite signal. Biological signals that are limited to low frequencies (below 10 Hz) modulate the frequencies of respective sub-carriers. Other biological signals are carried in amplitude-modulated forms. It is recognized that recovering original signals from a composite signal at the receiver side is a technical challenge when a telemetry system with narrow bandwidth capacity is used, since such a system leaves little frequency spacing between information channels. A filter bank is therefore utilized for recovering biological signals that are transmitted. The filter bank contains filter units comprising switched-capacitor filter integrated circuits. The filters have two distinct and opposing outputs (band-stop (notch) and band-pass). Since most biological signals are at low frequencies, and modulated signals occupy a narrow band around the carrier, notch filters can be used to efficiently stop signals in the narrow frequency range. Once the interim channels are removed, other channels become well separated from each other, and band-pass filters can select them. In the proposed system, efficient filtering of closely packed channels is achieved, with low interference, from neighboring channels. The filter bank is applied to a system that carries four biological signals and a battery status indicator signal. Experimental results reinforce theoretical predictions that the filter bank successfully de-multiplexes closely packed information channels with low crosstalk between them. It is concluded that the proposed filter bank allows utilization of cost-effective multichannel biotelemetry systems that are designed around commercial audio devices, and that it can be readily adapted to a broad range of physiological recording requirements.

  12. Applications of the magneto-optical filter to stellar pulsation measurements

    NASA Technical Reports Server (NTRS)

    Rhodes, Edward J., Jr.; Cacciani, Alessandro; Tomczyk, Steven

    1986-01-01

    A proposed method of employing the Cacciani magneto-optical filter (MOF) for stellar seismology studies is described. The method relies on the fact that the separation of the filter bandpasses in the MOF can be changed by varying the level of input power to the filter cells. With the use of a simple servosystem the bandpass of a MOF can be tuned to compensate for the changes in the radial velocity of a star introduced by the orbital motion of the earth. Such a tuned filter can then be used to record intensity fluctuations through the MOF bandpass over an extended period of time for each given star. Also, the use of a two cell version of the MOF makes it possible to alternately chop between the bandpass located in the stellar line wing and a second bandpass located in the stellar continuum. Rapid interchange between the two channels makes it possible for atmospheric-introduced noise to be removed from the time series.

  13. Applications of the magneto-optical filter to stellar pulsation measurements

    NASA Technical Reports Server (NTRS)

    Rhodes, E. J., Jr.; Cacciani, A.; Tomczyk, S.

    1984-01-01

    A proposed method of employing the Cacciani magneto-optical filter (MOF) for stellar seismology studies is described. The method relies on the fact that the separation of the filter bandpasses in the MOF can be changed by varying the level of input power to the filter cells. With the use of a simple servosystem the bandpass of a MOF can be tuned to compensate for the changes in the radial velocity of a star introduced by the orbital motion of the Earth. Such a tuned filter can then be used to record intensity fluctuations through the MOF bandpass over an extended period of time for each given star. Also, the use of a two cell version of the MOF makes it possible to alternately chop between the bandpass located in the stellar line wing and a second bandpass located in the stellar continuum. Rapid interchange between the two channels makes it possible for atmospheric-introduced noise to be removed from the time series.

  14. Applications of the magneto-optical filter to stellar pulsation measurements

    NASA Technical Reports Server (NTRS)

    Rhodes, Edward J., Jr.; Cacciani, Alessandro; Tomczyk, Steven

    1986-01-01

    A proposed method of employing the Cacciani magneto-optical filter (MOF) for stellar seismology studies is described. The method relies on the fact that the separation of the filter bandpasses in the MOF can be changed by varying the level of input power to the filter cells. With the use of a simple servosystem the bandpass of a MOF can be tuned to compensate for the changes in the radial velocity of a star introduced by the orbital motion of the earth. Such a tuned filter can then be used to record intensity fluctuations through the MOF bandpass over an extended period of time for each given star. Also, the use of a two cell version of the MOF makes it possible to alternately chop between the bandpass located in the stellar line wing and a second bandpass located in the stellar continuum. Rapid interchange between the two channels makes it possible for atmospheric-introduced noise to be removed from the time series.

  15. Electronically Tunable High Input Impedance Voltage-Mode Multifunction Filter

    NASA Astrophysics Data System (ADS)

    Chen, Hua-Pin; Yang, Wan-Shing

    A novel electronically tunable high input impedance voltage-mode multifunction filter with single inputs and three outputs employing two single-output-operational transconductance amplifiers, one differential difference current conveyor and two capacitors is proposed. The presented filter can be realized the highpass, bandpass and lowpass functions, simultaneously. The input of the filter exhibits high input impedance so that the synthesized filter can be cascaded without additional buffers. The circuit needs no any external resistors and employs two grounded capacitors, which is suitable for integrated circuit implementation.

  16. Acousto-optic tunable filter imaging spectrometers

    NASA Technical Reports Server (NTRS)

    Chao, Tien-Hsin; Yu, Jeffrey; Reyes, George; Rider, David; Cheng, Li-Jen

    1991-01-01

    A remote sensing multispectral imaging instrument is being developed that uses a high resolution, fast programmable acoustooptic tunable filter (AOTF) as the spectral bandpass filter. A compact and fully computer controllable AOTF-based imaging spectrometer that operates in the visible wavelength range (0.5-0.8 microns) has been built and tested with success. A second imaging spectrometer operating in the near-infrared wavelength range (1.2-2.4 microns) is also under experimental investigation. The design criteria meeting various system issues, such as imaging quality, spectral response, and field of view (FOV), are discussed. An experiment using this AOTF imaging spectrometer breadboard is described.

  17. Analysis and composition of a new microwave filter configuration with inhomogeneous dielectric medium

    NASA Astrophysics Data System (ADS)

    Fukasawa, A.

    1982-09-01

    A theoretical study has been undertaken to solve inter-resonator coupling problems, and to design a new structure of microwave bandpass filter. This filter is composed of quarter-wavelength resonators arranged in a housing with the same ends short-circuited. This arrangement of resonators has never been utilized to compose bandpass filters because of the small inter-resonator coupling. The coupling coefficient of TEM resonant lines has been derived theoretically and expressed with capacitive parameters of the coupled lines. The accurate values of capacitances of the lines were obtained by the numerical analysis of the TEM field. By a simple method to make the medium inhomogeneous through removing the dielectric partially, a simplified structure of filter has first been realized based on this theory. Through numerical analysis by the finite difference method, this structure is also shown to have higher unloaded Q of resonator than conventional dielectric-filled coaxial filters to minimize the volume of filters.

  18. Wideband tunable optoelectronic oscillator based on a phase modulator and a tunable optical filter.

    PubMed

    Xie, Xiaopeng; Zhang, Cheng; Sun, Tao; Guo, Peng; Zhu, Xiaoqi; Zhu, Lixin; Hu, Weiwei; Chen, Zhangyuan

    2013-03-01

    A widely tunable optoelectronic oscillator (OEO) based on a broadband phase modulator and a tunable optical bandpass filter is proposed and experimentally demonstrated. A tunable range from 4.74 to 38.38 GHz is realized by directly tuning the bandwidth of the optical bandpass filter. To the best of our knowledge, this is the widest fundamental frequency tunable range ever achieved by an OEO. The phase noise performance of the generated signal is also investigated. The single-sideband phase noise is below -120 dBc/Hz at an offset of 10 KHz within the whole tunable range.

  19. Feasibility of nanofluid-based optical filters.

    PubMed

    Taylor, Robert A; Otanicar, Todd P; Herukerrupu, Yasitha; Bremond, Fabienne; Rosengarten, Gary; Hawkes, Evatt R; Jiang, Xuchuan; Coulombe, Sylvain

    2013-03-01

    In this article we report recent modeling and design work indicating that mixtures of nanoparticles in liquids can be used as an alternative to conventional optical filters. The major motivation for creating liquid optical filters is that they can be pumped in and out of a system to meet transient needs in an application. To demonstrate the versatility of this new class of filters, we present the design of nanofluids for use as long-pass, short-pass, and bandpass optical filters using a simple Monte Carlo optimization procedure. With relatively simple mixtures, we achieve filters with <15% mean-squared deviation in transmittance from conventional filters. We also discuss the current commercial feasibility of nanofluid-based optical filters by including an estimation of today's off-the-shelf cost of the materials. While the limited availability of quality commercial nanoparticles makes it hard to compete with conventional filters, new synthesis methods and economies of scale could enable nanofluid-based optical filters in the near future. As such, this study lays the groundwork for creating a new class of selective optical filters for a wide range of applications, namely communications, electronics, optical sensors, lighting, photography, medicine, and many more.

  20. Multi-frequency weak signal detection based on wavelet transform and parameter compensation band-pass multi-stable stochastic resonance

    NASA Astrophysics Data System (ADS)

    Han, Dongying; li, Pei; An, Shujun; Shi, Peiming

    2016-03-01

    In actual fault diagnosis, useful information is often submerged in heavy noise, and the feature information is difficult to extract. A novel weak signal detection method aimed at the problem of detecting multi-frequency signals buried under heavy background noise is proposed based on wavelet transform and parameter compensation band-pass multi-stable stochastic resonance (SR). First, the noisy signal is processed by parameter compensation, with the noise and system parameters expanded 10 times to counteract the effect of the damping term. The processed signal is decomposed into multiple signals of different scale frequencies by wavelet transform. Following this, we adjust the size of the scaled signals' amplitudes and reconstruct the signals; the weak signal frequency components are then enhanced by multi-stable stochastic resonance. The enhanced components of the signal are processed through a band-pass filter, leaving the enhanced sections of the signal. The processed signal is analyzed by FFT to achieve detection of the multi-frequency weak signals. The simulation and experimental results show that the proposed method can enhance the signal amplitude, can effectively detect multi-frequency weak signals buried under heavy noise and is valuable and usable for bearing fault signal analysis.

  1. Bandpass Sampling--An Opportunity to Stress the Importance of In-Depth Understanding

    ERIC Educational Resources Information Center

    Stern, Harold P. E.

    2010-01-01

    Many bandpass signals can be sampled at rates lower than the Nyquist rate, allowing significant practical advantages. Illustrating this phenomenon after discussing (and proving) Shannon's sampling theorem provides a valuable opportunity for an instructor to reinforce the principle that innovation is possible when students strive to have a complete…

  2. Polarization and angle insensitive dual-band bandpass frequency selective surface using all-dielectric metamaterials

    NASA Astrophysics Data System (ADS)

    Yu, Fei; Wang, Jun; Wang, Jiafu; Ma, Hua; Du, Hongliang; Xu, Zhuo; Qu, Shaobo

    2016-04-01

    In this paper, we demonstrate a dual-band bandpass all-dielectric frequency selective surface (FSS), the building elements of which are high-permittivity ceramic particles rather than metallic patterns. With proper structural design and parameter adjustment, the resonant frequency can be tuned at will. Dual-band bandpass response can be realized due to the coupling between electric and magnetic resonances. As an example, a dual-band bandpass FSS is designed in Ku band, which is composed of two-dimensional periodic arrays of complementary quatrefoil structures (CQS) cut from dielectric plates. Moreover, cylindrical dielectric resonators are introduced and placed in the center of each CQS to broaden the bandwidth and to sharpen the cut-off frequency. Theoretical analysis shows that the bandpass response arises from impedance matching caused by electric and magnetic resonances. In addition, effective electromagnetic parameters and dynamic field distributions are presented to explain the mechanism of impedance matching. The proposed FSS has the merits of polarization independence, stable transmission, and sharp roll-off frequency. The method can also be used to design all-dielectric FSSs with continuum structures at other frequencies.

  3. Noise-Coupled Image Rejection Architecture of Complex Bandpass ΔΣAD Modulator

    NASA Astrophysics Data System (ADS)

    San, Hao; Kobayashi, Haruo

    This paper proposes a new realization technique of image rejection function by noise-coupling architecture, which is used for a complex bandpass ΔΣAD modulator. The complex bandpass ΔΣAD modulator processes just input I and Q signals, not image signals, and the AD conversion can be realized with low power dissipation. It realizes an asymmetric noise-shaped spectra, which is desirable for such low-IF receiver applications. However, the performance of the complex bandpass ΔΣAD modulator suffers from the mismatch between internal analog I and Q paths. I/Q path mismatch causes an image signal, and the quantization noise of the mirror image band aliases into the desired signal band, which degrades the SQNDR (Signal to Quantization Noise and Distortion Ratio) of the modulator. In our proposed modulator architecture, an extra notch for image rejection is realized by noise-coupled topology. We just add some passive capacitors and switches to the modulator; the additional integrator circuit composed of an operational amplifier in the conventional image rejection realization is not necessary. Therefore, the performance of the complex modulator can be effectively raised without additional power dissipation. We have performed simulation with MATLAB to confirm the validity of the proposed architecture. The simulation results show that the proposed architecture can achieve the realization of image-rejection effectively, and improve the SQNDR of the complex bandpass ΔΣAD modulator.

  4. Digital frequency tracking filter design

    NASA Astrophysics Data System (ADS)

    Yeh, Hen-Geul

    In this paper, three design approaches of the digital frequency tracking filter are presented. The common structure of these approaches are: (1) to have a bank of filters to process the received signals (signals are separated into a few sections as the excitation frequency sweeps from low to high) from the test specimen, (2) to use the Welsh method to compute the spectral density via the FFT (Fast Fourier Transform) algorithm. The bandpass filter bank is employed in the 1st approach to remove the noise which is contained in all sections of received signals. The decimation and interpolation schemes are used in the 2nd approach to reduce the unnecessary computations which exist in the over sampled sections of received signals. The modulation and demodulation schemes (for high-frequency sections only) combined with decimation and interpolation schemes (for over sampled section only) are employed in the 3rd approach. The modulation and demodulation schemes are used to shift the spectrum from high-frequency to low-frequency for simplying the filtering process via LPFs (Low Pass Filters).

  5. Application of nonlinearity to wavelet-transformed images to improve correlation filter performance

    NASA Astrophysics Data System (ADS)

    Jamal-Aldin, Lamia S.; Young, Rupert C. D.; Chatwin, Chris R.

    1997-12-01

    A useful filter for pattern recognition must strike a compromise between the conflicting requirements of in-class distortion tolerance and out-of-class discrimination. Such a filter will be bandpass in nature, the high-frequency response being attenuated to provide less sensitivity to in-class variations, while the low frequencies must be removed, since they compromise the discrimination ability of the filter. A convenient bandpass is the difference of Gaussian (DOG) function, which provides a close approximation to the Laplacian of Gaussian. We describe the effect of a preprocessing operation applied to a DOG filtered image. This operation is shown to result in greater tolerance to in-class variation while maintaining an excellent discrimination ability. Additionally, the introduction of nonlinearity is shown to provide greater robustness in the filter response to noise and background clutter in the input scene.

  6. Metal-mesh optical filter technology for mid-IR, far-IR, and submillimeter

    NASA Astrophysics Data System (ADS)

    McGovern, William R.; Swinehart, Philip R.; Hogue, Eric L.; Daughton, David R.; DeLombard, Jay V.

    2012-06-01

    The innovative, high transmission band-pass filter technology presented here for the mid infrared (IR), terahertz (THz) and submillimeter ranges can tolerate cryogenic temperatures (down to 4K and below), are radiation-hard, vacuum-compatible and vibration-tolerant making them launch-capable and durable for potential space applications. In addition, Lake Shore band-pass filters (BPF) are light weight, as they employ no heavy substrates, nor have any vibronic bands due to polymer support layers. The filters are less than 2 mm thick (mostly the mounting frame) which allows insertion into tight spaces and standard filter wheels. The thin, light weight, vacuum compatible design can be incorporated into almost any detector setup. Filters are available for quick delivery in 29 standard center wavelengths (CWL) with 4 standard diameter sizes, up to 40mm inner diameter (ID).

  7. Large filters for wide-field survey telescope LSST

    NASA Astrophysics Data System (ADS)

    Morgado, Nazario; Pinard, Laurent; Sassolas, Benoit; Flaminio, Raffaele; Forest, Daniéle; Lagrange, Bernard; Michel, Christophe; Antilogus, Pierre

    2012-09-01

    The LSST design foresees the use of six wide-band large optical filters that can alternatively be moved in front of the CCD camera. Each of the six filters has a different band-pass covering all the wavelengths from 300 nm to 1200 nm. The way to achieve this is to coat an optimized optical thin films stack on a filter substrate. Each filter requires a specific design using specific appropriate materials. The main characteristics of these filters, that constitute a real technological challenge, are: their relatively large size - their radii of curvature (about 5.6 m) that represent a sagitta of 12,5 mm that increases the uniformity complexity, the large rejection band requirements with transmission lower than 0.01 % out of the band and a transmission of 95 % over the band-pass. This paper proposes to show the problematic and the results obtained at LMA (Laboratoire des Matériaux Avancés-FRANCE) to the purpose of realizing these filters using the IBS (Ion Beam Sputtering) deposition technique. The results obtained with High-Pass/Low-Pass structures will be presented. Experimental results will be shown concerning the R-band filter (552-691 nm). An overview of the work to be done to realize transmittance map over large filters will be given.

  8. MSK and offset QPSK modulation with bandlimiting filters

    NASA Astrophysics Data System (ADS)

    Prabhu, V. K.

    1981-01-01

    It is considered by some that minimum shift keying (MSK) is spectrally more efficient than quaternary phase-shift keying/offset quadrature phase-shift keying (QPSK/OQPSK). An analytical method is presented here for determining the detection efficiencies of MSK and QPSK/OQPSK when the constant-envelope signal is passed through a set of filters and when the resulting signal is corrupted by Gaussian noise. The detection efficiency of MSK is compared with that of QPSK/OQPSK when a four-pole Butterworth filter is used as a transmit filter and for two different receive filter functions. When the two-sided 3-dB bandwidth of the transmit filter is between approximately 1.00/T and 1.50/T, it is shown that the detection efficiency of MSK is not substantially different from that of QPSK/OQPSK. For more severe bandlimiting of the signal, the performance of MSK is shown to be inferior to that of QPSK/OQPSK. It is, therefore, concluded that MSK does not have significantly better detection efficiency when the effect of bandlimiting filters is taken into account.

  9. Isotropically sensitive optical filter employing atomic resonance transitions

    DOEpatents

    Marling, J.B.

    An ultra-high Q isotropically sensitive optical filter or optical detector is disclosed employing atomic resonance transitions. More specifically, atomic resonance transitions utilized in conjunction with two optical bandpass filters provide an optical detector having a wide field of view (approx. 2 ..pi.. steradians) and very narrow acceptance bandwidth approaching 0.01A. A light signal to be detected is transmitted through an outer bandpass filter into a resonantly absorbing atomic vapor, the excited atomic vapor than providing a fluorescence signal at a different wavelength which is transmitted through an inner bandpass filters have no common transmission band, therby resulting in complete blockage of all optical signals that are not resonantly shifted in wavelength by the intervening atomic vapor. Two embodiments are disclosed, one in which the light signal raises atoms contained in the atomic vapor from the ground state to an excited state from which fluorescence occurs, and the other in which a pump laser is used to raise the atoms in the ground state to a first excited state from which the light signal then is resonantly absorbed, thereby raising the atoms to a second excited state from which fluorescence occurs. A specific application is described in which an optical detector according to the present invention can be located in an orbiting satellite.

  10. Input-Feedforward Two-Path Band-Pass Delta-Sigma Modulator Based on Horizontal or Vertical Opamp Sharing Technique

    NASA Astrophysics Data System (ADS)

    Waki, Naoya; Sato, Hiroki; Hyogo, Akira; Sekine, Keitaro

    In this paper, horizontal (where an opamp is shared in two adjacent stages) and vertical (where an opamp is shared across two paths) opamp sharing techniques for a two-path band-pass (BP) ΔΣ modulator are described, and input-feedforward two-path fourth-order BP ΔΣ modulators that have only two opamps are proposed. The proposed modulators are based on the horizontal or vertical opamp sharing technique. They can be realized with both a summation circuit using a switched capacitor (SC) network and a second-order high-pass filter (HPF) with a horizontal shared opamp or a double-sampling first-order HPF with a vertical shared opamp, which are based on an SC first-order HPF with an opamp. These techniques can reduce the number of opamps with no additional component and the chip area as well as realize lower power consumption.

  11. A MEMS disk resonator-based band pass filter electrical equivalent circuit simulation

    SciTech Connect

    Sundaram, G. M.; Angira, Mahesh; Gupta, Navneet; Rangra, Kamaljit

    2016-04-13

    In this paper, coupled beam bandpass Disk filter is designed for 1 MHz bandwidth. Filter electrical equivalent circuit simulation is performed using circuit simulators. Important filter parameters such as insertion loss, shape factor and Q factor aresetimated using coventorware simulation. Disk resonator based radial contour mode filter provides 1.5 MHz bandwidth and unloaded quality factor of resonator and filter as 233480, 21797 respectively. From the simulation result it’s found that insertion loss minimum is 151.49 dB, insertion loss maximum is 213.94 dB, and 40 dB shape factor is 4.17.

  12. Low-power Gm-C filter employing current-reuse differential difference amplifiers

    DOE PAGES

    Mincey, John S.; Briseno-Vidrios, Carlos; Silva-Martinez, Jose; ...

    2016-08-10

    This study deals with the design of low-power, high performance, continuous-time filters. The proposed OTA architecture employs current-reuse differential difference amplifiers in order to produce more power efficient Gm-C filter solutions. To demonstrate this, a 6th order low-pass Butterworth filter was designed in 0.18 m CMOS achieving a 65-MHz -3-dB frequency, an in-band input-referred third-order intercept point of 12.0 dBm, and an input referred noise density of 40 nV/Hz1=2, while only consuming 8.07 mW from a 1.8 V supply and occupying a total chip area of 0.21 mm2 with a power consumption of only 1.19 mW per pole.

  13. Spectral and Wavefront Error Performance of WFIRST/AFTA Prototype Filters

    NASA Technical Reports Server (NTRS)

    Quijada, Manuel; Seide, Laurie; Marx, Cathy; Pasquale, Bert; McMann, Joseph; Hagopian, John; Dominguez, Margaret; Gong, Qian; Morey, Peter

    2016-01-01

    The Cycle 5 design baseline for the Wide-Field Infrared Survey Telescope Astrophysics Focused Telescope Assets (WFIRSTAFTA) instrument includes a single wide-field channel (WFC) instrument for both imaging and slit-less spectroscopy. The only routinely moving part during scientific observations for this wide-field channel is the element wheel (EW) assembly. This filter-wheel assembly will have 8 positions that will be populated with 6 bandpass filters, a blank position, and a Grism that will consist of a three-element assembly to disperse the full field with an undeviated central wavelength for galaxy redshift surveys. All filter elements in the EW assembly will be made out of fused silica substrates (110 mm diameter) that will have the appropriate bandpass coatings according to the filter designations (Z087, Y106, J129, H158, F184, W149 and Grism). This paper presents and discusses the performance (including spectral transmission and reflectedtransmitted wavefront error measurements) of a subset of bandpass filter coating prototypes that are based on the WFC instrument filter compliment. The bandpass coating prototypes that are tested in this effort correspond to the Z087, W149, and Grism filter elements. These filter coatings have been procured from three different vendors to assess the most challenging aspects in terms of the in-band throughput, out of band rejection (including the cut-on and cutoff slopes), and the impact the wavefront error distortions of these filter coatings will have on the imaging performance of the de-field channel in the WFIRSTAFTA observatory.

  14. Parasitic analysis and π-type Butterworth-Van Dyke model for complementary-metal-oxide-semiconductor Lamb wave resonator with accurate two-port Y-parameter characterizations

    NASA Astrophysics Data System (ADS)

    Wang, Yong; Goh, Wang Ling; Chai, Kevin T.-C.; Mu, Xiaojing; Hong, Yan; Kropelnicki, Piotr; Je, Minkyu

    2016-04-01

    The parasitic effects from electromechanical resonance, coupling, and substrate losses were collected to derive a new two-port equivalent-circuit model for Lamb wave resonators, especially for those fabricated on silicon technology. The proposed model is a hybrid π-type Butterworth-Van Dyke (PiBVD) model that accounts for the above mentioned parasitic effects which are commonly observed in Lamb-wave resonators. It is a combination of interdigital capacitor of both plate capacitance and fringe capacitance, interdigital resistance, Ohmic losses in substrate, and the acoustic motional behavior of typical Modified Butterworth-Van Dyke (MBVD) model. In the case studies presented in this paper using two-port Y-parameters, the PiBVD model fitted significantly better than the typical MBVD model, strengthening the capability on characterizing both magnitude and phase of either Y11 or Y21. The accurate modelling on two-port Y-parameters makes the PiBVD model beneficial in the characterization of Lamb-wave resonators, providing accurate simulation to Lamb-wave resonators and oscillators.

  15. Parasitic analysis and π-type Butterworth-Van Dyke model for complementary-metal-oxide-semiconductor Lamb wave resonator with accurate two-port Y-parameter characterizations.

    PubMed

    Wang, Yong; Goh, Wang Ling; Chai, Kevin T-C; Mu, Xiaojing; Hong, Yan; Kropelnicki, Piotr; Je, Minkyu

    2016-04-01

    The parasitic effects from electromechanical resonance, coupling, and substrate losses were collected to derive a new two-port equivalent-circuit model for Lamb wave resonators, especially for those fabricated on silicon technology. The proposed model is a hybrid π-type Butterworth-Van Dyke (PiBVD) model that accounts for the above mentioned parasitic effects which are commonly observed in Lamb-wave resonators. It is a combination of interdigital capacitor of both plate capacitance and fringe capacitance, interdigital resistance, Ohmic losses in substrate, and the acoustic motional behavior of typical Modified Butterworth-Van Dyke (MBVD) model. In the case studies presented in this paper using two-port Y-parameters, the PiBVD model fitted significantly better than the typical MBVD model, strengthening the capability on characterizing both magnitude and phase of either Y11 or Y21. The accurate modelling on two-port Y-parameters makes the PiBVD model beneficial in the characterization of Lamb-wave resonators, providing accurate simulation to Lamb-wave resonators and oscillators.

  16. Performance of a Y-Ba-Cu-O superconducting filter/GaAs low noise amplifier hybrid circuit

    NASA Technical Reports Server (NTRS)

    Bhasin, Kul B.; Toncich, S. S.; Chorey, C. M.; Bonetti, R. R.; Williams, A. E.

    1992-01-01

    A superconducting 7.3 GHz two-pole microstrip bandpass filter and a GaAs low noise amplifier (LNA) were combined into a hybrid circuit and characterized at liquid nitrogen temperatures. This superconducting/seismology circuit's performance was compared to a gold filter/GaAs LNA hybrid circuit. The superconducting filter/GaAs LNA hybrid circuit showed higher gain and lower noise figure than its gold counterpart.

  17. Performance of a Y-Ba-Cu-O superconducting filter/GaAs low noise amplifier hybrid circuit

    NASA Technical Reports Server (NTRS)

    Bhasin, K. B.; Toncich, S. S.; Chorey, C. M.; Bonetti, R. R.; Williams, A. E.

    1992-01-01

    A superconducting 7.3 GHz two-pole microstrip bandpass filter and a GaAs low noise amplifier (LNA) were combined into an active circuit and characterized at liquid nitrogen temperatures. This superconducting/semiconducting circuit's performance was compared to a gold filter/GaAs LNA hybrid circuit. The superconducting filter/GaAs LNA hybrid circuit showed higher gain and lower noise figure than its gold counterpart.

  18. Development of filter exchangeable 3CCD camera for multispectral imaging acquisition

    NASA Astrophysics Data System (ADS)

    Lee, Hoyoung; Park, Soo Hyun; Kim, Moon S.; Noh, Sang Ha

    2012-05-01

    There are a lot of methods to acquire multispectral images. Dynamic band selective and area-scan multispectral camera has not developed yet. This research focused on development of a filter exchangeable 3CCD camera which is modified from the conventional 3CCD camera. The camera consists of F-mounted lens, image splitter without dichroic coating, three bandpass filters, three image sensors, filer exchangeable frame and electric circuit for parallel image signal processing. In addition firmware and application software have developed. Remarkable improvements compared to a conventional 3CCD camera are its redesigned image splitter and filter exchangeable frame. Computer simulation is required to visualize a pathway of ray inside of prism when redesigning image splitter. Then the dimensions of splitter are determined by computer simulation which has options of BK7 glass and non-dichroic coating. These properties have been considered to obtain full wavelength rays on all film planes. The image splitter is verified by two line lasers with narrow waveband. The filter exchangeable frame is designed to make swap bandpass filters without displacement change of image sensors on film plane. The developed 3CCD camera is evaluated to application of detection to scab and bruise on Fuji apple. As a result, filter exchangeable 3CCD camera could give meaningful functionality for various multispectral applications which need to exchange bandpass filter.

  19. Photonic aided bandpass sampling in coherent phase modulated radio-over-fiber links

    NASA Astrophysics Data System (ADS)

    Cao, Minghua; Li, Jianqiang; Dai, Jian; Dai, Yitang; Yin, Feifei; Zhou, Yue; Xu, Kun

    2016-06-01

    We have experimentally presented a digital coherent receiver employing photonic aided bandpass sampling technology for phase-modulated radio-over-fiber (RoF) links. An optical intensity modulator (IM) is utilized as the bandpass sampler which performs encoded on-off keyed pulse sequence on the optical local oscillator. Quaternary Phase Shift Keying (QPSK) modulated data signal with 20 MHz bandwidth at 5.2 GHz, 10.2 GHz and 15.2 GHz RF carrier frequency is experimentally demonstrated to be successfully detected by using balanced photodiodes (BPDs) with only 800 MHz analog bandwidth. It demonstrates that the required analog bandwidth of BPDs and ADCs can be dramatically reduced in a direct sampled coherent RoF communications system.

  20. Filter arrays

    DOEpatents

    Page, Ralph H.; Doty, Patrick F.

    2017-08-01

    The various technologies presented herein relate to a tiled filter array that can be used in connection with performance of spatial sampling of optical signals. The filter array comprises filter tiles, wherein a first plurality of filter tiles are formed from a first material, the first material being configured such that only photons having wavelengths in a first wavelength band pass therethrough. A second plurality of filter tiles is formed from a second material, the second material being configured such that only photons having wavelengths in a second wavelength band pass therethrough. The first plurality of filter tiles and the second plurality of filter tiles can be interspersed to form the filter array comprising an alternating arrangement of first filter tiles and second filter tiles.

  1. Disk filter

    DOEpatents

    Bergman, W.

    1985-01-09

    An electric disk filter provides a high efficiency at high temperature. A hollow outer filter of fibrous stainless steel forms the ground electrode. A refractory filter material is placed between the outer electrode and the inner electrically isolated high voltage electrode. Air flows through the outer filter surfaces through the electrified refractory filter media and between the high voltage electrodes and is removed from a space in the high voltage electrode.

  2. Disk filter

    DOEpatents

    Bergman, Werner

    1986-01-01

    An electric disk filter provides a high efficiency at high temperature. A hollow outer filter of fibrous stainless steel forms the ground electrode. A refractory filter material is placed between the outer electrode and the inner electrically isolated high voltage electrode. Air flows through the outer filter surfaces through the electrified refractory filter media and between the high voltage electrodes and is removed from a space in the high voltage electrode.

  3. Digital linearization of multi-carrier RF link with photonic bandpass sampling.

    PubMed

    Dai, Yitang; Liang, Xiaodong; Yin, Feifei; Zhou, Yue; Zhang, Junyi; Yu, Lan; Li, Jianqiang; Xu, Kun

    2015-09-07

    Due to the capacity in simultaneously down-converting and receiving ultra-wideband, multi-carrier radio frequency (RF) or microwave signals, the photonic bandpass sampling has found more and more applications in multi-carrier communication, frequency-agile coherent radar, compressive sensing, etc. The nonlinear transfer during the electronics-to-optics conversion results in distortions, which are bandpass sampled and frequency-folded within the first Nyquist zone, together with the target signals. Because of the multi-octave-span operation, all nonlinearities must be considered besides the usually-concerned third-order inter-modulation distortion (IMD3). We show theoretically that a photonic bandpass sampling link is equivalent to a baseband digital nonlinear link, and then propose a corresponding linearization scheme for the output signal. Such digital linearization is capable of suppressing all types of distortions. Both numerical and experimental examples are demonstrated, where all of the 3rd-order nonlinearities, including the internal and external IMD3, the cross modulation, and 3rd-order harmonics, are well eliminated.

  4. A miniature filter on a suspended substrate with a two-sided pattern of strip conductors

    NASA Astrophysics Data System (ADS)

    Belyaev, B. A.; Voloshin, A. S.; Bulavchuk, A. S.; Galeev, R. G.

    2016-06-01

    A miniature bandpass filter of new design with original stripline resonators on suspended substrate has been studied. The proposed filters of third to sixth order are distinguished for their high frequency-selective properties and mush smaller size in comparison to analogs. It is shown that a broad stopband extending above three-fold central bandpass frequency is determined by weak coupling of resonators at resonances of the second and third modes. A prototype sixth-order filter with a central frequency of 1 GHz, manufactured on a ceramic substrate with dielectric permittivity ɛ = 80, has contour dimensions of 36.6 × 4.8 × 0.5 mm3. Parametric synthesis of the filter, based on electrodynamic 3D model simulations, showed quite good agreement with the results of measurements.

  5. Wide bandwidth and high resolution planar filter array based on DBR-metasurface-DBR structures

    DOE PAGES

    Horie, Yu; Arbabi, Amir; Arbabi, Ehsan; ...

    2016-05-19

    Here, we propose and experimentally demonstrate a planar array of optical bandpass filters composed of low loss dielectric metasurface layers sandwiched between two distributed Bragg reflectors (DBRs). The two DBRs form a Fabry-Perot resonator whose center wavelength is controlled by the design of the transmissive metasurface layer which functions as a phase shifting element. We demonstrate an array of bandpass filters with spatially varying center wavelengths covering a wide range of operation wavelengths of 250nm around λ = 1550nm (Δλ/λ = 16%). The center wavelengths of each filter are independently controlled only by changing the in-plane geometry of the sandwichedmore » metasurfaces, and the experimentally measured quality factors are larger than 700. The demonstrated filter array can be directly integrated on top of photodetector arrays to realize on-chip high-resolution spectrometers with free-space coupling.« less

  6. Wide bandwidth and high resolution planar filter array based on DBR-metasurface-DBR structures

    SciTech Connect

    Horie, Yu; Arbabi, Amir; Arbabi, Ehsan; Kamali, Seyedeh Mahsa; Faraon, Andrei

    2016-05-19

    Here, we propose and experimentally demonstrate a planar array of optical bandpass filters composed of low loss dielectric metasurface layers sandwiched between two distributed Bragg reflectors (DBRs). The two DBRs form a Fabry-Perot resonator whose center wavelength is controlled by the design of the transmissive metasurface layer which functions as a phase shifting element. We demonstrate an array of bandpass filters with spatially varying center wavelengths covering a wide range of operation wavelengths of 250nm around λ = 1550nm (Δλ/λ = 16%). The center wavelengths of each filter are independently controlled only by changing the in-plane geometry of the sandwiched metasurfaces, and the experimentally measured quality factors are larger than 700. The demonstrated filter array can be directly integrated on top of photodetector arrays to realize on-chip high-resolution spectrometers with free-space coupling.

  7. Gas refractometry based on an all-fiber spatial optical filter.

    PubMed

    Silva, Susana; Coelho, L; André, R M; Frazão, O

    2012-08-15

    A spatial optical filter based on splice misalignment between optical fibers with different diameters is proposed for gas refractometry. The sensing head is formed by a 2 mm long optical fiber with 50 μm diameter that is spliced with a strong misalignment between two single-mode fibers (SMF28) and interrogated in transmission. The misalignment causes a Fabry-Perot behavior along the reduced-size fiber and depending on the lead-out SMF28 position, it is possible to obtain different spectral responses, namely, bandpass or band-rejection filters. It is shown that the spatial filter device is highly sensitive to refractive index changes on a nitrogen environment by means of the gas pressure variation. A maximum sensitivity of -1390 nm/RIU for the bandpass filter was achieved. Both devices have shown similar temperature responses with an average sensitivity of 25.7 pm/°C.

  8. Application of high-pass filtering techniques on gravity and magnetic data of the eastern Qattara Depression area, Western Desert, Egypt

    NASA Astrophysics Data System (ADS)

    Zahra, Hesham Shaker; Oweis, Hesham T.

    2016-06-01

    In this work, a reconnaissance study is presented to delineate the subsurface tectonics and lithological inferences of the eastern area of Qattara Depression using the Bouguer gravity and aeromagnetic data. To achieve this goal, several transformation techniques and filtering processes are accomplished on these maps. At first, the total intensity aeromagnetic map is processed through the application of reduction to the magnetic north pole technique. The fast Fourier transform is carried out on the gravity and RTP magnetic data for establishing and defining the residual (shallow) sources. The frequency high-pass filtering is used to enhance the anomaly wavelengths associated with the shallow sources. The used processing techniques are the polynomial surface fitting enhancement, Laplacian, Strike Filtering, Enhancement Utilization, Suppression Utilization, Butterworth Filtering Utilization, Butterworth high-pass filter, Euler's deconvolution and forward modeling. The equivalent depths of the isolated short wavelength anomalies are 0.759 and 0.340 km below the flight surface, and the depths of the intermediate wavelength anomalies are 1.28 and 2.00 km for the gravity and magnetic data, respectively. Finally, the quantitative interpretations of the Bouguer gravity and RTP magnetic maps of the study area, reflect the occurrence of the various types of structures and their components. The main tectonic deformations of the study area have NNW-SSE, NNE-SSW, NE-SW, NW-SE and E-W trends.

  9. The effect of filtering on Granger causality based multivariate causality measures.

    PubMed

    Florin, Esther; Gross, Joachim; Pfeifer, Johannes; Fink, Gereon R; Timmermann, Lars

    2010-04-01

    In the past, causality measures based on Granger causality have been suggested for assessing directionality in neural signals. In frequency domain analyses (power or coherence) of neural data, it is common to preprocess the time series by filtering or decimating. However, in other fields, it has been shown theoretically that filtering in combination with Granger causality may lead to spurious or missed causalities. We investigated whether this result translates to multivariate causality methods derived from Granger causality with (a) a simulation study and (b) an application to magnetoencephalographic data. To this end, we performed extensive simulations of the effect of applying different filtering techniques and evaluated the performance of five different multivariate causality measures in combination with two numerical significance measures (random permutation and leave one out method). The analysis included three of the most widely used filters (high-pass, low-pass, notch filter), four different filter types (Butterworth, Chebyshev I and II, elliptic filter), variation of filter order, decimating and interpolation. The simulation results suggest that preprocessing without a strong prior about the artifact to be removed disturbs the information content and time ordering of the data and leads to spurious and missed causalities. Only if apparent artifacts like a current or movement artifact are present, filtering out the respective disturbance seems advisable. While oversampling poses no problem, decimation by a factor greater than the minimum time shift between the time series may lead to wrong inferences. In general, the multivariate causality measures are very sensitive to data preprocessing.

  10. Hyperspectral imaging acousto-optic system with spatial filtering for optical phase visualization

    NASA Astrophysics Data System (ADS)

    Yushkov, Konstantin B.; Molchanov, Vladimir Ya.

    2017-06-01

    We report a method for phase visualization in the images of transparent specimens using analog image processing in incoherent light. The experimental technique is based on adaptive bandpass spatial filtering with an amplitude mask matched with an acousto-optic tunable filter in a telecentric optical system. We demonstrate the processing of microscopic images of unstained and stained histological sections of human thyroid tumor with improved contrast.

  11. Water Filters

    NASA Technical Reports Server (NTRS)

    1993-01-01

    The Aquaspace H2OME Guardian Water Filter, available through Western Water International, Inc., reduces lead in water supplies. The filter is mounted on the faucet and the filter cartridge is placed in the "dead space" between sink and wall. This filter is one of several new filtration devices using the Aquaspace compound filter media, which combines company developed and NASA technology. Aquaspace filters are used in industrial, commercial, residential, and recreational environments as well as by developing nations where water is highly contaminated.

  12. On spatial filtering for angle-of-arrival estimation in a scattering environment by eigendecomposition-based methods

    NASA Astrophysics Data System (ADS)

    Zhou, Changguo; Haber, Fred; Shi, Qun

    1990-06-01

    A method of spatial filtering is proposed as a preprocessor to restore the high resolution performance of eigendecomposition-based methods when used with a linear array for angle-of-arrival (AOA) estimation in the presence of spatially distributed coherent interference (SDCI). Applying the conventional bandpass filters used in the spatial frequency domain, the spatial filtering method effectively suppresses the unwanted coherence interference outside a specified frequency region. Therefore, the success of the method hinges on the assumption that direct arrival and its coherent interference are well separated in spatial frequency (in angle). Under this assumption, the eigendecomposition methods with a spatial filtering preprocessor can give accurate AOA estimates of direct arrivals in spite of the presence of SDCI. Simulation results are shown for the case of scattering from an infinite circular cylinder, using discrete prolate spheroidal sequences as the optimum band-pass preprocessing filters, and a uniformly spaced linear array, in a conjunction with the MUSIC algorithm.

  13. An R-peak detection method that uses an SVD filter and a search back system.

    PubMed

    Jung, Woo-Hyuk; Lee, Sang-Goog

    2012-12-01

    In this paper, we present a method for detecting the R-peak of an ECG signal by using an singular value decomposition (SVD) filter and a search back system. The ECG signal was detected in two phases: the pre-processing phase and the decision phase. The pre-processing phase consisted of the stages for the SVD filter, Butterworth High Pass Filter (HPF), moving average (MA), and squaring, whereas the decision phase consisted of a single stage that detected the R-peak. In the pre-processing phase, the SVD filter removed noise while the Butterworth HPF eliminated baseline wander. The MA removed the remaining noise of the signal that had gone through the SVD filter to make the signal smooth, and squaring played a role in strengthening the signal. In the decision phase, the threshold was used to set the interval before detecting the R-peak. When the latest R-R interval (RRI), suggested by Hamilton et al., was greater than 150% of the previous RRI, the method of detecting the R-peak in such an interval was modified to be 150% or greater than the smallest interval of the two most latest RRIs. When the modified search back system was used, the error rate of the peak detection decreased to 0.29%, compared to 1.34% when the modified search back system was not used. Consequently, the sensitivity was 99.47%, the positive predictivity was 99.47%, and the detection error was 1.05%. Furthermore, the quality of the signal in data with a substantial amount of noise was improved, and thus, the R-peak was detected effectively.

  14. Biological Filters.

    ERIC Educational Resources Information Center

    Klemetson, S. L.

    1978-01-01

    Presents the 1978 literature review of wastewater treatment. The review is concerned with biological filters, and it covers: (1) trickling filters; (2) rotating biological contractors; and (3) miscellaneous reactors. A list of 14 references is also presented. (HM)

  15. Biological Filters.

    ERIC Educational Resources Information Center

    Klemetson, S. L.

    1978-01-01

    Presents the 1978 literature review of wastewater treatment. The review is concerned with biological filters, and it covers: (1) trickling filters; (2) rotating biological contractors; and (3) miscellaneous reactors. A list of 14 references is also presented. (HM)

  16. Measuring Redshifts of Emission-line Galaxies Using Ramp Filters

    NASA Astrophysics Data System (ADS)

    Lesser, Ryan William; Bohman, John; McNeff, Mathew; Holden, Marcus; Moody, Joseph; Joner, Michael D.; Barnes, Jonathan

    2016-01-01

    Photometric redshifts are routinely obtained for galaxies without emission using broadband photometry. It is possible in theory to derive reasonably accurate (< 200 km/sec) photometric redshift values for emission-line objects using "ramp" filters with a linearly increasing/decreasing transmission through the bandpass. To test this idea we have obtained a set of filters tuned for isolating H-alpha at a redshift range of 0-10,000 km/sec. These filters consist of two that vary close to linearly in transmission, have opposite slope, and cover the wavelength range from 655nm - 685nm, plus a Stromgren y and 697nm filter to measure the continuum. Redshifts are derived from the ratio of the ramp filters indices after the continuum has been subtracted out. We are finishing the process of obtaining photometric data on a set of about 100 galaxies with known redshift to calibrate the technique and will report on our results.

  17. Low-frequency shift Raman spectroscopy using atomic filters.

    PubMed

    Xue, Xiaobo; Janisch, Corey; Chen, Yizhu; Liu, Zhiwen; Chen, Jingbiao

    2016-11-15

    A Faraday anomalous dispersion optical filter (FADOF) and an atomic resonant absorption filter are used in tandem to demonstrate a low-frequency shift Raman measurement down to few cm-1. The FADOF, with an ultralow bandwidth of 0.08  cm-1 at 780 nm, serves as a bandpass filter, while the rubidium atomic cell acts as a notch filter which has a bandwidth of 0.3  cm-1. A proof-of-concept study to measure a Raman signal generated from a silica optical fiber is performed, demonstrating a low-frequency measurement of both the Stokes and the anti-Stokes shift down to 3  cm-1 at an equivalent signal level. These results indicate the prospect for gigahertz-terahertz low-energy Raman spectroscopy based on atomic filters.

  18. Advanced astronomical filter design: challenges, strategy, and results to meet current and future requirements

    NASA Astrophysics Data System (ADS)

    Reichel, S.; Biertümpfel, R.; Brauneck, U.; Bourquin, S.; Marín-Franch, A.

    2016-07-01

    The Observatorio Astrofisico de Javalambre in Spain will conduct an all-sky astronomical survey using multi-bands, where optical filters are needed. These filters are narrow bandpass steep edge filters (FWHM = 14.5 nm) in a spectrum between 390 to 920 nm with 10.0 nm steps. In order to fulfill the demanding requirements for final scientific image quality and transmitted wavefront error a new white-light Shack Hartmann sensor and difficult refractive index measurements of the sub-assembly were needed. In addition due to the spectral requirements the design and manufacturing of the filters were pushed at its technological limit.

  19. Microwave photonic filter with multiple taps based on single semiconductor optical amplifier

    NASA Astrophysics Data System (ADS)

    Li, Xiang; Xu, Enming; Zhou, Lina; Yu, Yuan; Dong, Jianji; Zhang, Xinliang

    2010-08-01

    A novel technique to implement a microwave photonic filter structure with multiple taps and arbitrary frequency response is presented. The proposed filter is based on Four-Wave Mixing (FWM) and Cross-Gain Modulation (XGM) in a semiconductor optical amplifier (SOA). Two-tap notch filter and three-tap bandpass filter with arbitrary bipolar tap generation, high rejection ratio, and widely tunability are successfully demonstrated in the experiment. Extensions to this concept by adding new probe light to provide more taps and improve the bandwidth to high frequency regime are also discussed.

  20. Filter validation.

    PubMed

    Madsen, Russell E

    2006-01-01

    Validation of a sterilizing filtration process is critical since it is impossible with currently available technology to measure the sterility of each filled container; therefore, sterility assurance of the filtered product must be achieved through validation of the filtration process. Validating a pharmaceutical sterile filtration process involves three things: determining the effect of the liquid on the filter, determining the effect of the filter on the liquid, and demonstrating that the filter removes all microorganisms from the liquid under actual processing conditions.

  1. Metallic Filters

    NASA Technical Reports Server (NTRS)

    1985-01-01

    Filtration technology originated in a mid 1960's NASA study. The results were distributed to the filter industry, an HR Textron responded, using the study as a departure for the development of 421 Filter Media. The HR system is composed of ultrafine steel fibers metallurgically bonded and compressed so that the pore structure is locked in place. The filters are used to filter polyesters, plastics, to remove hydrocarbon streams, etc. Several major companies use the product in chemical applications, pollution control, etc.

  2. FILTER TREATMENT

    DOEpatents

    Sutton, J.B.; Torrey, J.V.P.

    1958-08-26

    A process is described for reconditioning fused alumina filters which have become clogged by the accretion of bismuth phosphate in the filter pores, The method consists in contacting such filters with faming sulfuric acid, and maintaining such contact for a substantial period of time.

  3. Water Filters

    NASA Technical Reports Server (NTRS)

    1987-01-01

    A compact, lightweight electrolytic water filter generates silver ions in concentrations of 50 to 100 parts per billion in the water flow system. Silver ions serve as effective bactericide/deodorizers. Ray Ward requested and received from NASA a technical information package on the Shuttle filter, and used it as basis for his own initial development, a home use filter.

  4. Multispectral Filter Arrays: Recent Advances and Practical Implementation

    PubMed Central

    Lapray, Pierre-Jean; Wang, Xingbo; Thomas, Jean-Baptiste; Gouton, Pierre

    2014-01-01

    Thanks to some technical progress in interferencefilter design based on different technologies, we can finally successfully implement the concept of multispectral filter array-based sensors. This article provides the relevant state-of-the-art for multispectral imaging systems and presents the characteristics of the elements of our multispectral sensor as a case study. The spectral characteristics are based on two different spatial arrangements that distribute eight different bandpass filters in the visible and near-infrared area of the spectrum. We demonstrate that the system is viable and evaluate its performance through sensor spectral simulation. PMID:25407904

  5. Tailoring of the Brillouin gain for on-chip widely tunable and reconfigurable broadband microwave photonic filters.

    PubMed

    Choudhary, Amol; Aryanfar, Iman; Shahnia, Shayan; Morrison, Blair; Vu, Khu; Madden, Stephen; Luther-Davies, Barry; Marpaung, David; Eggleton, Benjamin J

    2016-02-01

    An unprecedented Brillouin gain of 44 dB in a photonic chip enables the realization of broadly tunable and reconfigurable integrated microwave photonic filters. More than a decade bandwidth reconfigurability from 30 up to 440 MHz, with a passband ripple <1.9  dB is achieved by tailoring the Brillouin pump. The filter central frequency is continuously tuned up to 30 GHz with no degradation of the passband response, which is a major improvement over electronic filters. Furthermore, we demonstrate pump tailoring to realize multiple bandpass filters with different bandwidths and central frequencies, paving the way for multiple on-chip microwave filters and channelizers.

  6. The rule of 1s for padding kinematic data prior to digital filtering: influence of sampling and filter cutoff frequencies.

    PubMed

    Howarth, Samuel J; Callaghan, Jack P

    2009-10-01

    The influence of signal sampling frequency and the low-pass digital filter cutoff frequency on the minimum number of padding points when applied to kinematic data are factors often absent in data processing descriptions. This investigation determined a relationship between the number of padding points and the ratio of filter cutoff to signal sampling frequencies (f(c)/f(s)). Two kinematic recordings were used which represented signals with high and low deterministic variation magnitudes at the signals' beginning. Signal sampling rates (40-128 Hz) were generated at intervals of 1 Hz. Filter cutoff frequency was iterated from 2 to 10 Hz at 0.5 Hz intervals. Data extrapolation was performed using three different techniques (first order polynomial, third order polynomial, and data reflection). A maximum of 2s of padding points were added to the beginning of each test signal which was then dual-pass filtered using a second order Butterworth filter. For each successive increase in the number of padding points, the filtered test signal was compared to a criterion signal and the root mean square difference (RMSD) over the first second was calculated. The number of padding points required to attain a constant RMSD was recorded as the minimum number of padding points needed for that ratio of filter cutoff to sampling frequency. As f(c)/f(s) increased, the number of padding points decreased non-linearly. More padding points were required for the signal with higher deterministic variation at the beginning than the signal with lower deterministic variation. Additional padding points (beyond the determined minimum) did not further reduce the RMSD. The largest temporal extrapolation determined by the algorithm to produce a stable RMSD was 1s. It is suggested that a minimum of 1s of extraneous data be used when using a low-pass recursive digital filter to remove noise from kinematic data.

  7. Tunable narrow-bandpass filter based on an asymmetric photonic bandgap structure with a dual-mode liquid crystal.

    PubMed

    Wang, Hsiao-Tsung; Timofeev, Ivan V; Chang, Kai; Zyryanov, Victor Ya; Lee, Wei

    2014-06-16

    A one-dimensional asymmetric photonic crystal with dual-frequency liquid crystal as a central defect layer was demonstrated. Such asymmetric structure was characterized by the dramatic increase in intensity of the electric field of light localized at the overlapped photonic bandgap edges, thereby enhancing the observed transmittance of the spectral windows originating from the defect layer. The defect layer was made of a dual-mode liquid crystal that exhibited not only electrical tunability and switchability but also optical bistability. Consequently, tunable and bistable defect modes can be realized in the photonic structure. This asymmetric photonic crystal structure is promising and should be further explored for photonic device applications.

  8. Deriving a MODIS-compatible EVI from VIIRS bandpasses: An assessment using hyperspectral data

    NASA Astrophysics Data System (ADS)

    Obata, K.; Miura, T.; Yoshioka, H.; Huete, A. R.

    2012-12-01

    The Visible Infrared Imager/Radiometer Suite (VIIRS) sensor series of the Suomi-National Polar-orbiting Partnership (NPP) and Joint Polar Satellite System (JPSS) programs is slated not only to replace the Advanced Very High Resolution Radiometer (AVHRR) sensor series, but also to continue a highly-calibrated data stream begun with Moderate Resolution Imaging Spectroradiometer (MODIS). Geophysical products derived from VIIRS data, termed Environmental Data Records (EDR), include two vegetation indices: Top-of-Atmosphere (TOA) Normalized Difference Vegetation Index (NDVI) and Top-of-Canopy (TOC) Enhanced Vegetation Index (EVI). There, however, exist systematic differences in input reflectances between VIIRS and MODIS due to their spectral bandpass differences, which propagate into VIs and potentially result in systematic differences in index values between VIIRS and MODIS. In this study, we focused on EVI continuity and derived a MODIS-compatible EVI equation with VIIRS reflectances based on radiative transfer theory, and assessed the characteristics of this "MODIS-like" EVI equation using both radiative transfer model-simulated and airborne observational hyperspectral data. These hyperspectral data were spectrally convolved to simulate VIIRS and MODIS bandpass reflectances. The parameters in the derived MODIS-like EVI equation were an explicit function of vegetation (e.g., leaf area index) and atmosphere (i.e., aerosol optical thickness, AOT) properties. An optimization of the parameters by the unconstrained nonlinear optimization technique resulted in finding a single optimum set of parameter values that reduced systematic differences between the MODIS-like VIIRS EVI and the MODIS EVI to less than one-fourth (< .002 EVI units) of those between the VIIRS EVI and MODIS EVI (~.007 EVI units). The results of this study indicate that the EVI time series begun with MODIS can be continued with the VIIRS spectral bandpasses.

  9. Quantitative Determination of Bandpasses for Producing Vegetation Indices from Recombined NEON Hyperspectral Imagery

    NASA Astrophysics Data System (ADS)

    Hulslander, D.

    2015-12-01

    Hyperspectral imaging systems can be used to produce spectral reflectance curves giving rich information about composition, relative abundances of materials, mixes and combinations. However, as each spectral return from these systems is a vector with several hundred elements, they can be very difficult to process and analyze, and problemeatic to compare within, across, and between datasets over time and space. Vegetation indices (e.g. NDVI, ARVI, EVI, et al) attempt to combine spectral features in to single-value scores. When derived from calibrated and atmospherically compensated reflectance data, these indices can be quantitatively compared. Historically, these indices have been calculated from multispectral sensor data. These sensors have a handful (4 to 16 or so) of bandbasses ranging from 20 nm to 200 nm FWHM covering specific spectral regions for a variety of reasons, including both intended applications and system limitations. Hyperspectral sensors, however, cover the spectrum with many, many narrow (5 to 10 nm) bandpasses. This allows for analyses using the full, detailed spectral curve, or combination of the bands in to regions by averaging or in to composites using transforms or other techniques. This raises the question of exactly which bands should be used and combined in what manner for ideally deriving well-known vegetation indices typically made from multispectral data. In this study we use derivatives and other curve and signal analysis techniques to analyze vegetation reflectance spectra to quantitatively define optimal bandpasses for several vegetation indices and combine the 5 nm hypserspectral bandpasses of the NEON Imaging Spectrometer to synthesize them.

  10. Double-gabor filters are independent components of small translation-invariant image patches.

    PubMed

    Saremi, Saeed; Sejnowski, Terrence J; Sharpee, Tatyana O

    2013-04-01

    The analysis of natural images with independent component analysis (ICA) yields localized bandpass Gabor-type filters similar to receptive fields of simple cells in visual cortex. We applied ICA on a subset of patches called position-centered patches, selected for forming a translation-invariant representation of small patches. The resulting filters were qualitatively different in two respects. One novel feature was the emergence of filters we call double-Gabor filters. In contrast to Gabor functions that are modulated in one direction, double-Gabor filters are sinusoidally modulated in two orthogonal directions. In addition the filters were more extended in space and frequency compared to standard ICA filters and better matched the distribution in experimental recordings from neurons in primary visual cortex. We further found a dual role for double-Gabor filters as edge and texture detectors, which could have engineering applications.

  11. Double-Gabor Filters Are Independent Components of Small Translation-Invariant Image Patches

    PubMed Central

    Saremi, Saeed; Sejnowski, Terrence J.; Sharpee, Tatyana O.

    2013-01-01

    The analysis of natural images with independent component analysis (ICA) yields localized bandpass Gabor-type filters similar to receptive fields of simple cells in visual cortex. We applied ICA on a subset of patches called position-centered patches, selected for forming a translation-invariant representation of small patches. The resulting filters were qualitatively different in two respects. One novel feature was the emergence of filters we call double-Gabor filters. In contrast to Gabor functions that are modulated in one direction, double-Gabor filters are sinusoidally modulated in two orthogonal directions. In addition the filters were more extended in space and frequency compared to standard ICA filters and better matched the distribution in experimental recordings from neurons in primary visual cortex. We further found a dual role for double-Gabor filters as edge and texture detectors, which could have engineering applications. PMID:23339617

  12. Variational filtering.

    PubMed

    Friston, K J

    2008-07-01

    This note presents a simple Bayesian filtering scheme, using variational calculus, for inference on the hidden states of dynamic systems. Variational filtering is a stochastic scheme that propagates particles over a changing variational energy landscape, such that their sample density approximates the conditional density of hidden and states and inputs. The key innovation, on which variational filtering rests, is a formulation in generalised coordinates of motion. This renders the scheme much simpler and more versatile than existing approaches, such as those based on particle filtering. We demonstrate variational filtering using simulated and real data from hemodynamic systems studied in neuroimaging and provide comparative evaluations using particle filtering and the fixed-form homologue of variational filtering, namely dynamic expectation maximisation.

  13. Low-Resistant Band-Passing Noise and Its Dynamical Effects

    NASA Astrophysics Data System (ADS)

    Bai, Zhan-Wu

    2007-07-01

    We propose an n-order noise, which is realized by driving an n-order linear differential equation with a Gaussian white noise. The time-derivative noise is a low-resistant band-passing noise. If the derivative noise is regarded as a thermal one, the system has a vanishing effective friction and it should induce ballistic diffusion of a free particle at long times. The simulation method for the generalized Langevin equation driven by the n-order noise is discussed systematically. The features of three-order derivative noises are presented when they are applied to a ratchet system.

  14. Low-power Gm-C filter employing current-reuse differential difference amplifiers

    SciTech Connect

    Mincey, John S.; Briseno-Vidrios, Carlos; Silva-Martinez, Jose; Rodenbeck, Christopher T.

    2016-08-10

    This study deals with the design of low-power, high performance, continuous-time filters. The proposed OTA architecture employs current-reuse differential difference amplifiers in order to produce more power efficient Gm-C filter solutions. To demonstrate this, a 6th order low-pass Butterworth filter was designed in 0.18 m CMOS achieving a 65-MHz -3-dB frequency, an in-band input-referred third-order intercept point of 12.0 dBm, and an input referred noise density of 40 nV/Hz1=2, while only consuming 8.07 mW from a 1.8 V supply and occupying a total chip area of 0.21 mm2 with a power consumption of only 1.19 mW per pole.

  15. Low-power Gm-C filter employing current-reuse differential difference amplifiers

    SciTech Connect

    Mincey, John S.; Briseno-Vidrios, Carlos; Silva-Martinez, Jose; Rodenbeck, Christopher T.

    2016-08-10

    This study deals with the design of low-power, high performance, continuous-time filters. The proposed OTA architecture employs current-reuse differential difference amplifiers in order to produce more power efficient Gm-C filter solutions. To demonstrate this, a 6th order low-pass Butterworth filter was designed in 0.18 m CMOS achieving a 65-MHz -3-dB frequency, an in-band input-referred third-order intercept point of 12.0 dBm, and an input referred noise density of 40 nV/Hz1=2, while only consuming 8.07 mW from a 1.8 V supply and occupying a total chip area of 0.21 mm2 with a power consumption of only 1.19 mW per pole.

  16. RF-MEMS tunable interdigitated capacitor and fixed spiral inductor for band pass filter applications

    NASA Astrophysics Data System (ADS)

    Bade, Ladon Ahmed; Dennis, John Ojur; Khir, M. Haris Md; Wen, Wong Peng

    2016-11-01

    This research presents the tunable Radio Frequency Micro Electromechanical Systems (RF-MEMS) coupled band-pass filter (BPF), which possess a wide tuning range and constructed by using the Chebyshev fourth degree equivalent circuit consisting of fixed inductors and interdigitated tunable capacitors. The suggested method was authenticated by designing a new tunable BPF with a 100% tuning range from 3.1 GHz to 4.9 GHz. The Metal Multi-User MEMS Process (Metal MUMPs) was involved in the process of design of this band-pass filter. It aimed to achieve the reconfiguration of frequencies and show high efficiency of RF in the applications that using Ultra Wide Band (UWB) such as wireless sensor networks. The RF performance of this filter was found to be very satisfactory due to its simple fabrication. Moreover, it showed less insertion loss of around 4 dB and high return loss of around 20 dB.

  17. Novel Utilization of Terminators in the Design of Biologically Adjustable Synthetic Filters.

    PubMed

    Lin, Mei-Ting; Wang, Chun-Ying; Xie, Hui-Juan; Cheung, Chantal Hoi Yin; Hsieh, Chiao-Hui; Juan, Hsueh-Fen; Chen, Bor-Sen; Lin, Che

    2016-05-20

    Terminators, which signal the end of transcription processes, are typically placed behind the last coding sequence of an operon to prevent interference between transcript units in most biologically synthetic systems. Here, we seek to extend the usability of terminators in genetic system design by using terminators as regulatory genetic parts. Terminators with different impacts on their upstream and downstream genes are characterized in detail via dynamic modeling to predict the behavior of the overall genetic system. Some nonlinear effects of terminators observed in our terminator measurements potentially facilitate regulation of gene expression. Through dynamic modeling in silico, we find that such genetic systems may behave like genetic filters. In agreement with the simulations, we successfully implement genetic high-pass and bandpass filters in vivo, demonstrating the potential of using terminators as regulatory parts. The genetic bandpass filter in this work is implemented through the interdependence between genetic parts, in which the termination efficiency of a terminator varies with the strength of the upstream promoter. This design strategy for a bandpass filter requires fewer base pairs than the conventional strategy of concatenating high-pass and low-pass filters. Our results show that this novel utilization of terminators as regulatory parts may provide a new perspective for efficient design of genetic circuits. We believe that further exploration of the complicated dynamics of terminators is important in the development of synthetic biology.

  18. Perception of Filtered Speech by Children with Developmental Dyslexia and Children with Specific Language Impairments.

    PubMed

    Goswami, Usha; Cumming, Ruth; Chait, Maria; Huss, Martina; Mead, Natasha; Wilson, Angela M; Barnes, Lisa; Fosker, Tim

    2016-01-01

    Here we use two filtered speech tasks to investigate children's processing of slow (<4 Hz) versus faster (∼33 Hz) temporal modulations in speech. We compare groups of children with either developmental dyslexia (Experiment 1) or speech and language impairments (SLIs, Experiment 2) to groups of typically-developing (TD) children age-matched to each disorder group. Ten nursery rhymes were filtered so that their modulation frequencies were either low-pass filtered (<4 Hz) or band-pass filtered (22 - 40 Hz). Recognition of the filtered nursery rhymes was tested in a picture recognition multiple choice paradigm. Children with dyslexia aged 10 years showed equivalent recognition overall to TD controls for both the low-pass and band-pass filtered stimuli, but showed significantly impaired acoustic learning during the experiment from low-pass filtered targets. Children with oral SLIs aged 9 years showed significantly poorer recognition of band pass filtered targets compared to their TD controls, and showed comparable acoustic learning effects to TD children during the experiment. The SLI samples were also divided into children with and without phonological difficulties. The children with both SLI and phonological difficulties were impaired in recognizing both kinds of filtered speech. These data are suggestive of impaired temporal sampling of the speech signal at different modulation rates by children with different kinds of developmental language disorder. Both SLI and dyslexic samples showed impaired discrimination of amplitude rise times. Implications of these findings for a temporal sampling framework for understanding developmental language disorders are discussed.

  19. Development of superconducting bandpass delta-sigma analog-to-digital converter

    NASA Astrophysics Data System (ADS)

    Bulzacchelli, John F.; Lee, Hae-Seung; Misewich, James A.; Ketchen, Mark B.

    2004-10-01

    This paper recounts the development of a superconducting bandpass delta-sigma (ΔΣ) modulator for direct analog-to-digital conversion of radio frequency signals in the GHz range. The modulator design benefits from several advantages of superconducting electronics: high-Q resonators, fast Josephson comparators, naturally quantized single flux quantum pulses, and high circuit sensitivity. The measured center frequency (2.23 GHz), sampling rate (up to 45 GHz), dynamic range (greater than 57 dB over a 19.6 MHz bandwidth), and input sensitivity (-17.4 dBm full-scale) of the bandpass modulator are the highest reported to date in any technology. The SNR (49 dB over a 20.8 MHz bandwidth) is limited by the frequency resolution of the measurement but still exceeds the SNRs of semiconductor modulators with comparable center frequencies. The design of the modulator test chip and the high speed testing methodology are reviewed. Finally, the paper examines the prospects for improved performance with more advanced modulator architectures.

  20. Filtering apparatus

    DOEpatents

    Haldipur, G.B.; Dilmore, W.J.

    1992-09-01

    A vertical vessel is described having a lower inlet and an upper outlet enclosure separated by a main horizontal tube sheet. The inlet enclosure receives the flue gas from a boiler of a power system and the outlet enclosure supplies cleaned gas to the turbines. The inlet enclosure contains a plurality of particulate-removing clusters, each having a plurality of filter units. Each filter unit includes a filter clean-gas chamber defined by a plate and a perforated auxiliary tube sheet with filter tubes suspended from each tube sheet and a tube connected to each chamber for passing cleaned gas to the outlet enclosure. The clusters are suspended from the main tube sheet with their filter units extending vertically and the filter tubes passing through the tube sheet and opening in the outlet enclosure. The flue gas is circulated about the outside surfaces of the filter tubes and the particulate is absorbed in the pores of the filter tubes. Pulses to clean the filter tubes are passed through their inner holes through tubes free of bends which are aligned with the tubes that pass the clean gas. 18 figs.

  1. Filtering apparatus

    DOEpatents

    Haldipur, Gaurang B.; Dilmore, William J.

    1992-01-01

    A vertical vessel having a lower inlet and an upper outlet enclosure separated by a main horizontal tube sheet. The inlet enclosure receives the flue gas from a boiler of a power system and the outlet enclosure supplies cleaned gas to the turbines. The inlet enclosure contains a plurality of particulate-removing clusters, each having a plurality of filter units. Each filter unit includes a filter clean-gas chamber defined by a plate and a perforated auxiliary tube sheet with filter tubes suspended from each tube sheet and a tube connected to each chamber for passing cleaned gas to the outlet enclosure. The clusters are suspended from the main tube sheet with their filter units extending vertically and the filter tubes passing through the tube sheet and opening in the outlet enclosure. The flue gas is circulated about the outside surfaces of the filter tubes and the particulate is absorbed in the pores of the filter tubes. Pulses to clean the filter tubes are passed through their inner holes through tubes free of bends which are aligned with the tubes that pass the clean gas.

  2. Recursive implementations of temporal filters for image motion computation.

    PubMed

    Clifford, C W; Langley, K

    2000-05-01

    Efficient algorithms for image motion computation are important for computer vision applications and the modelling of biological vision systems. Intensity-based image motion computation proceeds in two stages: the convolution of linear spatiotemporal filter kernels with the image sequence, followed by the non-linear combination of the filter outputs. If the spatiotemporal extent of the filter kernels is large, then the convolution stage can be very intensive computationally. One effective means of reducing the storage required and computation involved in implementing the temporal convolutions is the introduction of recursive filtering. Non-recursive methods require the number of frames of the image sequence stored at any given time to be equal to the temporal extent of the slowest temporal filter. In contrast, recursive methods encode recent stimulus history implicitly in the values of a small number of variables updated through a series of feedback equations. Recursive filtering reduces the number of values stored in memory during convolution and the number of mathematical operations involved in computing the filters' outputs. This paper extends previous recursive implementations of gradient- and correlation-based motion analysis algorithms [Fleet DJ, Langley K (1995) IEEE PAMI 17: 61-67; Clifford CWG, Ibbotson MR, Langley K (1997) Vis Neurosci 14: 741-749], describing a recursive implementation of causal band-pass temporal filters suitable for use in energy- and phase-based algorithms for image motion computation. It is shown that the filters' temporal frequency tuning curves fit psychophysical estimates of the temporal properties of human visual filters.

  3. Acousto-optic tunable filter as a notch filter

    NASA Astrophysics Data System (ADS)

    Gupta, Neelam

    2016-05-01

    An acousto-optic tunable filter (AOTF) is an all solid-state robust device with no-moving parts that has been used in the development of hyperspectral imagers from the ultraviolet to the longwave infrared. Such a device is developed by bonding a piezoelectric transducer on a specially cut prism in a birefringent crystal. When broadband white light is incident on the prism input facet, two orthogonally polarized diffracted beams at a wavelength with a narrowband bandpass are transmitted. The transmitted wavelength can be tuned by varying the applied radio frequency (RF). This is what is done in a hyperspectral imager. An AOTF can also be used with multiple RFs applied at the same time to diffract a number of different wavelengths. This mode can be exploited to design a tunable optical notch filter where multiple RFs are applied simultaneously such that all wavelength in a specific range can transmit except for a specific wavelength which is notched. We designed an optical system using a TeO2 AOTF with telecentric confocal optics operating in the shortwave infrared (SWIR) with a 16-channel RF driver where both the amplitude and frequency can be controlled independently for each channel. We will discuss the optical system, its characterization and present results obtained.

  4. The J-PAS filter system

    NASA Astrophysics Data System (ADS)

    Marin-Franch, Antonio; Taylor, Keith; Cenarro, Javier; Cristobal-Hornillos, David; Moles, Mariano

    2015-08-01

    J-PAS (Javalambre-PAU Astrophysical Survey) is a Spanish-Brazilian collaboration to conduct a narrow-band photometric survey of 8500 square degrees of northern sky using an innovative filter system of 59 filters, 56 relatively narrow-band (FWHM=14.5 nm) filters continuously populating the spectrum between 350 to 1000nm in 10nm steps, plus 3 broad-band filters. This filter system will be able to produce photometric redshifts with a precision of 0.003(1 + z) for Luminous Red Galaxies, allowing J-PAS to measure the radial scale of the Baryonic Acoustic Oscillations. The J-PAS survey will be carried out using JPCam, a 14-CCD mosaic camera using the new e2v 9k-by-9k, 10μm pixel, CCDs mounted on the JST/T250, a dedicated 2.55m wide-field telescope at the Observatorio Astrofísico de Javalambre (OAJ) near Teruel, Spain. The filters will operate in a fast (f/3.6) converging beam. The requirements for average transmissions greater than 85% in the passband, <10-5 blocking from 250 to 1050nm, steep bandpass edges and high image quality impose significant challenges for the production of the J-PAS filters that have demanded the development of new design solutions. This talk presents the J-PAS filter system and describes the most challenging requirements and adopted design strategies. Measurements and tests of the first manufactured filters are also presented.

  5. A matched filter algorithm for acoustic signal detection

    NASA Astrophysics Data System (ADS)

    Jordan, D. W.

    1985-06-01

    This thesis is a presentation of several alternative acoustic filter designs which allow Space Shuttle payload experiment initiation prior to launch. This initiation is accomplished independently of any spacecraft services by means of a matched band-pass filter tuned to the acoustic signal characteristic of the Auxiliary Power Unit (APU) which is brought up to operating RPM's approximately five minutes prior to launch. These alternative designs include an analog filter built around operational amplifiers, a digital IIR design implemented with an INTEL 2920 Signal Processor, and an Adaptive FIR Weiner design. Working prototypes of the first two filters are developed and a discussion of the advantage of the 2920 digital design is presented.

  6. Complex optical interference filters with stress compensation for space applications

    NASA Astrophysics Data System (ADS)

    Begou, Thomas; Krol, Hélène; Stojcevski, Dragan; Lemarchand, Fabien; Lequime, Michel; Grezes-Besset, Catherine; Lumeau, Julien

    2017-04-01

    We present hereafter a study of complex bandpass optical interference filters with central wavelengths ranging in blue region or in the near infrared. For these applications, the required functions are particularly complex as they must present a very narrow bandwidth as well as a high level of rejection over a broad spectral range. Moreover, these components must have a good flatness meaning that the stress induced by the different layers has to be taken in account in the filter design. We present a thorough study of these filters including their design, fabrication using Plasma Assisted Reactive Magnetron Sputtering (PARMS) and characterization. Excellent agreement between experimental and theoretical spectral performances associated with a final sag of 326 and 13 nm, and uniformity from -0.05 to 0.10 and -0.10 to 0.20% are demonstrated for the two manufactured filters.

  7. A novel current mode biquadratic filter employing two current conveyors

    NASA Astrophysics Data System (ADS)

    Zhao, Jing; Jiang, Jinguang; Liu, Jingnan

    2008-10-01

    The paper introduces a new current-mode biquadratic filter with three input terminals and one output terminal. The filter proposed in this paper uses one plus-type second-generation current conveyor (CCII+), one dual-output second-generation current conveyor (DOCCII), two grounded capacitors and three resistors. The circuit can realize all the standard filter functions: high-pass, band-pass, low-pass, notch-pass, and all-pass by choosing appropriate input branches without changing the passive elements. It has very low active and passive sensitivities, and can tune the circuit pole parameters orthogonally. The performance of the proposed biquadratic filter was examined by PSPICE simulation.

  8. Effect of Group-Velocity Dispersion on Photon-Number Squeezing of Optical Pulses using Optical Fibers and Spectral Filter

    NASA Astrophysics Data System (ADS)

    Nishizawa, Norihiko; Horio, Takeo; Mori, Masakazu; Goto, Toshio; Yamane, Kazuo

    1999-04-01

    Photon-number squeezing of optical pulses using optical fibers and band-pass spectral filters is numerically analyzed. The evolution of the quantum noise in the optical pulse propagation is calculated in both the spectral and time domains. The mechanism of filtering squeezing and the role of the group-velocity dispersion are investigated.It is shown that the squeezing is realized owing to the interaction between the self-phase modulation and the group-velocity dispersion.

  9. Ultraviolet filters.

    PubMed

    Shaath, Nadim A

    2010-04-01

    The chemistry, photostability and mechanism of action of ultraviolet filters are reviewed. The worldwide regulatory status of the 55 approved ultraviolet filters and their optical properties are documented. The photostabilty of butyl methoxydibenzoyl methane (avobenzone) is considered and methods to stabilize it in cosmetic formulations are presented.

  10. Developing metal coated mesh filters for mid-infrared astronomy

    NASA Astrophysics Data System (ADS)

    Sako, Shigeyuki; Miyata, Takashi; Kamizuka, Takafumi; Nakamura, Tomohiko; Asano, Kentaro; Uchiyama, Mizuho; Onaka, Takashi; Sakon, Itsuki; Wada, Takehiko

    2012-09-01

    A metal mesh filter is appropriate to a band-pass filter for astronomy in the long mid-infrared between 25 and 40 μm, where most of optical materials are opaque. The mesh filter does not require transparent dielectric materials unlike interference filters because the transmission characteristics bare determined by surface plasmon-polariton (SPP) resonances excited on a metal surface with a periodic structure. In this study, we have developed the mesh filters optimized to atmospheric windows at 31.8 and 37.5 μm accessible from the Chajnantor site of 5,640 m altitude. First, mesh filters made of a gold film of 2 μm thickness have been fabricated. Four identical film-type filters are stacked incoherently to suppress leakages at stop-bands. The transmissions of the stacked filters have been measured to be 0.8 at the peaks and below 1 x 10-3 at the stop-bands at 4 K. The ground-based mid-infrared camera MAX38 has been equipped with the stacked filters and successfully obtained diffraction-limited stellar images at the Chajnantor site. The film-type mesh filter does not have sufficient mechanical strength for a larger aperture and for use in space. We have developed mesh filters with higher strength by applying the membrane technology for x-ray optics. The membrane-type mesh filter is made of SiC and coated with a thin gold layer. The optical performance of the mesh filter is independent of internal materials in principle because the SPP resonances are excited only on the metal surface. The fabricated membrane-type mesh filter has been confirmed to provide comparable optical performance to the film-type mesh filter.

  11. Small d-spacing WSi{sub 2}/Si narrow bandpass multilayers.

    SciTech Connect

    Liu, C.; Conley, R.; Macrander, A. T.; Graber, T.; Morawe, C.; Borel, C.; Dufresne, E. M.; Experimental Facilities Division; Univ. of Chicago; European Synchrotron Radiation Facility; Univ. of Michigan

    2004-01-01

    To develop narrow-bandpass multilayer monochromators, we have studied small d-spacing WSi{sub 2}/Si multilayers. We found that WSi{sub 2}/Si is an excellent multilayer system for achieving both the desired spectral resolution and peak reflectivity. Compared to other traditional multilayer systems such as W/Si, WSi{sub 2}/Si not only has a lower density and lower absorption, but also is a chemically more stable system, since WSi{sub 2} is already a silicide. One thus expects better thermal stability and sharper interfaces for WSi2/Si multilayers. There are two approaches to achieve high-resolution multilayers: either decrease the d spacing or use low absorption materials. By using WSi{sub 2}/Si, we can utilize both approaches in the same system to achieve good energy resolution and peak reflectivity. Another advantage of this system is that the sputtering rate for Si is much higher than other traditional low-Z materials. Several WSi{sub 2}/Si multilayers have been fabricated at the Advanced Photon Source (APS) deposition lab using dc magnetron sputtering with constant currents of 0.5 A in Ar at a pressure of 2.3 mTorr. A test sample of [9.65 Angstrom-WSi{sub 2}/10.05 Angstrom-Si] x 300 was studied at four institutions: using laboratory x-ray diffractometers with Cu K{alpha} (8.048 keV) wavelength at the APS x-ray lab and at European Synchrotron Radiation Facility (ESRF), and using synchrotron undulator x-rays at 10 keV at MHATT-CAT and at 25 keV at ChemMatCARS-CAT of the APS. The measured first-order reflectivity was 54% with a bandpass of 0.46% at 10 keV and 66% reflectivity with a bandpass of 0.67% at 25 keV of undulator x-rays. Similar results were obtained from Cu K{alpha} x-rays. This result is very attractive for the design of a multilayer monochromator for the ChemMatCARS-CAT to be used in the 20 to 25 keV range. Other small d-spacing multilayers are being studied. Comparison between WSi{sub 2}/Si and W/Si multilayers will be discussed.

  12. Acoustic wave filter based on periodically poled lithium niobate.

    PubMed

    Courjon, Emilie; Bassignot, Florent; Ulliac, Gwenn; Benchabane, Sarah; Ballandras, Sylvain

    2012-09-01

    Solutions for the development of compact RF passive transducers as an alternative to standard surface or bulk acoustic wave devices are receiving increasing interest. This article presents results on the development of an acoustic band-pass filter based on periodically poled ferroelectric domains in lithium niobate. The fabrication of periodically poled transducers (PPTs) operating in the range of 20 to 650 MHz has been achieved on 3-in (76.2-mm) 500-μm-thick wafers. This kind of transducer is able to excite elliptical as well as longitudinal modes, yielding phase velocities of about 3800 and 6500 ms(-1), respectively. A new type of acoustic band-pass filter is proposed, based on the use of PPTs instead of the SAWs excited by classical interdigital transducers. The design and the fabrication of such a filter are presented, as well as experimental measurements of its electrical response and transfer function. The feasibility of such a PPT-based filter is thereby demonstrated and the limitations of this method are discussed.

  13. Graphene-based tunable terahertz filter with rectangular ring resonator containing double narrow gaps

    NASA Astrophysics Data System (ADS)

    Su, Wei; Chen, Bingyan

    2017-09-01

    A plasmonic band-pass filter based on graphene rectangular ring resonator with double narrow gaps is proposed and numerically investigated by finite-difference time-domain (FDTD) simulations. For the filter with or without gaps, the resonant frequencies can be effectively adjusted by changing the width of the graphene nanoribbon, the coupling distance and chemical potential of graphene. In addition, by introducing narrow gaps in the rectangular ring resonators, it shows the single frequency filtering effect. Moreover, the structure also shows high sensitivity for different surrounding mediums. This work provides a novel method for designing all-optical integrated components in optical communication.

  14. High-efficiency microwave photonic harmonic down-conversion with tunable and reconfigurable filtering.

    PubMed

    Liao, Jinxin; Zheng, Xiaoping; Li, Shangyuan; Zhang, Hanyi; Zhou, Bingkun

    2014-12-01

    A new optical-frequency comb-based microwave photonic harmonic down-convertor with tunable and reconfigurable filtering is proposed and experimentally demonstrated. The coherent evenly spaced optical carriers offer harmonic down-conversion for ultrahigh radio frequency signals with low-frequency local oscillator, and construct a tunable and reconfigurable bandpass filter for the intermediate-frequency (IF) signal combined with dispersion. This implementation features high conversion efficiency. Experimental results show the filtered output IF signal has a clean spectrum with high quality. Measured conversion loss is 8.3 dB without extra electrical amplification.

  15. A nonlinear Bayesian filtering framework for ECG denoising.

    PubMed

    Sameni, Reza; Shamsollahi, Mohammad B; Jutten, Christian; Clifford, Gari D

    2007-12-01

    In this paper, a nonlinear Bayesian filtering framework is proposed for the filtering of single channel noisy electrocardiogram (ECG) recordings. The necessary dynamic models of the ECG are based on a modified nonlinear dynamic model, previously suggested for the generation of a highly realistic synthetic ECG. A modified version of this model is used in several Bayesian filters, including the Extended Kalman Filter, Extended Kalman Smoother, and Unscented Kalman Filter. An automatic parameter selection method is also introduced, to facilitate the adaptation of the model parameters to a vast variety of ECGs. This approach is evaluated on several normal ECGs, by artificially adding white and colored Gaussian noises to visually inspected clean ECG recordings, and studying the SNR and morphology of the filter outputs. The results of the study demonstrate superior results compared with conventional ECG denoising approaches such as bandpass filtering, adaptive filtering, and wavelet denoising, over a wide range of ECG SNRs. The method is also successfully evaluated on real nonstationary muscle artifact. This method may therefore serve as an effective framework for the model-based filtering of noisy ECG recordings.

  16. Design Considerations for High-Q Bandpass Microwave Oscillator Sensors Based Upon Resonant Amplification

    SciTech Connect

    Jones, Anthony M.; Kelly, James F.; Tedeschi, Jonathan R.; McCloy, John S.

    2014-06-23

    A series of microwave resonant oscillator sensors were designed and characterized using bandpass planar and volumetric electrical resonators having loaded quality factor (Q) values in the range of 2 to 20. The use of these resonators in positive feedback circuits yielded sensor Q-factors of up to 2 x 107, demonstrating Q-factor amplifications on the order of 106. It is shown that the Q-factor amplification can be increased in a positive feedback system through the selection of feedback loop group delay, allowing use of resonators with lower Qstat values. A low-frequency electromagnetic interference sensing application is demonstrated for two resonant oscillator configurations, showing considerable frequency sensitivity to 45 kHz emitters.

  17. A model of band-pass phenotypic resistance in a modified Beverton-Holt framework.

    PubMed

    Nemzer, Louis R

    2014-06-01

    A new mathematical model of phenotypic bacterial resistance to a periodically applied antibiotic is presented. Using a modified Beverton-Holt framework, and without appealing to any explicit internal timescale or heritable mutations, we map the parameter-space regions corresponding to bacterial colony survival or extinction. It is demonstrated that band-pass behavior, in which colony survival occurs at intermediate - but not short or long - antibiotic application periods, is a possible regime for some initial population values if the bactericidal activity is sufficient. However, below this threshold value of antibiotic efficacy, a "fixed-point catastrophe" occurs, and colony extinction does not occur when the bacteria are challenged with long application periods. These results suggest that the dosing schedule of antibiotics within a clinical setting merits additional scrutiny, since even seemingly unimportant modifications to the frequency of administration may lead to widely diverging patient outcomes. Copyright © 2014 Elsevier Inc. All rights reserved.

  18. The inoculum effect and band-pass bacterial response to periodic antibiotic treatment.

    PubMed

    Tan, Cheemeng; Smith, Robert Phillip; Srimani, Jaydeep K; Riccione, Katherine A; Prasada, Sameer; Kuehn, Meta; You, Lingchong

    2012-01-01

    The inoculum effect (IE) refers to the decreasing efficacy of an antibiotic with increasing bacterial density. It represents a unique strategy of antibiotic tolerance and it can complicate design of effective antibiotic treatment of bacterial infections. To gain insight into this phenomenon, we have analyzed responses of a lab strain of Escherichia coli to antibiotics that target the ribosome. We show that the IE can be explained by bistable inhibition of bacterial growth. A critical requirement for this bistability is sufficiently fast degradation of ribosomes, which can result from antibiotic-induced heat-shock response. Furthermore, antibiotics that elicit the IE can lead to 'band-pass' response of bacterial growth to periodic antibiotic treatment: the treatment efficacy drastically diminishes at intermediate frequencies of treatment. Our proposed mechanism for the IE may be generally applicable to other bacterial species treated with antibiotics targeting the ribosomes.

  19. New class of filter functions generated most directly by Christoffel-Darboux formula for Gegenbauer orthogonal polynomials

    NASA Astrophysics Data System (ADS)

    Ilić, Aleksandar D.; Pavlović, Vlastimir D.

    2011-01-01

    A new original formulation of all pole low-pass filter functions is proposed in this article. The starting point in solving the approximation problem is a direct application of the Christoffel-Darboux formula for the set of orthogonal polynomials, including Gegenbauer orthogonal polynomials in the finite interval [-1, +1] with the application of a weighting function with a single free parameter. A general solution for the filter functions is obtained in a compact explicit form, which is shown to enable generation of the Gegenbauer filter functions in a simple way by choosing the value of the free parameter. Moreover, the proposed solution with the same criterion of approximation could be used to generate Legendre and Chebyshev filter functions of the first and second kind as well. The examples of proposed filter functions of even (10th) and odd (11th) order are illustrated. The approximation is shown to yield a good compromise solution with respect to the filter frequency characteristics (magnitude as well as phase characteristics). The influence of tolerance of the filter critical component (inductor) on the proposed magnitude and group delay characteristics of a resistively terminated LC lossless ladder filter is analysed as well. The proposed filter functions are superior in terms of the excellent magnitude characteristic, which approximates an ideal filter almost perfectly over the entire pass-band range and exhibits the summed sensitivity function better than that of a Butterworth filter. In the article, we present the filter function solution that exhibits optimum amplitude as well as optimum group delay characteristics that are of crucial importance for implementation of digital processing as well as RF analogue parts of communication networks. Derivation of the other band range filter functions, which could be realised either by continuous or digital filters, is also generally possible with the procedure proposed in this article.

  20. The effects of sinusoidal interference on the second-order carrier tracking loop preceded by a bandpass limiter in the Block 4 receiver

    NASA Technical Reports Server (NTRS)

    Ruggier, C. J.

    1989-01-01

    Drop-lock relationships for the second-order phase-locked loop are derived when the carrier and a sinusoidal signal lie within the predetection filter bandwidth of the Block 4 receiver. Limiter suppression factors are calculated when a bandpass hard limiter is used to maintain constant total power at the loop. The parameters of interest are the interference-to-signal power ratio (ISR), the input signal-to-noise power ratio (NSR), and the interference signal frequency offset from carrier delta f. Limiter suppression caused by the combined effects of the noise and the interference signal accounts for the variability in the drop-lock threshold for given values of the input SNR and ISR parameters. Going beyond earlier published work that focused on the limiter's effect on the drop-lock threshold; an account is made for the limiter action in the interference mode and an overall imporvement is provided in the prediction accuracy of the drop-lock model.

  1. SEMICONDUCTOR INTEGRATED CIRCUITS: A low power Gm-C filter with on-chip automatic tuning for a WLAN transceiver

    NASA Astrophysics Data System (ADS)

    Silin, Liu; Heping, Ma; Yin, Shi

    2010-06-01

    A sixth-order Butterworth Gm-C low-pass filter (LPF) with a continuous tuning architecture has been implemented for a wireless LAN (WLAN) transceiver in 0.35 μm CMOS technology. An interior node scaling technique has been applied directly to the LPF to improve the dynamic range and the structure of the LPF has been optimized to reduce both the die size and the current consumption. Measurement results show that the filter has 77.5 dB dynamic range, 16.3 ns group delay variation, better than 3% cutoff frequency accuracy, and 0 dBm passband IIP3. The whole LPF with the tuning circuit dissipates only 1.42 mA (5 MHz cutoff frequency) or 2.81 mA (10 MHz cutoff frequency) from 2.85 V supply voltage, and only occupies 0.175 mm2 die size.

  2. Demonstration and experimental evaluation of a bi-directional 10-GHz microwave photonic filter

    NASA Astrophysics Data System (ADS)

    Zaldívar-Huerta, I. E.; Correa-Mena, A. G.; Hernández-Nava, P.; García-Juárez, A.; Rodríguez-Asomoza, J.; Lee, Min Won

    2016-09-01

    A bi-directional 10-GHz microwave photonic filter is proposed and experimentally evaluated. Its frequency response consists of a series of microwave band-pass windows obtained by the interaction of externally modulated multimode laser diodes emitting around of 1550 nm associated to the chromatic dispersion parameter of an optical fiber, as well as the length of the optical link. Microwave band-pass windows exhibit on average a-3 dB bandwidth of 378 MHz. This electro-optical system shows an efficient configuration and good performance. Potentially, filtered microwave signals can be used as electrical carriers in optical communication systems to transmit and distribute services such as video, voice and data.

  3. Microwave photonic notch filter with complex coefficient based on four wave mixing

    NASA Astrophysics Data System (ADS)

    Xu, Dong; Cao, Ye; Tong, Zheng-rong; Yang, Jing-peng

    2016-11-01

    A microwave photonic notch filter with a complex coefficient is proposed and demonstrated based on four wave mixing (FWM). FWM effect of two single-frequency laser beams occurs in a highly nonlinear fiber (HNLF), and multi-wavelength optical signals are generated and used to generate the multi-tap of microwave photonic filter (MPF). The complex coefficient is generated by using a Fourier-domain optical processor (FD-OP) to control the amplitude and phase of the optical carrier and phase modulation sidebands. The results show that this filter can be changed from bandpass filter to notch filter by controlling the FD-OP. The center frequency of the notch filter can be continuously tuned from 5.853 GHz to 29.311 GHz with free spectral range ( FSR) of 11.729 GHz. The shape of the frequency response keeps unchanged when the phase is tuned.

  4. Photonic crystal ring resonator based optical filters for photonic integrated circuits

    SciTech Connect

    Robinson, S.

    2014-10-15

    In this paper, a two Dimensional (2D) Photonic Crystal Ring Resonator (PCRR) based optical Filters namely Add Drop Filter, Bandpass Filter, and Bandstop Filter are designed for Photonic Integrated Circuits (PICs). The normalized output response of the filters is obtained using 2D Finite Difference Time Domain (FDTD) method and the band diagram of periodic and non-periodic structure is attained by Plane Wave Expansion (PWE) method. The size of the device is minimized from a scale of few tens of millimeters to the order of micrometers. The overall size of the filters is around 11.4 μm × 11.4 μm which is highly suitable of photonic integrated circuits.

  5. Universal filters of arbitrary order and type employing square-root-domain technique

    NASA Astrophysics Data System (ADS)

    Khanday, F. A.; Psychalinos, C.; Shah, N. A.

    2014-07-01

    Novel Single Input Multiple Output (SIMO) and Multiple Input Single Output (MISO) universal filter topologies of arbitrary order and type are introduced in this paper. The proposed topologies have been realised by employing Square-Root Domain (SRD) technique. An offered benefit of the universal filter topologies is that only grounded capacitors are required for their implementations and the resonant frequency of the filters can be electronically controlled by an appropriate dc current. The proposed universal filters simultaneously offer all the five standard filtering functions i.e. Lowpass (LP), Highpass (HP) and Bandpass (BP), Bandstop (BS) and Allpass (AP) frequency responses. In addition, the SIMO topology is generic in the sense that it can yield four different stable filter configurations. Two design examples are provided in each configuration and the correct operation of the corresponding topologies has been evaluated through the PSPICE software with BSIM 0.35-µm CMOS process model parameters.

  6. Optimal filter design for shielded and unshielded ambient noise reduction in fetal magnetocardiography

    NASA Astrophysics Data System (ADS)

    Comani, S.; Mantini, D.; Alleva, G.; Di Luzio, S.; Romani, G. L.

    2005-12-01

    The greatest impediment to extracting high-quality fetal signals from fetal magnetocardiography (fMCG) is environmental magnetic noise, which may have peak-to-peak intensity comparable to fetal QRS amplitude. Being an unstructured Gaussian signal with large disturbances at specific frequencies, ambient field noise can be reduced with hardware-based approaches and/or with software algorithms that digitally filter magnetocardiographic recordings. At present, no systematic evaluation of filters' performances on shielded and unshielded fMCG is available. We designed high-pass and low-pass Chebychev II-type filters with zero-phase and stable impulse response; the most commonly used band-pass filters were implemented combining high-pass and low-pass filters. The achieved ambient noise reduction in shielded and unshielded recordings was quantified, and the corresponding signal-to-noise ratio (SNR) and signal-to-distortion ratio (SDR) of the retrieved fetal signals was evaluated. The study regarded 66 fMCG datasets at different gestational ages (22-37 weeks). Since the spectral structures of shielded and unshielded magnetic noise were very similar, we concluded that the same filter setting might be applied to both conditions. Band-pass filters (1.0-100 Hz) and (2.0-100 Hz) provided the best combinations of fetal signal detection rates, SNR and SDR; however, the former should be preferred in the case of arrhythmic fetuses, which might present spectral components below 2 Hz.

  7. Optimal filter design for shielded and unshielded ambient noise reduction in fetal magnetocardiography.

    PubMed

    Comani, S; Mantini, D; Alleva, G; Di Luzio, S; Romani, G L

    2005-12-07

    The greatest impediment to extracting high-quality fetal signals from fetal magnetocardiography (fMCG) is environmental magnetic noise, which may have peak-to-peak intensity comparable to fetal QRS amplitude. Being an unstructured Gaussian signal with large disturbances at specific frequencies, ambient field noise can be reduced with hardware-based approaches and/or with software algorithms that digitally filter magnetocardiographic recordings. At present, no systematic evaluation of filters' performances on shielded and unshielded fMCG is available. We designed high-pass and low-pass Chebychev II-type filters with zero-phase and stable impulse response; the most commonly used band-pass filters were implemented combining high-pass and low-pass filters. The achieved ambient noise reduction in shielded and unshielded recordings was quantified, and the corresponding signal-to-noise ratio (SNR) and signal-to-distortion ratio (SDR) of the retrieved fetal signals was evaluated. The study regarded 66 fMCG datasets at different gestational ages (22-37 weeks). Since the spectral structures of shielded and unshielded magnetic noise were very similar, we concluded that the same filter setting might be applied to both conditions. Band-pass filters (1.0-100 Hz) and (2.0-100 Hz) provided the best combinations of fetal signal detection rates, SNR and SDR; however, the former should be preferred in the case of arrhythmic fetuses, which might present spectral components below 2 Hz.

  8. Design and Implementation of Digital Filters for Analysis of F/A-18 Flight Test Data

    DTIC Science & Technology

    1992-05-01

    International Follow On Structural Test Program ( IFOSTP ), and in 1989 a series of flight trials were performed at the Aerospace Engineering...effort between Canada and Australia to perform a full-scale structural fatigue test on the F/A- 18 Hornet aircraft is currently underway. This project is...1) STOP END 22 APPENDIX E A Fortran Program For Studying The Effects of FIR Bandpass Filtering on Pulse-Type Transients The following

  9. Evaluation of a morphological filter in mean cardiac output determination: application to left ventricular assist devices.

    PubMed

    Stevens, Michael Charles; Bradley, Andrew P; Wilson, Stephen J; Mason, David Glen

    2013-08-01

    A morphological filter (MF) is presented for the determination of beat-to-beat mean rotary left ventricular assist device (LVAD) flow rate, measured using an implanted flow probe. The performance of this non-linear filter was assessed using LVAD flow rate (QLVAD) data sets obtained from in silico and in vivo sources. The MF was compared with a third-order Butterworth filter (BWF) and a 10-s moving average filter (MAF). Performance was assessed by calculating the response time and steady state error across a range of heart rates and levels of noise. The response time of the MF was 3.5 times faster than the MAF, 0.5 s slower than the BWF, and had a steady state error of 2.61 %. It completely removed pulsatile signal components caused by residual ventricular function, and tracked sharp transient changes in QLVAD better than the BWF. The use of a two-stage MF improved the noise immunity compared to the single-stage MF. This study showed that the good performance characteristics of the non-linear MF make it a more suitable candidate for embedded real-time processing of QLVAD than linear filters.

  10. A 4th-order reconfigurable analog baseband filter for software-defined radio applications

    NASA Astrophysics Data System (ADS)

    Weiwei, Wang; Xuegui, Chang; Xiao, Wang; Kefeng, Han; Xi, Tan; Na, Yan; Hao, Min

    2011-04-01

    This paper presents a 4th-order reconfigurable analog baseband filter for software-defined radios. The design exploits an active-RC low pass filter (LPF) structure with digital assistant, which is flexible for tunability of filter characteristics, such as cut-off frequency, selectivity, type, noise, gain and power. A novel reconfigurable operational amplifier is proposed to realize the optimization of noise and scalability of power dissipation. The chip was fabricated in an SMIC 0.13 μm CMOS process. The main filter and frequency calibration circuit occupy 1.8 × 0.8 mm2 and 0.48 × 0.25 mm2 areas, respectively. The measurement results indicate that the filter provides Butterworth and Chebyshev responses with a wide frequency tuning range from 280 kHz to 15 MHz and a gain range from 0 to 18 dB. An IIP3 of 29 dBm is achieved under a 1.2 V power supply. The input inferred noise density varies from 41 to 133 according to a given standard, and the power consumptions are 5.46 mW for low band (from 280 kHz to 3 MHz) and 8.74 mW for high band (from 3 to 15 MHz) mode.

  11. Rekonfigurationstechniken und Anwendungsgebiete für ein programmierbares Gm-C Analog-Filter

    NASA Astrophysics Data System (ADS)

    Becker, J.; Henrici, F.; Manoli, Y.

    2006-09-01

    FPAAs (Field Programmable Analog Arrays) erlauben es, analoge Signalübertragungsfunktionen auf Hardware abzubilden, die von veränderbaren digitalen Konfigurationsdaten abhängen. Sowohl für das Design von Filterstrukturen auf Systemebene als auch für die genaue Simulation ihrer analogen Übertragungsfunktion auf Transistorebene ist es dabei notwendig, die entsprechenden Konfigurationsdaten einzugeben bevor die Phasen/Betragsanalyse durchgeführt werden kann. Die vorliegende Arbeit stellt ein graphisches Entwurfsprogramm zur Instantiierung von analogen Filtern für ein FPAA mit 17 gm-C Blöcken vor. Es wird über erste Simulationsergebnisse berichtet, die die Machbarkeit mit Eckfrequenzen bis zu hundert Mhz bestätigen. Simulierte Übertragungsfunktionen von grundlegenden Bausteinen werden mit der Theorie verglichen und zu einer exemplarischen Instantiierung eines Butterworth-Filters der vierten Ordnung weitergeführt.

  12. Feature Identification and Filtering for Engine Misfire Detection (EMD) Using Zirconia Oxygen Sensor

    NASA Astrophysics Data System (ADS)

    Pauzi, Muhammad Zaim Mohamed; Abu Bakar, Elmi; Fauzi Ismail, Mohd

    2016-02-01

    Vehicles as transportation are popular and mainly use among peoples around the world for various kind of purpose either personal or not. Over hundreds of year internal combustion engines widely used because of high efficiency and low maintenance compare to new technology which are using cells of battery. Nevertheless, emission cause of incomplete combustion such engine misfire normally occurs as well. For instances, some mechanical, sensors or actuators failure and environmental condition contribute to the engine misfire. The importance of engine misfire detection (EMD) is to ensure engine emissions not harmful to the environments and avoid damage of catalytic converter. By using low cost narrowband oxygen sensor to acquire air to fuel ratio (AFR) signal behavior under misfire condition and analyst by digital signal processing method using Discrete Fourier Transform (DFT) algorithm for Digital Butterworth Filter designation is discussed in this paper.

  13. Exploiting nonlinearities of micro-machined resonators for filtering applications

    NASA Astrophysics Data System (ADS)

    Ilyas, S.; Chappanda, K. N.; Younis, M. I.

    2017-06-01

    We demonstrate the exploitation of the nonlinear behavior of two electrically coupled microbeam resonators to realize a band-pass filter. More specifically, we combine their nonlinear hardening and softening responses to realize a near flat pass band filter with sharp roll-off characteristics. The device is composed of two near identical doubly clamped and electrostatically actuated microbeams made of silicon. One of the resonators is buckled via thermal loading to produce a softening frequency response. It is then further tuned to create the desired overlap with the second resonator response of hardening behavior. This overlapping improves the pass band flatness. Also, the sudden jumps due to the softening and hardening behaviors create sharp roll-off characteristics. This approach can be promising for the future generation of filters with superior characteristics.

  14. Microscope system with on axis programmable Fourier transform filtering

    NASA Astrophysics Data System (ADS)

    Martínez, José Luis; García-Martínez, Pascuala; Moreno, Ignacio

    2017-02-01

    We propose an on-axis microscope optical system to implement programmable optical Fourier transform image processing operations, taking advantage of phase and polarization modulation of a liquid crystal on silicon (LCOS) display. We use a Hamamatsu spatial light modulator (SLM), free of flickering, which therefore can be tuned to fully eliminate the zero order component of the encoded diffractive filter. This allows the realization of filtering operation on axis (as opposed to other systems in the literature that require operating off axis), therefore making use of the full space bandwidth provided by the SLM. The system is first demonstrated by implementing different optical processing operations based on phase-only blazed gratings such as phase contrast, band-pass filtering, or additive and substractive imaging. Then, a simple Differential interference contrast (DIC) imaging is obtained changing to a polarization modulation scheme, achieved simply by selecting a different incident state of polarization on the incident beam.

  15. Effect of different thickness of material filter on Tc-99m spectra and performance parameters of gamma camera

    NASA Astrophysics Data System (ADS)

    Nazifah, A.; Norhanna, S.; Shah, S. I.; Zakaria, A.

    2014-11-01

    This study aimed to investigate the effects of material filter technique on Tc-99m spectra and performance parameters of Philip ADAC forte dual head gamma camera. Thickness of material filter was selected on the basis of percentage attenuation of various gamma ray energies by different thicknesses of zinc material. A cylindrical source tank of NEMA single photon emission computed tomography (SPECT) Triple Line Source Phantom filled with water and Tc-99m radionuclide injected was used for spectra, uniformity and sensitivity measurements. Vinyl plastic tube was used as a line source for spatial resolution. Images for uniformity were reconstructed by filtered back projection method. Butterworth filter of order 5 and cut off frequency 0.35 cycles/cm was selected. Chang's attenuation correction method was applied by selecting 0.13/cm linear attenuation coefficient. Count rate was decreased with material filter from the compton region of Tc-99m energy spectrum, also from the photopeak region. Spatial resolution was improved. However, uniformity of tomographic image was equivocal, and system volume sensitivity was reduced by material filter. Material filter improved system's spatial resolution. Therefore, the technique may be used for phantom studies to improve the image quality.

  16. Design methodology for multilayer microwave filters and Balun circuits

    NASA Astrophysics Data System (ADS)

    Cho, Choonsik

    A systematic and efficient approach to the design for a broad class of passive microwave circuits in multilayer configurations is presented. Multilayer configurations are becoming popular at microwave frequencies due to their several advantages over single layer configurations. However, systematic design procedures for multilayer circuits have not been yet available. Design procedures for several types of microwave circuits in multilayer configurations have been developed. Parallel coupled-line band-pass filters, end-coupled bandpass filters and three-line baluns have been designed with the systematic design procedures developed. Procedures developed have been verified by comparing the results with full-wave electromagnetic simulations. These circuits have also been fabricated and measured to verify the design procedures. Wide bandwidth, size/volume compaction, flexible design and physically realizable dimensions are the factors that multilayer structures provide compared to single layer configurations. A network modeling is employed to characterize multilayer multi-conductor transmission line systems. Since the microwave circuits developed utilize multiple coupled lines in multilayer configurations, the characterization of these coupled lines plays a significant role in derivation of design equations and generation of design procedures. Using this modeling approach, a multiple coupled line system can be transformed to a multiple uncoupled line system. These equivalent uncoupled lines are used to derive network parameters ([S], [Y] or [Z] matrix) for coupled lines. The normal mode parameters (NMPs) for coupled lines derived in terms of system specifications are utilized to obtain the physical geometries. An optimization process is employed to find the geometries which yield the desired NMPs calculated from circuit specifications. For optimizing the geometry, a quasi-static field analysis program, Segmentation and Boundary Element Method (SBEM), is employed to

  17. Potential-controlled filtering in quantum star graphs

    SciTech Connect

    Turek, Ondrej Cheon, Taksu

    2013-03-15

    We study the scattering in a quantum star graph with a Fueloep-Tsutsui coupling in its vertex and with external potentials on the lines. We find certain special couplings for which the probability of the transmission between two given lines of the graph is strongly influenced by the potential applied on another line. On the basis of this phenomenon we design a tunable quantum band-pass spectral filter. The transmission from the input to the output line is governed by a potential added on the controlling line. The strength of the potential directly determines the passband position, which allows to control the filter in a macroscopic manner. Generalization of this concept to quantum devices with multiple controlling lines proves possible. It enables the construction of spectral filters with more controllable parameters or with more operation modes. In particular, we design a band-pass filter with independently adjustable multiple passbands. We also address the problem of the physical realization of Fueloep-Tsutsui couplings and demonstrate that the couplings needed for the construction of the proposed quantum devices can be approximated by simple graphs carrying only {delta} potentials. - Highlights: Black-Right-Pointing-Pointer Spectral filtering devices based on quantum graphs are designed theoretically. Black-Right-Pointing-Pointer The passband is controlled by the application of macroscopic potentials on lines. Black-Right-Pointing-Pointer The filters are built upon special Fulop-Tsutsui type couplings at graph vertices. Black-Right-Pointing-Pointer A method of construction of Fulop-Tsutsui vertices from delta potentials is devised.

  18. Water Filters

    NASA Technical Reports Server (NTRS)

    1988-01-01

    Seeking to find a more effective method of filtering potable water that was highly contaminated, Mike Pedersen, founder of Western Water International, learned that NASA had conducted extensive research in methods of purifying water on board manned spacecraft. The key is Aquaspace Compound, a proprietary WWI formula that scientifically blends various types of glandular activated charcoal with other active and inert ingredients. Aquaspace systems remove some substances; chlorine, by atomic adsorption, other types of organic chemicals by mechanical filtration and still others by catalytic reaction. Aquaspace filters are finding wide acceptance in industrial, commercial, residential and recreational applications in the U.S. and abroad.

  19. Filter apparatus

    DOEpatents

    Kuban, D.P.; Singletary, B.H.; Evans, J.H.

    A plurality of holding tubes are respectively mounted in apertures in a partition plate fixed in a housing receiving gas contaminated with particulate material. A filter cartridge is removably held in each holding tube, and the cartridges and holding tubes are arranged so that gas passes through apertures therein and across the the partition plate while particulate material is collected in the cartridges. Replacement filter cartridges are respectively held in holding canisters mounted on a support plate which can be secured to the aforesaid housing, and screws mounted on said canisters are arranged to push replacement cartridges into the cartridge holding tubes and thereby eject used cartridges therefrom.

  20. Filter apparatus

    DOEpatents

    Kuban, Daniel P.; Singletary, B. Huston; Evans, John H.

    1984-01-01

    A plurality of holding tubes are respectively mounted in apertures in a partition plate fixed in a housing receiving gas contaminated with particulate material. A filter cartridge is removably held in each holding tube, and the cartridges and holding tubes are arranged so that gas passes through apertures therein and across the partition plate while particulate material is collected in the cartridges. Replacement filter cartridges are respectively held in holding canisters mounted on a support plate which can be secured to the aforesaid housing, and screws mounted on said canisters are arranged to push replacement cartridges into the cartridge holding tubes and thereby eject used cartridges therefrom.

  1. Sigma Filter

    NASA Technical Reports Server (NTRS)

    Balgovind, R. C.

    1985-01-01

    The GLA Fourth-Order model is needed to smooth the topography. This is to remove the Gibbs phenomenon. The Gibbs phenomenon occurs whenever we truncate a Fourier Series. The Sigma factors were introduced to reduce the Gibbs phenomenon. It is found that the smooth Fourier series is nothing but the original Fourier series with its coefficients multiplied by corresponding sigma factors. This operator can be applied many times to obtain high order sigma filtered field and is easily applicable using FFT. It is found that this filter is beneficial in deriving the topography.

  2. DKIST visible broadband imager interference filters

    NASA Astrophysics Data System (ADS)

    Wöger, Friedrich

    2014-08-01

    The Visible Broadband Imager (VBI) is one of several first-light instruments of the Daniel K. Inouye Solar Telescope (DKIST, formerly known as the Advanced Technology Solar Telescope (ATST)). Operating at discrete wavelengths within a range of 390-860 nm, the VBI will be capable of sampling the solar atmosphere in several layers at the diffraction limit of DKIST's 4 meter aperture. The layers are selected by the peak wavelength and bandpass width of its interference filters that have to be manufactured to very tight specifications. We present the results of testing performed at the National Solar Observatory's Dunn Solar Telescope (DST) to confirm that the requirements were met by the vendor.

  3. Impurity density derivation from bandpass soft x-ray tomography: applicability, perspectives and limitations

    NASA Astrophysics Data System (ADS)

    Vezinet, D.; Mazon, D.; Guirlet, R.; Decker, J.; Peysson, Y.

    2014-08-01

    Deriving impurity density from local soft x-ray (SXR) emissivity (reconstructed by background-subtracted tomography during trace injections) by line-emission modelling leads to uncertainties due to the unknown ionization balance, especially for medium-Z impurities. This paper proposes a paradigm shift in the way SXR tomography is used, from one that maximizes signal at the expense of uncertain modelling to one that relies on sharper spectral resolution used to better understand what exactly is being measured. It is indeed shown that the measured SXR emissivity of an impurity may be robust with respect to changes to its unknown ionization balance (i.e. with respect to impurity transport) under two conditions. First, the electron temperature must be above a certain threshold (typically 4-5 keV or higher for metals like Ni or Fe). Second, the spectral response of SXR detectors must have a tuneable band-pass and should focus on a specific spectral region for each considered impurity. Both these conditions aim at maximizing the Bremsstrahlung contribution, which has the weakest dependence on ion charge. Prospective applications for several impurities are discussed as well as practical limitations. Since this method offers diagnostics-designing potential, possible technological solutions are also discussed.

  4. Segmented correlation measurements on superconducting bandpass delta sigma modulator with and without input tone

    NASA Astrophysics Data System (ADS)

    Bulzacchelli, John F.; Lee, Hae-Seung; Hong, Merit Y.; Misewich, James A.; Ketchen, Mark B.

    2003-12-01

    Segmented correlation is a useful technique for testing a superconducting analogue-to-digital converter, as it allows the output spectrum to be estimated with fine frequency resolution even when data record lengths are limited by small on-chip acquisition memories. Previously, we presented segmented correlation measurements on a superconducting bandpass delta-sigma modulator sampling at 40.2 GHz under idle channel (no input) conditions. This paper compares the modulator output spectra measured by segmented correlation with and without an input tone. Important practical considerations of calculating segmented correlations are discussed in detail. Resolution enhancement by segmented correlation does reduce the spectral width of the input tone in the desired manner, but the signal power due to the input increases the variance of the spectral estimate near the input frequency, hindering accurate calculation of the in-band noise. This increased variance, which is predicted by theory, must be considered carefully in the application of segmented correlation. Methods for obtaining more accurate estimates of the quantization noise spectrum which are closer to those measured with no input are described.

  5. The effects of bandpass limiters on n-phase tracking systems

    NASA Technical Reports Server (NTRS)

    Butman, S. A.; Lesh, J. R.

    1977-01-01

    The combination of a bandpass limiter and an n(th) power tracking loop is considered. It is shown that the performance of the combination does not depend on the form of the nonlinear function used to create the n(th) harmonic signal so long as some energy in that zone is produced. Furthermore, the order in which the limiter and n(th) power nonlinearity occur is unimportant so that the results apply equally well to the n-phase Costas type of implementation of the n(th) power loops. Closed form expressions for the signal suppression factors are obtained and it is shown that the coherent and noncoherent SNR's out of the n(th) power-limiter combination can be expressed in terms of two of these suppression factors. This later point enables one to estimate the loop SNR of an n(th) power-limiter phase locked loop by simply calculating the suppression factors for n(th) and 2n(th) power loops. Finally, n(th) power phase locked loops without limiters are compared with similar loops with limiters where it is shown that the presence of the limiter can actually enhance the output SNR at moderate to large values of input SNR.

  6. The effects of bandpass limiters on n-phase tracking systems

    NASA Technical Reports Server (NTRS)

    Butman, S. A.; Lesh, J. R.

    1977-01-01

    The combination of a bandpass limiter and an n-th power tracking loop is considered. Performance of the combination does not depend on the form of the nonlinear function used to create the n-th harmonic signal as long as some energy in that zone is produced. The order in which the limiter and n-th power nonlinearity occur is unimportant so that the results apply equally well to the n-phase Costas type of implementations of the n-th power loops. Closed form expressions for the signal suppression factors are obtained. Coherent and noncoherent SNR's out of the n-th power-limiter combination can be expressed in terms of two of these suppression factors. The loop SNR of an n-th power-limited phase locked loop is estimated by simply calculating the suppression factors for n-th and 2n-th power loops. Finally, n-th power phase locked loops without limiters are compared with similar loops with limiters; the limiter can actually enhance output SNR at moderate to large input SNR.

  7. Processing of band-passed noise in the lateral auditory belt cortex of the rhesus monkey.

    PubMed

    Rauschecker, Josef P; Tian, Biao

    2004-06-01

    Neurons in the lateral belt areas of rhesus monkey auditory cortex were stimulated with band-passed noise (BPN) bursts of different bandwidths and center frequencies. Most neurons responded much more vigorously to these sounds than to tone bursts of a single frequency, and it thus became possible to elicit a clear response in 85% of lateral belt neurons. Tuning to center frequency and bandwidth of the BPN bursts was analyzed. Best center frequency varied along the rostrocaudal direction, with 2 reversals defining borders between areas. We confirmed the existence of 2 belt areas (AL and ML) that were laterally adjacent to the core areas (R and A1, respectively) and a third area (CL) adjacent to area CM on the supratemporal plane (STP). All 3 lateral belt areas were cochleotopically organized with their frequency gradients collinear to those of the adjacent STP areas. Although A1 neurons responded best to pure tones and their responses decreased with increasing bandwidth, 63% of the lateral belt neurons were tuned to bandwidths between 1/3 and 2 octaves and showed either one or multiple peaks. The results are compared with previous data from visual cortex and are discussed in the context of spectral integration, whereby the lateral belt forms a relatively early stage of processing in the cortical hierarchy, giving rise to parallel streams for the identification of auditory objects and their localization in space.

  8. Condensation reaction in the bandpass reaction cell improves sensitivity for uranium, thorium, neodymium and praseodymium measurements.

    PubMed

    Vais, Vladimir; Li, Chunsheng; Cornett, Jack

    2003-09-01

    Condensation reactions in the bandpass reaction cell or dynamic reaction cell (DRC) were used for the determination of actinides and lanthanides such as uranium, thorium, neodymium and praseodymium. These elements react with oxygen reagent gas in the dynamic reaction cell of the ELAN DRC II instrument to give mono- and/or dioxo cationic species (UO(2)+, ThO+, NdO+ and PrO+, respectively). Increasing the oxygen flow rate in the dynamic reaction cell leads to the rapid decrease of the singly charged metal ions accompanied by the fast increase in the intensity of the oxide ion. This phenomenon is used to improve considerably the sensitivity of ICP-MS instruments equipped with a dynamic reaction cell for actinides and lanthanides. Estimated detection limits (EDL) obtained in this work for uranium, thorium, neodymium-144 and praseodymium are 0.022, 1.0, 0.045, and 0.10 ng L(-1), respectively. The detection limit for uranium measured in the standard (vented) mode of an ELAN DRC II was found to be 0.22 ng L(-1), which is an order of magnitude higher compared to the pressurized mode.

  9. Notch filter

    NASA Technical Reports Server (NTRS)

    Shelton, G. B. (Inventor)

    1977-01-01

    A notch filter for the selective attenuation of a narrow band of frequencies out of a larger band was developed. A helical resonator is connected to an input circuit and an output circuit through discrete and equal capacitors, and a resistor is connected between the input and the output circuits.

  10. Design of multichannel filter banks for subband coding of audio signals using multirate signal processing techniques

    NASA Astrophysics Data System (ADS)

    Goel, Aditya

    2007-09-01

    This paper presents a design technique for multi channel filter banks for subband coding of audio signal. In sub-band coding, the speech is first split into frequency bands using a bank of bandpass filters. The individual band pass signals are then decimated by a factor 'N' and encoded for transmission. A filter bank is a collection of bandpass filters, all processing the same input signal. The important parameters in sub-band coders are the number of frequency bands and the frequency range of the system, and the sub-band coding technique. The total number of filters required are 2N. The sub-band signals can be reconstructed perfectly with linear-phase FIR filters. The filter bank is designed so as to overcome the effect of non-ideal transition-band and stop-bands filtering. With real-world filters, the non-zero signal energy in the transition and stop bands is reflected back into the pass-band during the interpolation process at the receiver causing aliasing. This aliasing is canceled in the filter bank during reconstruction of the signal. This paper deals with the designing of 8 band filter banks and coding the subband signals at various bit rates using DPCM technique. In this we used a sampling rate of 44.1Khz. The first two bands are coded at 8 bits/sample, next three bands are coded at 4bits/sample and last 3 bands are coded at 2 bits/sample. Lower frequency spectrum is encoded at higher bit rate, as more energy is concentrated in the lower range. Simulated results using MATLAB Software shows that a compression ratio of 3.76:1 is achieved with perceptual quality. Beyond this we find that the signal quality degraded to reasonable extent, which is not recommended. There has to be a tradeoff between the compression ratio and Quality of transmitted signal.

  11. Experiences with thin film filter development for the Extreme Ultraviolet Explorer

    NASA Technical Reports Server (NTRS)

    Vallerga, J. V.; Vedder, P. W.; Siegmund, O. H. W.

    1993-01-01

    The design, development, and optimization of the thin film filters used on the Extreme Ultraviolet Explorer (EUVE) Satellite to define the EUV wavelength bandpasses of the individual instruments was a complicated task. The bandpasses had to be optimized for the astrophysical goals of the EUVE mission and constrained by the strong geocoronal EUV background emission. Materials with optical constants that met these requirements had to be found and tested. In many cases these materials were not compatible or were not strong enough to survive the intense vibrations of a rocket launch. Other effects, such as photoelectron 'halo' produced in the filters, were not discovered until flight qualification. The final set of flight filters included: lexan/boron, aluminum/carbon, titanium/antimony/aluminum, and tin/silicon monoxide. This paper discusses the lessons learned in the development of these filters, including the optimization process, material interactions and problems, calibration techniques, vibration susceptibility, thermal tests, and photoelectron emission. We feel the experiences gained over the last 10 years creating the filter sets for EUVE will be invaluable for future missions that use thin film filters.

  12. Clutter filtering influence on blood velocity estimation using speckle tracking.

    PubMed

    Fadnes, Solveig; Bjærum, Steinar; Torp, Hans; Lovstakken, Lasse

    2015-12-01

    Blood speckle tracking has shown potential for solving the angle-dependency limitation in color flow imaging. However, as clutter filtering is still Doppler-based, flow velocities at near-perpendicular beam-to-flow angles can be severely attenuated. It is shown that the clutter filter also alters the speckle appearance through a decrease in the lateral imaging bandwidth, leading to poorer lateral resolution and thus tracking performance. Interestingly, at perpendicular beam-to-flow angles lateral band-pass characteristics are inferred, and the resulting lateral amplitude modulation could help improve tracking estimates. Simulations and flow phantom experiments showed that substantially improved results could be achieved by utilizing time-variant clutter filters (e.g., polynomial regression filters) despite the inherent decorrelation inferred by these filters, but only for higher ensemble sizes (N > 36). We found that, compared with color flow imaging, speckle tracking could yield consistent estimates well below the clutter filter cutoff, but with a higher variance attributed to the low signalto- noise ratio inferred by filter attenuation. Overall, provided that a low f-number and high ensemble lengths (N approx. > 36) can be used, speckle tracking can consistently provide angle- independent flow velocity estimates, limited only by a lower bound on the flow velocity itself.

  13. Indium phosphide all air-gap Fabry-Pérot filters for near-infrared spectroscopic applications

    NASA Astrophysics Data System (ADS)

    Ullah, A.; Butt, M. A.; Fomchenkov, S. A.; Khonina, S. N.

    2016-08-01

    Food quality can be characterized by noninvasive techniques such as spectroscopy in the Near Infrared wavelength range. For example, 930 -1450 nm wavelength range can be used to detect diseases and differentiate between meat samples. Miniaturization of such NIR spectrometers is useful for quick and mobile characterization of food samples. Spectrometers can be miniaturized, without compromising the spectral resolution, using Fabry-Pérot (FP) filters consisting of two highly reflecting mirrors with a central cavity in between. The most commonly used mirrors in the design of FP filters are Distributed Bragg Reflections (DBRs) consisting of alternating high and low refractive index material pairs, due to their high reflectivity compared to metal mirrors. However, DBRs have high reflectivity for a selected range of wavelengths known as the stopband of the DBR. This range is usually much smaller than the sensitivity range of the spectrometer detector. Therefore, a bandpass filter is usually required to restrict wavelengths outside the stopband of the FP DBRs. Such bandpass filters are difficult to design and implement. Alternatively, high index contrast materials must be can be used to broaden the stopband width of the FP DBRs. In this work, Indium phosphide all air-gap filters are proposed in conjunction with InGaAs based detectors. The designed filter has a wide stopband covering the entire InGaAs detector sensitivity range. The filter can be tuned in the 950-1450 nm with single mode operation. The designed filter can hence be used for noninvasive meat quality control.

  14. An OTA-C filter for ECG acquisition systems with highly linear range and less passband attenuation

    NASA Astrophysics Data System (ADS)

    Jihai, Duan; Chuang, Lan; Weilin, Xu; Baolin, Wei

    2015-05-01

    A fifth order operational transconductance amplifier-C (OTA-C) Butterworth type low-pass filter with highly linear range and less passband attenuation is presented for wearable bio-telemetry monitoring applications in a UWB wireless body area network. The source degeneration structure applied in typical small transconductance circuit is improved to provide a highly linear range for the OTA-C filter. Moreover, to reduce the passband attenuation of the filter, a cascode structure is employed as the output stage of the OTA. The OTA-based circuit is operated in weak inversion due to strict power limitation in the biomedical chip. The filter is fabricated in a SMIC 0.18-μm CMOS process. The measured results for the filter have shown a passband gain of -6.2 dB, while the -3-dB frequency is around 276 Hz. For the 0.8 VPP sinusoidal input at 100 Hz, a total harmonic distortion (THD) of -56.8 dB is obtained. An electrocardiogram signal with noise interference is fed into this chip to validate the function of the designed filter. Project supported by the National Natural Science Foundation of China (Nos. 61161003, 61264001, 61166004) and the Guangxi Natural Science Foundation (No. 2013GXNSFAA019333).

  15. FILTER-INDUCED BIAS IN Lyα EMITTER SURVEYS: A COMPARISON BETWEEN STANDARD AND TUNABLE FILTERS. GRAN TELESCOPIO CANARIAS PRELIMINARY RESULTS

    SciTech Connect

    De Diego, J. A.; De Leo, M. A.; Cepa, J.; Bongiovanni, A.; Verdugo, T.; Sánchez-Portal, M.

    2013-10-01

    Lyα emitter (LAE) surveys have successfully used the excess in a narrowband filter compared to a nearby broadband image to find candidates. However, the odd spectral energy distribution (SED) of LAEs combined with the instrumental profile has important effects on the properties of the candidate samples extracted from these surveys. We investigate the effect of the bandpass width and the transmission profile of the narrowband filters used for extracting LAE candidates at redshifts z ≅ 6.5 through Monte Carlo simulations, and we present pilot observations to test the performance of tunable filters to find LAEs and other emission-line candidates. We compare the samples obtained using a narrow ideal rectangular filter, the Subaru NB921 narrowband filter, and sweeping across a wavelength range using the ultra-narrow-band tunable filters of the instrument OSIRIS, installed at the 10.4 m Gran Telescopio Canarias. We use this instrument for extracting LAE candidates from a small set of real observations. Broadband data from the Subaru, Hubble Space Telescope, and Spitzer databases were used for fitting SEDs to calculate photometric redshifts and to identify interlopers. Narrowband surveys are very efficient in finding LAEs in large sky areas, but the samples obtained are not evenly distributed in redshift along the filter bandpass, and the number of LAEs with equivalent widths <60 Å can be underestimated. These biased results do not appear in samples obtained using ultra-narrow-band tunable filters. However, the field size of tunable filters is restricted because of the variation of the effective wavelength across the image. Thus, narrowband and ultra-narrow-band surveys are complementary strategies to investigate high-redshift LAEs.

  16. A Magneto-Electric Microwave Filter

    NASA Astrophysics Data System (ADS)

    Tatarenko, A. S.; Srinivasan, G.; Bichurin, M. I.

    2006-03-01

    A new class of electric field-tunable ferrite-ferroelectric microwave band-pass filter is discussed. The electric field tunability is possible through magnetoelectric (ME) interactions. The mechanical deformation due to piezoelectric effect in an electric field manifests as a magnetic field shift in the ferromagnetic resonance (FMR) for the ferrite. The filter was fabricated with an ME resonator consisting of bilayers of 30-110 micron thick (111) yttrium iron garnet (YIG) films and lead zirconate titanate (PZT). The bilayer was positioned between input and output antenna in a microstripline structure. The device insertion loss was measured as a function of frequency f, bias magnetic field H (applied parallel to bilayer plane) and the electrical field E applied across PZT. The minimum insertion loss was 4-5 dB at 5-10 GHz. The off-resonance losses were about 20 dB. The E-field tunability was 120 MHz for E = 3 kV/cm for bilayers with 110 micron thick YIG. The ME microwave filters discussed here are miniature in size, would facilitate high-speed operation, and are compatibility with integrated circuit technology. -- The work was supported by grants from ARO, ONR and NSF.

  17. Systematic Design and Modeling of a OTA-C Filter for Portable ECG Detection.

    PubMed

    Shuenn-Yuh Lee; Chih-Jen Cheng

    2009-02-01

    This study presents a systematic design of the fully differential operational transconductance amplifier-C (OTA-C) filter for a heart activities detection apparatus. Since the linearity and noise of the filter is dependent on the building cell, a precise behavioral model for the real OTA circuit is created. To reduce the influence of coefficient sensitivity and maintain an undistorted biosignal, a fifth-order ladder-type lowpass Butterworth is employed. Based on this topology, a chip fabricated in a 0.18- mum CMOS process is simulated and measured to validate the system estimation. Since the battery life and the integration with the low-voltage digital processor are the most critical requirement for the portable diagnosis device, the OTA-based circuit is operated in the subthreshold region to save power under the supply voltage of 1V. Measurement results show that this low-voltage and low-power filter possesses the HD3 of -48.9 dB, dynamic range (DR) of 50 dB, and power consumption of 453 nW. Therefore, the OTA-C filter can be adopted to eliminate the out-of-band interference of the electrocardiogram (ECG) whose signal bandwidth is located within 250 Hz.

  18. Water Filter

    NASA Technical Reports Server (NTRS)

    1982-01-01

    A compact, lightweight electrolytic water sterilizer available through Ambassador Marketing, generates silver ions in concentrations of 50 to 100 parts per billion in water flow system. The silver ions serve as an effective bactericide/deodorizer. Tap water passes through filtering element of silver that has been chemically plated onto activated carbon. The silver inhibits bacterial growth and the activated carbon removes objectionable tastes and odors caused by addition of chlorine and other chemicals in municipal water supply. The three models available are a kitchen unit, a "Tourister" unit for portable use while traveling and a refrigerator unit that attaches to the ice cube water line. A filter will treat 5,000 to 10,000 gallons of water.

  19. Plasmonic filters.

    SciTech Connect

    Passmore, Brandon Scott; Shaner, Eric Arthur; Barrick, Todd A.

    2009-09-01

    Metal films perforated with subwavelength hole arrays have been show to demonstrate an effect known as Extraordinary Transmission (EOT). In EOT devices, optical transmission passbands arise that can have up to 90% transmission and a bandwidth that is only a few percent of the designed center wavelength. By placing a tunable dielectric in proximity to the EOT mesh, one can tune the center frequency of the passband. We have demonstrated over 1 micron of passive tuning in structures designed for an 11 micron center wavelength. If a suitable midwave (3-5 micron) tunable dielectric (perhaps BaTiO{sub 3}) were integrated with an EOT mesh designed for midwave operation, it is possible that a fast, voltage tunable, low temperature filter solution could be demonstrated with a several hundred nanometer passband. Such an element could, for example, replace certain components in a filter wheel solution.

  20. Design of Bessel low-pass filter using DGS for RF/microwave applications

    NASA Astrophysics Data System (ADS)

    Kumar, Ashwani; Verma, A. K.

    2016-09-01

    A synthesis method to design a defected ground structures (DGS)-based Bessel low-pass filter (LPF) using a triangular and an open-square (OS)-type DGS is reported. For the five-pole Bessel LPF at fc = 2.5 GHz, we get 10.6 dB/GHz selectivity using the triangular DGS; while the OS-type DGS provides 39 dB/GHz selectivity. For these two filters, the 10 dB impedance matching BW is 76% and 84%, respectively. It is a much wider BW that is obtained for a lumped element Bessel LPF. The maximum group delay (GD) variation within the pass band is 25pS and 28pS, respectively. The 20 dB rejection BW can be increased from 5.8 GHz to 18.8 GHz with increase in the order of filter from 5 to 11. We have also presented the design of a compact five-pole DGS-based elliptic filter with selectivity 38.2 dB/GHz and 17.8 dB return loss. Results on the DGS-based elliptic filter, Butterworth and Chebyshev filters are also presented. The experimental results are compared against the recently reported LPFs. Our reported filters perform better with respect to selectivity and group delay variation. The flatter GD and high selectivity, along with a wide 10 dB impedance matching BW, make the DGS Bessel filter a candidate for high-speed data communication, front end of a wideband communication system and efficiency improvement of a power amplifier.

  1. Tunable Microwave Filter Design Using Thin-Film Ferroelectric Varactors

    NASA Astrophysics Data System (ADS)

    Haridasan, Vrinda

    Military, space, and consumer-based communication markets alike are moving towards multi-functional, multi-mode, and portable transceiver units. Ferroelectric-based tunable filter designs in RF front-ends are a relatively new area of research that provides a potential solution to support wideband and compact transceiver units. This work presents design methodologies developed to optimize a tunable filter design for system-level integration, and to improve the performance of a ferroelectric-based tunable bandpass filter. An investigative approach to find the origins of high insertion loss exhibited by these filters is also undertaken. A system-aware design guideline and figure of merit for ferroelectric-based tunable band- pass filters is developed. The guideline does not constrain the filter bandwidth as long as it falls within the range of the analog bandwidth of a system's analog to digital converter. A figure of merit (FOM) that optimizes filter design for a specific application is presented. It considers the worst-case filter performance parameters and a tuning sensitivity term that captures the relation between frequency tunability and the underlying material tunability. A non-tunable parasitic fringe capacitance associated with ferroelectric-based planar capacitors is confirmed by simulated and measured results. The fringe capacitance is an appreciable proportion of the tunable capacitance at frequencies of X-band and higher. As ferroelectric-based tunable capac- itors form tunable resonators in the filter design, a proportionally higher fringe capacitance reduces the capacitance tunability which in turn reduces the frequency tunability of the filter. Methods to reduce the fringe capacitance can thus increase frequency tunability or indirectly reduce the filter insertion-loss by trading off the increased tunability achieved to lower loss. A new two-pole tunable filter topology with high frequency tunability (> 30%), steep filter skirts, wide stopband

  2. Envelope analysis with a genetic algorithm-based adaptive filter bank for bearing fault detection.

    PubMed

    Kang, Myeongsu; Kim, Jaeyoung; Choi, Byeong-Keun; Kim, Jong-Myon

    2015-07-01

    This paper proposes a fault detection methodology for bearings using envelope analysis with a genetic algorithm (GA)-based adaptive filter bank. Although a bandpass filter cooperates with envelope analysis for early identification of bearing defects, no general consensus has been reached as to which passband is optimal. This study explores the impact of various passbands specified by the GA in terms of a residual frequency components-to-defect frequency components ratio, which evaluates the degree of defectiveness in bearings and finally outputs an optimal passband for reliable bearing fault detection.

  3. Filter-free nondispersive infrared sensing using narrow-bandwidth mid-infrared thermal emitters

    NASA Astrophysics Data System (ADS)

    Inoue, Takuya; De Zoysa, Menaka; Asano, Takashi; Noda, Susumu

    2014-01-01

    We experimentally demonstrate filter-free nondispersive infrared (NDIR) sensing of organic solvents using single-peak narrow-bandwidth mid-infrared thermal emitters. Our emitters are based on multiple quantum wells (MQWs) and two-dimensional (2D) photonic crystal (PC) slabs, and show a single thermal emission peak with a quality factor of over 100 at the fingerprint wavelength (around 9 µm) of the target organic solvents. Using these narrow-bandwidth thermal emitters and commercial pyroelectric sensors without any optical bandpass filters, we successfully distinguish and determine the concentration of the target solvents among other solvents.

  4. Voltage-mode multifunction biquadratic filter with one input and six outputs using two ICCIIs.

    PubMed

    Chen, Hua-Pin

    2014-01-01

    A novel voltage-mode multifunction biquadratic filter with one input and six outputs is presented. The proposed circuit can realize inverting and noninverting low-pass, bandpass, and high-pass filters, simultaneously, by using two inverting second-generation current conveyors (ICCIIs), two grounded capacitors, and four resistors. Moreover, the proposed circuit offers the following attractive advantages: no requirements for component matching conditions, the use of only grounded capacitors, and low active and passive sensitivities. HSPICE and MATLAB simulations results are provided to demonstrate the theoretical analysis.

  5. A 240-GHz Wideband Ridged Waveguide Filter Based on MEMS Process

    NASA Astrophysics Data System (ADS)

    Ding, Jiangqiao; Hu, Jie; Liu, Dong; Wang, Daowei; Shi, Shengcai; Wu, Wen

    2017-03-01

    Terahertz (THz) bandpass filter (BPF) is one of important components in some detectors for astronomical observations. In this paper, a BPF with a relative bandwidth of 50% centered at 240 GHz is presented. This wideband BPF is made up of six ridged waveguide resonators and developed by silicon-based micro-electro-mechanical systems (MEMS) process. The transmission response of the filter is measured by a quasi-optical setup incorporating a sensitive superconducting mixer, and the result is in good agreement with the simulated one. Details of the design, simulation, and measurement are discussed in this paper.

  6. Voltage-Mode Multifunction Biquadratic Filter with One Input and Six Outputs Using Two ICCIIs

    PubMed Central

    Chen, Hua-Pin

    2014-01-01

    A novel voltage-mode multifunction biquadratic filter with one input and six outputs is presented. The proposed circuit can realize inverting and noninverting low-pass, bandpass, and high-pass filters, simultaneously, by using two inverting second-generation current conveyors (ICCIIs), two grounded capacitors, and four resistors. Moreover, the proposed circuit offers the following attractive advantages: no requirements for component matching conditions, the use of only grounded capacitors, and low active and passive sensitivities. HSPICE and MATLAB simulations results are provided to demonstrate the theoretical analysis. PMID:24895651

  7. Calibration of the Multi-Spectral Solar Telescope Array multilayer mirrors and XUV filters

    NASA Technical Reports Server (NTRS)

    Allen, Maxwell J.; Willis, Thomas D.; Kankelborg, Charles C.; O'Neal, Ray H.; Martinez-Galarce, Dennis S.; Deforest, Craig E.; Jackson, Lisa; Lindblom, Joakim; Walker, Arthur B. C., Jr.; Barbee, Troy W., Jr.

    1993-01-01

    The Multi-Spectral Solar Telescope Array (MSSTA), a rocket-borne solar observatory, was successfully flown in May, 1991, obtaining solar images in eight XUV and FUV bands with 12 compact multilayer telescopes. Extensive measurements have recently been carried out on the multilayer telescopes and thin film filters at the Stanford Synchrotron Radiation Laboratory. These measurements are the first high spectral resolution calibrations of the MSSTA instruments. Previous measurements and/or calculations of telescope throughputs have been confirmed with greater accuracy. Results are presented on Mo/Si multilayer bandpass changes with time and experimental potassium bromide and tellurium filters.

  8. Nonlinear Filtering

    DTIC Science & Technology

    1975-07-01

    agree to say four places by successive choices of finer subdivisions of the grid. The accuracy obtained by this method Is rot quite unexpected—see for...iltering, " R~v . Francais d’ ~•_!o:n~ti~, ~. l ’J73 , 3-54. ( 2L ; H. S . U•JLy , "Pedliza tion of nonlinear filters," ~!:Q~-·-~..c!.5E£...... .Q

  9. Eyeglass Filters

    NASA Technical Reports Server (NTRS)

    1987-01-01

    Biomedical Optical Company of America's suntiger lenses eliminate more than 99% of harmful light wavelengths. NASA derived lenses make scenes more vivid in color and also increase the wearer's visual acuity. Distant objects, even on hazy days, appear crisp and clear; mountains seem closer, glare is greatly reduced, clouds stand out. Daytime use protects the retina from bleaching in bright light, thus improving night vision. Filtering helps prevent a variety of eye disorders, in particular cataracts and age related macular degeneration.

  10. Self-emission glucose monitoring system with single chip guided-mode resonance filters

    NASA Astrophysics Data System (ADS)

    Yeh, Yen-Chun; Yang, Sheng; Schmidt, Dominik

    2016-03-01

    In this study, we designed and simulated an array of bandpass filters as a spectral separator for mid-infrared self-emission noninvasive glucose monitoring, using the human body as the background radiation emitter. The filters were based on the guided-mode resonance (GMR) effect. The human body is a good black body radiator that provides a stable temperature and continuous radiation energy in the mid-infrared range. We can thus use self-emission from the human body to measure certain fingerprint peaks of glucose spectrum between 8 μm to 10 μm, which allows estimation of glucose concentration. The GMR filter set includes at least four filters on one chip fabricated at the same time. By using fixed thicknesses and the same thin-film material for all the filters on the chip, a structure period adjustment alone can theoretically achieve multiple bandpass filters between the glucose fingerprint ranges - and achieve these coplanar filters on a single chip. By using all CMOS-compatible materials, COMSOL simulations show that a series of peaks with transmittances up to 70% and bandwidths of around 200nm can be achieved. This filter set can be fabricated with just a few thin layers that can simplify the typical thin-film deposition process. The proposed GMR filter array can then be combined with a thermometer array to achieve the non-invasive glucose monitoring. We compare the results obtained with the first version of the fabricated filter set with the measurements of Fourier transform infrared (FT-IR) spectroscopy.

  11. CRYSTAL FILTER TEST SET

    DTIC Science & Technology

    CRYSTAL FILTERS, *HIGH FREQUENCY, *RADIOFREQUENCY FILTERS, AMPLIFIERS, ELECTRIC POTENTIAL, FREQUENCY, IMPEDANCE MATCHING , INSTRUMENTATION, RADIOFREQUENCY, RADIOFREQUENCY AMPLIFIERS, TEST EQUIPMENT, TEST METHODS

  12. Order-sorting filter transmittance measured with an array detector

    NASA Technical Reports Server (NTRS)

    Heaney, James B.; Bradley, Scott E.; Bly, Vincent T.; Ewin, Audrey J.; La, Anh T.

    1993-01-01

    The simultaneous measurement of the spectrally and spatially variant transmittance of a linear variable order-sorting filter in a manner that closely resembles its conditions of actual use is described. The transmittance of a prototype order-sorting filter was measured in the 400- to 880-nm wavelength region by illuminating it with the output beam of a spectrophotometer while the filter was attached to the front of a 30 x 32 pixel silicon array detector. The filter was designed to be used in the output beam of a grating spectrometer to prevent the dispersal of higher diffracted orders onto an array detector. Areas of the filter that were spatially matched to the corresponding detector pixel column had measured peak transmittances of about 90 percent that were uniform to within +/- 1.5 percent along a given column. Transmittances for incident wavelengths shorter than the desired bandpass, corresponding to the order overlap region, were measured in the 0.003 range. Line spread function measurements made with the array detector indicated no significant beam spreading caused by inserting the filter into the beam.

  13. Active integrated filters for RF-photonic channelizers.

    PubMed

    El Nagdi, Amr; Liu, Ke; LaFave, Tim P; Hunt, Louis R; Ramakrishna, Viswanath; Dabkowski, Mieczyslaw; MacFarlane, Duncan L; Christensen, Marc P

    2011-01-01

    A theoretical study of RF-photonic channelizers using four architectures formed by active integrated filters with tunable gains is presented. The integrated filters are enabled by two- and four-port nano-photonic couplers (NPCs). Lossless and three individual manufacturing cases with high transmission, high reflection, and symmetric couplers are assumed in the work. NPCs behavior is dependent upon the phenomenon of frustrated total internal reflection. Experimentally, photonic channelizers are fabricated in one single semiconductor chip on multi-quantum well epitaxial InP wafers using conventional microelectronics processing techniques. A state space modeling approach is used to derive the transfer functions and analyze the stability of these filters. The ability of adapting using the gains is demonstrated. Our simulation results indicate that the characteristic bandpass and notch filter responses of each structure are the basis of channelizer architectures, and optical gain may be used to adjust filter parameters to obtain a desired frequency magnitude response, especially in the range of 1-5 GHz for the chip with a coupler separation of ∼9 mm. Preliminarily, the measurement of spectral response shows enhancement of quality factor by using higher optical gains. The present compact active filters on an InP-based integrated photonic circuit hold the potential for a variety of channelizer applications. Compared to a pure RF channelizer, photonic channelizers may perform both channelization and down-conversion in an optical domain.

  14. Active Integrated Filters for RF-Photonic Channelizers

    PubMed Central

    Nagdi, Amr El; Liu, Ke; LaFave, Tim P.; Hunt, Louis R.; Ramakrishna, Viswanath; Dabkowski, Mieczyslaw; MacFarlane, Duncan L.; Christensen, Marc P.

    2011-01-01

    A theoretical study of RF-photonic channelizers using four architectures formed by active integrated filters with tunable gains is presented. The integrated filters are enabled by two- and four-port nano-photonic couplers (NPCs). Lossless and three individual manufacturing cases with high transmission, high reflection, and symmetric couplers are assumed in the work. NPCs behavior is dependent upon the phenomenon of frustrated total internal reflection. Experimentally, photonic channelizers are fabricated in one single semiconductor chip on multi-quantum well epitaxial InP wafers using conventional microelectronics processing techniques. A state space modeling approach is used to derive the transfer functions and analyze the stability of these filters. The ability of adapting using the gains is demonstrated. Our simulation results indicate that the characteristic bandpass and notch filter responses of each structure are the basis of channelizer architectures, and optical gain may be used to adjust filter parameters to obtain a desired frequency magnitude response, especially in the range of 1–5 GHz for the chip with a coupler separation of ∼9 mm. Preliminarily, the measurement of spectral response shows enhancement of quality factor by using higher optical gains. The present compact active filters on an InP-based integrated photonic circuit hold the potential for a variety of channelizer applications. Compared to a pure RF channelizer, photonic channelizers may perform both channelization and down-conversion in an optical domain. PMID:22319352

  15. Digital Filter Design with Harmonics Estimation for Power Supplies

    NASA Astrophysics Data System (ADS)

    Shah, P. J.; Saxena, R.; Chawla, M. P. S.

    2012-06-01

    The quality of voltage waveforms is nowadays an issue of the utmost importance for power utilities and electronic equipment. Modern frequency power converters generate a wide spectrum of harmonic components, which deteriorate the quality of the delivered energy, increase the energy losses as well as decrease their liability of a power supplies. In large converters systems not only harmonics, but also considerable interharmonics strongly deteriorate the quality of the power supply voltage. The estimation of the components parameters is very important for control and protection tasks. Digital low pass filter overcome the voltage drift, temperature drift and time drift problems and can be used for harmonic detection for better utilization in real-time. Real-time detection of harmonics can be implemented using MATLAB software and developing simulation circuit set up. With the appropriate cutoff frequency f c and nth order of filter, low pass filter and band-pass filter for real-time harmonic detection can be analyzed. In this paper the aim is to design filters using different methods including Prony analysis. The monitoring of power system harmonics an important issue in the frame of modern power system management and control can be achieved easily using digital filters.

  16. A moving hum filter to suppress rotor noise in high-resolution airborne magnetic data

    USGS Publications Warehouse

    Xia, J.; Doll, W.E.; Miller, R.D.; Gamey, T.J.; Emond, A.M.

    2005-01-01

    A unique filtering approach is developed to eliminate helicopter rotor noise. It is designed to suppress harmonic noise from a rotor that varies slightly in amplitude, phase, and frequency and that contaminates aero-magnetic data. The filter provides a powerful harmonic noise-suppression tool for data acquired with modern large-dynamic-range recording systems. This three-step approach - polynomial fitting, bandpass filtering, and rotor-noise synthesis - significantly reduces rotor noise without altering the spectra of signals of interest. Two steps before hum filtering - polynomial fitting and bandpass filtering - are critical to accurately model the weak rotor noise. During rotor-noise synthesis, amplitude, phase, and frequency are determined. Data are processed segment by segment so that there is no limit on the length of data. The segment length changes dynamically along a line based on modeling results. Modeling the rotor noise is stable and efficient. Real-world data examples demonstrate that this method can suppress rotor noise by more than 95% when implemented in an aeromagnetic data-processing flow. ?? 2005 Society of Exploration Geophysicists. All rights reserved.

  17. Filtered or Unfiltered?

    ERIC Educational Resources Information Center

    Curry, Ann; Haycock, Ken

    2001-01-01

    Discusses results of a survey questionnaire of public and school libraries that investigated the use of Internet filtering software. Considers filter alternatives; reasons for filtering or not filtering; brand names; satisfaction with site blocking; satisfaction with the decision to install filter software; and guidelines for considering filters.…

  18. Multifunction optical filter with a Michelson-Gires-Tournois interferometer for wavelength-division-multiplexed network system applications.

    PubMed

    Dingel, B B; Izutsu, M

    1998-07-15

    We propose using a novel multifunction optical filter with a Michelson-Gires-Tournois interferometer (MGTI) for future smart wavelength-division-multiplexed network system applications. The MGTI filter is a typical Michelson interferometer in which one of its reflecting mirrors is replaced with a Gires-Tournois resonator. One unique feature of this device is that it can function as a channel-passing (CP), a channel-dropping (CD), or a wide-bandpass (BP) filter, depending on the interferometer arm-length difference. Other interesting features are that (1) the linewidths of both the CP and the CD filter are twice as narrow as that of a typical Fabry-Perot filter with similar parameters, (2) theoretical visibility is always unity regardless of the mirror reflectance value, and (3) the BP filter has an excellent boxlike response function. Numerical results showing these characteristics are presented.

  19. Ceramic filters

    SciTech Connect

    Holmes, B.L.; Janney, M.A.

    1995-12-31

    Filters were formed from ceramic fibers, organic fibers, and a ceramic bond phase using a papermaking technique. The distribution of particulate ceramic bond phase was determined using a model silicon carbide system. As the ceramic fiber increased in length and diameter the distance between particles decreased. The calculated number of particles per area showed good agreement with the observed value. After firing, the papers were characterized using a biaxial load test. The strength of papers was proportional to the amount of bond phase included in the paper. All samples exhibited strain-tolerant behavior.

  20. Planar Superconducting Millimeter-Wave/Terahertz Channelizing Filter

    NASA Technical Reports Server (NTRS)

    Ehsan, Negar; U-yen, Kongpop; Brown, Ari; Hsieh, Wen-Ting; Wollack, Edward; Moseley, Samuel

    2013-01-01

    This innovation is a compact, superconducting, channelizing bandpass filter on a single-crystal (0.45 m thick) silicon substrate, which operates from 300 to 600 GHz. This device consists of four channels with center frequencies of 310, 380, 460, and 550 GHz, with approximately 50-GHz bandwidth per channel. The filter concept is inspired by the mammalian cochlea, which is a channelizing filter that covers three decades of bandwidth and 3,000 channels in a very small physical space. By using a simplified physical cochlear model, and its electrical analog of a channelizing filter covering multiple octaves bandwidth, a large number of output channels with high inter-channel isolation and high-order upper stopband response can be designed. A channelizing filter is a critical component used in spectrometer instruments that measure the intensity of light at various frequencies. This embodiment was designed for MicroSpec in order to increase the resolution of the instrument (with four channels, the resolution will be increased by a factor of four). MicroSpec is a revolutionary wafer-scale spectrometer that is intended for the SPICA (Space Infrared Telescope for Cosmology and Astrophysics) Mission. In addition to being a vital component of MicroSpec, the channelizing filter itself is a low-resolution spectrometer when integrated with only an antenna at its input, and a detector at each channel s output. During the design process for this filter, the available characteristic impedances, possible lumped element ranges, and fabrication tolerances were identified for design on a very thin silicon substrate. Iterations between full-wave and lumped-element circuit simulations were performed. Each channel s circuit was designed based on the availability of characteristic impedances and lumped element ranges. This design was based on a tabular type bandpass filter with no spurious harmonic response. Extensive electromagnetic modeling for each channel was performed. Four channels

  1. Spatial filtering and neocortical dynamics: estimates of EEG coherence.

    PubMed

    Srinivasan, R; Nunez, P L; Silberstein, R B

    1998-07-01

    The spatial statistics of scalp electroencephalogram (EEG) are usually presented as coherence in individual frequency bands. These coherences result both from correlations among neocortical sources and volume conduction through the tissues of the head. The scalp EEG is spatially low-pass filtered by the poorly conducting skull, introducing artificial correlation between the electrodes. A four concentric spheres (brain, CSF, skull, and scalp) model of the head and stochastic field theory are used here to derive an analytic estimate of the coherence at scalp electrodes due to volume conduction of uncorrelated source activity, predicting that electrodes within 10-12 cm can appear correlated. The surface Laplacian estimate of cortical surface potentials spatially bandpass filters the scalp potentials reducing this artificial coherence due to volume conduction. Examination of EEG data confirms that the coherence estimates from raw scalp potentials and Laplacians are sensitive to different spatial bandwidths and should be used in parallel in studies of neocortical dynamic function.

  2. Acousto-optic tunable filter multispectral imaging system

    NASA Technical Reports Server (NTRS)

    Cheng, Li-Jen; Chao, Tien-Hsin; Reyes, George

    1992-01-01

    This paper discusses recent activities of Jet Propulsion Laboratory in the development of a new type of remote sensing multispectral imaging instruments using acousto-optic tunable filter (AOTF) as programmable bandpass filter. This remote sensor provides real-time operation; observational flexibility; measurements of spectral, spatial, and polarization information using a single instrument; and compact, solid state structure without moving parts. Two microcomputer-controlled AOTF imaging spectrometer breadboard systems were designed and built. One operates in the wavelength range of 0.48-0.76 micron and the other in the range of 1.2-2.5 micron. Experiments were performed using these two systems to observe geological and botanical objects in laboratory and outdoor environment. Results have demonstrated the feasibility of using the AOTF multispectral imaging system as a real-time versatile remote sensor with operational flexibility for future Army tactical applications.

  3. Acousto-optic tunable filter multispectral imaging system

    NASA Technical Reports Server (NTRS)

    Cheng, Li-Jen; Chao, Tien-Hsin; Reyes, George

    1992-01-01

    This paper discusses recent activities of Jet Propulsion Laboratory in the development of a new type of remote sensing multispectral imaging instruments using acousto-optic tunable filter (AOTF) as programmable bandpass filter. This remote sensor provides real-time operation; observational flexibility; measurements of spectral, spatial, and polarization information using a single instrument; and compact, solid state structure without moving parts. Two microcomputer-controlled AOTF imaging spectrometer breadboard systems were designed and built. One operates in the wavelength range of 0.48-0.76 micron and the other in the range of 1.2-2.5 micron. Experiments were performed using these two systems to observe geological and botanical objects in laboratory and outdoor environment. Results have demonstrated the feasibility of using the AOTF multispectral imaging system as a real-time versatile remote sensor with operational flexibility for future Army tactical applications.

  4. Rocket noise filtering system using digital filters

    NASA Technical Reports Server (NTRS)

    Mauritzen, David

    1990-01-01

    A set of digital filters is designed to filter rocket noise to various bandwidths. The filters are designed to have constant group delay and are implemented in software on a general purpose computer. The Parks-McClellan algorithm is used. Preliminary tests are performed to verify the design and implementation. An analog filter which was previously employed is also simulated.

  5. All-optical NRZ wavelength conversion based on a single hybrid III-V/Si SOA and optical filtering.

    PubMed

    Wu, Yingchen; Huang, Qiangsheng; Keyvaninia, Shahram; Katumba, Andrew; Zhang, Jing; Xie, Weiqiang; Morthier, Geert; He, Jian-Jun; Roelkens, Gunther

    2016-09-05

    We demonstrate all-optical wavelength conversion (AOWC) of non-return-to-zero (NRZ) signal based on cross-gain modulation in a single heterogeneously integrated III-V-on-silicon semiconductor optical amplifier (SOA) with an optical bandpass filter. The SOA is 500 μm long and consumes less than 250 mW electrical power. We experimentally demonstrate 12.5 Gb/s and 40 Gb/s AOWC for both wavelength up and down conversion.

  6. Perception of Filtered Speech by Children with Developmental Dyslexia and Children with Specific Language Impairments

    PubMed Central

    Goswami, Usha; Cumming, Ruth; Chait, Maria; Huss, Martina; Mead, Natasha; Wilson, Angela M.; Barnes, Lisa; Fosker, Tim

    2016-01-01

    Here we use two filtered speech tasks to investigate children’s processing of slow (<4 Hz) versus faster (∼33 Hz) temporal modulations in speech. We compare groups of children with either developmental dyslexia (Experiment 1) or speech and language impairments (SLIs, Experiment 2) to groups of typically-developing (TD) children age-matched to each disorder group. Ten nursery rhymes were filtered so that their modulation frequencies were either low-pass filtered (<4 Hz) or band-pass filtered (22 – 40 Hz). Recognition of the filtered nursery rhymes was tested in a picture recognition multiple choice paradigm. Children with dyslexia aged 10 years showed equivalent recognition overall to TD controls for both the low-pass and band-pass filtered stimuli, but showed significantly impaired acoustic learning during the experiment from low-pass filtered targets. Children with oral SLIs aged 9 years showed significantly poorer recognition of band pass filtered targets compared to their TD controls, and showed comparable acoustic learning effects to TD children during the experiment. The SLI samples were also divided into children with and without phonological difficulties. The children with both SLI and phonological difficulties were impaired in recognizing both kinds of filtered speech. These data are suggestive of impaired temporal sampling of the speech signal at different modulation rates by children with different kinds of developmental language disorder. Both SLI and dyslexic samples showed impaired discrimination of amplitude rise times. Implications of these findings for a temporal sampling framework for understanding developmental language disorders are discussed. PMID:27303348

  7. Metallic nano-structures for polarization-independent multi-spectral filters.

    PubMed

    Tang, Yongan; Vlahovic, Branislav; Brady, David Jones

    2011-05-23

    Cross-shaped-hole arrays (CSHAs) are selected for diminishing the polarization-dependent transmission differences of incident plane waves. We investigate the light transmission spectrum of the CSHAs in a thin gold film over a wide range of features. It is observed that two well-separated and high transmission efficiency peaks could be obtained by designing the parameters in the CSHAs for both p-polarized and s-polarized waves; and a nice transmission band-pass is also observed by specific parameters of a CSHA too. It implicates the possibility to obtain a desired polarization-independent transmission spectrum from the CSHAs by designing their parameters. These findings provide potential applications of the metallic nano-structures in optical filters, optical band-pass, optical imaging, optical sensing, and biosensors.

  8. On the estimation of phase synchronization, spurious synchronization and filtering.

    PubMed

    Rios Herrera, Wady A; Escalona, Joaquín; Rivera López, Daniel; Müller, Markus F

    2016-12-01

    Phase synchronization, viz., the adjustment of instantaneous frequencies of two interacting self-sustained nonlinear oscillators, is frequently used for the detection of a possible interrelationship between empirical data recordings. In this context, the proper estimation of the instantaneous phase from a time series is a crucial aspect. The probability that numerical estimates provide a physically relevant meaning depends sensitively on the shape of its power spectral density. For this purpose, the power spectrum should be narrow banded possessing only one prominent peak [M. Chavez et al., J. Neurosci. Methods 154, 149 (2006)]. If this condition is not fulfilled, band-pass filtering seems to be the adequate technique in order to pre-process data for a posterior synchronization analysis. However, it was reported that band-pass filtering might induce spurious synchronization [L. Xu et al., Phys. Rev. E 73, 065201(R), (2006); J. Sun et al., Phys. Rev. E 77, 046213 (2008); and J. Wang and Z. Liu, EPL 102, 10003 (2013)], a statement that without further specification causes uncertainty over all measures that aim to quantify phase synchronization of broadband field data. We show by using signals derived from different test frameworks that appropriate filtering does not induce spurious synchronization. Instead, filtering in the time domain tends to wash out existent phase interrelations between signals. Furthermore, we show that measures derived for the estimation of phase synchronization like the mean phase coherence are also useful for the detection of interrelations between time series, which are not necessarily derived from coupled self-sustained nonlinear oscillators.

  9. On the estimation of phase synchronization, spurious synchronization and filtering

    NASA Astrophysics Data System (ADS)

    Rios Herrera, Wady A.; Escalona, Joaquín; Rivera López, Daniel; Müller, Markus F.

    2016-12-01

    Phase synchronization, viz., the adjustment of instantaneous frequencies of two interacting self-sustained nonlinear oscillators, is frequently used for the detection of a possible interrelationship between empirical data recordings. In this context, the proper estimation of the instantaneous phase from a time series is a crucial aspect. The probability that numerical estimates provide a physically relevant meaning depends sensitively on the shape of its power spectral density. For this purpose, the power spectrum should be narrow banded possessing only one prominent peak [M. Chavez et al., J. Neurosci. Methods 154, 149 (2006)]. If this condition is not fulfilled, band-pass filtering seems to be the adequate technique in order to pre-process data for a posterior synchronization analysis. However, it was reported that band-pass filtering might induce spurious synchronization [L. Xu et al., Phys. Rev. E 73, 065201(R), (2006); J. Sun et al., Phys. Rev. E 77, 046213 (2008); and J. Wang and Z. Liu, EPL 102, 10003 (2013)], a statement that without further specification causes uncertainty over all measures that aim to quantify phase synchronization of broadband field data. We show by using signals derived from different test frameworks that appropriate filtering does not induce spurious synchronization. Instead, filtering in the time domain tends to wash out existent phase interrelations between signals. Furthermore, we show that measures derived for the estimation of phase synchronization like the mean phase coherence are also useful for the detection of interrelations between time series, which are not necessarily derived from coupled self-sustained nonlinear oscillators.

  10. Tunable birefringent filters

    NASA Technical Reports Server (NTRS)

    Title, A. M.; Rosenberg, W. J.

    1981-01-01

    This article reviews the types and capabilities of birefringent filters. The general operating principles of Lyot (perfect polarizers), partial polarizing, and Solc (no internal polarizers) filters are introduced. Appropriate techniques for tuning each filter type are presented. Field of view of birefringent filters is discussed and is compared to Fabry-Perot and interference filters. The transmission and throughput advantages of birefringent filters are shown. Finally, the current state of the art in practical filters is reviewed.

  11. Dichroic filters to protect milliwatt far-infrared detectors from megawatt ECRH radiation.

    PubMed

    Bertschinger, G; Endres, C P; Lewen, F; Oosterbeek, J W

    2008-10-01

    Dichroic filters have been used to shield effectively the far infrared (FIR) detectors at the interferometer/polarimeter on TEXTOR. The filters consist of metal foils with regular holes, the hole diameter, the mutual spacing and the thickness of the foils are chosen to transmit radiation at the design frequency with transmission >90%. The attenuation at the low frequency end of the bandpass filter is about 30 dB per octave, the high frequency transmission is between 20% and 40%. The filters have been used to block the stray radiation from the megawatt microwave heating beam to the detectors of the FIR interferometer, operating with power on the detector in the milliwatt range. If required, the low frequency attenuation can be still enhanced, without compromising the transmission in the passband. The FIR interferometer used for plasma density and position control is no longer disturbed by electromagnetic waves used for plasma heating.

  12. Sharp tunable optical filters based on the polarization attributes of stimulated Brillouin scattering.

    PubMed

    Wise, Assaf; Tur, Moshe; Zadok, Avi

    2011-10-24

    Sharp and highly-selective tunable optical band-pass filters, based on stimulated Brillouin scattering (SBS) amplification in standard fibers, are described and demonstrated. Polarization pulling of the SBS-amplified signal wave is used to increase the selectivity of the filters to 30 dB. Pump broadening via synthesized direct modulation was used to provide a tunable, sharp and uniform amplification window: Pass-band widths of 700 MHz at half maximum and 1 GHz at the -20 dB points were obtained. The central frequency, bandwidth and shape of the filter can be arbitrarily set. Compared with scalar SBS-based filters, the polarization-enhanced design provides a higher selectivity and an elevated depletion threshold. © 2011 Optical Society of America

  13. Dichroic filters to protect milliwatt far-infrared detectors from megawatt ECRH radiation

    SciTech Connect

    Bertschinger, G.; Oosterbeek, J. W.; Endres, C. P.; Lewen, F.

    2008-10-15

    Dichroic filters have been used to shield effectively the far infrared (FIR) detectors at the interferometer/polarimeter on TEXTOR. The filters consist of metal foils with regular holes, the hole diameter, the mutual spacing and the thickness of the foils are chosen to transmit radiation at the design frequency with transmission >90%. The attenuation at the low frequency end of the bandpass filter is about 30 dB per octave, the high frequency transmission is between 20% and 40%. The filters have been used to block the stray radiation from the megawatt microwave heating beam to the detectors of the FIR interferometer, operating with power on the detector in the milliwatt range. If required, the low frequency attenuation can be still enhanced, without compromising the transmission in the passband. The FIR interferometer used for plasma density and position control is no longer disturbed by electromagnetic waves used for plasma heating.

  14. Multispectral filter-wheel cameras: geometric distortion model and compensation algorithms.

    PubMed

    Brauers, Johannes; Schulte, Nils; Aach, Til

    2008-12-01

    Multispectral image acquisition considerably improves color accuracy in comparison to RGB technology. A common multispectral camera design concept features a filter-wheel consisting of six or more optical bandpass filters. By shifting the filters sequentially into the optical path, the electromagnetic spectrum is acquired through the channels, thus making an approximate reconstruction of the spectrum feasible. However, since the optical filters exhibit different thicknesses, refraction indices and may not be aligned in a perfectly coplanar manner, geometric distortions occur in each spectral channel: The reconstructed RGB images thus show rainbow-like color fringes. To compensate for these, we analyze the optical path and derive a mathematical model of the distortions. Based on this model we present two different algorithms for compensation and show that the color fringes vanish completely after application of our algorithms. We also evaluate our compensation algorithms in terms of accuracy and execution time.

  15. JPL activities on development of acousto-optic tunable filter imaging spectrometer

    NASA Technical Reports Server (NTRS)

    Cheng, Li-Jen; Chao, Tien-Hsin; Reyes, George

    1992-01-01

    Recent activities of JPL in the development of a new type of imaging spectrometers for earth observation and planetary exploration are reported. This instrument uses the acousto-optic tunable filter (AOTF) as high resolution and fast programmable bandpass filter. AOTF operates in the principle of acousto-optic interaction in an anisotropic medium. This filter can be tuned in sequential, random, and multiwavelength access modes, providing observational flexibility. The diffraction process in the filter generates two diffracted monochromatic beams with polarization orthogonal to each other, creating a unique capability to measure both polarimetric and spectral properties of the incoming light simultaneously with a single instrument. The device gives wide wavelength operations with reasonably large throughput. In addition, it is in a compact solid-state structure without moving parts, providing system reliability. These attractive features give promising opportunities to develop a new generation of airborne/spaceborne and ground, real-time, imaging spectrometer systems for remote sensing applications.

  16. Structured filtering

    NASA Astrophysics Data System (ADS)

    Granade, Christopher; Wiebe, Nathan

    2017-08-01

    A major challenge facing existing sequential Monte Carlo methods for parameter estimation in physics stems from the inability of existing approaches to robustly deal with experiments that have different mechanisms that yield the results with equivalent probability. We address this problem here by proposing a form of particle filtering that clusters the particles that comprise the sequential Monte Carlo approximation to the posterior before applying a resampler. Through a new graphical approach to thinking about such models, we are able to devise an artificial-intelligence based strategy that automatically learns the shape and number of the clusters in the support of the posterior. We demonstrate the power of our approach by applying it to randomized gap estimation and a form of low circuit-depth phase estimation where existing methods from the physics literature either exhibit much worse performance or even fail completely.

  17. Applications of Multidimensional Wavelet Filtering in Geosciences

    NASA Astrophysics Data System (ADS)

    Yuen, D. A.; Vincent, A. P.; Kido, M.

    2001-12-01

    Today we are facing a severe crisis of being flooded with huge amounts of data being generated by higher-resolution numerical simulations , laboratory instrumentions and satellite observations. Since there is no way one can visualize the full data set, we must extract essential features from the data-set. One way of addressing this problem is to use mathematical filters , such as multidimensional wavelets. We present imaging results in the geosciences based on using multidimensional Gaussian wavelets as a filter. This approach has been applied to a wide-range of problems, which span from the nanoscale in mineral surfaces imaged by atomic force microscopy to hundreds of kilometers in geoidal undulations determined from satellite orbits or small-scale plumes in high Rayleigh number convection. Besides decomposing the field under consideration into various scales , called a scalogram, we have also constructed two-dimensional maps, delineating the spatial distributions of the maximum of the wavelet transformed quantity E-max and the associated local wave-number. We have generalized the application of multidimensional wavelets to quantify in terms of a two-dimensional map the correlation C for two multidimensional fields A and B. We will show a simple 2D isotropic wavelet-like transform for a spherical surface. We have analyzed the transformed geoid data with a band-pass filter in the spherical harmonic domain and have shown the equivalency of the two representations. This spherical wavelet-like filter can be applied also to problems in planetary science, such as the surface topography and geoid of other planetary bodies, like Mars.

  18. Effects of Filtering on Experimental Blast Overpressure Measurements.

    PubMed

    Alphonse, Vanessa D; Kemper, Andrew R; Duma, Stefan M

    2015-01-01

    When access to live-fire test facilities is limited, experimental studies of blast-related injuries necessitate the use of a shock tube or Advanced Blast Simulator (ABS) to mimic free-field blast overpressure. However, modeling blast overpressure in a laboratory setting potentially introduces experimental artifacts in measured responses. Due to the high sampling rates required to capture a blast overpressure event, proximity to alternating current (AC-powered electronics) and poorly strain-relieved or unshielded wires can result in artifacts in the recorded overpressure trace. Data in this study were collected for tests conducted on an empty ABS (“Empty Tube”) using high frequency pressure sensors specifically designed for blast loading rates (n=5). Additionally, intraocular overpressure data (“IOP”) were collected for porcine eyes potted inside synthetic orbits located inside the ABS using an unshielded miniature pressure sensor (n=3). All tests were conducted at a 30 psi static overpressure level. A 4th order phaseless low pass Butterworth software filter was applied to the data. Various cutoff frequencies were examined to determine if the raw shock wave parameters values could be preserved while eliminating noise and artifacts. A Fast Fourier Transform (FFT) was applied to each test to examine the frequency spectra of the raw and filtered signals. Shock wave parameters (time of arrival, peak overpressure, positive duration, and positive impulse) were quantified using a custom MATLAB® script. Lower cutoff frequencies attenuated the raw signal, effectively decreasing the peak overpressure and increasing the positive duration. Rise time was not preserved the filtered data. A CFC 6000 filter preserved the remaining shock wave parameters within ±2.5% of the average raw values for the Empty Tube test data. A CFC 7000 filter removed experimental high-frequency artifacts and preserved the remaining shock wave parameters within ±2.5% of the average raw values for

  19. A new design of a miniature filter on microstrip resonators with an interdigital structure of conductors

    NASA Astrophysics Data System (ADS)

    Belyaev, B. A.; Serzhantov, A. M.; Bal'va, Ya. F.; Leksikov, An. A.; Galeev, R. G.

    2015-05-01

    A microstrip bandpass filter of new design based on original resonators with an interdigital structure of conductors has been studied. The proposed filters of third to sixth order are distinguished for their high frequency-selective properties and much smaller size than analogs. It is established that a broad stop band, extending up to a sixfold central bandpass frequency, is determined by low unloaded Q of higher resonance mode and weak coupling of resonators in the pass band. It is shown for the first time that, as the spacing of interdigital stripe conductors decreases, the Q of higher resonance mode monotonically drops, while the Q value for the first operating mode remains high. A prototype fourth-order filter with a central frequency of 0.9 GHz manufactured on a ceramic substrate with dielectric permittivity ɛ = 80 has microstrip topology dimensions of 9.5 × 4.6 × 1 mm3. The electrodynamic 3D model simulations of the filter characteristics agree well with the results of measurements.

  20. Optoelectronic approach to adaptive radio-frequency transversal filter implementation with negative coefficients by using optical spectrum shaping.

    PubMed

    Arain, Muzammil A; Riza, Nabeel A

    2006-04-10

    A multitap negative and positive coefficient radio-frequency transversal filter is implemented by using a digital-micromirror-device spatial light modulator for weighting-factor control and a chirped fiber Bragg grating for time-delay control. The demonstrated architecture is reconfigurable, has high speed and low loss, and is robust through digital programmability for a wide variety of filtering algorithms. A design using an interleaver for differential detection realizes an ultrahigh bandwidth with a maximum processable frequency of 33.7 GHz. A multitap low-pass filter, a negative tap notch filter with 40 dB attenuation, and a multitap negative coefficient bandpass filter are experimentally demonstrated. The results are in agreement with theory.

  1. The use of linear programming techniques to design optimal digital filters for pulse shaping and channel equalization

    NASA Technical Reports Server (NTRS)

    Houts, R. C.; Burlage, D. W.

    1972-01-01

    A time domain technique is developed to design finite-duration impulse response digital filters using linear programming. Two related applications of this technique in data transmission systems are considered. The first is the design of pulse shaping digital filters to generate or detect signaling waveforms transmitted over bandlimited channels that are assumed to have ideal low pass or bandpass characteristics. The second is the design of digital filters to be used as preset equalizers in cascade with channels that have known impulse response characteristics. Example designs are presented which illustrate that excellent waveforms can be generated with frequency-sampling filters and the ease with which digital transversal filters can be designed for preset equalization.

  2. Filter quality of pleated filter cartridges.

    PubMed

    Chen, Chun-Wan; Huang, Sheng-Hsiu; Chiang, Che-Ming; Hsiao, Ta-Chih; Chen, Chih-Chieh

    2008-04-01

    The performance of dust cartridge filters commonly used in dust masks and in room ventilation depends both on the collection efficiency of the filter material and the pressure drop across the filter. Currently, the optimization of filter design is based only on minimizing the pressure drop at a set velocity chosen by the manufacturer. The collection efficiency, an equally important factor, is rarely considered in the optimization process. In this work, a filter quality factor, which combines the collection efficiency and the pressure drop, is used as the optimization criterion for filter evaluation. Most respirator manufacturers pleat the filter to various extents to increase the filtration area in the limit space within the dust cartridge. Six sizes of filter holders were fabricated to hold just one pleat of filter, simulating six different pleat counts, ranging from 0.5 to 3.33 pleats cm(-1). The possible electrostatic charges on the filter were removed by dipping in isopropyl alcohol, and the air velocity is fixed at 100 cm s(-1). Liquid dicotylphthalate particles generated by a constant output atomizer were used as challenge aerosols to minimize particle loading effects. A scanning mobility particle sizer was used to measure the challenge aerosol number concentrations and size distributions upstream and downstream of the pleated filter. The pressure drop across the filter was monitored by using a calibrated pressure transducer. The results showed that the performance of pleated filters depend not only on the size of the particle but also on the pleat count of the pleated filter. Based on filter quality factor, the optimal pleat count (OPC) is always higher than that based on pressure drop by about 0.3-0.5 pleats cm(-1). For example, the OPC is 2.15 pleats cm(-1) from the standpoint of pressure drop, but for the highest filter quality factor, the pleated filter needed to have a pleat count of 2.65 pleats cm(-1) at particle diameter of 122 nm. From the aspect of

  3. Exclusive examples of high-performance thin-film optical filters for fluorescence spectroscopy made by plasma-assisted reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Lappschies, M.; Schallenberg, U.; Jakobs, S.

    2011-09-01

    For more than four decades band-pass filters are important components of microscopes used for the fluorescence spectroscopy. During all the time this special field of application has been one of the main drivers for research and development in thin-film optics, particularly for the thin-film design software and the coating technology. With a shortwave pass filter, a multi-notch filter, and a classical band-pass filter as examples of such filters provided for the latest generation of fluorescence microscopes we present the state-of-the-art in coating design and technology. Manufacturing these filters is a great challenge because the required spectral characteristics need necessarily multilayers with up to 300 layers and overall thicknesses up to 30 μm. In addition, the designs require also 3 to 5 nm as thinnest layers and all the layers are completely of non-quarterwave type. The filters were manufactured in a rapid-prototyping regime by a Leybold Helios plant using plasma-assisted reactive magnetron sputtering of thin films of different metal oxides. Designed and real spectra are compared and differences are discussed. Measurement results of other optical and non-optical characteristics as film stress, total integrated scattering, and micro roughness are presented.

  4. High Q printed helical resonators for oscillators and filters.

    PubMed

    Everard, Jeremy K A; Broomfield, Carl D

    2007-09-01

    High Q compact printed helical resonators which operate from around 1.8 to 2 GHz are described. These consist of a multilayer printed circuit board (PCB) incorporating a printed helical transmission line. Loss in the via hole is reduced by ensuring that the standing wave current at this point is near zero. This ensures a significant increase in Q. Further increased energy storage per unit volume is achieved due to the 3-D helical nature of the resonator. Unloaded Qs of 235 and 195 have been obtained on low loss PCBs with dielectric constants of 2.2 and 10.5, respectively. Two applications for these resonators are described in this paper. The first is the design of a compact low noise oscillator where the ratio of QL/Q0, and hence insertion loss, is adjusted for low noise. The 2-GHz oscillator demonstrates a phase noise of -120 dBc/Hz at 10 kHz which is predicted exactly by the theory. The second is a three-section filter designed to offer the response required by the front end filter of a modern GSM mobile telephone. In the filter design three helical resonators are coupled together to produce a completely printed triplate bandpass filter.

  5. In situ calibration of tunable filters: Lyot and Michelson.

    PubMed

    Mudge, Jason; Tarbell, Theodore

    2014-08-01

    Solar imaging optical filter technology has progressed significantly over the past 75 years, and the ability to tune narrowband filters is particularly valuable for solar atmosphere sensing. For example, imaging while tuning over a narrow solar spectral line (emission or absorption) provides two-dimensional measurements of Doppler shifts and magnetic fields. While tuning ability has improved significantly, tuning accuracy can be a challenge over time given system actuator drifts. For many cases, the ability to calibrate these actuators in situ is convenient and cost effective (e.g., ground-based observatories), and for other cases it is required (e.g., in a spacecraft). It is ideal to calibrate in situ without the need for additional hardware such as a spectrometer, and if that cannot be achieved, the next best thing is to do so with minimum additional hardware. Two examples of solar filters that need to be calibrated periodically are: (1) a liquid crystal variable retarder Lyot filter and (2) a tunable Michelson interferometer. For the first, the filter can have a number of stages back-to-back to achieve the desired finesse. Within each stage there is a liquid crystal variable retarder that adds some amount of retardance to the stage's fixed birefringent crystal; this provides wavelength bandpass tuning. For the second, there can be several Michelson interferometers in series each with an actuator to adjust the optical path length in one of its optical paths for tuning. The stacking of these filters implies there is a need to calibrate more than one actuator. An algorithm has been developed to calibrate these types of stacked and nonstacked filters in situ with minimal, if any, hardware additions.

  6. HEPA filter dissolution process

    DOEpatents

    Brewer, K.N.; Murphy, J.A.

    1994-02-22

    A process is described for dissolution of spent high efficiency particulate air (HEPA) filters and then combining the complexed filter solution with other radioactive wastes prior to calcining the mixed and blended waste feed. The process is an alternate to a prior method of acid leaching the spent filters which is an inefficient method of treating spent HEPA filters for disposal. 4 figures.

  7. Hepa filter dissolution process

    DOEpatents

    Brewer, Ken N.; Murphy, James A.

    1994-01-01

    A process for dissolution of spent high efficiency particulate air (HEPA) filters and then combining the complexed filter solution with other radioactive wastes prior to calcining the mixed and blended waste feed. The process is an alternate to a prior method of acid leaching the spent filters which is an inefficient method of treating spent HEPA filters for disposal.

  8. Recirculating electric air filter

    DOEpatents

    Bergman, W.

    1985-01-09

    An electric air filter cartridge has a cylindrical inner high voltage electrode, a layer of filter material, and an outer ground electrode formed of a plurality of segments moveably connected together. The outer electrode can be easily opened to remove or insert filter material. Air flows through the two electrodes and the filter material and is exhausted from the center of the inner electrode.

  9. Recirculating electric air filter

    DOEpatents

    Bergman, Werner

    1986-01-01

    An electric air filter cartridge has a cylindrical inner high voltage eleode, a layer of filter material, and an outer ground electrode formed of a plurality of segments moveably connected together. The outer electrode can be easily opened to remove or insert filter material. Air flows through the two electrodes and the filter material and is exhausted from the center of the inner electrode.

  10. Secondary air filter assembly

    SciTech Connect

    Ortonville, A.J.

    1991-02-26

    This patent describes a filter cartridge assembly used for filtering air of a crankcase ventilating system of an internal combustion engine. It comprises: first (108) and second (110) air permeable filter platforms; vertical support columns; leg members; and a filter retainer.

  11. HEPA filter dissolution process

    SciTech Connect

    Brewer, K.N.; Murphy, J.A.

    1992-12-31

    This invention is comprised of a process for dissolution of spent high efficiency particulate air (HEPA) filters and then combining the complexed filter solution with other radioactive wastes prior to calcining the mixed and blended waste feed. The process is an alternate to a prior method of acid leaching the spent filters which is an inefficient method of treating spent HEPA filters for disposal.

  12. Separation of plutonium from uranium using reactive chemistry in a bandpass reaction cell of an inductively coupled plasma mass spectrometer.

    PubMed

    Vais, Vladimir; Li, Chunsheng; Cornett, Jack

    2004-09-01

    Oxygen and ammonia were evaluated as reaction gases for the chemical separation between uranium and plutonium in the bandpass reaction cell or dynamic reaction cell (DRC) of the ELAN DRC II mass spectrometer. Both uranium and plutonium demonstrated similar reactivity with oxygen giving rise to corresponding oxides. At the same time, remarkable selectivity in the reaction with ammonia was observed. While uranium was rapidly converted into UNH 2+ and UN2H 4+, plutonium remained unreactive in the DRC pressurized with ammonia. This difference in the reactivity allowed the determination of plutonium isotopes in urine and water samples containing excess uranium without preceding separation procedure. Detection limits of 0.245, 0.092, 0.270 and 0.237 ng L(-1) were obtained for 238Pu, 239Pu, 240Pu and 242Pu, respectively, in urine spiked with 10 microg L(-1) of U.

  13. Interaction between Liénard and Ikeda dynamics in a nonlinear electro-optical oscillator with delayed bandpass feedback

    NASA Astrophysics Data System (ADS)

    Marquez, Bicky A.; Larger, Laurent; Brunner, Daniel; Chembo, Yanne K.; Jacquot, Maxime

    2016-12-01

    We report on experimental and theoretical analysis of the complex dynamics generated by a nonlinear time-delayed electro-optic bandpass oscillator. We investigate the interaction between the slow- and fast-scale dynamics of autonomous oscillations in the breather regime. We analyze in detail the coupling between the fast-scale behavior associated to a characteristic low-pass Ikeda behavior and the slow-scale dynamics associated to a Liénard limit-cycle. Finally, we show that when projected onto a two-dimensional phase space, the attractors corresponding to periodic and chaotic breathers display a spiral-like pattern, which strongly depends on the shape of the nonlinear function.

  14. Interaction between Liénard and Ikeda dynamics in a nonlinear electro-optical oscillator with delayed bandpass feedback.

    PubMed

    Marquez, Bicky A; Larger, Laurent; Brunner, Daniel; Chembo, Yanne K; Jacquot, Maxime

    2016-12-01

    We report on experimental and theoretical analysis of the complex dynamics generated by a nonlinear time-delayed electro-optic bandpass oscillator. We investigate the interaction between the slow- and fast-scale dynamics of autonomous oscillations in the breather regime. We analyze in detail the coupling between the fast-scale behavior associated to a characteristic low-pass Ikeda behavior and the slow-scale dynamics associated to a Liénard limit-cycle. Finally, we show that when projected onto a two-dimensional phase space, the attractors corresponding to periodic and chaotic breathers display a spiral-like pattern, which strongly depends on the shape of the nonlinear function.

  15. Auditory cortical tuning to band-pass noise in primate A1 and CM: a comparison to pure tones

    PubMed Central

    Kajikawa, Yoshinao; Camalier, Corrie R.; de la Mothe, Lisa A.; D’Angelo, William R.; Sterbing-D’Angelo, Susanne J.; Hackett, Troy A.

    2011-01-01

    We examined multiunit responses to tones and to 1/3 and 2/3 octave band-pass noise (BPN) in the marmoset primary auditory cortex (A1) and the caudomedial belt (CM). In both areas, BPN was more effective than tones, evoking multiunit responses at lower intensity and across a wider frequency range. Typically, the best responses to BPN remained at the characteristic frequency. Additionally, in both areas responses to BPN tended to be of greater magnitude and shorter latency than responses to tones. These effects are consistent with the integration of more excitatory inputs driven by BPN than by tones. While it is generally thought that single units in A1 prefer narrow band sounds such as tones, we found that best responses for multi units in both A1 and CM were obtained with noises of narrow spectral bandwidths. PMID:21540062

  16. Anti-aliasing filters for deriving high-accuracy DEMs from TLS data: A case study from Freeport, Texas

    NASA Astrophysics Data System (ADS)

    Xiong, Lin.; Wang, Guoquan; Wessel, Paul

    2017-03-01

    Terrestrial laser scanning (TLS), also known as ground-based Light Detection and Ranging (LiDAR), has been frequently applied to build bare-earth digital elevation models (DEMs) for high-accuracy geomorphology studies. The point clouds acquired from TLS often achieve a spatial resolution at fingerprint (e.g., 3 cm×3 cm) to handprint (e.g., 10 cm×10 cm) level. A downsampling process has to be applied to decimate the massive point clouds and obtain manageable DEMs. It is well known that downsampling can result in aliasing that causes different signal components to become indistinguishable when the signal is reconstructed from the datasets with a lower sampling rate. Conventional DEMs are mainly the results of upsampling of sparse elevation measurements from land surveying, satellite remote sensing, and aerial photography. As a consequence, the effects of aliasing caused by downsampling have not been fully investigated in the open literature of DEMs. This study aims to investigate the spatial aliasing problem of regridding dense TLS data. The TLS data collected from the beach and dune area near Freeport, Texas in the summer of 2015 are used for this study. The core idea of the anti-aliasing procedure is to apply a low-pass spatial filter prior to conducting downsampling. This article describes the successful use of a fourth-order Butterworth low-pass spatial filter employed in the Generic Mapping Tools (GMT) software package as an anti-aliasing filter. The filter can be applied as an isotropic filter with a single cutoff wavelength or as an anisotropic filter with two different cutoff wavelengths in the X and Y directions. The cutoff wavelength for the isotropic filter is recommended to be three times the grid size of the target DEM.

  17. An optical fiber MEMS pressure sensor using microwave photonics filtering technique

    NASA Astrophysics Data System (ADS)

    Wang, Yiping; Wang, Ming; Ni, Xiaoqi; Xia, Wei; Guo, Dongmei; Hao, Hui; Ma, Qingyu; Zhuang, Wei

    2017-04-01

    A fiber-optic micro-electromechanical systems (MEMS) extrinsic Fabry-Perot interferometer (EFPI) pressure sensor exploiting microwave photonics filtering technique is firstly proposed and experimentally demonstrated. A single-bandpass microwave photonic filter (MPF) which mainly consists of a spectrum-sliced light source, a pressurized EFPI, a phase modulator (PM) and a length of dispersion compensating fiber (DCF) is demonstrated. The frequency response of the filter with respect to the pressure is studied. By detecting the resonance frequency shifts of the MPF, the pressure can be determined. The theoretical and experimental results show that the proposed EFPI pressure sensor has a higher resolution and higher speed than traditional methods based on optical spectrum analysis. The sensitivity of the sensor is measured to be as high as 86 MHz/MPa in the range of 0-4MPa.

  18. Fault diagnosis for wind turbine planetary ring gear via a meshing resonance based filtering algorithm.

    PubMed

    Wang, Tianyang; Chu, Fulei; Han, Qinkai

    2017-03-01

    Identifying the differences between the spectra or envelope spectra of a faulty signal and a healthy baseline signal is an efficient planetary gearbox local fault detection strategy. However, causes other than local faults can also generate the characteristic frequency of a ring gear fault; this may further affect the detection of a local fault. To address this issue, a new filtering algorithm based on the meshing resonance phenomenon is proposed. In detail, the raw signal is first decomposed into different frequency bands and levels. Then, a new meshing index and an MRgram are constructed to determine which bands belong to the meshing resonance frequency band. Furthermore, an optimal filter band is selected from this MRgram. Finally, the ring gear fault can be detected according to the envelope spectrum of the band-pass filtering result. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

  19. Cooled optical filters for Q-band infrared astronomy (15-40 μm)

    NASA Astrophysics Data System (ADS)

    Hawkins, Gary J.; Sherwood, Richard E.; Djotni, Karim; Threadgold, Timothy M.

    2016-07-01

    With a growing interest in mid- and far-infrared astronomy using cooled imaging and spectrometer instruments in highaltitude observatories and spaceflight telescopes, it is becoming increasingly important to characterise and assess the spectral performance of cooled multilayer filters across the Q-band atmospheric window. This region contains spectral features emitted by many astrophysical phenomena and objects fundamental to circumstellar and planetary formation theories. However extending interference filtering to isolate radiation at progressively longer wavelengths and improve photometric accuracy is an area of ongoing and challenging thin-film research. We have successfully fabricated cooled bandpass and edge filters with high durability for operation across the 15-30 μm Q-band region. In this paper we describe the rationale for selection of optical materials and properties of fabricated thin-film coatings for this region, together with FTIR spectral measurements and assessment of environmental durability.

  20. State-selective detection of velocity-filtered ND{sub 3} molecules

    SciTech Connect

    Bertsche, Benjamin; Osterwalder, Andreas

    2010-09-15

    Translationally cold and slow ND{sub 3} is prepared by filtering the slow molecules from a thermal gas-phase sample using a curved electrostatic hexapole guide. This filter, like the curved quadrupole guide introduced by Rangwala et al. [Phys. Rev. A 67, 043406 (2003)] selects molecules by their forward velocity and effective electric dipole moment. Here we describe two main modifications with respect to previous work: (1) A segmented hexapole guide is used that produces a harmonic potential for the linearly Stark-shifted levels of ND{sub 3}. A curved guide is combined with a straight hexapole guide, and independent high-voltage supplies are employed to allow for bandpass velocity filtering. (2) State-selective laser ionization is used to obtain time- and state-selective detection of the guided molecules. This enables the experimental determination of the rotational state population of the guided molecules.

  1. Guided-mode resonant filters and reflectors: Principles, design, and fabrication

    NASA Astrophysics Data System (ADS)

    Niraula, Manoj

    In this dissertation, we overview the operational principles of these resonant periodic structures, discuss the methods of their design and fabrication, and propose and demonstrate novel functionalities for spatial and spectral filtering, and unpolarized wideband reflection. Fashioned with materially sparse gratings, these optical devices are easy to fabricate and integration friendly compared to their traditional multi-layer counterparts making their research and development critical for practical applications. We study, theoretically, modal properties and parametric dependence of resonant periodic bandpass filters operating in the mid- and near-infrared spectral domains. We investigate three different device architectures consisting of single, double, and triple layers based on all-transparent dielectric and semiconductor thin films. We present three modal coupling configurations forming complex mixtures of two or three distinct leaky modes coupling at different evanescent diffraction orders. Our modal analysis demonstrates key attributes of subwavelength periodic thin-film structures in multiple-modal blending to achieve desired transmission spectra. We provide the first experimental demonstration of high-efficiency and narrow-linewidth resonant bandpass filter applying a single patterned silicon layer on a quartz substrate. Its performance corresponds to bandpass filters requiring 15 traditional Si/SiO2 thin-film layers. The feasibility of sparse narrowband, high-efficiency bandpass filters with extremely wide, flat, and low sidebands is thereby demonstrated. The proposed technology is integration-friendly and opens doors for further development in various disciplines and spectral regions where thin-film solutions are traditionally applied. We demonstrate concurrent spatial and spectral filtering as a new outstanding attribute of resonant periodic devices. This functionality is enabled by a unique, near-complete, reflection state that is discrete in both

  2. Multichroic bandpass seashell antenna with cold-electron bolometers for CMB measurements

    NASA Astrophysics Data System (ADS)

    Kuzmin, Leonid S.; Chiginev, Alexander V.

    2016-07-01

    novel type of the multichroic "seashell" resonant antenna is developed for CMB measurements. The polarized slot antennas are arranged in the compact form of a seashell with individual slots for each frequency and each polarization. Such an arrangement gives unique opportunity for independent adjusting individual parameters of slots with microstrip lines (MSL) and bolometers. For each frequency band the seashell antenna contains two pairs of orthogonal slots for each polarization connected by microstrip lines (MSL) with a bolometer in the middle for in-phase operation. To fit slots in λ/2 area for the best beam shape, lumped capacitances in the form of H-slot were introduced. Ellipticity of a beam was improved to the level of better than 1%. The seashell antenna gives a unique opportunity to select needed bandwidth by resonant properties of slots themselves. Slots are phased by MSLs connecting two opposite slots with a resistive Cold-Electron Bolometer (CEB) placed just in middle of two MSLs. MSLs and CEBs are placed just in the area of the seashell antenna. The resonant seashell antenna with CEBs avoids long MSLs bringing signal outside the antenna to large external filters as in the case of sinuous antenna. This innovation avoids losses in long MSLs and increases frequency range.

  3. Fabrication of multispectral imaging technology driven MEMS-based micro-arrayed multichannel optical filter mosaic

    NASA Astrophysics Data System (ADS)

    Yi, Dingrong; Kong, Linghua; Wang, Jiwu; Zhao, Futing

    2011-02-01

    Multispectral imaging is becoming a new powerful tool in a wide range of biological studies by adding spectral, spatial and temporal dimensions to tissue abnormity and the underlying biological processes. A standard spectral imaging setup includes two major components, a band pass selection device (such as liquid crystal tunable filter and diffraction grating) and a scientific-grade monochrome camera. Contemporary multispectral imaging technologies typically use traditional optical filters e.g., filter wheels, a generalized Lyot filter, an electrically tunable filter, multiple-band pass filters or the methods of dispersing light, e.g., optic-acoustic crystals. The instrumented systems are bulky, expensive, require multiple exposures or extensive post-processing to align up multiple images of pure spectral components. Recently a break-through technology has emerged to instrument multispectral imaging technology into handheld real-time devices using miniaturized filter mosaic containing micro-arrayed multiple channel band-pass optical filters. The filter mosaic can be directly placed near the focal plane immediately in front of the imaging sensor of an off-shelf CCD/CMOS camera, with potentially one such micro-filter covers one pixel of the imaging sensor. This paper reveals the technical details of how such a micro-arrayed multi channel optical filter is fabricated using traditional multi-film vacuum deposition and the modern micro-lithography technologies. The selection of different coating materials, their structures and effects to the adhesive forces between film and substrate, the spatial resolution, width of passing band, and the transmittance of the resulting miniaturized optical filter is discussed.

  4. On-chip copper-dielectric interference filters for manufacturing of ambient light and proximity CMOS sensors.

    PubMed

    Frey, Laurent; Masarotto, Lilian; D'Aillon, Patrick Gros; Pellé, Catherine; Armand, Marilyn; Marty, Michel; Jamin-Mornet, Clémence; Lhostis, Sandrine; Le Briz, Olivier

    2014-07-10

    Filter technologies implemented on CMOS image sensors for spectrally selective applications often use a combination of on-chip organic resists and an external substrate with multilayer dielectric coatings. The photopic-like and near-infrared bandpass filtering functions respectively required by ambient light sensing and user proximity detection through time-of-flight can be fully integrated on chip with multilayer metal-dielectric filters. Copper, silicon nitride, and silicon oxide are the materials selected for a technological proof-of-concept on functional wafers, due to their immediate availability in front-end semiconductor fabs. Filter optical designs are optimized with respect to specific performance criteria, and the robustness of the designs regarding process errors are evaluated for industrialization purposes.

  5. ARRANGEMENT FOR REPLACING FILTERS

    DOEpatents

    Blomgren, R.A.; Bohlin, N.J.C.

    1957-08-27

    An improved filtered air exhaust system which may be continually operated during the replacement of the filters without the escape of unfiltered air is described. This is accomplished by hermetically sealing the box like filter containers in a rectangular tunnel with neoprene covered sponge rubber sealing rings coated with a silicone impregnated pneumatic grease. The tunnel through which the filters are pushed is normal to the exhaust air duct. A number of unused filters are in line behind the filters in use, and are moved by a hydraulic ram so that a fresh filter is positioned in the air duct. The used filter is pushed into a waiting receptacle and is suitably disposed. This device permits a rapid and safe replacement of a radiation contaminated filter without interruption to the normal flow of exhaust air.

  6. Method of securing filter elements

    SciTech Connect

    Brown, Erik P.; Haslam, Jeffery L.; Mitchell, Mark A.

    2016-10-04

    A filter securing system including a filter unit body housing; at least one tubular filter element positioned in the filter unit body housing, the tubular filter element having a closed top and an open bottom; a dimple in either the filter unit body housing or the top of the tubular filter element; and a socket in either the filter unit body housing or the top of the tubular filter element that receives the dimple in either the filter unit body housing or the top of the tubular filter element to secure the tubular filter element to the filter unit body housing.

  7. Rigid porous filter

    DOEpatents

    Chiang, Ta-Kuan; Straub, Douglas L.; Dennis, Richard A.

    2000-01-01

    The present invention involves a porous rigid filter including a plurality of concentric filtration elements having internal flow passages and forming external flow passages there between. The present invention also involves a pressure vessel containing the filter for the removal of particulates from high pressure particulate containing gases, and further involves a method for using the filter to remove such particulates. The present filter has the advantage of requiring fewer filter elements due to the high surface area-to-volume ratio provided by the filter, requires a reduced pressure vessel size, and exhibits enhanced mechanical design properties, improved cleaning properties, configuration options, modularity and ease of fabrication.

  8. Filter type gas sampler with filter consolidation

    DOEpatents

    Miley, H.S.; Thompson, R.C.; Hubbard, C.W.; Perkins, R.W.

    1997-03-25

    Disclosed is an apparatus for automatically consolidating a filter or, more specifically, an apparatus for drawing a volume of gas through a plurality of sections of a filter, where after the sections are subsequently combined for the purpose of simultaneously interrogating the sections to detect the presence of a contaminant. 5 figs.

  9. Filter type gas sampler with filter consolidation

    DOEpatents

    Miley, Harry S.; Thompson, Robert C.; Hubbard, Charles W.; Perkins, Richard W.

    1997-01-01

    Disclosed is an apparatus for automatically consolidating a filter or, more specifically, an apparatus for drawing a volume of gas through a plurality of sections of a filter, whereafter the sections are subsequently combined for the purpose of simultaneously interrogating the sections to detect the presence of a contaminant.

  10. Design and Experimental Investigation of a Compact Circularly Polarized Integrated Filtering Antenna for Wearable Biotelemetric Devices.

    PubMed

    Jiang, Zhi Hao; Gregory, Micah D; Werner, Douglas H

    2016-04-01

    A compact circularly polarized (CP) integrated filtering antenna is reported for wearable biotelemetric devices in the 2.4 GHz ISM band. The design is based on a mutual synthesis of a CP patch antenna connected to a bandpass filter composed of coupled stripline open-loop resonators, which provides an integrated low-profile radiating and filtering module with a compact form factor of 0.44λ(0)×0.44λ(0)×0.04λ(0). The optimized filtering antenna is fabricated and measured, achieving an S11 < -14 dB, an axial ratio of less than 3 dB and gain higher than 3.5 dBi in the targeted ISM band. With the integrated filtering functionality, the antenna exhibits good out-of-band rejection over an ultra-wide frequency range of 1-6 GHz. Further full-wave simulations and experiments were carried out, verifying that the proposed filtering antenna maintains these desirable properties even when mounted in close proximity to the human body at different positions. The stable impedance performance and the simultaneous wide axial ratio and radiated power beam widths make it an ideal candidate as a wearable antenna for off-body communications. The additional integrated filtering functionality further improves utility by greatly reducing interference and crosstalk with other existing wireless systems.

  11. An efficient tuning method for narrowband superconducting filters with interdigital capacitor resonators in the time domain

    NASA Astrophysics Data System (ADS)

    Song, X. K.; Zhang, X. P.; Cao, B. S.; Wei, B.; Gong, L. M.; Chen, Y. D.; Zheng, T. N.; Guo, X. B.; Zhang, G. Y.; Zhan, X.

    2014-04-01

    This article proposes an effective tuning method based on the time domain for improving the performance of high-temperature superconducting (HTS) bandpass filters with interdigital capacitor resonators (ICRs). Analysis of the causes of HTS filter performance deterioration reveal that such deterioration is primarily caused by the resonant frequency deviation of the resonator of the HTS filter; this deviation results from fabrication errors and from the non-uniformity of the thickness and dielectric constant of the substrate. The sensitivity of the filter, which arises from the non-uniformity of the substrate thickness and dielectric constant, is related to the type of the resonator and the group delay characteristic of the filter. A 0.4% fractional bandwidth HTS filter with ICRs at the UHF band is fabricated and tuned using mechanical rods in the time domain. By applying this method, the resonant frequency deviation of each resonator and the coupling coefficient between resonators can be measured and tuned individually. The insertion loss of the HTS filter is improved from 1.06 dB to 0.43 dB, whereas the return loss is improved from 9.57 dB to 15.1 dB.

  12. Study of quadrature FIR filters for extraction of low-frequency instantaneous information in biophysical signals

    NASA Astrophysics Data System (ADS)

    Arce-Guevara, Valdemar E.; Alba-Cadena, Alfonso; Mendez, Martín O.

    Quadrature bandpass filters take a real-valued signal and output an analytic signal from which the instantaneous amplitude and phase can be computed. For this reason, they represent a useful tool to extract time-varying, narrow-band information from electrophysiological signals such as electroencephalogram (EEG) or electrocardiogram. One of the defining characteristics of quadrature filters is its null response to negative frequencies. However, when the frequency band of interest is close to 0 Hz, a careless filter design could let through negative frequencies, producing distortions in the amplitude and phase of the output. In this work, three types of quadrature filters (Ideal, Gabor and Sinusoidal) have been evaluated using both artificial and real EEG signals. For the artificial signals, the performance of each filter was measured in terms of the distortion in amplitude and phase, and sensitivity to noise and bandwidth selection. For the real EEG signals, a qualitative evaluation of the dynamics of the synchronization between two EEG channels was performed. The results suggest that, while all filters under study behave similarly under noise, they differ in terms of their sensitivity to bandwidth choice. In this study, the Sinusoidal filter showed clear advantages for the estimation of low-frequency EEG synchronization.

  13. Generalized Hampel Filters

    NASA Astrophysics Data System (ADS)

    Pearson, Ronald K.; Neuvo, Yrjö; Astola, Jaakko; Gabbouj, Moncef

    2016-12-01

    The standard median filter based on a symmetric moving window has only one tuning parameter: the window width. Despite this limitation, this filter has proven extremely useful and has motivated a number of extensions: weighted median filters, recursive median filters, and various cascade structures. The Hampel filter is a member of the class of decsion filters that replaces the central value in the data window with the median if it lies far enough from the median to be deemed an outlier. This filter depends on both the window width and an additional tuning parameter t, reducing to the median filter when t=0, so it may be regarded as another median filter extension. This paper adopts this view, defining and exploring the class of generalized Hampel filters obtained by applying the median filter extensions listed above: weighted Hampel filters, recursive Hampel filters, and their cascades. An important concept introduced here is that of an implosion sequence, a signal for which generalized Hampel filter performance is independent of the threshold parameter t. These sequences are important because the added flexibility of the generalized Hampel filters offers no practical advantage for implosion sequences. Partial characterization results are presented for these sequences, as are useful relationships between root sequences for generalized Hampel filters and their median-based counterparts. To illustrate the performance of this filter class, two examples are considered: one is simulation-based, providing a basis for quantitative evaluation of signal recovery performance as a function of t, while the other is a sequence of monthly Italian industrial production index values that exhibits glaring outliers.

  14. Counting digital filter

    NASA Technical Reports Server (NTRS)

    Zohar, S.

    1977-01-01

    Overall design of filter combines radix converter with ADC in single functional unit that directly converts analog input to its negative binary representation. Four basic elements of filter are fixed register, shift register, counter, and accumulator.

  15. Bag filters for TPP

    SciTech Connect

    L.V. Chekalov; Yu.I. Gromov; V.V. Chekalov

    2007-05-15

    Cleaning of TPP flue gases with bag filters capable of pulsed regeneration is examined. A new filtering element with a three-dimensional filtering material formed from a needle-broached cloth in which the filtration area, as compared with a conventional smooth bag, is increased by more than two times, is proposed. The design of a new FRMI type of modular filter is also proposed. A standard series of FRMI filters with a filtration area ranging from 800 to 16,000 m{sup 2} is designed for an output more than 1 million m{sub 3}/h of with respect to cleaned gas. The new bag filter permits dry collection of sulfur oxides from waste gases at TPP operating on high-sulfur coals. The design of the filter makes it possible to replace filter elements without taking the entire unit out of service.

  16. Novel Backup Filter Device for Candle Filters

    SciTech Connect

    Bishop, B.; Goldsmith, R.; Dunham, G.; Henderson, A.

    2002-09-18

    The currently preferred means of particulate removal from process or combustion gas generated by advanced coal-based power production processes is filtration with candle filters. However, candle filters have not shown the requisite reliability to be commercially viable for hot gas clean up for either integrated gasifier combined cycle (IGCC) or pressurized fluid bed combustion (PFBC) processes. Even a single candle failure can lead to unacceptable ash breakthrough, which can result in (a) damage to highly sensitive and expensive downstream equipment, (b) unacceptably low system on-stream factor, and (c) unplanned outages. The U.S. Department of Energy (DOE) has recognized the need to have fail-safe devices installed within or downstream from candle filters. In addition to CeraMem, DOE has contracted with Siemens-Westinghouse, the Energy & Environmental Research Center (EERC) at the University of North Dakota, and the Southern Research Institute (SRI) to develop novel fail-safe devices. Siemens-Westinghouse is evaluating honeycomb-based filter devices on the clean-side of the candle filter that can operate up to 870 C. The EERC is developing a highly porous ceramic disk with a sticky yet temperature-stable coating that will trap dust in the event of filter failure. SRI is developing the Full-Flow Mechanical Safeguard Device that provides a positive seal for the candle filter. Operation of the SRI device is triggered by the higher-than-normal gas flow from a broken candle. The CeraMem approach is similar to that of Siemens-Westinghouse and involves the development of honeycomb-based filters that operate on the clean-side of a candle filter. The overall objective of this project is to fabricate and test silicon carbide-based honeycomb failsafe filters for protection of downstream equipment in advanced coal conversion processes. The fail-safe filter, installed directly downstream of a candle filter, should have the capability for stopping essentially all particulate

  17. MST Filterability Tests

    SciTech Connect

    Poirier, M. R.; Burket, P. R.; Duignan, M. R.

    2015-03-12

    The Savannah River Site (SRS) is currently treating radioactive liquid waste with the Actinide Removal Process (ARP) and the Modular Caustic Side Solvent Extraction Unit (MCU). The low filter flux through the ARP has limited the rate at which radioactive liquid waste can be treated. Recent filter flux has averaged approximately 5 gallons per minute (gpm). Salt Batch 6 has had a lower processing rate and required frequent filter cleaning. Savannah River Remediation (SRR) has a desire to understand the causes of the low filter flux and to increase ARP/MCU throughput. In addition, at the time the testing started, SRR was assessing the impact of replacing the 0.1 micron filter with a 0.5 micron filter. This report describes testing of MST filterability to investigate the impact of filter pore size and MST particle size on filter flux and testing of filter enhancers to attempt to increase filter flux. The authors constructed a laboratory-scale crossflow filter apparatus with two crossflow filters operating in parallel. One filter was a 0.1 micron Mott sintered SS filter and the other was a 0.5 micron Mott sintered SS filter. The authors also constructed a dead-end filtration apparatus to conduct screening tests with potential filter aids and body feeds, referred to as filter enhancers. The original baseline for ARP was 5.6 M sodium salt solution with a free hydroxide concentration of approximately 1.7 M.3 ARP has been operating with a sodium concentration of approximately 6.4 M and a free hydroxide concentration of approximately 2.5 M. SRNL conducted tests varying the concentration of sodium and free hydroxide to determine whether those changes had a significant effect on filter flux. The feed slurries for the MST filterability tests were composed of simple salts (NaOH, NaNO2, and NaNO3) and MST (0.2 – 4.8 g/L). The feed slurry for the filter enhancer tests contained simulated salt batch 6 supernate, MST, and filter enhancers.

  18. Combined tunable filters based swept laser source for optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Chen, Minghui; Ding, Zhihua; Wang, Cheng; Huang, Yimei; Chen, Rong; Song, Chengli

    2013-03-01

    We demonstrate a novel ultra-broad tunable bandwidth and narrow instantaneous line-width swept laser source using combined tunable filters working at 1290 nm center wavelength for application in optical coherence tomography. The combined filters consist of a fiber Fabry-Perot tunable filter (FFP-TF) and a polygon mirror with scanning grating based filter. The FFP-TF has the narrow free spectral range (FSR) but ultra-high spectral resolution (narrow instantaneous bandwidth) driven at high frequency far from resonant frequency. The polygon filter in the Littrow configuration is composed of fiber collimator, polygon mirror driven by function generator, and diffractive grating with low groove. Polygon filter coarsely tunes with wide turning range and then FFP-TF finely tunes with narrow band-pass filtering. In contrast to traditional method using single tunable filter, the trade-off between bandwidth and instantaneous line-width is alleviated. The combined filters can realize ultra wide scan range and fairly narrow instantaneous bandwidth simultaneously. Two semiconductor optical amplifiers (SOA) in the parallel manner are used as the gain medium. The wide bandwidth could be obtained by these parallel SOAs to be suitable for sufficient wide range of the polygon filter's FSR because each SOA generates its own spectrum independently. The proposed swept laser source provides an edge-to-edge scanning range of 180 nm covering 1220 to 1400 nm with instantaneous line-width of about 0.03 nm at sweeping rate of 23.3 kHz. The swept laser source with combined filters offers broadband tunable range with narrow instantaneous line-width, which especially benefits for high resolution and deep imaging depth optical frequency domain imaging.

  19. Survey of digital filtering

    NASA Technical Reports Server (NTRS)

    Nagle, H. T., Jr.

    1972-01-01

    A three part survey is made of the state-of-the-art in digital filtering. Part one presents background material including sampled data transformations and the discrete Fourier transform. Part two, digital filter theory, gives an in-depth coverage of filter categories, transfer function synthesis, quantization and other nonlinear errors, filter structures and computer aided design. Part three presents hardware mechanization techniques. Implementations by general purpose, mini-, and special-purpose computers are presented.

  20. Flight Performance of UV Filters on the ALEXIS Satellite

    SciTech Connect

    Bloch, J.J.; Roussel-Dupre, D.; Starin, S.

    1999-07-08

    The ALEXIS (Array of Low-Energy X-ray Imaging Sensors) mission, serving as the first dedicated all-sky monitor in the extreme UV, has been collecting data since its launch in 1993. ALEXIS operates in a 70{degree} inclination orbit at an altitude of 800 km. The ALEXIS science mission is to observe the cosmic UV background and to study variability of EUV sources. The ALEXIS experiment is composed of six telescopes. Although the telescopes were only designed for a one-year technology verification mission, they are still functioning with much the same effectiveness as at the beginning of the mission. The telescopes comprise: (1) layered synthetic microstructure (LSM) spherical mirrors, (2) thin foil filters, and (3) microchannel plate (MCP) detectors, all enshrouded within the telescope body. The LSM mirrors select the bandpass for each telescope, while rejecting some of the HeII 304{angstrom} geocoronal radiation. The filters, constructed either from aluminum/carbon or Lexan/titanium/boron, serve to strongly reject the geocoronal radiation, as well as longer wavelength emission from bright OB stars. Each telescope detector consists of two plates, the outermost of which is curved to accurately match the spherical focal surface of the mirror. By reviewing the ground and flight histories, this paper analyzes the flight performance of the filters, including the effects of long term exposure and the formation of pinholes.

  1. From filters to features: location, orientation, contrast and blur.

    PubMed

    Georgeson, M A

    1994-01-01

    Consider three main ideas about spatial filtering and feature coding in human spatial vision. (1) Computational theory: the representation of local luminance features--bars and edges--is a crucial step in human vision, forming the basis for many decisions in pattern discrimination. (2) Algorithm: features may be located and characterized in terms of polarity, blur and contrast by comparison of 1st, 2nd and 3rd spatial derivatives taken at a common point. Edges in compound (f + 3f) gratings are seen at or close to peaks of gradient magnitude. More tentatively, bars may be located at peaks of the 2nd derivative or at peaks in the Hilbert transform of the 1st derivative. Peaks of contrast energy do not predict all the features seen. An algorithm for recovering the blur of edges is derived as the square-root of the ratio of 1st to 3rd derivatives at the edge location. This successfully predicts blur matching between Gaussian edges and a variety of other test waveforms, including sine waves. Blur matching is (nearly) contrast invariant, as predicted by this ratio rule. (3) IMPLEMENTATION: experiments on the perception and discrimination of plaids imply that the outputs of tuned filters are combined before feature coding. The adaptive, weighted summation of bandpass filters may serve to synthesize the derivative operators while facilitating the segmentation of overlapping features and preventing the representation from being swamped by noise.

  2. The influence of digital filter type, amplitude normalisation method, and co-contraction algorithm on clinically relevant surface electromyography data during clinical movement assessments.

    PubMed

    Devaprakash, Daniel; Weir, Gillian J; Dunne, James J; Alderson, Jacqueline A; Donnelly, Cyril J

    2016-12-01

    There is a large and growing body of surface electromyography (sEMG) research using laboratory-specific signal processing procedures (i.e., digital filter type and amplitude normalisation protocols) and data analyses methods (i.e., co-contraction algorithms) to acquire practically meaningful information from these data. As a result, the ability to compare sEMG results between studies is, and continues to be challenging. The aim of this study was to determine if digital filter type, amplitude normalisation method, and co-contraction algorithm could influence the practical or clinical interpretation of processed sEMG data. Sixteen elite female athletes were recruited. During data collection, sEMG data was recorded from nine lower limb muscles while completing a series of calibration and clinical movement assessment trials (running and sidestepping). Three analyses were conducted: (1) signal processing with two different digital filter types (Butterworth or critically damped), (2) three amplitude normalisation methods, and (3) three co-contraction ratio algorithms. Results showed the choice of digital filter did not influence the clinical interpretation of sEMG; however, choice of amplitude normalisation method and co-contraction algorithm did influence the clinical interpretation of the running and sidestepping task. Care is recommended when choosing amplitude normalisation method and co-contraction algorithms if researchers/clinicians are interested in comparing sEMG data between studies.

  3. Filtering by nonlinear systems.

    PubMed

    Campos Cantón, E; González Salas, J S; Urías, J

    2008-12-01

    Synchronization of nonlinear systems forced by external signals is formalized as the response of a nonlinear filter. Sufficient conditions for a nonlinear system to behave as a filter are given. Some examples of generalized chaos synchronization are shown to actually be special cases of nonlinear filtering.

  4. Practical Active Capacitor Filter

    NASA Technical Reports Server (NTRS)

    Shuler, Robert L., Jr. (Inventor)

    2005-01-01

    A method and apparatus is described that filters an electrical signal. The filtering uses a capacitor multiplier circuit where the capacitor multiplier circuit uses at least one amplifier circuit and at least one capacitor. A filtered electrical signal results from a direct connection from an output of the at least one amplifier circuit.

  5. Nonlinear Attitude Filtering Methods

    NASA Technical Reports Server (NTRS)

    Markley, F. Landis; Crassidis, John L.; Cheng, Yang

    2005-01-01

    This paper provides a survey of modern nonlinear filtering methods for attitude estimation. Early applications relied mostly on the extended Kalman filter for attitude estimation. Since these applications, several new approaches have been developed that have proven to be superior to the extended Kalman filter. Several of these approaches maintain the basic structure of the extended Kalman filter, but employ various modifications in order to provide better convergence or improve other performance characteristics. Examples of such approaches include: filter QUEST, extended QUEST, the super-iterated extended Kalman filter, the interlaced extended Kalman filter, and the second-order Kalman filter. Filters that propagate and update a discrete set of sigma points rather than using linearized equations for the mean and covariance are also reviewed. A two-step approach is discussed with a first-step state that linearizes the measurement model and an iterative second step to recover the desired attitude states. These approaches are all based on the Gaussian assumption that the probability density function is adequately specified by its mean and covariance. Other approaches that do not require this assumption are reviewed, including particle filters and a Bayesian filter based on a non-Gaussian, finite-parameter probability density function on SO(3). Finally, the predictive filter, nonlinear observers and adaptive approaches are shown. The strengths and weaknesses of the various approaches are discussed.

  6. Filter service system

    DOEpatents

    Sellers, Cheryl L.; Nordyke, Daniel S.; Crandell, Richard A.; Tomlins, Gregory; Fei, Dong; Panov, Alexander; Lane, William H.; Habeger, Craig F.

    2008-12-09

    According to an exemplary embodiment of the present disclosure, a system for removing matter from a filtering device includes a gas pressurization assembly. An element of the assembly is removably attachable to a first orifice of the filtering device. The system also includes a vacuum source fluidly connected to a second orifice of the filtering device.

  7. The Ribosome Filter Redux

    PubMed Central

    Mauro, Vincent P.; Edelman, Gerald M.

    2010-01-01

    The ribosome filter hypothesis postulates that ribosomes are not simply translation machines but also function as regulatory elements that differentially affect or filter the translation of particular mRNAs. On the basis of new information, we take the opportunity here to review the ribosome filter hypothesis, suggest specific mechanisms of action, and discuss recent examples from the literature that support it. PMID:17890902

  8. HEPA filter encapsulation

    DOEpatents

    Gates-Anderson, Dianne D.; Kidd, Scott D.; Bowers, John S.; Attebery, Ronald W.

    2003-01-01

    A low viscosity resin is delivered into a spent HEPA filter or other waste. The resin is introduced into the filter or other waste using a vacuum to assist in the mass transfer of the resin through the filter media or other waste.

  9. Hybrid recursive active filters for duplexing in RF transmitter front-ends

    NASA Astrophysics Data System (ADS)

    Gottardo, Giuseppe; Donati, Giovanni; Musolff, Christian; Fischer, Georg; Felgentreff, Tilman

    2016-08-01

    Duplex filters in modern base transceiver stations shape the channel in order to perform common frequency division duplex operations. Usually, they are designed as cavity filters, which are expensive and have large dimensions. Thanks to the emerging digital technology and fast digital converters, it is possible to transfer the efforts of designing analog duplex filters into digital numeric algorithms applied to feedback structures, operating on power. This solution provides the shaping of the signal spectrum directly at the output of the radio frequency (RF) power amplifiers (PAs) relaxing the transmitter design especially in the duplexer and in the antenna sections. The design of a digital baseband feedback applied to the analog power RF amplifiers (hybrid filter) is presented and verified by measurements. A model to describe the hybrid system is investigated, and the relation between phase and resonance peaks of the resulting periodic band-pass transfer function is described. The stability condition of the system is analyzed using Nyquist criterion. A solution involving a number of digital feedback and forward branches is investigated defining the parameters of the recursive structure. This solution allows the closed loop system to show a periodic band pass with up to 500 kHz bandwidth at the output of the RF amplifier. The band-pass magnitude reaches up to 17 dB selectivity. The rejection of the PA noise in the out-of-band frequencies is verified by measurements. The filter is tested with a modulated LTE (Long Term Evolution) signal showing an ACPR (Adjacent Channel Power Ratio) enhancement of 10 dB of the transmitted signal.

  10. Regenerative particulate filter development

    NASA Technical Reports Server (NTRS)

    Descamp, V. A.; Boex, M. W.; Hussey, M. W.; Larson, T. P.

    1972-01-01

    Development, design, and fabrication of a prototype filter regeneration unit for regenerating clean fluid particle filter elements by using a backflush/jet impingement technique are reported. Development tests were also conducted on a vortex particle separator designed for use in zero gravity environment. A maintainable filter was designed, fabricated and tested that allows filter element replacement without any leakage or spillage of system fluid. Also described are spacecraft fluid system design and filter maintenance techniques with respect to inflight maintenance for the space shuttle and space station.

  11. A unified Kalman filter

    NASA Astrophysics Data System (ADS)

    Stubberud, Allen R.

    2017-01-01

    When considering problems of linear sequential estimation, two versions of the Kalman filter, the continuous-time version and the discrete-time version, are often used. (A hybrid filter also exists.) In many applications in which the Kalman filter is used, the system to which the filter is applied is a linear continuous-time system, but the Kalman filter is implemented on a digital computer, a discrete-time device. The two general approaches for developing a discrete-time filter for implementation on a digital computer are: (1) approximate the continuous-time system by a discrete-time system (called discretization of the continuous-time system) and develop a filter for the discrete-time approximation; and (2) develop a continuous-time filter for the system and then discretize the continuous-time filter. Generally, the two discrete-time filters will be different, that is, it can be said that discretization and filter generation are not, in general, commutative operations. As a result, any relationship between the discrete-time and continuous-time versions of the filter for the same continuous-time system is often obfuscated. This is particularly true when an attempt is made to generate the continuous-time version of the Kalman filter through a simple limiting process (the sample period going to zero) applied to the discrete-time version. The correct result is, generally, not obtained. In a 1961 research report, Kalman showed that the continuous-time Kalman filter can be obtained from the discrete-time Kalman filter by taking limits as the sample period goes to zero if the white noise process for the continuous-time version is appropriately defined. Using this basic concept, a discrete-time Kalman filter can be developed for a continuous-time system as follows: (1) discretize the continuous-time system using Kalman's technique; and (2) develop a discrete-time Kalman filter for that discrete-time system. Kalman's results show that the discrete-time filter generated in

  12. Determination of 90Sr in contaminated environmental samples by tuneable bandpass dynamic reaction cell ICP-MS.

    PubMed

    Taylor, V F; Evans, R D; Cornett, R J

    2007-01-01

    A rapid method for the extraction and determination of 90Sr in natural water, plant and sediment samples was developed using extraction chromatography and dynamic reaction cell ICP-MS, with O2 as a reaction gas. While isobaric interference from the stable isotope 90Zr was efficiently removed by this method, interferences produced from in-cell reactions with Fe+ and Ni+ required suppression by tuneable bandpass, and in sediments, additional chromatographic separation. Method detection limits were 0.1 pg g-1 (0.5 Bq g-1), 0.04 pg g-1(0.2 Bq g-1), and 3 pg L-1 (5 Bq L-1) for sediments, plant and water samples, respectively, and 90Sr concentrations determined by ICP-MS were in good agreement with activities determined by Cerenkov counting and with certified reference values. While mass spectrometric determination does not rival detection limits achievable by radiometric counting, radiometric determination of 90Sr, a pure beta-emitter, is hindered by long analysis times (several weeks); the comparatively fast analysis achieved via ICP-MS enables same-day preparation and analysis of samples, making this an important technique for the environmental monitoring of areas contaminated by radioactivity.

  13. Ceramic fiber filter technology

    SciTech Connect

    Holmes, B.L.; Janney, M.A.

    1996-06-01

    Fibrous filters have been used for centuries to protect individuals from dust, disease, smoke, and other gases or particulates. In the 1970s and 1980s ceramic filters were developed for filtration of hot exhaust gases from diesel engines. Tubular, or candle, filters have been made to remove particles from gases in pressurized fluidized-bed combustion and gasification-combined-cycle power plants. Very efficient filtration is necessary in power plants to protect the turbine blades. The limited lifespan of ceramic candle filters has been a major obstacle in their development. The present work is focused on forming fibrous ceramic filters using a papermaking technique. These filters are highly porous and therefore very lightweight. The papermaking process consists of filtering a slurry of ceramic fibers through a steel screen to form paper. Papermaking and the selection of materials will be discussed, as well as preliminary results describing the geometry of papers and relative strengths.

  14. Plasma Treatment to Remove Carbon from Indium UV Filters

    NASA Technical Reports Server (NTRS)

    Greer, Harold F.; Nikzad, Shouleh; Beasley, Matthew; Gantner, Brennan

    2012-01-01

    The sounding rocket experiment FIRE (Far-ultraviolet Imaging Rocket Experiment) will improve the science community fs ability to image a spectral region hitherto unexplored astronomically. The imaging band of FIRE (.900 to 1,100 Angstroms) will help fill the current wavelength imaging observation hole existing from approximately equal to 620 Angstroms to the GALEX band near 1,350 Angstroms. FIRE is a single-optic prime focus telescope with a 1.75-m focal length. The bandpass of 900 to 1100 Angstroms is set by a combination of the mirror coating, the indium filter in front of the detector, and the salt coating on the front of the detector fs microchannel plates. Critical to this is the indium filter that must reduce the flux from Lymanalpha at 1,216 Angstroms by a minimum factor of 10(exp -4). The cost of this Lyman-alpha removal is that the filter is not fully transparent at the desired wavelengths of 900 to 1,100 Angstroms. Recently, in a project to improve the performance of optical and solar blind detectors, JPL developed a plasma process capable of removing carbon contamination from indium metal. In this work, a low-power, low-temperature hydrogen plasma reacts with the carbon contaminants in the indium to form methane, but leaves the indium metal surface undisturbed. This process was recently tested in a proof-of-concept experiment with a filter provided by the University of Colorado. This initial test on a test filter showed improvement in transmission from 7 to 9 percent near 900 with no process optimization applied. Further improvements in this performance were readily achieved to bring the total transmission to 12% with optimization to JPL's existing process.

  15. Optical filtering properties of subwavelength Tai-chi-shaped metal hole arrays

    NASA Astrophysics Data System (ADS)

    Wang, Xinlin; Liu, Hui; Luo, Hu; Zhu, Weihua; Chen, Zhiyong; Liu, Jun; Guo, Wei

    2015-04-01

    Finite-difference time-domain (FDTD) method is employed to study the optical properties of a novel kind of periodic subwavelength hole arrays composed of Tai-chi-shaped holes in silver film, and the optical transmission properties of femtosecond optical pulse excitation is numerically calculated. We find that this Tai-chi-shaped device has better optical band-pass filtering properties, such as narrower pass band and higher transmissivity in visible wavelengths range, than other devices under consideration. Based on the generation of surface plasmons resonance mode in the dielectric-metal interface, the center wavelength of transmission can be tuned by changing the array periodicities. We observe that the tune ability mainly depends on the space period along the direction parallel to that of the incident pulse polarization. It is also found that both the strength and the wavelength of the transmission peaks of rectangularly distributed metal hole arrays are determined by the polarization of incident light. Additionally, we demonstrate the typical band-pass filtering properties of this Tai-Chi-shaped holes structure. The full-width at half-maximum (FWHM) of the narrow pass band is about 20 nm in visible wavelengths range.

  16. Compact planar microwave blocking filters

    NASA Technical Reports Server (NTRS)

    U-Yen, Kongpop (Inventor); Wollack, Edward J. (Inventor)

    2012-01-01

    A compact planar microwave blocking filter includes a dielectric substrate and a plurality of filter unit elements disposed on the substrate. The filter unit elements are interconnected in a symmetrical series cascade with filter unit elements being organized in the series based on physical size. In the filter, a first filter unit element of the plurality of filter unit elements includes a low impedance open-ended line configured to reduce the shunt capacitance of the filter.

  17. A New Ground Motion Intensity Measure, Peak Filtered Acceleration (PFA), to Estimate Collapse Vulnerability of Buildings in Earthquakes

    NASA Astrophysics Data System (ADS)

    Song, Shiyan

    In this thesis, we develop an efficient collapse prediction model, the PFA (Peak Filtered Acceleration) model, for buildings subjected to different types of ground motions. For the structural system, the PFA model covers modern steel and reinforced concrete moment-resisting frame buildings (potentially reinforced concrete shear wall buildings). For ground motions, the PFA model covers ramp-pulse-like ground motions, long-period ground motions, and short-period ground motions. To predict whether a building will collapse in response to a given ground motion, we first extract long-period components from the ground motion using a Butterworth low-pass filter with suggested order and cutoff frequency. The order depends on the type of ground motion, and the cutoff frequency depends on the building's natural frequency and ductility. We then compare the filtered acceleration time history with the capacity of the building. The capacity of the building is a constant for 2-dimentional buildings and a limit domain for 3-dimentional buildings. If the filtered acceleration exceeds the building's capacity, the building is predicted to collapse. Otherwise, it is expected to survive the ground motion. The parameters used in PFA model, which include fundamental period, global ductility and lateral capacity, can be obtained either from numerical analysis or interpolation based on the reference building system proposed in this thesis. The PFA collapse prediction model greatly reduces computational complexity while archiving good accuracy. It is verified by FEM simulations of 13 frame building models and 150 ground motion records. Based on the developed collapse prediction model, we propose to use PFA (Peak Filtered Acceleration) as a new ground motion intensity measure for collapse prediction. We compare PFA with traditional intensity measures PGA, PGV, PGD, and Sa in collapse prediction and find that PFA has the best performance among all the intensity measures. We also provide a

  18. Demonstration of a fast-reconfigurable silicon CMOS optical lattice filter.

    PubMed

    Ibrahim, Salah; Fontaine, Nicolas K; Djordjevic, Stevan S; Guan, Binbin; Su, Tiehui; Cheung, Stanley; Scott, Ryan P; Pomerene, Andrew T; Seaford, Liberty L; Hill, Craig M; Danziger, Steve; Ding, Zhi; Okamoto, K; Yoo, S J B

    2011-07-04

    We demonstrate a fully-reconfigurable fourth-order optical lattice filter built by cascading identical unit cells consisting of a Mach-Zehnder interferometer (MZI) and a ring resonator. The filter is fabricated using a commercial silicon complementary metal oxide semiconductor (CMOS) process and reconfigured by current injection into p-i-n diodes with a reconfiguration time of less than 10 ns. The experimental results show full control over the single unit cell pole and zero, switching the unit cell transfer function between a notch filter and a bandpass filter, narrowing the notch width down to 400 MHz, and tuning the center wavelength over the full free spectral range (FSR) of 10 GHz. Theoretical and experimental results show tuning dynamics and associated optical losses in the reconfigurable filters. The full-control of each of the four cascaded single unit cells resulted in demonstrations of a number of fourth-order transfer functions. The multimedia experimental data show live tuning and reconfiguration of optical lattice filters.

  19. Accounting for filter bandwidth improves the quantitative accuracy of bioluminescence tomography

    NASA Astrophysics Data System (ADS)

    Taylor, Shelley L.; Mason, Suzannah K. G.; Glinton, Sophie L.; Cobbold, Mark; Dehghani, Hamid

    2015-09-01

    Bioluminescence imaging is a noninvasive technique whereby surface weighted images of luminescent probes within animals are used to characterize cell count and function. Traditionally, data are collected over the entire emission spectrum of the source using no filters and are used to evaluate cell count/function over the entire spectrum. Alternatively, multispectral data over several wavelengths can be incorporated to perform tomographic reconstruction of source location and intensity. However, bandpass filters used for multispectral data acquisition have a specific bandwidth, which is ignored in the reconstruction. In this work, ignoring the bandwidth is shown to introduce a dependence of the recovered source intensity on the bandwidth of the filters. A method of accounting for the bandwidth of filters used during multispectral data acquisition is presented and its efficacy in increasing the quantitative accuracy of bioluminescence tomography is demonstrated through simulation and experiment. It is demonstrated that while using filters with a large bandwidth can dramatically decrease the data acquisition time, if not accounted for, errors of up to 200% in quantitative accuracy are introduced in two-dimensional planar imaging, even after normalization. For tomographic imaging, the use of this method to account for filter bandwidth dramatically improves the quantitative accuracy.

  20. Vibration control of a flexible beam driven by a ball-screw stage with adaptive notch filters and a line enhancer

    NASA Astrophysics Data System (ADS)

    Wu, Shang-Teh; Lian, Sing-Han; Chen, Sheng-Han

    2015-07-01

    For a low-stiffness beam driven by a ball-screw stage, the lateral vibrations cannot be adequately controlled by a collocated compensator based on rotary-encoder feedback alone. Acceleration signals at the tip of the flexible beam are measured for active vibration control in addition to the collocated compensator. A second-order bandpass filter (a line enhancer) and two notch filters are included in the acceleration-feedback loop to raise modal dampings for the first and the second flexible modes without exciting higher-frequency resonances. A novel adaptation algorithm is devised to tune the center frequencies of the notch filters in real time. It consists of a second-order low-pass filter, a second-order bandpass filter and a phase detector. Improvement of the control system is elaborated progressively with the root-locus and bode-plot analyses, along with a physical interpretation. Extensive testings are conducted on an experimental device to verify the effectiveness of the control method.