Application of multirate digital filter banks to wideband all-digital phase-locked loops design

NASA Astrophysics Data System (ADS)

Sadr, Ramin; Shah, Biren; Hinedi, Sami

1993-06-01

A new class of architecture for all-digital phase-locked loops (DPLL's) is presented in this article. These architectures, referred to as parallel DPLL (PDPLL), employ multirate digital filter banks (DFB's) to track signals with a lower processing rate than the Nyquist rate, without reducing the input (Nyquist) bandwidth. The PDPLL basically trades complexity for hardware-processing speed by introducing parallel processing in the receiver. It is demonstrated here that the DPLL performance is identical to that of a PDPLL for both steady-state and transient behavior. A test signal with a time-varying Doppler characteristic is used to compare the performance of both the DPLL and the PDPLL.

Application of multirate digital filter banks to wideband all-digital phase-locked loops design

NASA Astrophysics Data System (ADS)

Sadr, R.; Shah, B.; Hinedi, S.

1992-11-01

A new class of architecture for all-digital phase-locked loops (DPLL's) is presented in this article. These architectures, referred to as parallel DPLL (PDPLL), employ multirate digital filter banks (DFB's) to track signals with a lower processing rate than the Nyquist rate, without reducing the input (Nyquist) bandwidth. The PDPLL basically trades complexity for hardware-processing speed by introducing parallel processing in the receiver. It is demonstrated here that the DPLL performance is identical to that of a PDPLL for both steady-state and transient behavior. A test signal with a time-varying Doppler characteristic is used to compare the performance of both the DPLL and the PDPLL.

Application of multirate digital filter banks to wideband all-digital phase-locked loops design

NASA Technical Reports Server (NTRS)

Sadr, R.; Shah, B.; Hinedi, S.

1992-01-01

A new class of architecture for all-digital phase-locked loops (DPLL's) is presented in this article. These architectures, referred to as parallel DPLL (PDPLL), employ multirate digital filter banks (DFB's) to track signals with a lower processing rate than the Nyquist rate, without reducing the input (Nyquist) bandwidth. The PDPLL basically trades complexity for hardware-processing speed by introducing parallel processing in the receiver. It is demonstrated here that the DPLL performance is identical to that of a PDPLL for both steady-state and transient behavior. A test signal with a time-varying Doppler characteristic is used to compare the performance of both the DPLL and the PDPLL.

A method for reducing sampling jitter in digital control systems

NASA Technical Reports Server (NTRS)

Anderson, T. O.; HURBD W. J.; Hurd, W. J.

1969-01-01

Digital phase lock loop system is designed by smoothing the proportional control with a low pass filter. This method does not significantly affect the loop dynamics when the smoothing filter bandwidth is wide compared to loop bandwidth.

Digital off-axis holographic interferometry with simulated wavefront.

PubMed

Belashov, A V; Petrov, N V; Semenova, I V

2014-11-17

The paper presents a novel algorithm based on digital holographic interferometry and being promising for evaluation of phase variations from highly noisy or modulated by speckle-structures digital holograms. The suggested algorithm simulates an interferogram in finite width fringes, by analogy with classical double exposure holographic interferometry. Thus obtained interferogram is then processed as a digital hologram. The advantages of the suggested approach are demonstrated in numerical experiments on calculations of differences in phase distributions of wave fronts modulated by speckle structure, as well as in a physical experiment on the analysis of laser-induced heating dynamics of an aqueous solution of a photosensitizer. It is shown that owing to the inherent capability of the approach to perform adjustable smoothing of compared wave fronts, the resulting difference undergoes noise filtering. This capability of adjustable smoothing may be used to minimize losses in spatial resolution. Since the method allows to vary an observation angle of compared wave fields, an opportunity to compensate misalignment of optical axes of these wave fronts arises. This feature can be required, for example, when using two different setups in comparative digital holography or for compensation of recording system displacements during a set of exposures in studies of dynamic processes.

On the performance of digital phase locked loops in the threshold region

NASA Technical Reports Server (NTRS)

Hurst, G. T.; Gupta, S. C.

1974-01-01

Extended Kalman filter algorithms are used to obtain a digital phase lock loop structure for demodulation of angle modulated signals. It is shown that the error variance equations obtained directly from this structure enable one to predict threshold if one retains higher frequency terms. This is in sharp contrast to the similar analysis of the analog phase lock loop, where the higher frequency terms are filtered out because of the low pass filter in the loop. Results are compared to actual simulation results and threshold region results obtained previously.

3D mapping of breast surface using digital fringe projection

NASA Astrophysics Data System (ADS)

Vairavan, Rajendaran; Retnasamy, Vithyacharan; Mohamad Shahimin, Mukhzeer; Sauli, Zaliman; Leng, Lai Siang; Wan Norhaimi, Wan Mokhzani; Marimuthu, Rajeswaran; Abdullah, Othman; Kirtsaeng, Supap

2017-02-01

Optical sensing technique has inherited non-contact nature for generating 3D surface mapping where its application ranges from MEMS component characterization, corrosion analysis, and vibration analysis. In particular, the digital fringe projection is utilized for 3D mapping of objects through the illumination of structured light for medical application extending from oral dental measurements, lower back deformation analysis, monitoring of scoliosis and 3D face reconstruction for biometric identification. However, the usage of digital fringe projection for 3D mapping of human breast is very minimal. Thus, this paper addresses the application of digital fringe projection for 3D mapping of breast surface based on total non-contact nature. In this work, phase shift method is utilized to perform the 3D mapping. The phase shifted fringe pattern are displayed through a digital projector onto the breast surface, and the distorted fringe patterns are captured by a CCD camera. A phase map is produced, and phase unwrapping was executed to obtain the 3D surface mapping of the breast. The surface height profile from 3D fringe projection was compared with the surface height measured by a direct method using electronic digital vernier caliper. Preliminary results showed the feasibility of digital fringe projection in providing a 3D mapping of breast and its application could be further extended for breast carcinoma detection.

Sensing device and method for measuring emission time delay during irradiation of targeted samples utilizing variable phase tracking

NASA Technical Reports Server (NTRS)

Danielson, J. D. Sheldon (Inventor)

2006-01-01

An apparatus for measuring emission time delay during irradiation of targeted samples by utilizing digital signal processing to determine the emission phase shift caused by the sample is disclosed. The apparatus includes a source of electromagnetic radiation adapted to irradiate a target sample. A mechanism generates first and second digital input signals of known frequencies with a known phase relationship, and a device then converts the first and second digital input signals to analog sinusoidal signals. An element is provided to direct the first input signal to the electromagnetic radiation source to modulate the source by the frequency thereof to irradiate the target sample and generate a target sample emission. A device detects the target sample emission and produces a corresponding first output signal having a phase shift relative to the phase of the first input signal, the phase shift being caused by the irradiation time delay in the sample. A member produces a known phase shift in the second input signal to create a second output signal. A mechanism is then provided for converting each of the first and second analog output signals to digital signals. A mixer receives the first and second digital output signals and compares the signal phase relationship therebetween to produce a signal indicative of the change in phase relationship between the first and second output signals caused by the target sample emission. Finally, a feedback arrangement alters the phase of the second input signal based on the mixer signal to ultimately place the first and second output signals in quadrature. Mechanisms for enhancing this phase comparison and adjustment technique are also disclosed.

A synchronization technique for the on-board master clock of a regenerative TDMA satellite communications system

NASA Astrophysics Data System (ADS)

Pattini, F.; Porzio Giusto, P.

The design criteria and performance of the master clock (MCK) generator and the unique word (UW) detector are examined. A narrow band phase lock loop is used for the onboard MCK generator and it is implemented with an all-digital scheme that employs a D-type flip flop as the phase detector. The performance of the MCK generator is analyzed with a computer program which considers phase offset of the digital phase comparator. The characteristics and capabilities of the UW detector which provides strobe signals for the MCK generator and synchronization signals for the onboard switching matrix are described.

Digital Phase Meter for a Laser Heterodyne Interferometer

NASA Technical Reports Server (NTRS)

Loya, Frank

2008-01-01

The Digital Phase Meter is based on a modified phase-locked loop. When phase alignment between the reference input and the phase-shifted metrological input is achieved, the loop locks and the phase shift of the digital phase shifter equals the phase difference that one seeks to measure. This digital phase meter is being developed for incorporation into a laser heterodyne interferometer in a metrological apparatus, but could also be adapted to other uses. Relative to prior phase meters of similar capability, including digital ones, this digital phase meter is smaller, less complex, and less expensive. The phase meter has been constructed and tested in the form of a field-programmable gate array (FPGA).

Sensing device and method for measuring emission time delay during irradiation of targeted samples

NASA Technical Reports Server (NTRS)

Danielson, J. D. Sheldon (Inventor)

2000-01-01

An apparatus for measuring emission time delay during irradiation of targeted samples by utilizing digital signal processing to determine the emission phase shift caused by the sample is disclosed. The apparatus includes a source of electromagnetic radiation adapted to irradiate a target sample. A mechanism generates first and second digital input signals of known frequencies with a known phase relationship, and a device then converts the first and second digital input signals to analog sinusoidal signals. An element is provided to direct the first input signal to the electromagnetic radiation source to modulate the source by the frequency thereof to irradiate the target sample and generate a target sample emission. A device detects the target sample emission and produces a corresponding first output signal having a phase shift relative to the phase of the first input signal, the phase shift being caused by the irradiation time delay in the sample. A member produces a known phase shift in the second input signal to create a second output signal. A mechanism is then provided for converting each of the first and second analog output signals to digital signals. A mixer receives the first and second digital output signals and compares the signal phase relationship therebetween to produce a signal indicative of the change in phase relationship between the first and second output signals caused by the target sample emission. Finally, a feedback arrangement alters the phase of the second input signal based on the mixer signal to ultimately place the first and second output signals in quadrature. Mechanisms for enhancing this phase comparison and adjustment technique are also disclosed.

Design of a digital multiradian phase detector and its application in fusion plasma interferometry.

PubMed

Mlynek, A; Schramm, G; Eixenberger, H; Sips, G; McCormick, K; Zilker, M; Behler, K; Eheberg, J

2010-03-01

We discuss the circuit design of a digital multiradian phase detector that measures the phase difference between two 10 kHz square wave TTL signals and provides the result as a binary number. The phase resolution of the circuit is 1/64 period and its dynamic range is 256 periods. This circuit has been developed for fusion plasma interferometry with submillimeter waves on the ASDEX Upgrade tokamak. The results from interferometric density measurement are discussed and compared to those obtained with the previously used phase detectors, especially with respect to the occurrence of phase jumps. It is illustrated that the new phase measurement provides a powerful tool for automatic real-time validation of the measured density, which is important for feedback algorithms that are sensitive to spurious density signals.

Optimal space communications techniques. [using digital and phase locked systems for signal processing

NASA Technical Reports Server (NTRS)

Schilling, D. L.

1974-01-01

Digital multiplication of two waveforms using delta modulation (DM) is discussed. It is shown that while conventional multiplication of two N bit words requires N2 complexity, multiplication using DM requires complexity which increases linearly with N. Bounds on the signal-to-quantization noise ratio (SNR) resulting from this multiplication are determined and compared with the SNR obtained using standard multiplication techniques. The phase locked loop (PLL) system, consisting of a phase detector, voltage controlled oscillator, and a linear loop filter, is discussed in terms of its design and system advantages. Areas requiring further research are identified.

Differential carrier phase recovery for QPSK optical coherent systems with integrated tunable lasers.

PubMed

Fatadin, Irshaad; Ives, David; Savory, Seb J

2013-04-22

The performance of a differential carrier phase recovery algorithm is investigated for the quadrature phase shift keying (QPSK) modulation format with an integrated tunable laser. The phase noise of the widely-tunable laser measured using a digital coherent receiver is shown to exhibit significant drift compared to a standard distributed feedback (DFB) laser due to enhanced low frequency noise component. The simulated performance of the differential algorithm is compared to the Viterbi-Viterbi phase estimation at different baud rates using the measured phase noise for the integrated tunable laser.

A digital, constant-frequency pulsed phase-locked-loop instrument for real-time, absolute ultrasonic phase measurements

NASA Astrophysics Data System (ADS)

Haldren, H. A.; Perey, D. F.; Yost, W. T.; Cramer, K. E.; Gupta, M. C.

2018-05-01

A digitally controlled instrument for conducting single-frequency and swept-frequency ultrasonic phase measurements has been developed based on a constant-frequency pulsed phase-locked-loop (CFPPLL) design. This instrument uses a pair of direct digital synthesizers to generate an ultrasonically transceived tone-burst and an internal reference wave for phase comparison. Real-time, constant-frequency phase tracking in an interrogated specimen is possible with a resolution of 0.000 38 rad (0.022°), and swept-frequency phase measurements can be obtained. Using phase measurements, an absolute thickness in borosilicate glass is presented to show the instrument's efficacy, and these results are compared to conventional ultrasonic pulse-echo time-of-flight (ToF) measurements. The newly developed instrument predicted the thickness with a mean error of -0.04 μm and a standard deviation of error of 1.35 μm. Additionally, the CFPPLL instrument shows a lower measured phase error in the absence of changing temperature and couplant thickness than high-resolution cross-correlation ToF measurements at a similar signal-to-noise ratio. By showing higher accuracy and precision than conventional pulse-echo ToF measurements and lower phase errors than cross-correlation ToF measurements, the new digitally controlled CFPPLL instrument provides high-resolution absolute ultrasonic velocity or path-length measurements in solids or liquids, as well as tracking of material property changes with high sensitivity. The ability to obtain absolute phase measurements allows for many new applications than possible with previous ultrasonic pulsed phase-locked loop instruments. In addition to improved resolution, swept-frequency phase measurements add useful capability in measuring properties of layered structures, such as bonded joints, or materials which exhibit non-linear frequency-dependent behavior, such as dispersive media.

High-accuracy resolver-to-digital conversion via phase locked loop based on PID controller

NASA Astrophysics Data System (ADS)

Li, Yaoling; Wu, Zhong

2018-03-01

The problem of resolver-to-digital conversion (RDC) is transformed into the problem of angle tracking control, and a phase locked loop (PLL) method based on PID controller is proposed in this paper. This controller comprises a typical PI controller plus an incomplete differential which can avoid the amplification of higher-frequency noise components by filtering the phase detection error with a low-pass filter. Compared with conventional ones, the proposed PLL method makes the converter a system of type III and thus the conversion accuracy can be improved. Experimental results demonstrate the effectiveness of the proposed method.

Off-axis digital holographic camera for quantitative phase microscopy.

PubMed

Monemhaghdoust, Zahra; Montfort, Frédéric; Emery, Yves; Depeursinge, Christian; Moser, Christophe

2014-06-01

We propose and experimentally demonstrate a digital holographic camera which can be attached to the camera port of a conventional microscope for obtaining digital holograms in a self-reference configuration, under short coherence illumination and in a single shot. A thick holographic grating filters the beam containing the sample information in two dimensions through diffraction. The filtered beam creates the reference arm of the interferometer. The spatial filtering method, based on the high angular selectivity of the thick grating, reduces the alignment sensitivity to angular displacements compared with pinhole based Fourier filtering. The addition of a thin holographic grating alters the coherence plane tilt introduced by the thick grating so as to create high-visibility interference over the entire field of view. The acquired full-field off-axis holograms are processed to retrieve the amplitude and phase information of the sample. The system produces phase images of cheek cells qualitatively similar to phase images extracted with a standard commercial DHM.

System and method for regulating resonant inverters

DOEpatents

Stevanovic, Ljubisa Dragoljub [Clifton Park, NY; Zane, Regan Andrew [Superior, CO

2007-08-28

A technique is provided for direct digital phase control of resonant inverters based on sensing of one or more parameters of the resonant inverter. The resonant inverter control system includes a switching circuit for applying power signals to the resonant inverter and a sensor for sensing one or more parameters of the resonant inverter. The one or more parameters are representative of a phase angle. The resonant inverter control system also includes a comparator for comparing the one or more parameters to a reference value and a digital controller for determining timing of the one or more parameters and for regulating operation of the switching circuit based upon the timing of the one or more parameters.

Wideband aperture array using RF channelizers and massively parallel digital 2D IIR filterbank

NASA Astrophysics Data System (ADS)

Sengupta, Arindam; Madanayake, Arjuna; Gómez-García, Roberto; Engeberg, Erik D.

2014-05-01

Wideband receive-mode beamforming applications in wireless location, electronically-scanned antennas for radar, RF sensing, microwave imaging and wireless communications require digital aperture arrays that offer a relatively constant far-field beam over several octaves of bandwidth. Several beamforming schemes including the well-known true time-delay and the phased array beamformers have been realized using either finite impulse response (FIR) or fast Fourier transform (FFT) digital filter-sum based techniques. These beamforming algorithms offer the desired selectivity at the cost of a high computational complexity and frequency-dependant far-field array patterns. A novel approach to receiver beamforming is the use of massively parallel 2-D infinite impulse response (IIR) fan filterbanks for the synthesis of relatively frequency independent RF beams at an order of magnitude lower multiplier complexity compared to FFT or FIR filter based conventional algorithms. The 2-D IIR filterbanks demand fast digital processing that can support several octaves of RF bandwidth, fast analog-to-digital converters (ADCs) for RF-to-bits type direct conversion of wideband antenna element signals. Fast digital implementation platforms that can realize high-precision recursive filter structures necessary for real-time beamforming, at RF radio bandwidths, are also desired. We propose a novel technique that combines a passive RF channelizer, multichannel ADC technology, and single-phase massively parallel 2-D IIR digital fan filterbanks, realized at low complexity using FPGA and/or ASIC technology. There exists native support for a larger bandwidth than the maximum clock frequency of the digital implementation technology. We also strive to achieve More-than-Moore throughput by processing a wideband RF signal having content with N-fold (B = N Fclk/2) bandwidth compared to the maximum clock frequency Fclk Hz of the digital VLSI platform under consideration. Such increase in bandwidth is achieved without use of polyphase signal processing or time-interleaved ADC methods. That is, all digital processors operate at the same Fclk clock frequency without phasing, while wideband operation is achieved by sub-sampling of narrower sub-bands at the the RF channelizer outputs.

A digital receiver module with direct data acquisition for magnetic resonance imaging systems.

PubMed

Tang, Weinan; Sun, Hongyu; Wang, Weimin

2012-10-01

A digital receiver module for magnetic resonance imaging (MRI) with detailed hardware implementations is presented. The module is based on a direct sampling scheme using the latest mixed-signal circuit design techniques. A single field-programmable gate array chip is employed to perform software-based digital down conversion for radio frequency signals. The modular architecture of the receiver allows multiple acquisition channels to be implemented on a highly integrated printed circuit board. To maintain the phase coherence of the receiver and the exciter in the context of direct sampling, an effective phase synchronization method was proposed to achieve a phase deviation as small as 0.09°. The performance of the described receiver module was verified in the experiments for both low- and high-field (0.5 T and 1.5 T) MRI scanners and was compared to a modern commercial MRI receiver system.

Single Phase Dual-energy CT Angiography: One-stop-shop Tool for Evaluating Aneurysmal Subarachnoid Hemorrhage.

PubMed

Ni, Qian Qian; Tang, Chun Xiang; Zhao, Yan E; Zhou, Chang Sheng; Chen, Guo Zhong; Lu, Guang Ming; Zhang, Long Jiang

2016-05-25

Aneurysmal subarachnoid hemorrhages have extremely high case fatality in clinic. Early and rapid identifications of ruptured intracranial aneurysms seem to be especially important. Here we evaluate clinical value of single phase contrast-enhanced dual-energy CT angiograph (DE-CTA) as a one-stop-shop tool in detecting aneurysmal subarachnoid hemorrhage. One hundred and five patients who underwent true non-enhanced CT (TNCT), contrast-enhanced DE-CTA and digital subtraction angiography (DSA) were included. Image quality and detectability of intracranial hemorrhage were evaluated and compared between virtual non-enhanced CT (VNCT) images reconstructed from DE-CTA and TNCT. There was no statistical difference in image quality (P > 0.05) between VNCT and TNCT. The agreement of VNCT and TNCT in detecting intracranial hemorrhage reached 98.1% on a per-patient basis. With DSA as reference standard, sensitivity and specificity on a per-patient were 98.3% and 97.9% for DE-CTA in intracranial aneurysm detection. Effective dose of DE-CTA was reduced by 75.0% compared to conventional digital subtraction CTA. Thus, single phase contrast-enhanced DE-CTA is optimal reliable one-stop-shop tool for detecting intracranial hemorrhage with VNCT and intracranial aneurysms with DE-CTA with substantial radiation dose reduction compared with conventional digital subtraction CTA.

Single Phase Dual-energy CT Angiography: One-stop-shop Tool for Evaluating Aneurysmal Subarachnoid Hemorrhage

PubMed Central

Ni, Qian Qian; Tang, Chun Xiang; Zhao, Yan E; Zhou, Chang Sheng; Chen, Guo Zhong; Lu, Guang Ming; Zhang, Long Jiang

2016-01-01

Aneurysmal subarachnoid hemorrhages have extremely high case fatality in clinic. Early and rapid identifications of ruptured intracranial aneurysms seem to be especially important. Here we evaluate clinical value of single phase contrast-enhanced dual-energy CT angiograph (DE-CTA) as a one-stop-shop tool in detecting aneurysmal subarachnoid hemorrhage. One hundred and five patients who underwent true non-enhanced CT (TNCT), contrast-enhanced DE-CTA and digital subtraction angiography (DSA) were included. Image quality and detectability of intracranial hemorrhage were evaluated and compared between virtual non-enhanced CT (VNCT) images reconstructed from DE-CTA and TNCT. There was no statistical difference in image quality (P > 0.05) between VNCT and TNCT. The agreement of VNCT and TNCT in detecting intracranial hemorrhage reached 98.1% on a per-patient basis. With DSA as reference standard, sensitivity and specificity on a per-patient were 98.3% and 97.9% for DE-CTA in intracranial aneurysm detection. Effective dose of DE-CTA was reduced by 75.0% compared to conventional digital subtraction CTA. Thus, single phase contrast-enhanced DE-CTA is optimal reliable one-stop-shop tool for detecting intracranial hemorrhage with VNCT and intracranial aneurysms with DE-CTA with substantial radiation dose reduction compared with conventional digital subtraction CTA. PMID:27222163

Digital phase shifter synchronizes local oscillators

NASA Technical Reports Server (NTRS)

Ali, S. M.

1978-01-01

Digital phase-shifting network is used as synchronous frequency multiplier for applications such as phase-locking two signals that may differ in frequency. Circuit has various phase-shift capability. Possible applications include data-communication systems and hybrid digital/analog phase-locked loops.

Homodyne Phase-Shift-Keying Systems: Past Challenges and Future Opportunities

NASA Astrophysics Data System (ADS)

Kazovsky, Leonid G.; Kalogerakis, Georgios; Shaw, Wei-Tao

2006-12-01

Homodyne phase-shift-keying systems can achieve the best receiver sensitivity and the longest transmission distance among all optical communication systems. This paper reviews recent research efforts in the field and examines future possibilities that might lead toward potential practical use of these systems. Additionally, phase estimation techniques based on feed-forward phase recovery and digital delay-lock loop approaches are examined, simulated, and compared.

Superpixel-based spatial amplitude and phase modulation using a digital micromirror device.

PubMed

Goorden, Sebastianus A; Bertolotti, Jacopo; Mosk, Allard P

2014-07-28

We present a superpixel method for full spatial phase and amplitude control of a light beam using a digital micromirror device (DMD) combined with a spatial filter. We combine square regions of nearby micromirrors into superpixels by low pass filtering in a Fourier plane of the DMD. At each superpixel we are able to independently modulate the phase and the amplitude of light, while retaining a high resolution and the very high speed of a DMD. The method achieves a measured fidelity F = 0.98 for a target field with fully independent phase and amplitude at a resolution of 8 × 8 pixels per diffraction limited spot. For the LG10 orbital angular momentum mode the calculated fidelity is F = 0.99993, using 768 × 768 DMD pixels. The superpixel method reduces the errors when compared to the state of the art Lee holography method for these test fields by 50% and 18%, with a comparable light efficiency of around 5%. Our control software is publicly available.

Measuring optical phase digitally in coherent metrology systems

NASA Astrophysics Data System (ADS)

Kelly, Damien P.; Ryle, James; Zhao, Liang; Sheridan, John T.

2017-05-01

The accurate measurement of optical phase has many applications in metrology. For biological samples, which appear transparent, the phase data provides information about the refractive index of the sample. In speckle metrology, the phase can be used to estimate stress and strains of a rough surface with high sensitivity. In this theoretical manuscript we compare and contrast the properties of two techniques for estimating the phase distribution of a wave field under the paraxial approximation: (I) A digital holographic system, and (II) An idealized phase retrieval system. Both systems use a CCD or CMOS array to measure the intensities of the wave fields that are reflected from or transmitted through the sample of interest. This introduces a numerical aspect to the problem. For the two systems above we examine how numerical calculations can limit the performance of these systems leading to a near-infinite number of possible solutions.

Design of Digital Phase-Locked Loops For Advanced Digital Transponders

NASA Technical Reports Server (NTRS)

Nguyen, Tien M.

1994-01-01

For advanced digital space transponders, the Digital Phased-Locked Loops (DPLLs) can be designed using the available analog loops. DPLLs considered in this paper are derived from the Analog Phase-Locked Loop (APLL) using S-domain mapping techniques.

Analysis of digital communication signals and extraction of parameters

NASA Astrophysics Data System (ADS)

Al-Jowder, Anwar

1994-12-01

The signal classification performance of four types of electronics support measure (ESM) communications detection systems is compared from the standpoint of the unintended receiver (interceptor). Typical digital communication signals considered include binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), frequency shift keying (FSK), and on-off keying (OOK). The analysis emphasizes the use of available signal processing software. Detection methods compared include broadband energy detection, FFT-based narrowband energy detection, and two correlation methods which employ the fast Fourier transform (FFT). The correlation methods utilize modified time-frequency distributions, where one of these is based on the Wigner-Ville distribution (WVD). Gaussian white noise is added to the signal to simulate various signal-to-noise ratios (SNR's).

Dual-wavelength digital holographic imaging with phase background subtraction

NASA Astrophysics Data System (ADS)

Khmaladze, Alexander; Matz, Rebecca L.; Jasensky, Joshua; Seeley, Emily; Holl, Mark M. Banaszak; Chen, Zhan

2012-05-01

Three-dimensional digital holographic microscopic phase imaging of objects that are thicker than the wavelength of the imaging light is ambiguous and results in phase wrapping. In recent years, several unwrapping methods that employed two or more wavelengths were introduced. These methods compare the phase information obtained from each of the wavelengths and extend the range of unambiguous height measurements. A straightforward dual-wavelength phase imaging method is presented which allows for a flexible tradeoff between the maximum height of the sample and the amount of noise the method can tolerate. For highly accurate phase measurements, phase unwrapping of objects with heights higher than the beat (synthetic) wavelength (i.e. the product of the original two wavelengths divided by their difference), can be achieved. Consequently, three-dimensional measurements of a wide variety of biological systems and microstructures become technically feasible. Additionally, an effective method of removing phase background curvature based on slowly varying polynomial fitting is proposed. This method allows accurate volume measurements of several small objects with the same image frame.

Parallel Digital Phase-Locked Loops

NASA Technical Reports Server (NTRS)

Sadr, Ramin; Shah, Biren N.; Hinedi, Sami M.

1995-01-01

Wide-band microwave receivers of proposed type include digital phase-locked loops in which band-pass filtering and down-conversion of input signals implemented by banks of multirate digital filters operating in parallel. Called "parallel digital phase-locked loops" to distinguish them from other digital phase-locked loops. Systems conceived as cost-effective solution to problem of filtering signals at high sampling rates needed to accommodate wide input frequency bands. Each of M filters process 1/M of spectrum of signal.

Digital phase-locked loop

NASA Technical Reports Server (NTRS)

Cliff, R. A. (Inventor)

1975-01-01

An digital phase-locked loop is provided for deriving a loop output signal from an accumulator output terminal. A phase detecting exclusive OR gate is fed by the loop digital input and output signals. The output of the phase detector is a bi-level digital signal having a duty cycle indicative of the relative phase of the input and output signals. The accumulator is incremented at a first rate in response to a first output level of the phase detector and at a second rate in response to a second output level of the phase detector.

Direct-Sequence Spread Spectrum System

DTIC Science & Technology

1990-06-01

by directly modulating a conventional narrowband frequency-modulated (FM) carrier by a high rate digital code. The direct modulation is binary phase ...specification of the DSSS system will not be developed. The results of the evaluation phase of this research will be compared against theoretical...spread spectrum is called binary phase -shift keying 19 (BPSK). BPSK is a modulation in which a binary Ŕ" represents a 0-degree relative phase

A class of all digital phase locked loops - Modeling and analysis

NASA Technical Reports Server (NTRS)

Reddy, C. P.; Gupta, S. C.

1973-01-01

An all digital phase locked loop which tracks the phase of the incoming signal once per carrier cycle is proposed. The different elements and their functions, and the phase lock operation are explained in detail. The general digital loop operation is governed by a nonlinear difference equation from which a suitable model is developed. The lock range for the general model is derived. The performance of the digital loop for phase step and frequency step inputs for different levels of quantization without loop filter are studied. The analytical results are checked by simulating the actual system on the digital computer.

Detailed analysis of CAMS procedures for phase 3 using ground truth inventories

NASA Technical Reports Server (NTRS)

Carnes, J. G.

1979-01-01

The results of a study of Procedure 1 as used during LACIE Phase 3 are presented. The study was performed by comparing the Procedure 1 classification results with digitized ground-truth inventories. The proportion estimation accuracy, dot labeling accuracy, and clustering effectiveness are discussed.

Calculation and Error Analysis of a Digital Elevation Model of Hofsjokull, Iceland from SAR Interferometry

NASA Technical Reports Server (NTRS)

Barton, Jonathan S.; Hall, Dorothy K.; Sigurosson, Oddur; Williams, Richard S., Jr.; Smith, Laurence C.; Garvin, James B.

1999-01-01

Two ascending European Space Agency (ESA) Earth Resources Satellites (ERS)-1/-2 tandem-mode, synthetic aperture radar (SAR) pairs are used to calculate the surface elevation of Hofsjokull, an ice cap in central Iceland. The motion component of the interferometric phase is calculated using the 30 arc-second resolution USGS GTOPO30 global digital elevation product and one of the ERS tandem pairs. The topography is then derived by subtracting the motion component from the other tandem pair. In order to assess the accuracy of the resultant digital elevation model (DEM), a geodetic airborne laser-altimetry swath is compared with the elevations derived from the interferometry. The DEM is also compared with elevations derived from a digitized topographic map of the ice cap from the University of Iceland Science Institute. Results show that low temporal correlation is a significant problem for the application of interferometry to small, low-elevation ice caps, even over a one-day repeat interval, and especially at the higher elevations. Results also show that an uncompensated error in the phase, ramping from northwest to southeast, present after tying the DEM to ground-control points, has resulted in a systematic error across the DEM.

Calculation and error analysis of a digital elevation model of Hofsjokull, Iceland, from SAR interferometry

USGS Publications Warehouse

Barton, Jonathan S.; Hall, Dorothy K.; Sigurðsson, Oddur; Williams, Richard S.; Smith, Laurence C.; Garvin, James B.; Taylor, Susan; Hardy, Janet

1999-01-01

Two ascending European Space Agency (ESA) Earth Resources Satellites (ERS)-1/-2 tandem-mode, synthetic aperture radar (SAR) pairs are used to calculate the surface elevation of Hofsjokull, an ice cap in central Iceland. The motion component of the interferometric phase is calculated using the 30 arc-second resolution USGS GTOPO30 global digital elevation product and one of the ERS tandem pairs. The topography is then derived by subtracting the motion component from the other tandem pair. In order to assess the accuracy of the resultant digital elevation model (DEM), a geodetic airborne laser-altimetry swath is compared with the elevations derived from the interferometry. The DEM is also compared with elevations derived from a digitized topographic map of the ice cap from the University of Iceland Science Institute. Results show that low temporal correlation is a significant problem for the application of interferometry to small, low-elevation ice caps, even over a one-day repeat interval, and especially at the higher elevations. Results also show that an uncompensated error in the phase, ramping from northwest to southeast, present after tying the DEM to ground-control points, has resulted in a systematic error across the DEM.

Phase Response Design of Recursive All-Pass Digital Filters Using a Modified PSO Algorithm

PubMed Central

2015-01-01

This paper develops a new design scheme for the phase response of an all-pass recursive digital filter. A variant of particle swarm optimization (PSO) algorithm will be utilized for solving this kind of filter design problem. It is here called the modified PSO (MPSO) algorithm in which another adjusting factor is more introduced in the velocity updating formula of the algorithm in order to improve the searching ability. In the proposed method, all of the designed filter coefficients are firstly collected to be a parameter vector and this vector is regarded as a particle of the algorithm. The MPSO with a modified velocity formula will force all particles into moving toward the optimal or near optimal solution by minimizing some defined objective function of the optimization problem. To show the effectiveness of the proposed method, two different kinds of linear phase response design examples are illustrated and the general PSO algorithm is compared as well. The obtained results show that the MPSO is superior to the general PSO for the phase response design of digital recursive all-pass filter. PMID:26366168

Comparative Analysis of Various Single-tone Frequency Estimation Techniques in High-order Instantaneous Moments Based Phase Estimation Method

NASA Astrophysics Data System (ADS)

Rajshekhar, G.; Gorthi, Sai Siva; Rastogi, Pramod

2010-04-01

For phase estimation in digital holographic interferometry, a high-order instantaneous moments (HIM) based method was recently developed which relies on piecewise polynomial approximation of phase and subsequent evaluation of the polynomial coefficients using the HIM operator. A crucial step in the method is mapping the polynomial coefficient estimation to single-tone frequency determination for which various techniques exist. The paper presents a comparative analysis of the performance of the HIM operator based method in using different single-tone frequency estimation techniques for phase estimation. The analysis is supplemented by simulation results.

Nonlinearity response correction in phase-shifting deflectometry

NASA Astrophysics Data System (ADS)

Nguyen, Manh The; Kang, Pilseong; Ghim, Young-Sik; Rhee, Hyug-Gyo

2018-04-01

Owing to the nonlinearity response of digital devices such as screens and cameras in phase-shifting deflectometry, non-sinusoidal phase-shifted fringe patterns are generated and additional measurement errors are introduced. In this paper, a new deflectometry technique is described for overcoming these problems using a pre-distorted pattern combined with an advanced iterative algorithm. The experiment results show that this method can reconstruct the 3D surface map of a sample without fringe print-through caused by the nonlinearity response of digital devices. The proposed technique is verified by measuring the surface height variations in a deformable mirror and comparing them with the measurement result obtained using a coordinate measuring machine. The difference between the two measurement results is estimated to be less than 13 µm.

A class of all digital phase locked loops - Modelling and analysis.

NASA Technical Reports Server (NTRS)

Reddy, C. P.; Gupta, S. C.

1972-01-01

An all digital phase locked loop which tracks the phase of the incoming signal once per carrier cycle is proposed. The different elements and their functions, and the phase lock operation are explained in detail. The general digital loop operation is governed by a non-linear difference equation from which a suitable model is developed. The lock range for the general model is derived. The performance of the digital loop for phase step, and frequency step inputs for different levels of quantization without loop filter, are studied. The analytical results are checked by simulating the actual system on the digital computer.

Numerical Simulation of Electrical Properties of Carbonate Reservoir Rocks Using µCT Images

NASA Astrophysics Data System (ADS)

Colgin, J.; Niu, Q.; Zhang, C.; Zhang, F.

2017-12-01

Digital rock physics involves the modern microscopic imaging of geomaterials, digitalization of the microstructure, and numerical simulation of physical properties of rocks. This physics-based approach can give important insight into understanding properties of reservoir rocks, and help reveal the link between intrinsic rock properties and macroscopic geophysical responses. The focus of this study is the simulation of the complex conductivity of carbonate reservoir rocks using reconstructed 3D rock structures from high-resolution X-ray micro computed tomography (µCT). Carbonate core samples with varying lithofacies and pore structures from the Cambro-Ordovician Arbuckle Group and the Upper Pennsylvanian Lansing-Kansas City Group in Kansas are used in this study. The wide variations in pore geometry and connectivity of these samples were imaged using µCT. A two-phase segmentation method was used to reconstruct a digital rock of solid particles and pores. We then calculate the effective electrical conductivity of the digital rock volume using a pore-scale numerical approach. The complex conductivity of geomaterials is influenced by the electrical properties and geometry of each phase, i.e., the solid and fluid phases. In addition, the electrical double layer that forms between the solid and fluid phases can also affect the effective conductivity of the material. In the numerical modeling, the influence of the electrical double layer is quantified by a complex surface conductance and converted to an apparent volumetric complex conductivity of either solid particles or pore fluid. The effective complex conductivity resulting from numerical simulations based on µCT images will be compared to results from laboratory experiments on equivalent rock samples. The imaging and digital segmentation method, assumptions in the numerical simulation, and trends as compared to laboratory results will be discussed. This study will help us understand how microscale physics affects macroscale electrical conductivity in porous media.

Digital Terrain from a Two-Step Segmentation and Outlier-Based Algorithm

NASA Astrophysics Data System (ADS)

Hingee, Kassel; Caccetta, Peter; Caccetta, Louis; Wu, Xiaoliang; Devereaux, Drew

2016-06-01

We present a novel ground filter for remotely sensed height data. Our filter has two phases: the first phase segments the DSM with a slope threshold and uses gradient direction to identify candidate ground segments; the second phase fits surfaces to the candidate ground points and removes outliers. Digital terrain is obtained by a surface fit to the final set of ground points. We tested the new algorithm on digital surface models (DSMs) for a 9600km2 region around Perth, Australia. This region contains a large mix of land uses (urban, grassland, native forest and plantation forest) and includes both a sandy coastal plain and a hillier region (elevations up to 0.5km). The DSMs are captured annually at 0.2m resolution using aerial stereo photography, resulting in 1.2TB of input data per annum. Overall accuracy of the filter was estimated to be 89.6% and on a small semi-rural subset our algorithm was found to have 40% fewer errors compared to Inpho's Match-T algorithm.

Single-shot dual-wavelength in-line and off-axis hybrid digital holography

NASA Astrophysics Data System (ADS)

Wang, Fengpeng; Wang, Dayong; Rong, Lu; Wang, Yunxin; Zhao, Jie

2018-02-01

We propose an in-line and off-axis hybrid holographic real-time imaging technique. The in-line and off-axis digital holograms are generated simultaneously by two lasers with different wavelengths, and they are recorded using a color camera with a single shot. The reconstruction is carried using an iterative algorithm in which the initial input is designed to include the intensity of the in-line hologram and the approximate phase distributions obtained from the off-axis hologram. In this way, the complex field in the object plane and the output by the iterative procedure can produce higher quality amplitude and phase images compared to traditional iterative phase retrieval. The performance of the technique has been demonstrated by acquiring the amplitude and phase images of a green lacewing's wing and a living moon jellyfish.

Digital processing of RF signals from optical frequency combs

NASA Astrophysics Data System (ADS)

Cizek, Martin; Smid, Radek; Buchta, Zdeněk.; Mikel, Břetislav; Lazar, Josef; Cip, Ondřej

2013-01-01

The presented work is focused on digital processing of beat note signals from a femtosecond optical frequency comb. The levels of mixing products of single spectral components of the comb with CW laser sources are usually very low compared to products of mixing all the comb components together. RF counters are more likely to measure the frequency of the strongest spectral component rather than a weak beat note. Proposed experimental digital signal processing system solves this problem by analyzing the whole spectrum of the output RF signal and using software defined radio (SDR) algorithms. Our efforts concentrate in two main areas: Firstly, using digital servo-loop techniques for locking free running continuous laser sources on single components of the fs comb spectrum. Secondly, we are experimenting with digital signal processing of the RF beat note spectrum produced by f-2f 1 technique used for assessing the offset and repetition frequencies of the comb, resulting in digital servo-loop stabilization of the fs comb. Software capable of computing and analyzing the beat-note RF spectrums using FFT and peak detection was developed. A SDR algorithm performing phase demodulation on the f- 2f signal is used as a regulation error signal source for a digital phase-locked loop stabilizing the offset frequency of the fs comb.

Digital processing of signals from femtosecond combs

NASA Astrophysics Data System (ADS)

Čížek, Martin; Šmíd, Radek; Buchta, Zdeněk.; Mikel, Břetislav; Lazar, Josef; Číp, Ondrej

2012-01-01

The presented work is focused on digital processing of beat note signals from a femtosecond optical frequency comb. The levels of mixing products of single spectral components of the comb with CW laser sources are usually very low compared to products of mixing all the comb components together. RF counters are more likely to measure the frequency of the strongest spectral component rather than a weak beat note. Proposed experimental digital signal processing system solves this problem by analyzing the whole spectrum of the output RF signal and using software defined radio (SDR) algorithms. Our efforts concentrate in two main areas: Firstly, we are experimenting with digital signal processing of the RF beat note spectrum produced by f-2f 1 technique and with fully digital servo-loop stabilization of the fs comb. Secondly, we are using digital servo-loop techniques for locking free running continuous laser sources on single components of the fs comb spectrum. Software capable of computing and analyzing the beat-note RF spectrums using FFT and peak detection was developed. A SDR algorithm performing phase demodulation on the f- 2f signal is used as a regulation error signal source for a digital phase-locked loop stabilizing the offset and repetition frequencies of the fs comb.

Development of high precision digital driver of acoustic-optical frequency shifter for ROG

NASA Astrophysics Data System (ADS)

Zhang, Rong; Kong, Mei; Xu, Yameng

2016-10-01

We develop a high precision digital driver of the acoustic-optical frequency shifter (AOFS) based on the parallel direct digital synthesizer (DDS) technology. We use an atomic clock as the phase-locked loop (PLL) reference clock, and the PLL is realized by a dual digital phase-locked loop. A DDS sampling clock up to 320 MHz with a frequency stability as low as 10-12 Hz is obtained. By constructing the RF signal measurement system, it is measured that the frequency output range of the AOFS-driver is 52-58 MHz, the center frequency of the band-pass filter is 55 MHz, the ripple in the band is less than 1 dB@3MHz, the single channel output power is up to 0.3 W, the frequency stability is 1 ppb (1 hour duration), and the frequency-shift precision is 0.1 Hz. The obtained frequency stability has two orders of improvement compared to that of the analog AOFS-drivers. For the designed binary frequency shift keying (2-FSK) and binary phase shift keying (2-PSK) modulation system, the demodulating frequency of the input TTL synchronous level signal is up to 10 kHz. The designed digital-bus coding/decoding system is compatible with many conventional digital bus protocols. It can interface with the ROG signal detecting software through the integrated drive electronics (IDE) and exchange data with the two DDS frequency-shift channels through the signal detecting software.

Bandwidth controller for phase-locked-loop

NASA Technical Reports Server (NTRS)

Brockman, Milton H. (Inventor)

1992-01-01

A phase locked loop utilizing digital techniques to control the closed loop bandwidth of the RF carrier phase locked loop in a receiver provides high sensitivity and a wide dynamic range for signal reception. After analog to digital conversion, a digital phase locked loop bandwidth controller provides phase error detection with automatic RF carrier closed loop tracking bandwidth control to accommodate several modes of transmission.

Wirelessly Networked Digital Phased Array: Analysis and Development of a Phase Synchronization Concept

DTIC Science & Technology

2007-09-01

NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA THESIS Approved for public release; distribution is unlimited WIRELESSLY NETWORKED...DIGITAL PHASED ARRAY: ANALYSIS AND DEVELOPMENT OF A PHASE SYNCHRONIZATION CONCEPT by Micael Grahn September 2007 Thesis Advisor...September 2007 3. REPORT TYPE AND DATES COVERED Master’s Thesis 4. TITLE AND SUBTITLE Wirelessly Networked Digital Phased Array: Analysis and

Jitter and phase noise of ADPLL due to PSN with deterministic frequency

NASA Astrophysics Data System (ADS)

Deng, Xiaoying; Yang, Jun; Wu, Jianhui

2011-09-01

In this article, jitter and phase noise of all-digital phase-locked loop due to power supply noise (PSN) with deterministic frequency are analysed. It leads to the conclusion that jitter and phase noise heavily depend on the noise frequency. Compared with jitter, phase noise is much less affected by the deterministic PSN. Our method is utilised to study a CMOS ADPLL designed and simulated in SMIC 0.13 µm standard CMOS process. A comparison between the results obtained by our method and those obtained by simulation and measurement proves the accuracy of the predicted model. When the digital controlled oscillator was corrupted by PSN with 100 mVpk-pk, the measured jitters were 33.9 ps at the rate of fG = 192 MHz and 148.5 ps at the rate of fG = 40 MHz. However, the measured phase noise was exactly the same except for two impulses appearing at 192 and 40 MHz, respectively.

All-digital signal-processing open-loop fiber-optic gyroscope with enlarged dynamic range.

PubMed

Wang, Qin; Yang, Chuanchuan; Wang, Xinyue; Wang, Ziyu

2013-12-15

We propose and realize a new open-loop fiber-optic gyroscope (FOG) with an all-digital signal-processing (DSP) system where an all-digital phase-locked loop is employed for digital demodulation to eliminate the variation of the source intensity and suppress the bias drift. A Sagnac phase-shift tracking method is proposed to enlarge the dynamic range, and, with its aid, a new open-loop FOG, which can achieve a large dynamic range and high sensitivity at the same time, is realized. The experimental results show that compared with the conventional open-loop FOG with the same fiber coil and optical devices, the proposed FOG reduces the bias instability from 0.259 to 0.018 deg/h, and the angle random walk from 0.031 to 0.006 deg/h(1/2), moreover, enlarges the dynamic range to ±360 deg/s, exceeding the maximum dynamic range ±63 deg/s of the conventional open-loop FOG.

All-digital phase-lock loops for noise-free signals

NASA Technical Reports Server (NTRS)

Anderson, T. O.

1973-01-01

Bit-synchronizers utilize all-digital phase-lock loops that are referenced to a high frequency digital clock. Phase-lock loop of first design acquires frequency within nominal range and tracks phase; second design is modified for random binary data by addition of simple transition detector; and third design acquires frequency over wide dynamic range.

A study on mastectomy samples to evaluate breast imaging quality and potential clinical relevance of differential phase contrast mammography.

PubMed

Hauser, Nik; Wang, Zhentian; Kubik-Huch, Rahel A; Trippel, Mafalda; Singer, Gad; Hohl, Michael K; Roessl, Ewald; Köhler, Thomas; van Stevendaal, Udo; Wieberneit, Nataly; Stampanoni, Marco

2014-03-01

Differential phase contrast and scattering-based x-ray mammography has the potential to provide additional and complementary clinically relevant information compared with absorption-based mammography. The purpose of our study was to provide a first statistical evaluation of the imaging capabilities of the new technique compared with digital absorption mammography. We investigated non-fixed mastectomy samples of 33 patients with invasive breast cancer, using grating-based differential phase contrast mammography (mammoDPC) with a conventional, low-brilliance x-ray tube. We simultaneously recorded absorption, differential phase contrast, and small-angle scattering signals that were combined into novel high-frequency-enhanced images with a dedicated image fusion algorithm. Six international, expert breast radiologists evaluated clinical digital and experimental mammograms in a 2-part blinded, prospective independent reader study. The results were statistically analyzed in terms of image quality and clinical relevance. The results of the comparison of mammoDPC with clinical digital mammography revealed the general quality of the images to be significantly superior (P < 0.001); sharpness, lesion delineation, as well as the general visibility of calcifications to be significantly more assessable (P < 0.001); and delineation of anatomic components of the specimens (surface structures) to be significantly sharper (P < 0.001). Spiculations were significantly better identified, and the overall clinically relevant information provided by mammoDPC was judged to be superior (P < 0.001). Our results demonstrate that complementary information provided by phase and scattering enhanced mammograms obtained with the mammoDPC approach deliver images of generally superior quality. This technique has the potential to improve radiological breast diagnostics.

Topography of hidden objects using THz digital holography with multi-beam interferences.

PubMed

Valzania, Lorenzo; Zolliker, Peter; Hack, Erwin

2017-05-15

We present a method for the separation of the signal scattered from an object hidden behind a THz-transparent sample in the framework of THz digital holography in reflection. It combines three images of different interference patterns to retrieve the amplitude and phase distribution of the object beam. Comparison of simulated with experimental images obtained from a metallic resolution target behind a Teflon plate demonstrates that the interference patterns can be described in the simple form of three-beam interference. Holographic reconstructions after the application of the method show a considerable improvement compared to standard reconstructions exclusively based on Fourier transform phase retrieval.

An autonomous surface discontinuity detection and quantification method by digital image correlation and phase congruency

NASA Astrophysics Data System (ADS)

Cinar, A. F.; Barhli, S. M.; Hollis, D.; Flansbjer, M.; Tomlinson, R. A.; Marrow, T. J.; Mostafavi, M.

2017-09-01

Digital image correlation has been routinely used to measure full-field displacements in many areas of solid mechanics, including fracture mechanics. Accurate segmentation of the crack path is needed to study its interaction with the microstructure and stress fields, and studies of crack behaviour, such as the effect of closure or residual stress in fatigue, require data on its opening displacement. Such information can be obtained from any digital image correlation analysis of cracked components, but it collection by manual methods is quite onerous, particularly for massive amounts of data. We introduce the novel application of Phase Congruency to detect and quantify cracks and their opening. Unlike other crack detection techniques, Phase Congruency does not rely on adjustable threshold values that require user interaction, and so allows large datasets to be treated autonomously. The accuracy of the Phase Congruency based algorithm in detecting cracks is evaluated and compared with conventional methods such as Heaviside function fitting. As Phase Congruency is a displacement-based method, it does not suffer from the noise intensification to which gradient-based methods (e.g. strain thresholding) are susceptible. Its application is demonstrated to experimental data for cracks in quasi-brittle (Granitic rock) and ductile (Aluminium alloy) materials.

Digitally controlled distributed phase shifter

DOEpatents

Hietala, V.M.; Kravitz, S.H.; Vawter, G.A.

1993-08-17

A digitally controlled distributed phase shifter is comprised of N phase shifters. Digital control is achieved by using N binary length-weighted electrodes located on the top surface of a waveguide. A control terminal is attached to each electrode thereby allowing the application of a control signal. The control signal is either one or two discrete bias voltages. The application of the discrete bias voltages changes the modal index of a portion of the waveguide that corresponds to a length of the electrode to which the bias voltage is applied, thereby causing the phase to change through the underlying portion of the waveguide. The digitally controlled distributed phase shift network has a total phase shift comprised of the sum of the individual phase shifters.

Digitally controlled distributed phase shifter

DOEpatents

Hietala, Vincent M.; Kravitz, Stanley H.; Vawter, Gregory A.

1993-01-01

A digitally controlled distributed phase shifter is comprised of N phase shifters. Digital control is achieved by using N binary length-weighted electrodes located on the top surface of a waveguide. A control terminal is attached to each electrode thereby allowing the application of a control signal. The control signal is either one or two discrete bias voltages. The application of the discrete bias voltages changes the modal index of a portion of the waveguide that corresponds to a length of the electrode to which the bias voltage is applied, thereby causing the phase to change through the underlying portion of the waveguide. The digitally controlled distributed phase shift network has a total phase shift comprised of the sum of the individual phase shifters.

3D endoscopic pulsed digital holography

NASA Astrophysics Data System (ADS)

Saucedo Anaya, T.; Mendoza Santoyo, F.; Pedrini, G.; Osten, W.

2006-06-01

A rigid endoscope is used in pulsed digital holography to simultaneously evaluate the three orthogonal displacement components from hidden areas of a harmonically vibrating metallic cylinder. The cylinder is illuminated from three different illuminating directions. The optical path for each illumination direction is matched to its corresponding reference beam, but also in such a way that each object-reference beam pair optical path is mismatched such that they are incoherent and can be stored in a single CCD frame. As is typical in these types of interferometric arrangements, two digital holograms are needed in order to compare two different states of the cylinder. Each hologram is Fourier transformed and due to the incoherence introduced three separate spectra are readily identified, each belonging to a object-reference beam pair. On comparing by subtraction the phase obtained from the two pulsed digital holograms it is possible to gather quantitative 3D results from harmonic displacements.

Phase conjugate digital inline holography (PCDIH)

DOE PAGES

Guildenbecher, Daniel Robert; Hoffmeister, Kathryn N. Gabet; Kunzler, William Marley; ...

2018-01-12

We report digital inline holography (DIH) provides instantaneous three-dimensional (3D) measurements of diffracting objects; however, phase disturbances in the beam path can distort the imaging. In this Letter, a phase conjugate digital inline holography (PCDIH) configuration is proposed for removal of phase disturbances. Brillouin-enhanced four-wave mixing produces a phase conjugate signal that back propagates along the DIH beam path. Finally, the results demonstrate the removal of distortions caused by gas-phase shocks to recover 3D images of diffracting objects.

Phase conjugate digital inline holography (PCDIH)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guildenbecher, Daniel Robert; Hoffmeister, Kathryn N. Gabet; Kunzler, William Marley

We report digital inline holography (DIH) provides instantaneous three-dimensional (3D) measurements of diffracting objects; however, phase disturbances in the beam path can distort the imaging. In this Letter, a phase conjugate digital inline holography (PCDIH) configuration is proposed for removal of phase disturbances. Brillouin-enhanced four-wave mixing produces a phase conjugate signal that back propagates along the DIH beam path. Finally, the results demonstrate the removal of distortions caused by gas-phase shocks to recover 3D images of diffracting objects.

Phase unwrapping with a virtual Hartmann-Shack wavefront sensor.

PubMed

Akondi, Vyas; Falldorf, Claas; Marcos, Susana; Vohnsen, Brian

2015-10-05

The use of a spatial light modulator for implementing a digital phase-shifting (PS) point diffraction interferometer (PDI) allows tunability in fringe spacing and in achieving PS without the need for mechanically moving parts. However, a small amount of detector or scatter noise could affect the accuracy of wavefront sensing. Here, a novel method of wavefront reconstruction incorporating a virtual Hartmann-Shack (HS) wavefront sensor is proposed that allows easy tuning of several wavefront sensor parameters. The proposed method was tested and compared with a Fourier unwrapping method implemented on a digital PS PDI. The rewrapping of the Fourier reconstructed wavefronts resulted in phase maps that matched well the original wrapped phase and the performance was found to be more stable and accurate than conventional methods. Through simulation studies, the superiority of the proposed virtual HS phase unwrapping method is shown in comparison with the Fourier unwrapping method in the presence of noise. Further, combining the two methods could improve accuracy when the signal-to-noise ratio is sufficiently high.

Phase-locked loops. [in analog and digital circuits communication system

NASA Technical Reports Server (NTRS)

Gupta, S. C.

1975-01-01

An attempt to systematically outline the work done in the area of phase-locked loops which are now used in modern communication system design is presented. The analog phase-locked loops are well documented in several books but discrete, analog-digital, and digital phase-locked loop work is scattered. Apart from discussing the various analysis, design, and application aspects of phase-locked loops, a number of references are given in the bibliography.

Development of Coriolis mass flowmeter with digital drive and signal processing technology.

PubMed

Hou, Qi-Li; Xu, Ke-Jun; Fang, Min; Liu, Cui; Xiong, Wen-Jun

2013-09-01

Coriolis mass flowmeter (CMF) often suffers from two-phase flowrate which may cause flowtube stalling. To solve this problem, a digital drive method and a digital signal processing method of CMF is studied and implemented in this paper. A positive-negative step signal is used to initiate the flowtube oscillation without knowing the natural frequency of the flowtube. A digital zero-crossing detection method based on Lagrange interpolation is adopted to calculate the frequency and phase difference of the sensor output signals in order to synthesize the digital drive signal. The digital drive approach is implemented by a multiplying digital to analog converter (MDAC) and a direct digital synthesizer (DDS). A digital Coriolis mass flow transmitter is developed with a digital signal processor (DSP) to control the digital drive, and realize the signal processing. Water flow calibrations and gas-liquid two-phase flowrate experiments are conducted to examine the performance of the transmitter. The experimental results show that the transmitter shortens the start-up time and can maintain the oscillation of flowtube in two-phase flowrate condition. Copyright © 2013 ISA. Published by Elsevier Ltd. All rights reserved.

Performance evaluation of digital phase-locked loops for advanced deep space transponders

NASA Technical Reports Server (NTRS)

Nguyen, T. M.; Hinedi, S. M.; Yeh, H.-G.; Kyriacou, C.

1994-01-01

The performances of the digital phase-locked loops (DPLL's) for the advanced deep-space transponders (ADT's) are investigated. DPLL's considered in this article are derived from the analog phase-locked loop, which is currently employed by the NASA standard deep space transponder, using S-domain to Z-domain mapping techniques. Three mappings are used to develop digital approximations of the standard deep space analog phase-locked loop, namely the bilinear transformation (BT), impulse invariant transformation (IIT), and step invariant transformation (SIT) techniques. The performance in terms of the closed loop phase and magnitude responses, carrier tracking jitter, and response of the loop to the phase offset (the difference between in incoming phase and reference phase) is evaluated for each digital approximation. Theoretical results of the carrier tracking jitter for command-on and command-off cases are then validated by computer simulation. Both theoretical and computer simulation results show that at high sampling frequency, the DPLL's approximated by all three transformations have the same tracking jitter. However, at low sampling frequency, the digital approximation using BT outperforms the others. The minimum sampling frequency for adequate tracking performance is determined for each digital approximation of the analog loop. In addition, computer simulation shows that the DPLL developed by BT provides faster response to the phase offset than IIT and SIT.

3D fingerprint analysis using transmission-mode multi-wavelength digital holographic topography

NASA Astrophysics Data System (ADS)

Abeywickrema, Ujitha; Banerjee, Partha; Kota, Akash; Lakhtakia, Akhlesh; Swiontek, Stephen E.

2016-03-01

The analysis of fingerprints is important for biometric identification. Two-wavelength digital holographic interferometry is used to study the topography of various types of fingerprints. This topography depends on several conditions such as the temperature, time of the day, and the proportions of eccrine and sebaceous sweat. With two-wavelength holographic interferometry, surface information can be measured with a better accuracy compared to single-wavelength phase-retrieving techniques. Latent fingerprints on transparent glass, a forensically relevant substrate are first developed by the deposition of 50-1000-nm-thick columnar thin films, and then analyzed using the transmission-mode two-wavelength digital holographic technique. In this technique, a tunable Argon-ion laser (457.9 nm to 514.5 nm) is used and holograms are recorded on a CCD camera sequentially for several sets of two wavelengths. Then the phase is reconstructed for each wavelength, and the phase difference which corresponds to the synthetic wavelength (4 μm to 48 μm) is calculated. Finally, the topography is obtained by applying proper phase-unwrapping techniques to the phase difference. Interferometric setups that utilize light reflected from the surface of interest have several disadvantages such as the effect of multiple reflections as well as the effects of the tilt of the object and its shadow (for the Mach-Zehnder configuration). To overcome these drawbacks, digital holograms of fingerprints in a transmission geometry are used. An approximately in-line geometry employing a slightly tilted reference beam to facilitate separation of various diffraction orders during holographic reconstruction is employed.

Digital synchronization and communication techniques

NASA Technical Reports Server (NTRS)

Lindsey, William C.

1992-01-01

Information on digital synchronization and communication techniques is given in viewgraph form. Topics covered include phase shift keying, modems, characteristics of open loop digital synchronizers, an open loop phase and frequency estimator, and a digital receiver structure using an open loop estimator in a decision directed architecture.

A Digital Phase Lock Loop for an External Cavity Diode Laser

NASA Astrophysics Data System (ADS)

Wang, Xiao-Long; Tao, Tian-Jiong; Cheng, Bing; Wu, Bin; Xu, Yun-Fei; Wang, Zhao-Ying; Lin, Qiang

2011-08-01

A digital optical phase lock loop (OPLL) is implemented to synchronize the frequency and phase between two external cavity diode lasers (ECDL), generating Raman pulses for atom interferometry. The setup involves all-digital phase detection and a programmable digital proportional-integral-derivative (PID) loop in locking. The lock generates a narrow beat-note linewidth below 1 Hz and low phase-noise of 0.03rad2 between the master and slave ECDLs. The lock proves to be stable and robust, and all the locking parameters can be set and optimized on a computer interface with convenience, making the lock adaptable to various setups of laser systems.

A Synthetic Quadrature Phase Detector/Demodulator for Fourier Transform Transform Spectrometers

NASA Technical Reports Server (NTRS)

Campbell, Joel

2008-01-01

A method is developed to demodulate (velocity correct) Fourier transform spectrometer (FTS) data that is taken with an analog to digital converter that digitizes equally spaced in time. This method makes it possible to use simple low cost, high resolution audio digitizers to record high quality data without the need for an event timer or quadrature laser hardware, and makes it possible to use a metrology laser of any wavelength. The reduced parts count and simplicity implementation makes it an attractive alternative in space based applications when compared to previous methods such as the Brault algorithm.

A New Built-in Self Test Scheme for Phase-Locked Loops Using Internal Digital Signals

NASA Astrophysics Data System (ADS)

Kim, Youbean; Kim, Kicheol; Kim, Incheol; Kang, Sungho

Testing PLLs (phase-locked loops) is becoming an important issue that affects both time-to-market and production cost of electronic systems. Though a PLL is the most common mixed-signal building block, it is very difficult to test due to internal analog blocks and signals. In this paper, we propose a new PLL BIST (built-in self test) using the distorted frequency detector that uses only internal digital signals. The proposed BIST does not need to load any analog nodes of the PLL. Therefore, it provides an efficient defect-oriented structural test scheme, reduced area overhead, and improved test quality compared with previous approaches.

Coherent receiver design based on digital signal processing in optical high-speed intersatellite links with M-phase-shift keying

NASA Astrophysics Data System (ADS)

Schaefer, Semjon; Gregory, Mark; Rosenkranz, Werner

2016-11-01

We present simulative and experimental investigations of different coherent receiver designs for high-speed optical intersatellite links. We focus on frequency offset (FO) compensation in homodyne and intradyne detection systems. The considered laser communication terminal uses an optical phase-locked loop (OPLL), which ensures stable homodyne detection. However, the hardware complexity increases with the modulation order. Therefore, we show that software-based intradyne detection is an attractive alternative for OPLL-based homodyne systems. Our approach is based on digital FO and phase noise compensation, in order to achieve a more flexible coherent detection scheme. Analytic results will further show the theoretical impact of the different detection schemes on the receiver sensitivity. Finally, we compare the schemes in terms of bit error ratio measurements and optimal receiver design.

Behaviour of fractional loop delay zero crossing digital phase locked loop (FR-ZCDPLL)

NASA Astrophysics Data System (ADS)

Nasir, Qassim

2018-01-01

This article analyses the performance of the first-order zero crossing digital phase locked loops (FR-ZCDPLL) when fractional loop delay is added to loop. The non-linear dynamics of the loop is presented, analysed and examined through bifurcation behaviour. Numerical simulation of the loop is conducted to proof the mathematical analysis of the loop operation. The results of the loop simulation show that the proposed FR-ZCDPLL has enhanced the performance compared to the conventional zero crossing DPLL in terms of wider lock range, captured range and stable operation region. In addition, extensive experimental simulation was conducted to find the optimum loop parameters for different loop environmental conditions. The addition of the fractional loop delay network in the conventional loop also reduces the phase jitter and its variance especially when the signal-to-noise ratio is low.

THz holography in reflection using a high resolution microbolometer array.

PubMed

Zolliker, Peter; Hack, Erwin

2015-05-04

We demonstrate a digital holographic setup for Terahertz imaging of surfaces in reflection. The set-up is based on a high-power continuous wave (CW) THz laser and a high-resolution (640 × 480 pixel) bolometer detector array. Wave propagation to non-parallel planes is used to reconstruct the object surface that is rotated relative to the detector plane. In addition we implement synthetic aperture methods for resolution enhancement and compare Fourier transform phase retrieval to phase stepping methods. A lateral resolution of 200 μm and a relative phase sensitivity of about 0.4 rad corresponding to a depth resolution of 6 μm are estimated from reconstructed images of two specially prepared test targets, respectively. We highlight the use of digital THz holography for surface profilometry as well as its potential for video-rate imaging.

Hybrid network modeling and the effect of image resolution on digitally-obtained petrophysical and two-phase flow properties

NASA Astrophysics Data System (ADS)

Aghaei, A.

2017-12-01

Digital imaging and modeling of rocks and subsequent simulation of physical phenomena in digitally-constructed rock models are becoming an integral part of core analysis workflows. One of the inherent limitations of image-based analysis, at any given scale, is image resolution. This limitation becomes more evident when the rock has multiple scales of porosity such as in carbonates and tight sandstones. Multi-scale imaging and constructions of hybrid models that encompass images acquired at multiple scales and resolutions are proposed as a solution to this problem. In this study, we investigate the effect of image resolution and unresolved porosity on petrophysical and two-phase flow properties calculated based on images. A helical X-ray micro-CT scanner with a high cone-angle is used to acquire digital rock images that are free of geometric distortion. To remove subjectivity from the analyses, a semi-automated image processing technique is used to process and segment the acquired data into multiple phases. Direct and pore network based models are used to simulate physical phenomena and obtain absolute permeability, formation factor and two-phase flow properties such as relative permeability and capillary pressure. The effect of image resolution on each property is investigated. Finally a hybrid network model incorporating images at multiple resolutions is built and used for simulations. The results from the hybrid model are compared against results from the model built at the highest resolution and those from laboratory tests.

A gallium-arsenide digital phase shifter for clock and control signal distribution in high-speed digital systems

NASA Technical Reports Server (NTRS)

Fouts, Douglas J.

1992-01-01

The design, implementation, testing, and applications of a gallium-arsenide digital phase shifter and fan-out buffer are described. The integrated circuit provides a method for adjusting the phase of high-speed clock and control signals in digital systems, without the need for pruning cables, multiplexing between cables of different lengths, delay lines, or similar techniques. The phase of signals distributed with the described chip can be dynamically adjusted in eight different steps of approximately 60 ps per step. The IC also serves as a fan-out buffer and provides 12 in-phase outputs. The chip is useful for distributing high-speed clock and control signals in synchronous digital systems, especially if components are distributed over a large physical area or if there is a large number of components.

Digital Detection and Processing of Multiple Quadrature Harmonics for EPR Spectroscopy

PubMed Central

Ahmad, R.; Som, S.; Kesselring, E.; Kuppusamy, P.; Zweier, J.L.; Potter, L.C.

2010-01-01

A quadrature digital receiver and associated signal estimation procedure are reported for L-band electron paramagnetic resonance (EPR) spectroscopy. The approach provides simultaneous acquisition and joint processing of multiple harmonics in both in-phase and out-of-phase channels. The digital receiver, based on a high-speed dual-channel analog-to-digital converter, allows direct digital down-conversion with heterodyne processing using digital capture of the microwave reference signal. Thus, the receiver avoids noise and nonlinearity associated with analog mixers. Also, the architecture allows for low-Q anti-alias filtering and does not require the sampling frequency to be time-locked to the microwave reference. A noise model applicable for arbitrary contributions of oscillator phase noise is presented, and a corresponding maximum-likelihood estimator of unknown parameters is also reported. The signal processing is applicable for Lorentzian lineshape under nonsaturating conditions. The estimation is carried out using a convergent iterative algorithm capable of jointly processing the in-phase and out-of-phase data in the presence of phase noise and unknown microwave phase. Cramér-Rao bound analysis and simulation results demonstrate a significant reduction in linewidth estimation error using quadrature detection, for both low and high values of phase noise. EPR spectroscopic data are also reported for illustration. PMID:20971667

Digital detection and processing of multiple quadrature harmonics for EPR spectroscopy.

PubMed

Ahmad, R; Som, S; Kesselring, E; Kuppusamy, P; Zweier, J L; Potter, L C

2010-12-01

A quadrature digital receiver and associated signal estimation procedure are reported for L-band electron paramagnetic resonance (EPR) spectroscopy. The approach provides simultaneous acquisition and joint processing of multiple harmonics in both in-phase and out-of-phase channels. The digital receiver, based on a high-speed dual-channel analog-to-digital converter, allows direct digital down-conversion with heterodyne processing using digital capture of the microwave reference signal. Thus, the receiver avoids noise and nonlinearity associated with analog mixers. Also, the architecture allows for low-Q anti-alias filtering and does not require the sampling frequency to be time-locked to the microwave reference. A noise model applicable for arbitrary contributions of oscillator phase noise is presented, and a corresponding maximum-likelihood estimator of unknown parameters is also reported. The signal processing is applicable for Lorentzian lineshape under nonsaturating conditions. The estimation is carried out using a convergent iterative algorithm capable of jointly processing the in-phase and out-of-phase data in the presence of phase noise and unknown microwave phase. Cramér-Rao bound analysis and simulation results demonstrate a significant reduction in linewidth estimation error using quadrature detection, for both low and high values of phase noise. EPR spectroscopic data are also reported for illustration. Copyright © 2010 Elsevier Inc. All rights reserved.

A low jitter all - digital phase - locked loop in 180 nm CMOS technology

NASA Astrophysics Data System (ADS)

Shumkin, O. V.; Butuzov, V. A.; Normanov, D. D.; Ivanov, P. Yu

2016-02-01

An all-digital phase locked loop (ADPLL) was implemented in 180 nm CMOS technology. The proposed ADPLL uses a digitally controlled oscillator to achieve 3 ps resolution. The pure digital phase locked loop is attractive because it is less sensitive to noise and operating conditions than its analog counterpart. The proposed ADPLL can be easily applied to different process as a soft IP block, making it very suitable for system-on-chip applications.

A multi-frequency inverse-phase error compensation method for projector nonlinear in 3D shape measurement

NASA Astrophysics Data System (ADS)

Mao, Cuili; Lu, Rongsheng; Liu, Zhijian

2018-07-01

In fringe projection profilometry, the phase errors caused by the nonlinear intensity response of digital projectors needs to be correctly compensated. In this paper, a multi-frequency inverse-phase method is proposed. The theoretical model of periodical phase errors is analyzed. The periodical phase errors can be adaptively compensated in the wrapped maps by using a set of fringe patterns. The compensated phase is then unwrapped with multi-frequency method. Compared with conventional methods, the proposed method can greatly reduce the periodical phase error without calibrating measurement system. Some simulation and experimental results are presented to demonstrate the validity of the proposed approach.

In-line digital holography with phase-shifting Greek-ladder sieves

NASA Astrophysics Data System (ADS)

Xie, Jing; Zhang, Junyong; Zhang, Yanli; Zhou, Shenlei; Zhu, Jianqiang

2018-04-01

Phase shifting is the key technique in in-line digital holography, but traditional phase shifters have their own limitations in short wavelength regions. Here, phase-shifting Greek-ladder sieves with amplitude-only modulation are introduced into in-line digital holography, which are essentially a kind of diffraction lens with three-dimensional array diffraction-limited foci. In the in-line digital holographic experiment, we design two kinds of sieves by lithography and verify the validity of their phase-shifting function by measuring a 1951 U.S. Air Force resolution test target and three-dimensional array foci. With advantages of high resolving power, low cost, and no limitations at shorter wavelengths, phase-shifting Greek-ladder sieves have great potential in X-ray holography or biochemical microscopy for the next generation of synchrotron light sources.

An all-digital phase-locked loop demodulator based on FPGA

NASA Astrophysics Data System (ADS)

Gong, X. F.; Cui, Z. D.

2017-09-01

This paper studied the principle of analogue phase-locked loop demodulation and work process of digital phase-locked loop. It is found that the higher the reference signal frequency is, the smaller the duty ratio of the discriminator output signal is. Carrier detection is achieved by using this relationship. The experimental results indicate that the demodulator based on the principle could realize high-quality transmission of digital signals and could be an effective FM communication mode for studying wireless transmission of digital signals.

Digital signal processor and processing method for GPS receivers

NASA Technical Reports Server (NTRS)

Thomas, Jr., Jess B. (Inventor)

1989-01-01

A digital signal processor and processing method therefor for use in receivers of the NAVSTAR/GLOBAL POSITIONING SYSTEM (GPS) employs a digital carrier down-converter, digital code correlator and digital tracking processor. The digital carrier down-converter and code correlator consists of an all-digital, minimum bit implementation that utilizes digital chip and phase advancers, providing exceptional control and accuracy in feedback phase and in feedback delay. Roundoff and commensurability errors can be reduced to extremely small values (e.g., less than 100 nanochips and 100 nanocycles roundoff errors and 0.1 millichip and 1 millicycle commensurability errors). The digital tracking processor bases the fast feedback for phase and for group delay in the C/A, P.sub.1, and P.sub.2 channels on the L.sub.1 C/A carrier phase thereby maintaining lock at lower signal-to-noise ratios, reducing errors in feedback delays, reducing the frequency of cycle slips and in some cases obviating the need for quadrature processing in the P channels. Simple and reliable methods are employed for data bit synchronization, data bit removal and cycle counting. Improved precision in averaged output delay values is provided by carrier-aided data-compression techniques. The signal processor employs purely digital operations in the sense that exactly the same carrier phase and group delay measurements are obtained, to the last decimal place, every time the same sampled data (i.e., exactly the same bits) are processed.

Precision digital pulse phase generator

DOEpatents

McEwan, T.E.

1996-10-08

A timing generator comprises a crystal oscillator connected to provide an output reference pulse. A resistor-capacitor combination is connected to provide a variable-delay output pulse from an input connected to the crystal oscillator. A phase monitor is connected to provide duty-cycle representations of the reference and variable-delay output pulse phase. An operational amplifier drives a control voltage to the resistor-capacitor combination according to currents integrated from the phase monitor and injected into summing junctions. A digital-to-analog converter injects a control current into the summing junctions according to an input digital control code. A servo equilibrium results that provides a phase delay of the variable-delay output pulse to the output reference pulse that linearly depends on the input digital control code. 2 figs.

Precision digital pulse phase generator

DOEpatents

McEwan, Thomas E.

1996-01-01

A timing generator comprises a crystal oscillator connected to provide an output reference pulse. A resistor-capacitor combination is connected to provide a variable-delay output pulse from an input connected to the crystal oscillator. A phase monitor is connected to provide duty-cycle representations of the reference and variable-delay output pulse phase. An operational amplifier drives a control voltage to the resistor-capacitor combination according to currents integrated from the phase monitor and injected into summing junctions. A digital-to-analog converter injects a control current into the summing junctions according to an input digital control code. A servo equilibrium results that provides a phase delay of the variable-delay output pulse to the output reference pulse that linearly depends on the input digital control code.

Analysis of first and second order binary quantized digital phase-locked loops for ideal and white Gaussian noise inputs

NASA Technical Reports Server (NTRS)

Blasche, P. R.

1980-01-01

Specific configurations of first and second order all digital phase locked loops are analyzed for both ideal and additive white gaussian noise inputs. In addition, a design for a hardware digital phase locked loop capable of either first or second order operation is presented along with appropriate experimental data obtained from testing of the hardware loop. All parameters chosen for the analysis and the design of the digital phase locked loop are consistent with an application to an Omega navigation receiver although neither the analysis nor the design are limited to this application.

Optimum design of hybrid phase locked loops

NASA Technical Reports Server (NTRS)

Lee, P.; Yan, T.

1981-01-01

The design procedure of phase locked loops is described in which the analog loop filter is replaced by a digital computer. Specific design curves are given for the step and ramp input changes in phase. It is shown that the designed digital filter depends explicitly on the product of the sampling time and the noise bandwidth of the phase locked loop. This technique of optimization can be applied to the design of digital analog loops for other applications.

Digital signal processing in the radio science stability analyzer

NASA Technical Reports Server (NTRS)

Greenhall, C. A.

1995-01-01

The Telecommunications Division has built a stability analyzer for testing Deep Space Network installations during flight radio science experiments. The low-frequency part of the analyzer operates by digitizing wave signals with bandwidths between 80 Hz and 45 kHz. Processed outputs include spectra of signal, phase, amplitude, and differential phase; time series of the same quantities; and Allan deviation of phase and differential phase. This article documents the digital signal-processing methods programmed into the analyzer.

Phase retrieval in digital speckle pattern interferometry by application of two-dimensional active contours called snakes.

PubMed

Federico, Alejandro; Kaufmann, Guillermo H

2006-03-20

We propose a novel approach to retrieving the phase map coded by a single closed-fringe pattern in digital speckle pattern interferometry, which is based on the estimation of the local sign of the quadrature component. We obtain the estimate by calculating the local orientation of the fringes that have previously been denoised by a weighted smoothing spline method. We carry out the procedure of sign estimation by determining the local abrupt jumps of size pi in the orientation field of the fringes and by segmenting the regions defined by these jumps. The segmentation method is based on the application of two-dimensional active contours (snakes), with which one can also estimate absent jumps, i.e., those that cannot be detected from the local orientation of the fringes. The performance of the proposed phase-retrieval technique is evaluated for synthetic and experimental fringes and compared with the results obtained with the spiral-phase- and Fourier-transform methods.

Digital lock-in amplifier based on soundcard interface for physics laboratory

NASA Astrophysics Data System (ADS)

Sinlapanuntakul, J.; Kijamnajsuk, P.; Jetjamnong, C.; Chotikaprakhan, S.

2017-09-01

The purpose of this paper is to develop a digital lock-in amplifier based on soundcard interface for undergraduate physics laboratory. Both series and parallel RLC circuit laboratory are tested because of its well-known, easy to understand and simple confirm. The sinusoidal signal at the frequency of 10 Hz - 15 kHz is generated to the circuits. The amplitude and phase of the voltage drop across the resistor, R are measured in 10 step decade. The signals from soundcard interface and lock-in amplifier are compared. The results give a good correlation. It indicates that the design digital lock-in amplifier is promising for undergraduate physic laboratory.

FPGA implementation of digital down converter using CORDIC algorithm

NASA Astrophysics Data System (ADS)

Agarwal, Ashok; Lakshmi, Boppana

2013-01-01

In radio receivers, Digital Down Converters (DDC) are used to translate the signal from Intermediate Frequency level to baseband. It also decimates the oversampled signal to a lower sample rate, eliminating the need of a high end digital signal processors. In this paper we have implemented architecture for DDC employing CORDIC algorithm, which down converts an IF signal of 70MHz (3G) to 200 KHz baseband GSM signal, with an SFDR greater than 100dB. The implemented architecture reduces the hardware resource requirements by 15 percent when compared with other architecture available in the literature due to elimination of explicit multipliers and a quadrature phase shifter for mixing.

Interferenceless coded aperture correlation holography-a new technique for recording incoherent digital holograms without two-wave interference.

PubMed

Vijayakumar, A; Rosen, Joseph

2017-06-12

Recording digital holograms without wave interference simplifies the optical systems, increases their power efficiency and avoids complicated aligning procedures. We propose and demonstrate a new technique of digital hologram acquisition without two-wave interference. Incoherent light emitted from an object propagates through a random-like coded phase mask and recorded directly without interference by a digital camera. In the training stage of the system, a point spread hologram (PSH) is first recorded by modulating the light diffracted from a point object by the coded phase masks. At least two different masks should be used to record two different intensity distributions at all possible axial locations. The various recorded patterns at every axial location are superposed in the computer to obtain a complex valued PSH library cataloged to its axial location. Following the training stage, an object is placed within the axial boundaries of the PSH library and the light diffracted from the object is once again modulated by the same phase masks. The intensity patterns are recorded and superposed exactly as the PSH to yield a complex hologram of the object. The object information at any particular plane is reconstructed by a cross-correlation between the complex valued hologram and the appropriate element of the PSH library. The characteristics and the performance of the proposed system were compared with an equivalent regular imaging system.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fielding, E.J.; Barazangi, M.; Isacks, B.L.

Topography and heterogeneous crustal structure have major effects on the propagation of regional seismic phases. We are collecting topographical, geological, and geophysical datasets for Eurasia into an information system that can be accessed via Internet connections. Now available are digital topography, satellite imagery, and data on sedimentary basins and crustal structure thicknesses. New datasets for Eurasia include maps of depth to Moho beneath Europe and Scandinavia. We have created regularly spaced grids of the crustal thickness values from these maps that can be used to create profiles of crustal structure. These profiles can be compared by an analyst or anmore » automatic program with the crustal seismic phases received along the propagation path to better understand and predict the path effects on phase amplitudes, a key to estimating magnitudes and yields, and for understanding variations in travel-time delays for phases such as Pn, important for improving regional event locations. The gridded data could also be used to model propagation of crustal phases in three dimensions. Digital elevation models, Satellite imagery, Geographic information systems, Lg Propagation, Moho, Geology, Crustal structure, Topographic relief.« less

Low data rate digital space communications

NASA Technical Reports Server (NTRS)

Chen, C. H.

1973-01-01

The low available transmitter power and the large frequency uncertainty constrain the data rate to be low. An all-digital communication receiver is proposed, and its feasibility is established. Although coherent systems should be used whenever practical, the noncoherent MFSK system is more suitable for very low data rates. The effect of Rician fading on the performance of MFSK receiver is studied. Fading characteristics of the Venus channel are examined based on the exponential model and available experimental data on the Venus atmosphere. Because of the requirement of high communication efficiency, three codes are evaluated and compared. The rapidly varying phase error at low data rate has great effects on the tracking loop behaviors which are examined by extensive computer study of the phase plane trajectories.

An all digital phase locked loop for synchronization of a sinusoidal signal embedded in white Gaussian noise

NASA Technical Reports Server (NTRS)

Reddy, C. P.; Gupta, S. C.

1973-01-01

An all digital phase locked loop which tracks the phase of the incoming sinusoidal signal once per carrier cycle is proposed. The different elements and their functions and the phase lock operation are explained in detail. The nonlinear difference equations which govern the operation of the digital loop when the incoming signal is embedded in white Gaussian noise are derived, and a suitable model is specified. The performance of the digital loop is considered for the synchronization of a sinusoidal signal. For this, the noise term is suitably modelled which allows specification of the output probabilities for the two level quantizer in the loop at any given phase error. The loop filter considered increases the probability of proper phase correction. The phase error states in modulo two-pi forms a finite state Markov chain which enables the calculation of steady state probabilities, RMS phase error, transient response and mean time for cycle skipping.

Binary phase locked loops for Omega receivers

NASA Technical Reports Server (NTRS)

Chamberlin, K.

1974-01-01

An all-digital phase lock loop (PLL) is considered because of a number of problems inherent in an employment of analog PLL. The digital PLL design presented solves these problems. A single loop measures all eight Omega time slots. Memory-aiding leads to the name of this design, the memory-aided phase lock loop (MAPLL). Basic operating principles are discussed and the superiority of MAPLL over the conventional digital phase lock loop with regard to the operational efficiency for Omega applications is demonstrated.

All optical coherent receiver for self-homodyne detection of digitally phase modulated optical signals

NASA Astrophysics Data System (ADS)

Kiasaleh, Kamran

1994-02-01

A novel optical phase-locked loop (OPLL) system for the self-homodyne detection of digitally phase modulated optical signals is introduced. A Mach-Zehnder type interferometer is used to self-homodyne binary phase-modulated optical signals with an external phase modulator inserted in the control arm of the interferometer.

Optical Security System Based on the Biometrics Using Holographic Storage Technique with a Simple Data Format

NASA Astrophysics Data System (ADS)

Jun, An Won

2006-01-01

We implement a first practical holographic security system using electrical biometrics that combines optical encryption and digital holographic memory technologies. Optical information for identification includes a picture of face, a name, and a fingerprint, which has been spatially multiplexed by random phase mask used for a decryption key. For decryption in our biometric security system, a bit-error-detection method that compares the digital bit of live fingerprint with of fingerprint information extracted from hologram is used.

Digital forensics: an analytical crime scene procedure model (ACSPM).

PubMed

Bulbul, Halil Ibrahim; Yavuzcan, H Guclu; Ozel, Mesut

2013-12-10

In order to ensure that digital evidence is collected, preserved, examined, or transferred in a manner safeguarding the accuracy and reliability of the evidence, law enforcement and digital forensic units must establish and maintain an effective quality assurance system. The very first part of this system is standard operating procedures (SOP's) and/or models, conforming chain of custody requirements, those rely on digital forensics "process-phase-procedure-task-subtask" sequence. An acceptable and thorough Digital Forensics (DF) process depends on the sequential DF phases, and each phase depends on sequential DF procedures, respectively each procedure depends on tasks and subtasks. There are numerous amounts of DF Process Models that define DF phases in the literature, but no DF model that defines the phase-based sequential procedures for crime scene identified. An analytical crime scene procedure model (ACSPM) that we suggest in this paper is supposed to fill in this gap. The proposed analytical procedure model for digital investigations at a crime scene is developed and defined for crime scene practitioners; with main focus on crime scene digital forensic procedures, other than that of whole digital investigation process and phases that ends up in a court. When reviewing the relevant literature and interrogating with the law enforcement agencies, only device based charts specific to a particular device and/or more general perspective approaches to digital evidence management models from crime scene to courts are found. After analyzing the needs of law enforcement organizations and realizing the absence of crime scene digital investigation procedure model for crime scene activities we decided to inspect the relevant literature in an analytical way. The outcome of this inspection is our suggested model explained here, which is supposed to provide guidance for thorough and secure implementation of digital forensic procedures at a crime scene. In digital forensic investigations each case is unique and needs special examination, it is not possible to cover every aspect of crime scene digital forensics, but the proposed procedure model is supposed to be a general guideline for practitioners. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Simultaneous Transmit and Receive Performance of an 8-channel Digital Phased Array

DTIC Science & Technology

2017-01-16

Lincoln Laboratory Lexington, Massachusetts, USA Abstract—The Aperture- Level Simultaneous Transmit and Re- ceive (ALSTAR) architecture enables extremely...In [1], the Aperture- Level Simultaneous Transmit and Receive (ALSTAR) architecture was proposed for achieving STAR using a fully digital phased array...Aperture- Level Simultaneous Transmit and Receive (ALSTAR) architecture enables STAR functionality in a digital phased array without the use of specialized

Focusing light inside dynamic scattering media with millisecond digital optical phase conjugation (Conference Presentation)

NASA Astrophysics Data System (ADS)

Liu, Yan; Ma, Cheng; Shen, Yuecheng; Wang, Lihong V.

2017-02-01

Optical phase conjugation based wavefront shaping techniques are being actively developed to focus light through or inside scattering media such as biological tissue, and they promise to revolutionize optical imaging, manipulation, and therapy. The speed of digital optical phase conjugation (DOPC) has been limited by the low speeds of cameras and spatial light modulators (SLMs), preventing DOPC from being applied to thick living tissue. Recently, a fast DOPC system was developed based on a single-shot wavefront measurement method, a field programmable gate array (FPGA) for data processing, and a digital micromirror device (DMD) for fast modulation. However, this system has the following limitations. First, the reported single-shot wavefront measurement method does not work when our goal is to focus light inside, instead of through, scattering media. Second, the DMD performed binary amplitude modulation, which resulted in a lower focusing contrast compared with that of phase modulations. Third, the optical fluence threshold causing DMDs to malfunction under pulsed laser illumination is lower than that of liquid crystal based SLMs, and the system alignment is significantly complicated by the oblique reflection angle of the DMD. Here, we developed a simple but high-speed DOPC system using a ferroelectric liquid crystal based SLM (512 × 512 pixels), and focused light through three diffusers within 4.7 ms. Using focused-ultrasound-guided DOPC along with a double exposure scheme, we focused light inside a scattering medium containing two diffusers within 7.7 ms, thus achieving the fastest digital time-reversed ultrasonically encoded (TRUE) optical focusing to date.

A finite state machine read-out chip for integrated surface acoustic wave sensors

NASA Astrophysics Data System (ADS)

Rakshit, Sambarta; Iliadis, Agis A.

2015-01-01

A finite state machine based integrated sensor circuit suitable for the read-out module of a monolithically integrated SAW sensor on Si is reported. The primary sensor closed loop consists of a voltage controlled oscillator (VCO), a peak detecting comparator, a finite state machine (FSM), and a monolithically integrated SAW sensor device. The output of the system oscillates within a narrow voltage range that correlates with the SAW pass-band response. The period of oscillation is of the order of the SAW phase delay. We use timing information from the FSM to convert SAW phase delay to an on-chip 10 bit digital output operating on the principle of time to digital conversion (TDC). The control inputs of this digital conversion block are generated by a second finite state machine operating under a divided system clock. The average output varies with changes in SAW center frequency, thus tracking mass sensing events in real time. Based on measured VCO gain of 16 MHz/V our system will convert a 10 kHz SAW frequency shift to a corresponding mean voltage shift of 0.7 mV. A corresponding shift in phase delay is converted to a one or two bit shift in the TDC output code. The system can handle alternate SAW center frequencies and group delays simply by adjusting the VCO control and TDC delay control inputs. Because of frequency to voltage and phase to digital conversion, this topology does not require external frequency counter setups and is uniquely suitable for full monolithic integration of autonomous sensor systems and tags.

Digital Phase-Locked Loop With Phase And Frequency Feedback

NASA Technical Reports Server (NTRS)

Thomas, J. Brooks

1991-01-01

Advanced design for digital phase-lock loop (DPLL) allows loop gains higher than those used in other designs. Divided into two major components: counterrotation processor and tracking processor. Notable features include use of both phase and rate-of-change-of-phase feedback instead of frequency feedback alone, normalized sine phase extractor, improved method for extracting measured phase, and improved method for "compressing" output rate.

Implementation and extension of the impulse transfer function method for future application to the space shuttle project. Volume 2: Program description and user's guide

NASA Technical Reports Server (NTRS)

Patterson, G.

1973-01-01

The data processing procedures and the computer programs were developed to predict structural responses using the Impulse Transfer Function (ITF) method. There are three major steps in the process: (1) analog-to-digital (A-D) conversion of the test data to produce Phase I digital tapes (2) processing of the Phase I digital tapes to extract ITF's and storing them in a permanent data bank, and (3) predicting structural responses to a set of applied loads. The analog to digital conversion is performed by a standard package which will be described later in terms of the contents of the resulting Phase I digital tape. Two separate computer programs have been developed to perform the digital processing.

Analysis of an all-digital maximum likelihood carrier phase and clock timing synchronizer for eight phase-shift keying modulation

NASA Astrophysics Data System (ADS)

Degaudenzi, Riccardo; Vanghi, Vieri

1994-02-01

In all-digital Trellis-Coded 8PSK (TC-8PSK) demodulator well suited for VLSI implementation, including maximum likelihood estimation decision-directed (MLE-DD) carrier phase and clock timing recovery, is introduced and analyzed. By simply removing the trellis decoder the demodulator can efficiently cope with uncoded 8PSK signals. The proposed MLE-DD synchronization algorithm requires one sample for the phase and two samples per symbol for the timing loop. The joint phase and timing discriminator characteristics are analytically derived and numerical results checked by means of computer simulations. An approximated expression for steady-state carrier phase and clock timing mean square error has been derived and successfully checked with simulation findings. Synchronizer deviation from the Cramer Rao bound is also discussed. Mean acquisition time for the digital synchronizer has also been computed and checked, using the Monte Carlo simulation technique. Finally, TC-8PSK digital demodulator performance in terms of bit error rate and mean time to lose lock, including digital interpolators and synchronization loops, is presented.

Digital interactive learning of oral radiographic anatomy.

PubMed

Vuchkova, J; Maybury, T; Farah, C S

2012-02-01

Studies reporting high number of diagnostic errors made from radiographs suggest the need to improve the learning of radiographic interpretation in the dental curriculum. Given studies that show student preference for computer-assisted or digital technologies, the purpose of this study was to develop an interactive digital tool and to determine whether it was more successful than a conventional radiology textbook in assisting dental students with the learning of radiographic anatomy. Eighty-eight dental students underwent a learning phase of radiographic anatomy using an interactive digital tool alongside a conventional radiology textbook. The success of the digital tool, when compared to the textbook, was assessed by quantitative means using a radiographic interpretation test and by qualitative means using a structured Likert scale survey, asking students to evaluate their own learning outcomes from the digital tool. Student evaluations of the digital tool showed that almost all participants (95%) indicated that the tool positively enhanced their learning of radiographic anatomy and interpretation. The success of the digital tool in assisting the learning of radiographic interpretation is discussed in the broader context of learning and teaching curricula, and preference (by students) for the use of this digital form when compared to the conventional literate form of the textbook. Whilst traditional textbooks are still valued in the dental curriculum, it is evident that the preference for computer-assisted learning of oral radiographic anatomy enhances the learning experience by enabling students to interact and better engage with the course material. © 2011 John Wiley & Sons A/S.

All-digital GPS receiver mechanization

NASA Astrophysics Data System (ADS)

Ould, P. C.; van Wechel, R. J.

The paper describes the all-digital baseband correlation processing of GPS signals, which is characterized by (1) a potential for improved antijamming performance, (2) fast acquisition by a digital matched filter, (3) reduction of adjustment, (4) increased system reliability, and (5) provision of a basis for the realization of a high degree of VLSI potential for the development of small economical GPS sets. The basic technical approach consists of a broadband fix-tuned RF converter followed by a digitizer; digital-matched-filter acquisition section; phase- and delay-lock tracking via baseband digital correlation; software acquisition logic and loop filter implementation; and all-digital implementation of the feedback numerical controlled oscillators and code generator. Broadband in-phase and quadrature tracking is performed by an arctangent angle detector followed by a phase-unwrapping algorithm that eliminates false locks induced by sampling and data bit transitions, and yields a wide pull-in frequency range approaching one-fourth of the loop iteration frequency.

Deformation analysis of MEMS structures by modified digital moiré methods

NASA Astrophysics Data System (ADS)

Liu, Zhanwei; Lou, Xinhao; Gao, Jianxin

2010-11-01

Quantitative deformation analysis of micro-fabricated electromechanical systems is of importance for the design and functional control of microsystems. In this paper, two modified digital moiré processing methods, Gaussian blurring algorithm combined with digital phase shifting and geometrical phase analysis (GPA) technique based on digital moiré method, are developed to quantitatively analyse the deformation behaviour of micro-electro-mechanical system (MEMS) structures. Measuring principles and experimental procedures of the two methods are described in detail. A digital moiré fringe pattern is generated by superimposing a specimen grating etched directly on a microstructure surface with a digital reference grating (DRG). Most of the grating noise is removed from the digital moiré fringes, which enables the phase distribution of the moiré fringes to be obtained directly. Strain measurement result of a MEMS structure demonstrates the feasibility of the two methods.

Lossless and lossy compression of quantitative phase images of red blood cells obtained by digital holographic imaging.

PubMed

Jaferzadeh, Keyvan; Gholami, Samaneh; Moon, Inkyu

2016-12-20

In this paper, we evaluate lossless and lossy compression techniques to compress quantitative phase images of red blood cells (RBCs) obtained by an off-axis digital holographic microscopy (DHM). The RBC phase images are numerically reconstructed from their digital holograms and are stored in 16-bit unsigned integer format. In the case of lossless compression, predictive coding of JPEG lossless (JPEG-LS), JPEG2000, and JP3D are evaluated, and compression ratio (CR) and complexity (compression time) are compared against each other. It turns out that JP2k can outperform other methods by having the best CR. In the lossy case, JP2k and JP3D with different CRs are examined. Because some data is lost in a lossy way, the degradation level is measured by comparing different morphological and biochemical parameters of RBC before and after compression. Morphological parameters are volume, surface area, RBC diameter, sphericity index, and the biochemical cell parameter is mean corpuscular hemoglobin (MCH). Experimental results show that JP2k outperforms JP3D not only in terms of mean square error (MSE) when CR increases, but also in compression time in the lossy compression way. In addition, our compression results with both algorithms demonstrate that with high CR values the three-dimensional profile of RBC can be preserved and morphological and biochemical parameters can still be within the range of reported values.

An investigation comparing traditional recitation instruction to computer tutorials which combine three-dimensional animation with varying levels of visual complexity, including digital video in teaching various chemistry topics

NASA Astrophysics Data System (ADS)

Graves, A. Palmer

This study examines the effect of increasing the visual complexity used in computer assisted instruction in general chemistry. Traditional recitation instruction was used as a control for the experiment. One tutorial presented a chemistry topic using 3-D animation showing molecular activity and symbolic representation of the macroscopic view of a chemical phenomenon. A second tutorial presented the same topic but simultaneously presented students with a digital video movie showing the phenomena and 3-D animation showing the molecular view of the phenomena. This experimental set-up was used in two different experiments during the first semester of college level general chemistry course. The topics covered were the molecular effect of heating water through the solid-liquid phase change and the kinetic molecular theory used in explaining pressure changes. The subjects used in the experiment were 236 college students enrolled in a freshman chemistry course at a large university. The data indicated that the simultaneous presentation of digital video, showing the solid to liquid phase change of water, with a molecular animation, showing the molecular behavior during the phase change, had a significant effect on student particulate understanding when compared to traditional recitation. Although the effect of the KMT tutorial was not statistically significant, there was a positive effect on student particulate understanding. The use of computer tutorial also had a significant effect on student attitude toward their comprehension of the lesson.

SNR Degradation in Undersampled Phase Measurement Systems

PubMed Central

Salido-Monzú, David; Meca-Meca, Francisco J.; Martín-Gorostiza, Ernesto; Lázaro-Galilea, José L.

2016-01-01

A wide range of measuring applications rely on phase estimation on sinusoidal signals. These systems, where the estimation is mainly implemented in the digital domain, can generally benefit from the use of undersampling to reduce the digitizer and subsequent digital processing requirements. This may be crucial when the application characteristics necessarily imply a simple and inexpensive sensor. However, practical limitations related to the phase stability of the band-pass filter prior digitization establish restrictions to the reduction of noise bandwidth. Due to this, the undersampling intensity is practically defined by noise aliasing, taking into account the amount of signal-to-noise ratio (SNR) reduction caused by it considering the application accuracy requirements. This work analyzes the relationship between undersampling frequency and SNR reduction, conditioned by the stability requirements of the filter that defines the noise bandwidth before digitization. The effect of undersampling is quantified in a practical situation where phase differences are measured by in-phase and quadrature (I/Q) demodulation for an infrared ranging application. PMID:27783033

An all digital phase locked loop for FM demodulation.

NASA Technical Reports Server (NTRS)

Greco, J.; Garodnick, J.; Schilling, D. L.

1972-01-01

A phase-locked loop designed with all-digital circuitry which avoids certain problems, and a digital voltage controlled oscillator algorithm are described. The system operates synchronously and performs all required digital calculations within one sampling period, thereby performing as a real-time special-purpose computer. The SNR ratio is computed for frequency offsets and sinusoidal modulation, and experimental results verify the theoretical calculations.

The Setup Phase of Project Open Book: A Report to the Commission on Preservation and Access on the Status of an Effort to Convert Microfilm to Digital Imagery.

ERIC Educational Resources Information Center

Conway, Paul; Weaver, Shari

1994-01-01

This report documents the second phase of Yale University's Project Open Book, which explored the uses of digital technology for preservation of and access to deteriorating documents. Highlights include preconditions for project implementation; quality digital conversion; characteristics of source materials; digital document indexing; workflow…

The performance and limitations of FPGA-based digital servos for atomic, molecular, and optical physics experiments

NASA Astrophysics Data System (ADS)

Yu, Shi Jing; Fajeau, Emma; Liu, Lin Qiao; Jones, David J.; Madison, Kirk W.

2018-02-01

In this work, we address the advantages, limitations, and technical subtleties of employing field programmable gate array (FPGA)-based digital servos for high-bandwidth feedback control of lasers in atomic, molecular, and optical physics experiments. Specifically, we provide the results of benchmark performance tests in experimental setups including noise, bandwidth, and dynamic range for two digital servos built with low and mid-range priced FPGA development platforms. The digital servo results are compared to results obtained from a commercially available state-of-the-art analog servo using the same plant for control (intensity stabilization). The digital servos have feedback bandwidths of 2.5 MHz, limited by the total signal latency, and we demonstrate improvements beyond the transfer function offered by the analog servo including a three-pole filter and a two-pole filter with phase compensation to suppress resonances. We also discuss limitations of our FPGA-servo implementation and general considerations when designing and using digital servos.

The performance and limitations of FPGA-based digital servos for atomic, molecular, and optical physics experiments.

PubMed

Yu, Shi Jing; Fajeau, Emma; Liu, Lin Qiao; Jones, David J; Madison, Kirk W

2018-02-01

In this work, we address the advantages, limitations, and technical subtleties of employing field programmable gate array (FPGA)-based digital servos for high-bandwidth feedback control of lasers in atomic, molecular, and optical physics experiments. Specifically, we provide the results of benchmark performance tests in experimental setups including noise, bandwidth, and dynamic range for two digital servos built with low and mid-range priced FPGA development platforms. The digital servo results are compared to results obtained from a commercially available state-of-the-art analog servo using the same plant for control (intensity stabilization). The digital servos have feedback bandwidths of 2.5 MHz, limited by the total signal latency, and we demonstrate improvements beyond the transfer function offered by the analog servo including a three-pole filter and a two-pole filter with phase compensation to suppress resonances. We also discuss limitations of our FPGA-servo implementation and general considerations when designing and using digital servos.

From Geocentrism to Allocentrism: Teaching the Phases of the Moon in a Digital Full-Dome Planetarium

NASA Astrophysics Data System (ADS)

Chastenay, Pierre

2016-02-01

An increasing number of planetariums worldwide are turning digital, using ultra-fast computers, powerful graphic cards, and high-resolution video projectors to create highly realistic astronomical imagery in real time. This modern technology makes it so that the audience can observe astronomical phenomena from a geocentric as well as an allocentric perspective (the view from space). While the dome creates a sense of immersion, the digital planetarium introduces a new way to teach astronomy, especially for topics that are inherently three-dimensional and where seeing the phenomenon from different points of view is essential. Like a virtual-reality environment, an immersive digital planetarium helps learners create a more scientifically accurate visualization of astronomical phenomena. In this study, a digital planetarium was used to teach the phases of the Moon to children aged 12 to 14. To fully grasp the lunar phases, one must imagine the spherical Moon (as perceived from space), revolving around the Earth while being illuminated by the Sun, and then reconcile this view with the geocentric perspective. Digital planetariums allow learners to have both an allocentric and a geocentric perspective on the lunar phases. Using a Design experiment approach, we tested an educational scenario in which the lunar phases were taught in an allocentric digital planetarium. Based on qualitative data collected before, during, and after the planetarium intervention, we were able to demonstrate that five out of six participants had a better understanding of the lunar phases after the planetarium session.

A digitally implemented phase-locked loop detection scheme for analysis of the phase and power stability of a calibration tone

NASA Technical Reports Server (NTRS)

Densmore, A. C.

1988-01-01

A digital phase-locked loop (PLL) scheme is described which detects the phase and power of a high SNR calibration tone. The digital PLL is implemented in software directly from the given description. It was used to evaluate the stability of the Goldstone Deep Space Station open loop receivers for Radio Science. Included is a derivative of the Allan variance sensitivity of the PLL imposed by additive white Gaussian noise; a lower limit is placed on the carrier frequency.

Fast, optically controlled Kerr phase shifter for digital signal processing.

PubMed

Li, R B; Deng, L; Hagley, E W; Payne, M G; Bienfang, J C; Levine, Z H

2013-05-01

We demonstrate an optically controlled Kerr phase shifter using a room-temperature 85Rb vapor operating in a Raman gain scheme. Phase shifts from zero to π relative to an unshifted reference wave are observed, and gated operations are demonstrated. We further demonstrate the versatile digital manipulation of encoded signal light with an encoded phase-control light field using an unbalanced Mach-Zehnder interferometer. Generalizations of this scheme should be capable of full manipulation of a digitized signal field at high speed, opening the door to future applications.

Digital Receiver Phase Meter

NASA Technical Reports Server (NTRS)

Marcin, Martin; Abramovici, Alexander

2008-01-01

The software of a commercially available digital radio receiver has been modified to make the receiver function as a two-channel low-noise phase meter. This phase meter is a prototype in the continuing development of a phase meter for a system in which radiofrequency (RF) signals in the two channels would be outputs of a spaceborne heterodyne laser interferometer for detecting gravitational waves. The frequencies of the signals could include a common Doppler-shift component of as much as 15 MHz. The phase meter is required to measure the relative phases of the signals in the two channels at a sampling rate of 10 Hz at a root power spectral density <5 microcycle/(Hz)1/2 and to be capable of determining the power spectral density of the phase difference over the frequency range from 1 mHz to 1 Hz. Such a phase meter could also be used on Earth to perform similar measurements in laser metrology of moving bodies. To illustrate part of the principle of operation of the phase meter, the figure includes a simplified block diagram of a basic singlechannel digital receiver. The input RF signal is first fed to the input terminal of an analog-to-digital converter (ADC). To prevent aliasing errors in the ADC, the sampling rate must be at least twice the input signal frequency. The sampling rate of the ADC is governed by a sampling clock, which also drives a digital local oscillator (DLO), which is a direct digital frequency synthesizer. The DLO produces samples of sine and cosine signals at a programmed tuning frequency. The sine and cosine samples are mixed with (that is, multiplied by) the samples from the ADC, then low-pass filtered to obtain in-phase (I) and quadrature (Q) signal components. A digital signal processor (DSP) computes the ratio between the Q and I components, computes the phase of the RF signal (relative to that of the DLO signal) as the arctangent of this ratio, and then averages successive such phase values over a time interval specified by the user.

Real time flight simulation methodology

NASA Technical Reports Server (NTRS)

Parrish, E. A.; Cook, G.; Mcvey, E. S.

1976-01-01

An example sensitivity study is presented to demonstrate how a digital autopilot designer could make a decision on minimum sampling rate for computer specification. It consists of comparing the simulated step response of an existing analog autopilot and its associated aircraft dynamics to the digital version operating at various sampling frequencies and specifying a sampling frequency that results in an acceptable change in relative stability. In general, the zero order hold introduces phase lag which will increase overshoot and settling time. It should be noted that this solution is for substituting a digital autopilot for a continuous autopilot. A complete redesign could result in results which more closely resemble the continuous results or which conform better to original design goals.

Common-path digital holographic microscopy based on a beam displacer unit

NASA Astrophysics Data System (ADS)

Di, Jianglei; Zhang, Jiwei; Song, Yu; Wang, Kaiqiang; Wei, Kun; Zhao, Jianlin

2018-02-01

Digital holographic microscopy (DHM) has become a novel tool with advantages of full field, non-destructive, high-resolution and 3D imaging, which captures the quantitative amplitude and phase information of microscopic specimens. It's a well-established method for digital recording and numerical reconstructing the full complex field of wavefront of the samples with a diffraction-limited lateral resolution down to 0.3 μm depending on the numerical aperture of microscope objective. Meanwhile, its axial resolution through axial direction is less than 10 nm due to the interferometric nature in phase imaging. Compared with the typical optical configurations such as Mach-Zehnder interferometer and Michelson interferometer, the common-path DHM has the advantages of simple and compact configuration, high stability, and so on. Here, a simple, compact, and low-cost common-path DHM based on a beam displacer unit is proposed for quantitative phase imaging of biological cells. The beam displacer unit is completely compatible with commercial microscope and can be easily set up in the output port of the microscope as a compact independent device. This technique can be used to achieve the quantitative phase measurement of biological cells with an excellent temporal stability of 0.51 nm, which makes it having a good prospect in the fields of biological and medical science. Living mouse osteoblastic cells are quantitatively measured with the system to demonstrate its capability and applicability.

Fringe pattern demodulation with a two-frame digital phase-locked loop algorithm.

PubMed

Gdeisat, Munther A; Burton, David R; Lalor, Michael J

2002-09-10

A novel technique called a two-frame digital phase-locked loop for fringe pattern demodulation is presented. In this scheme, two fringe patterns with different spatial carrier frequencies are grabbed for an object. A digital phase-locked loop algorithm tracks and demodulates the phase difference between both fringe patterns by employing the wrapped phase components of one of the fringe patterns as a reference to demodulate the second fringe pattern. The desired phase information can be extracted from the demodulated phase difference. We tested the algorithm experimentally using real fringe patterns. The technique is shown to be suitable for noncontact measurement of objects with rapid surface variations, and it outperforms the Fourier fringe analysis technique in this aspect. Phase maps produced withthis algorithm are noisy in comparison with phase maps generated with the Fourier fringe analysis technique.

Programmable rate modem utilizing digital signal processing techniques

NASA Technical Reports Server (NTRS)

Naveh, Arad

1992-01-01

The need for a Programmable Rate Digital Satellite Modem capable of supporting both burst and continuous transmission modes with either Binary Phase Shift Keying (BPSK) or Quadrature Phase Shift Keying (QPSK) modulation is discussed. The preferred implementation technique is an all digital one which utilizes as much digital signal processing (DSP) as possible. The design trade-offs in each portion of the modulator and demodulator subsystem are outlined.

A tunable, double-wavelength heterodyne detection interferometer with frequency-locked diode-pumped Nd:YAG sources for absolute measurements

NASA Astrophysics Data System (ADS)

Gelmini, E.; Minoni, U.; Docchio, F.

1995-08-01

A double heterodyne interferometric instrument using a tunable synthetic wavelength for the absolute measurements of distance and position is presented. The optical synthetic wavelength is generated by a pair of PZT-tunable diode-pumped Nd:YAG lasers operating at 1.064 μm. Based on a closed-loop scheme, a suitable electronic circuit has been developed to implement the frequency locking of the two lasers. A digital frequency comparator provides an error signal, used to control the slave laser, by comparing the laser beat frequency to a reference oscillator. Demodulation of the superheterodyne signals is obtained by a rf detector followed by low-pass filtering. Distance measurements are obtained by a digital phase meter gauging the phase difference between the demodulated signals from a measuring interferometer and from a reference interferometer. The paper presents the optical and the electronic layouts of the instrument as well as experimental results from a laboratory prototype.

New spatial diversity equalizer based on PLL

NASA Astrophysics Data System (ADS)

Rao, Wei

2011-10-01

A new Spatial Diversity Equalizer (SDE) based on phase-locked loop (PLL) is proposed to overcome the inter-symbol interference (ISI) and phase rotations simultaneously in the digital communication system. The proposed SDE consists of equal gain combining technique based on a famous blind equalization algorithm constant modulus algorithm (CMA) and a PLL. Compared with conventional SDE, the proposed SDE has not only faster convergence rate and lower residual error but also the ability to recover carrier phase rotation. The efficiency of the method is proved by computer simulation.

Receiver concepts for data transmission at 10 microns

NASA Astrophysics Data System (ADS)

Scholtz, A. L.; Philipp, H. K.; Leeb, W. R.

1984-05-01

Receivers for digitally modulated CO2 laser signals are compared. Incoherent heterodyne receivers and coherent homodyne setups, including the linear phase locked loop (PLL) receiver, the low intermediate frequency translation loop, and the Costas loop receiver were studied. Experiments covered the homodyne systems, emphasizing the linear PLL receiver. Reliable phase lock of the receiver is achieved at carrier levels as low as 3 nW. Reception of signals phase shift keyed with a data rate of up to 150 Mbit/sec is demonstrated at subnanowatt sideband power levels.

Polarization microscopy by use of digital holography: application to optical-fiber birefringence measurements.

PubMed

Colomb, Tristan; Dürr, Florian; Cuche, Etienne; Marquet, Pierre; Limberger, Hans G; Salathé, René-Paul; Depeursinge, Christian

2005-07-20

We present a digital holographic microscope that permits one to image polarization state. This technique results from the coupling of digital holographic microscopy and polarization digital holography. The interference between two orthogonally polarized reference waves and the wave transmitted by a microscopic sample, magnified by a microscope objective, is recorded on a CCD camera. The off-axis geometry permits one to reconstruct separately from this single hologram two wavefronts that are used to image the object-wave Jones vector. We applied this technique to image the birefringence of a bent fiber. To evaluate the precision of the phase-difference measurement, the birefringence induced by internal stress in an optical fiber is measured and compared to the birefringence profile captured by a standard method, which had been developed to obtain high-resolution birefringence profiles of optical fibers.

Hybrid Analog/Digital Receiver

NASA Technical Reports Server (NTRS)

Brown, D. H.; Hurd, W. J.

1989-01-01

Advanced hybrid analog/digital receiver processes intermediate-frequency (IF) signals carrying digital data in form of phase modulation. Uses IF sampling and digital phase-locked loops to track carrier and subcarrier signals and to synchronize data symbols. Consists of three modules: IF assembly, signal-processing assembly, and test-signal assembly. Intended for use in Deep Space Network, but presumably basic design modified for such terrestrial uses as communications or laboratory instrumentation where signals weak and/or noise strong.

Pupillary dilation as an index of task demands.

PubMed

Cabestrero, Raúl; Crespo, Antonio; Quirós, Pilar

2009-12-01

To analyze how pupillary responses reflect mental effort and allocation of processing resources under several load conditions, the pupil diameter of 18 participants was recorded during an auditory digit-span recall task under three load conditions: Low (5 digits), Moderate (8 digits), and Overload (11 digits). In previous research, under all load conditions a significant linear enlargement in pupil diameter was observed as each digit was presented. Significant dilations from the end of the presentation phase to the beginning of the recall phase were also observed but only under low and moderate loads. Contrary to previous research, under the Overload condition, no reduction in pupil diameter was observed when resource limits were exceeded; however, a plateau was observed when the ninth digit was presented until the beginning of the recall phase. Overall, pupillometric data seem to indicate that participants may keep processing actively even though resources are exceeded.

Analog quadrature signal to phase angle data conversion by a quadrature digitizer and quadrature counter

DOEpatents

Buchenauer, C.J.

1981-09-23

The quadrature phase angle phi (t) of a pair of quadrature signals S/sub 1/(t) and S/sub 2/(t) is digitally encoded on a real time basis by a quadrature digitizer for fractional phi (t) rotational excursions and by a quadrature up/down counter for full phi (t) rotations. The pair of quadrature signals are of the form S/sub 1/(t) = k(t) sin phi (t) and S/sub 2/(t) = k(t) cos phi (t) where k(t) is a signal common to both. The quadrature digitizer and the quadrature up/down counter may be used together or singularly as desired or required. Optionally, a digital-to-analog converter may follow the outputs of the quadrature digitizer and the quadrature up/down counter to provide an analog signal output of the quadrature phase angle phi (t).

Analog quadrature signal to phase angle data conversion by a quadrature digitizer and quadrature counter

DOEpatents

Buchenauer, C. Jerald

1984-01-01

The quadrature phase angle .phi.(t) of a pair of quadrature signals S.sub.1 (t) and S.sub.2 (t) is digitally encoded on a real time basis by a quadrature digitizer for fractional .phi.(t) rotational excursions and by a quadrature up/down counter for full .phi.(t) rotations. The pair of quadrature signals are of the form S.sub.1 (t)=k(t) sin .phi.(t) and S.sub.2 (t)=k(t) cos .phi.(t) where k(t) is a signal common to both. The quadrature digitizer and the quadrature up/down counter may be used together or singularly as desired or required. Optionally, a digital-to-analog converter may follow the outputs of the quadrature digitizer and the quadrature up/down counter to provide an analog signal output of the quadrature phase angle .phi.(t).

Phase-locked loops. [analog, hybrid, discrete and digital systems

NASA Technical Reports Server (NTRS)

Gupta, S. C.

1974-01-01

The basic analysis and design procedures are described for the realization of analog phase-locked loops (APLL), hybrid phase-locked loops (HPLL), discrete phase-locked loops, and digital phase-locked loops (DPLL). Basic configurations are diagrammed, and performance curves are given. A discrete communications model is derived and developed. The use of the APLL as an optimum angle demodulator and the Kalman-Bucy approach to APLL design are discussed. The literature in the area of phase-locked loops is reviewed, and an extensive bibliography is given. Although the design of APLLs is fairly well documented, work on discrete, hybrid, and digital PLLs is scattered, and more will have to be done in the future to pinpoint the formal design of DPLLs.

Investigation of air transportation technology at Ohio University, 1980. [general aviation aircraft and navigation aids

NASA Technical Reports Server (NTRS)

Mcfarland, R. H.

1981-01-01

Specific configurations of first and second order all digital phase locked loops were analyzed for both ideal and additive gaussian noise inputs. In addition, a design for a hardware digital phase locked loop capable of either first or second order operation was evaluated along with appropriate experimental data obtained from testing of the hardware loop. All parameters chosen for the analysis and the design of the digital phase locked loop were consistent with an application to an Omega navigation receiver although neither the analysis nor the design are limited to this application. For all cases tested, the experimental data showed close agreement with the analytical results indicating that the Markov chain model for first and second order digital phase locked loops are valid.

3D motion picture of transparent gas flow by parallel phase-shifting digital holography

NASA Astrophysics Data System (ADS)

Awatsuji, Yasuhiro; Fukuda, Takahito; Wang, Yexin; Xia, Peng; Kakue, Takashi; Nishio, Kenzo; Matoba, Osamu

2018-03-01

Parallel phase-shifting digital holography is a technique capable of recording three-dimensional (3D) motion picture of dynamic object, quantitatively. This technique can record single hologram of an object with an image sensor having a phase-shift array device and reconstructs the instantaneous 3D image of the object with a computer. In this technique, a single hologram in which the multiple holograms required for phase-shifting digital holography are multiplexed by using space-division multiplexing technique pixel by pixel. We demonstrate 3D motion picture of dynamic and transparent gas flow recorded and reconstructed by the technique. A compressed air duster was used to generate the gas flow. A motion picture of the hologram of the gas flow was recorded at 180,000 frames/s by parallel phase-shifting digital holography. The phase motion picture of the gas flow was reconstructed from the motion picture of the hologram. The Abel inversion was applied to the phase motion picture and then the 3D motion picture of the gas flow was obtained.

Loran digital phase-locked loop and RF front-end system error analysis

NASA Technical Reports Server (NTRS)

Mccall, D. L.

1979-01-01

An analysis of the system performance of the digital phase locked loops (DPLL) and RF front end that are implemented in the MINI-L4 Loran receiver is presented. Three of the four experiments deal with the performance of the digital phase locked loops. The other experiment deals with the RF front end and DPLL system error which arise in the front end due to poor signal to noise ratios. The ability of the DPLLs to track the offsets is studied.

Background field removal technique based on non-regularized variable kernels sophisticated harmonic artifact reduction for phase data for quantitative susceptibility mapping.

PubMed

Kan, Hirohito; Arai, Nobuyuki; Takizawa, Masahiro; Omori, Kazuyoshi; Kasai, Harumasa; Kunitomo, Hiroshi; Hirose, Yasujiro; Shibamoto, Yuta

2018-06-11

We developed a non-regularized, variable kernel, sophisticated harmonic artifact reduction for phase data (NR-VSHARP) method to accurately estimate local tissue fields without regularization for quantitative susceptibility mapping (QSM). We then used a digital brain phantom to evaluate the accuracy of the NR-VSHARP method, and compared it with the VSHARP and iterative spherical mean value (iSMV) methods through in vivo human brain experiments. Our proposed NR-VSHARP method, which uses variable spherical mean value (SMV) kernels, minimizes L2 norms only within the volume of interest to reduce phase errors and save cortical information without regularization. In a numerical phantom study, relative local field and susceptibility map errors were determined using NR-VSHARP, VSHARP, and iSMV. Additionally, various background field elimination methods were used to image the human brain. In a numerical phantom study, the use of NR-VSHARP considerably reduced the relative local field and susceptibility map errors throughout a digital whole brain phantom, compared with VSHARP and iSMV. In the in vivo experiment, the NR-VSHARP-estimated local field could sufficiently achieve minimal boundary losses and phase error suppression throughout the brain. Moreover, the susceptibility map generated using NR-VSHARP minimized the occurrence of streaking artifacts caused by insufficient background field removal. Our proposed NR-VSHARP method yields minimal boundary losses and highly precise phase data. Our results suggest that this technique may facilitate high-quality QSM. Copyright © 2017. Published by Elsevier Inc.

Monitoring of live cell cultures during apoptosis by phase imaging and Raman spectroscopy

NASA Astrophysics Data System (ADS)

Sharikova, Anna; Saide, George; Sfakis, Lauren; Park, Jun Yong; Desta, Habben; Maloney, Maxwell C.; Castracane, James; Mahajan, Supriya D.; Khmaladze, Alexander

2017-02-01

Non-invasive live cell measurements are an important tool in biomedical research. We present a combined digital holography/Raman spectroscopy technique to study live cell cultures during apoptosis. Digital holographic microscopy records an interference pattern between object and reference waves, so that the computationally reconstructed holographic image contains both amplitude and phase information about the sample. When the phase is mapped across the sample and converted into height information for each pixel, a three dimensional image is obtained. The measurement of live cell cultures by digital holographic microscopy yields information about cell shape and volume, changes to which are reflective of alterations in cell cycle and initiation of cell death mechanisms. Raman spectroscopy, on the other hand, is sensitive to rotational and vibrational molecular transitions, as well as intermolecular vibrations. Therefore, Raman spectroscopy provides complementary information about cells, such as protein, lipid and nucleic acid content, and, particularly, the spectral signatures associated with structural changes in molecules. The cell cultures are kept in the temperature-controlled environmental chamber during the experiment, which allows monitoring over multiple cell cycles. The DHM system combines a visible (red) laser source with conventional microscope base, and LabVIEW-run data processing. We analyzed and compared cell culture information obtained by these two methods.

Performance Analysis of Digital Tracking Loops for Telemetry Ranging Applications

NASA Astrophysics Data System (ADS)

Vilnrotter, V.; Hamkins, J.; Xie, H.; Ashrafi, S.

2015-08-01

In this article, we analyze mathematical models of digital loops used to track the phase and timing of communications and navigation signals. The limits on the accuracy of phase and timing estimates play a critical role in the accuracy achievable in telemetry ranging applications. We describe in detail a practical algorithm to compute the loop parameters for discrete update (DU) and continuous update (CU) loop formulations, and we show that a simple power-series approximation to the DU model is valid over a large range of time-bandwidth product . Several numerical examples compare the estimation error variance of the DU and CU models to each other and to Cramer-Rao lower bounds. Finally, the results are applied to the problem of ranging, by evaluating the performance of a phase-locked loop designed to track a typical ambiguity-resolving pseudonoise (PN) code received and demodulated at the spacecraft on the uplink part of the two-way ranging link, and a data transition tracking loop (DTTL) on the downlink part.

A comparison of methods for DPLL loop filter design

NASA Technical Reports Server (NTRS)

Aguirre, S.; Hurd, W. J.; Kumar, R.; Statman, J.

1986-01-01

Four design methodologies for loop filters for a class of digital phase-locked loops (DPLLs) are presented. The first design maps an optimum analog filter into the digital domain; the second approach designs a filter that minimizes in discrete time weighted combination of the variance of the phase error due to noise and the sum square of the deterministic phase error component; the third method uses Kalman filter estimation theory to design a filter composed of a least squares fading memory estimator and a predictor. The last design relies on classical theory, including rules for the design of compensators. Linear analysis is used throughout the article to compare different designs, and includes stability, steady state performance and transient behavior of the loops. Design methodology is not critical when the loop update rate can be made high relative to loop bandwidth, as the performance approaches that of continuous time. For low update rates, however, the miminization method is significantly superior to the other methods.

The digital phase-locked loop as a near-optimum FM demodulator.

NASA Technical Reports Server (NTRS)

Kelly, C. N.; Gupta, S. C.

1972-01-01

This paper presents an approach to the optimum digital demodulation of a continuous-time FM signal using stochastic estimation theory. The primary result is a digital phase-locked loop realization possessing performance characteristics that approach those of the analog counterpart. Some practical considerations are presented and simulation results for a first-order message model are presented.

Digital Resource Exchange About Music (DREAM): Phase 2 Usability Testing

ERIC Educational Resources Information Center

Upitis, Rena; Boese, Karen; Abrami, Philip C.; Anwar, Zaeem

2015-01-01

The Digital Resource Exchange About Music (DREAM) is a virtual space for exchanging information about digital learning tools. The purpose of the present study was to determine how users responded to DREAM in the first four months after its public release. This study is the second phase of usability research on DREAM, and was conducted to guide…

Influence of sample preparation and identification of subcelluar structures in quantitative holographic phase contrast microscopy

NASA Astrophysics Data System (ADS)

Kemper, Björn; Schmidt, Lisa; Przibilla, Sabine; Rommel, Christina; Vollmer, Angelika; Ketelhut, Steffi; Schnekenburger, Jürgen; von Bally, Gert

2010-04-01

Digital holographic microscopy (DHM) provides label-free quantitative phase contrast with low demands on sample preparation. Nevertheless, for DHM measurements on fixed cells the mounting medium has to be considered while the phase contrast of living cells may be influenced by the used buffer solution. To quantify these effects, the maximum cell caused phase contrast and the visibility of the nucleoli were analyzed. A second aim of the study was to identify subcellular components in DHM phase contrast images. Therefore, comparative investigations using bright field imaging, DHM and fluorescence microscopy with 4',6- Diamidino-2-phenylindol (DAPI) staining were performed. DAPI-staining visualizes cell components containing DNA. The obtained results demonstrate exemplarily for two tumor cell lines that from DHM phase contrast images of fixed cells in phosphate buffer saline (PBS) cell thickness values are obtained which are comparable to living cells. Furthermore, it is shown that in many cases nucleus components can be identified only by DHM phase contrast.

Cognitive performance in adolescents with Delayed Sleep-Wake Phase Disorder: Treatment effects and a comparison with good sleepers.

PubMed

Richardson, C; Micic, G; Cain, N; Bartel, K; Maddock, B; Gradisar, M

2018-06-01

The present study aimed to investigate whether Australian adolescents with Delayed Sleep-Wake Phase Disorder have impaired cognitive performance and whether chronobiological treatment for Delayed Sleep-Wake Phase Disorder improves adolescents' sleep, daytime functioning and cognitive performance. Adolescents with Delayed Sleep-Wake Phase Disorder (mean = 15.68 ± 2.1 y, 62% f) reported significantly later sleep timing (d = 1.03-1.45), less total sleep time (d = 0.82) and greater daytime sleepiness (d = 2.66), fatigue (d = 0.63) and impairment (d = 2.41), compared to good sleeping adolescents (mean = 15.9 ± 2.4 y, 75% f). However, there were no significant between-group differences (all p > 0.05) in performance on the Operation Span (ηp 2  = 0.043), Digit Span (forwards: ηp 2  = 0.002, backwards: ηp 2  = 0.003), Letter Number Sequencing (ηp 2  < 0.001) (working memory) and Digit-Symbol Substitution Tasks (ηp 2  = 0.010) (processing speed). Adolescents with Delayed Sleep-Wake Phase Disorder went on to receive 3 weeks of light therapy. At 3 months post-treatment, adolescents with Delayed Sleep-Wake Phase Disorder reported significantly advanced sleep timing (d = 0.56-0.65), greater total sleep time (d = 0.52) and improved daytime sleepiness (d = 1.33), fatigue (d = 0.84) and impairment (d = 0.78). Performance on the Operation Span (d = 0.46), Letter Number Sequencing (d = 0.45) and Digit-Symbol Substitution tasks (d = 0.57) also significantly improved. Copyright © 2018. Published by Elsevier Ltd.

Digital second-order phase-locked loop

NASA Technical Reports Server (NTRS)

Holmes, J. K.; Carl, C. C.; Tagnelia, C. R.

1975-01-01

Actual tests with second-order digital phase-locked loop at simulated relative Doppler shift of 1x0.0001 produced phase lock with timing error of 6.5 deg and no appreciable Doppler bias. Loop thus appears to achieve subcarrier synchronization and to remove bias due to Doppler shift in range of interest.

High-speed single-pixel digital holography

NASA Astrophysics Data System (ADS)

González, Humberto; Martínez-León, Lluís.; Soldevila, Fernando; Araiza-Esquivel, Ma.; Tajahuerce, Enrique; Lancis, Jesús

2017-06-01

The complete phase and amplitude information of biological specimens can be easily determined by phase-shifting digital holography. Spatial light modulators (SLMs) based on liquid crystal technology, with a frame-rate around 60 Hz, have been employed in digital holography. In contrast, digital micro-mirror devices (DMDs) can reach frame rates up to 22 kHz. A method proposed by Lee to design computer generated holograms (CGHs) permits the use of such binary amplitude modulators as phase-modulation devices. Single-pixel imaging techniques record images by sampling the object with a sequence of micro-structured light patterns and using a simple photodetector. Our group has reported some approaches combining single-pixel imaging and phase-shifting digital holography. In this communication, we review these techniques and present the possibility of a high-speed single-pixel phase-shifting digital holography system with phase-encoded illumination. This system is based on a Mach-Zehnder interferometer, with a DMD acting as the modulator for projecting the sampling patterns on the object and also being used for phase-shifting. The proposed sampling functions are phaseencoded Hadamard patterns generated through a Lee hologram approach. The method allows the recording of the complex amplitude distribution of an object at high speed on account of the high frame rates of the DMD. Reconstruction may take just a few seconds. Besides, the optical setup is envisaged as a true adaptive system, which is able to measure the aberration induced by the optical system in the absence of a sample object, and then to compensate the wavefront in the phasemodulation stage.

Advanced Receiver For Phase-Shift-Keyed Signals

NASA Technical Reports Server (NTRS)

Hinedi, Sami M.

1992-01-01

ARX II is second "breadboard" version of advanced receiver, a hybrid digital/analog receiving subsystem, extracting symbols and Doppler shifts from weak phase-shift-keyed signals. Useful in terrestrial digital communication systems.

BPSK Demodulation Using Digital Signal Processing

NASA Technical Reports Server (NTRS)

Garcia, Thomas R.

1996-01-01

A digital communications signal is a sinusoidal waveform that is modified by a binary (digital) information signal. The sinusoidal waveform is called the carrier. The carrier may be modified in amplitude, frequency, phase, or a combination of these. In this project a binary phase shift keyed (BPSK) signal is the communication signal. In a BPSK signal the phase of the carrier is set to one of two states, 180 degrees apart, by a binary (i.e., 1 or 0) information signal. A digital signal is a sampled version of a "real world" time continuous signal. The digital signal is generated by sampling the continuous signal at discrete points in time. The rate at which the signal is sampled is called the sampling rate (f(s)). The device that performs this operation is called an analog-to-digital (A/D) converter or a digitizer. The digital signal is composed of the sequence of individual values of the sampled BPSK signal. Digital signal processing (DSP) is the modification of the digital signal by mathematical operations. A device that performs this processing is called a digital signal processor. After processing, the digital signal may then be converted back to an analog signal using a digital-to-analog (D/A) converter. The goal of this project is to develop a system that will recover the digital information from a BPSK signal using DSP techniques. The project is broken down into the following steps: (1) Development of the algorithms required to demodulate the BPSK signal; (2) Simulation of the system; and (3) Implementation a BPSK receiver using digital signal processing hardware.

Phase-lock-loop application for fiber optic receiver

NASA Astrophysics Data System (ADS)

Ruggles, Stephen L.; Wills, Robert W.

1991-02-01

Phase-locked loop circuits are frequently employed in communication systems. In recent years, digital phase-locked loop circuits were utilized in optical communications systems. In an optical transceiver system, the digital phase-locked loop circuit is connected to the output of the receiver to extract a clock signal from the received coded data (NRZ, Bi-Phase, or Manchester). The clock signal is then used to reconstruct or recover the original data from the coded data. A theoretical approach to the design of a digital phase-locked loop circuit operation at 1 and 50 MHz is described. Hardware implementation of a breadboard design to function at 1 MHz and a printed-circuit board designed to function at 50 MHz were assembled using emitter coupled logic (ECL) to verify experimentally the theoretical design.

Phase-lock-loop application for fiber optic receiver

NASA Technical Reports Server (NTRS)

Ruggles, Stephen L.; Wills, Robert W.

1991-01-01

Phase-locked loop circuits are frequently employed in communication systems. In recent years, digital phase-locked loop circuits were utilized in optical communications systems. In an optical transceiver system, the digital phase-locked loop circuit is connected to the output of the receiver to extract a clock signal from the received coded data (NRZ, Bi-Phase, or Manchester). The clock signal is then used to reconstruct or recover the original data from the coded data. A theoretical approach to the design of a digital phase-locked loop circuit operation at 1 and 50 MHz is described. Hardware implementation of a breadboard design to function at 1 MHz and a printed-circuit board designed to function at 50 MHz were assembled using emitter coupled logic (ECL) to verify experimentally the theoretical design.

Quantification of Vocal Fold Vibration in Various Laryngeal Disorders Using High-Speed Digital Imaging.

PubMed

Yamauchi, Akihito; Yokonishi, Hisayuki; Imagawa, Hiroshi; Sakakibara, Ken-Ichi; Nito, Takaharu; Tayama, Niro; Yamasoba, Tatsuya

2016-03-01

To quantify vibratory characteristics of various laryngeal disorders seen by high-speed digital imaging (HSDI). HSDI was performed on 78 patients with various laryngeal disorders (20 with polyp, 16 with carcinoma, 13 with leukoplakia, 6 with vocal fold nodule, and 33 with others) and 29 vocally healthy subjects. Obtained data were quantitatively evaluated by frame-by-frame analysis, laryngotopography, digital kymography, and glottal area waveform. Overall, patients with laryngeal pathologies showed greater asymmetry in amplitude, mucosal wave and phase, smaller mucosal wave, and poorer glottal closure than vocally healthy subjects. Furthermore, disease-specific vibratory disturbances that generally agreed with the findings in the literature were quantified: comparing polyp with nodule, differences were noted in longitudinal phase difference, amplitude, and mucosal wave. In comparison with leukoplakia and cancer, nonvibrating area was more frequently noted in cancer. The HSDI analysis of various voice disorders using multiple methods can help phonosurgeons to properly diagnose various laryngeal pathologies and to estimate the degree of their vocal disturbances. Copyright © 2016 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

Improving Estimates Of Phase Parameters When Amplitude Fluctuates

NASA Technical Reports Server (NTRS)

Vilnrotter, V. A.; Brown, D. H.; Hurd, W. J.

1989-01-01

Adaptive inverse filter applied to incoming signal and noise. Time-varying inverse-filtering technique developed to improve digital estimate of phase of received carrier signal. Intended for use where received signal fluctuates in amplitude as well as in phase and signal tracked by digital phase-locked loop that keeps its phase error much smaller than 1 radian. Useful in navigation systems, reception of time- and frequency-standard signals, and possibly spread-spectrum communication systems.

Controlled-Root Approach To Digital Phase-Locked Loops

NASA Technical Reports Server (NTRS)

Stephens, Scott A.; Thomas, J. Brooks

1995-01-01

Performance tailored more flexibly and directly to satisfy design requirements. Controlled-root approach improved method for analysis and design of digital phase-locked loops (DPLLs). Developed rigorously from first principles for fully digital loops, making DPLL theory and design simpler and more straightforward (particularly for third- or fourth-order DPLL) and controlling performance more accurately in case of high gain.

Digital tanlock loop architecture with no delay

NASA Astrophysics Data System (ADS)

Al-Kharji AL-Ali, Omar; Anani, Nader; Al-Araji, Saleh; Al-Qutayri, Mahmoud; Ponnapalli, Prasad

2012-02-01

This article proposes a new architecture for a digital tanlock loop which eliminates the time-delay block. The ? (rad) phase shift relationship between the two channels, which is generated by the delay block in the conventional time-delay digital tanlock loop (TDTL), is preserved using two quadrature sampling signals for the loop channels. The proposed system outperformed the original TDTL architecture, when both systems were tested with frequency shift keying input signal. The new system demonstrated better linearity and acquisition speed as well as improved noise performance compared with the original TDTL architecture. Furthermore, the removal of the time-delay block enables all processing to be digitally performed, which reduces the implementation complexity. Both the original TDTL and the new architecture without the delay block were modelled and simulated using MATLAB/Simulink. Implementation issues, including complexity and relation to simulation of both architectures, are also addressed.

Designing Estimator/Predictor Digital Phase-Locked Loops

NASA Technical Reports Server (NTRS)

Statman, J. I.; Hurd, W. J.

1988-01-01

Signal delays in equipment compensated automatically. New approach to design of digital phase-locked loop (DPLL) incorporates concepts from estimation theory and involves decomposition of closed-loop transfer function into estimator and predictor. Estimator provides recursive estimates of phase, frequency, and higher order derivatives of phase with respect to time, while predictor compensates for delay, called "transport lag," caused by PLL equipment and by DPLL computations.

Coherent-Phase Monitoring Of Cavitation In Turbomachines

NASA Technical Reports Server (NTRS)

Jong, Jen-Yi

1996-01-01

Digital electronic signal-processing system analyzes outputs of accelerometers mounted on turbomachine to detect vibrations characteristic of cavitation. Designed to overcome limitation imposed by interference from discrete components. System digitally implements technique called "coherent-phase wide-band demodulation" (CPWBD), using phase-only (PO) filtering along envelope detection to search for unique coherent-phase relationship associated with cavitation and to minimize influence of large-amplitude discrete components.

Radar wideband digital beamforming based on time delay and phase compensation

NASA Astrophysics Data System (ADS)

Fu, Wei; Jiang, Defu

2018-07-01

In conventional phased array radars, analogue time delay devices and phase shifters have been used for wideband beamforming. These methods suffer from insertion losses, gain mismatches and delay variations, and they occupy a large chip area. To solve these problems, a compact architecture of digital array antennas based on subarrays was considered. In this study, the receiving beam patterns of wideband linear frequency modulation (LFM) signals were constructed by applying analogue stretch processing via mixing with delayed reference signals at the subarray level. Subsequently, narrowband digital time delaying and phase compensation of the tone signals were implemented with reduced arithmetic complexity. Due to the differences in amplitudes, phases and time delays between channels, severe performance degradation of the beam patterns occurred without corrections. To achieve good beamforming performance, array calibration was performed in each channel to adjust the amplitude, frequency and phase of the tone signal. Using a field-programmable gate array, wideband LFM signals and finite impulse response filters with continuously adjustable time delays were implemented in a polyphase structure. Simulations and experiments verified the feasibility and effectiveness of the proposed digital beamformer.

Field-programmable beam reconfiguring based on digitally-controlled coding metasurface

NASA Astrophysics Data System (ADS)

Wan, Xiang; Qi, Mei Qing; Chen, Tian Yi; Cui, Tie Jun

2016-02-01

Digital phase shifters have been applied in traditional phased array antennas to realize beam steering. However, the phase shifter deals with the phase of the induced current; hence, it has to be in the path of each element of the antenna array, making the phased array antennas very expensive. Metamaterials and/or metasurfaces enable the direct modulation of electromagnetic waves by designing subwavelength structures, which opens a new way to control the beam scanning. Here, we present a direct digital mechanism to control the scattered electromagnetic waves using coding metasurface, in which each unit cell loads a pin diode to produce binary coding states of “1” and “0”. Through data lines, the instant communications are established between the coding metasurface and the internal memory of field-programmable gate arrays (FPGA). Thus, we realize the digital modulation of electromagnetic waves, from which we present the field-programmable reflective antenna with good measurement performance. The proposed mechanism and functional device have great application potential in new-concept radar and communication systems.

All-digital phase-locked loop with 50-cycle lock time suitable for high-performance microprocessors

NASA Astrophysics Data System (ADS)

Dunning, Jim; Garcia, Gerald; Lundberg, Jim; Nuckolls, Ed

1995-04-01

A frequency-synthesizing, all-digital phase-locked loop (ADPLL) is fully integrated with a 0.5 micron CMOS microprocessor. The ADPLL has a 50-cycle phase lock, has a gain mechanism independent of process, voltage, and temperature, and is immune to input jitter. A digitally-controlled oscillator (DCO) forms the core of the ADPLL and operates from 50 to 550 MHz, running at 4x the reference clock frequency. The DCO has 16 b of binarily weighted control and achieves LSB resolution under 500 fs.

Highly integrated digital electronic control: Digital flight control, aircraft model identification, and adaptive engine control

NASA Technical Reports Server (NTRS)

Baer-Riedhart, Jennifer L.; Landy, Robert J.

1987-01-01

The highly integrated digital electronic control (HIDEC) program at NASA Ames Research Center, Dryden Flight Research Facility is a multiphase flight research program to quantify the benefits of promising integrated control systems. McDonnell Aircraft Company is the prime contractor, with United Technologies Pratt and Whitney Aircraft, and Lear Siegler Incorporated as major subcontractors. The NASA F-15A testbed aircraft was modified by the HIDEC program by installing a digital electronic flight control system (DEFCS) and replacing the standard F100 (Arab 3) engines with F100 engine model derivative (EMD) engines equipped with digital electronic engine controls (DEEC), and integrating the DEEC's and DEFCS. The modified aircraft provides the capability for testing many integrated control modes involving the flight controls, engine controls, and inlet controls. This paper focuses on the first two phases of the HIDEC program, which are the digital flight control system/aircraft model identification (DEFCS/AMI) phase and the adaptive engine control system (ADECS) phase.

User Requirements Analysis For Digital Library Application Using Quality Function Deployment.

NASA Astrophysics Data System (ADS)

Wulandari, Lily; Sularto, Lana; Yusnitasari, Tristyanti; Ikasari, Diana

2017-03-01

This study attemp to build Smart Digital Library to be used by the wider community wherever they are. The system is built in the form of Smart Digital Library portal which uses semantic similarity method (Semantic Similarity) to search journals, articles or books by title or author name. This method is also used to determine the recommended books to be read by visitors of Smart Digital Library based on testimony from a previous reader automatically. Steps being taken in the development of Smart Digital Library system is the analysis phase, design phase, testing and implementation phase. At this stage of the analysis using WebQual for the preparation of the instruments to be distributed to the respondents and the data obtained from the respondents will be processed using Quality Function Deployment. In the analysis phase has the purpose of identifying consumer needs and technical requirements. The analysis was performed to a digital library on the web digital library Gunadarma University, Bogor Institute of Agriculture, University of Indonesia, etc. The questionnaire was distributed to 200 respondents. The research methodology begins with the collection of user requirements and analyse it using QFD. Application design is funded by the government through a program of Featured Universities Research by the Directorate General of Higher Education (DIKTI). Conclusions from this research are identified which include the Consumer Requirements of digital library application. The elements of the consumers requirements consists of 13 elements and 25 elements of Engineering Characteristics digital library requirements. Therefore the design of digital library applications that will be built, is designed according to the findings by eliminating features that are not needed by restaurant based on QFD House of Quality.

Using digital inline holographic microscopy and quantitative phase contrast imaging to assess viability of cultured mammalian cells

NASA Astrophysics Data System (ADS)

Missan, Sergey; Hrytsenko, Olga

2015-03-01

Digital inline holographic microscopy was used to record holograms of mammalian cells (HEK293, B16, and E0771) in culture. The holograms have been reconstructed using Octopus software (4Deep inwater imaging) and phase shift maps were unwrapped using the FFT-based phase unwrapping algorithm. The unwrapped phase shifts were used to determine the maximum phase shifts in individual cells. Addition of 0.5 mM H2O2 to cell media produced rapid rounding of cultured cells, followed by cell membrane rupture. The cell morphology changes and cell membrane ruptures were detected in real time and were apparent in the unwrapped phase shift images. The results indicate that quantitative phase contrast imaging produced by the digital inline holographic microscope can be used for the label-free real time automated determination of cell viability and confluence in mammalian cell cultures.

Digital micromirror device as amplitude diffuser for multiple-plane phase retrieval

NASA Astrophysics Data System (ADS)

Abregana, Timothy Joseph T.; Hermosa, Nathaniel P.; Almoro, Percival F.

2017-06-01

Previous implementations of the phase diffuser used in the multiple-plane phase retrieval method included a diffuser glass plate with fixed optical properties or a programmable yet expensive spatial light modulator. Here a model for phase retrieval based on a digital micromirror device as amplitude diffuser is presented. The technique offers programmable, convenient and low-cost amplitude diffuser for a non-stagnating iterative phase retrieval. The technique is demonstrated in the reconstructions of smooth object wavefronts.

A low noise and ultra-narrow bandwidth frequency-locked loop based on the beat method.

PubMed

Gao, Wei; Sui, Jianping; Chen, Zhiyong; Yu, Fang; Sheng, Rongwu

2011-06-01

A novel frequency-locked loop (FLL) based on the beat method is proposed in this paper. Compared with other frequency feedback loops, this FLL is a digital loop with simple structure and very low noise. As shown in the experimental results, this FLL can be used to reduce close-in phase noise on atomic frequency standards, through which a composite frequency standard with ultra-low phase noise and low cost can be easily realized.

Demodulation of messages received with low signal to noise ratio

NASA Astrophysics Data System (ADS)

Marguinaud, A.; Quignon, T.; Romann, B.

The implementation of this all-digital demodulator is derived from maximum likelihood considerations applied to an analytical representation of the received signal. Traditional adapted filters and phase lock loops are replaced by minimum variance estimators and hypothesis tests. These statistical tests become very simple when working on phase signal. These methods, combined with rigorous control data representation allow significant computation savings as compared to conventional realizations. Nominal operation has been verified down to energetic signal over noise of -3 dB upon a QPSK demodulator.

Design of a High Speed Data Capture Device for a Coherent Radar Application

DTIC Science & Technology

2006-11-01

of the RGASM is discussed, then the primary differences between coherent and non-coherent processing are compared. A basic digital receiver is then...IPP. 19 In-Phase Data Transfer Quadrature Data Transfer Label: Fuction : IQ-Sel Signifies whether data present on the bus is In-Phase or Quadrature...430S_IIZ _ l -.. t....!.... Label: Fuction : ADRS 16-bit address bus value DATA Actual 16-bit value of the data on the bus BUSEN* Bus enable READY* Bus

Compression of computer generated phase-shifting hologram sequence using AVC and HEVC

NASA Astrophysics Data System (ADS)

Xing, Yafei; Pesquet-Popescu, Béatrice; Dufaux, Frederic

2013-09-01

With the capability of achieving twice the compression ratio of Advanced Video Coding (AVC) with similar reconstruction quality, High Efficiency Video Coding (HEVC) is expected to become the newleading technique of video coding. In order to reduce the storage and transmission burden of digital holograms, in this paper we propose to use HEVC for compressing the phase-shifting digital hologram sequences (PSDHS). By simulating phase-shifting digital holography (PSDH) interferometry, interference patterns between illuminated three dimensional( 3D) virtual objects and the stepwise phase changed reference wave are generated as digital holograms. The hologram sequences are obtained by the movement of the virtual objects and compressed by AVC and HEVC. The experimental results show that AVC and HEVC are efficient to compress PSDHS, with HEVC giving better performance. Good compression rate and reconstruction quality can be obtained with bitrate above 15000kbps.

Anticipatory synergy adjustments reflect individual performance of feedforward force control.

PubMed

Togo, Shunta; Imamizu, Hiroshi

2016-10-06

We grasp and dexterously manipulate an object through multi-digit synergy. In the framework of the uncontrolled manifold (UCM) hypothesis, multi-digit synergy is defined as the coordinated control mechanism of fingers to stabilize variable important for task success, e.g., total force. Previous studies reported anticipatory synergy adjustments (ASAs) that correspond to a drop of the synergy index before a quick change of the total force. The present study compared ASA's properties with individual performances of feedforward force control to investigate a relationship of those. Subjects performed a total finger force production task that consisted of a phase in which subjects tracked target line with visual information and a phase in which subjects produced total force pulse without visual information. We quantified their multi-digit synergy through UCM analysis and observed significant ASAs before producing total force pulse. The time of the ASA initiation and the magnitude of the drop of the synergy index were significantly correlated with the error of force pulse, but not with the tracking error. Almost all subjects showed a significant increase of the variance that affected the total force. Our study directly showed that ASA reflects the individual performance of feedforward force control independently of target-tracking performance and suggests that the multi-digit synergy was weakened to adjust the multi-digit movements based on a prediction error so as to reduce the future error. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Accuracy concerns in digital speckle photography combined with Fresnel digital holographic interferometry

NASA Astrophysics Data System (ADS)

Zhao, Yuchen; Zemmamouche, Redouane; Vandenrijt, Jean-François; Georges, Marc P.

2018-05-01

A combination of digital holographic interferometry (DHI) and digital speckle photography (DSP) allows in-plane and out-of-plane displacement measurement between two states of an object. The former can be determined by correlating the two speckle patterns whereas the latter is given by the phase difference obtained from DHI. We show that the amplitude of numerically reconstructed object wavefront obtained from Fresnel in-line digital holography (DH), in combination with phase shifting techniques, can be used as speckle patterns in DSP. The accuracy of in-plane measurement is improved after correcting the phase errors induced by reference wave during reconstruction process. Furthermore, unlike conventional imaging system, Fresnel DH offers the possibility to resize the pixel size of speckle patterns situated on the reconstruction plane under the same optical configuration simply by zero-padding the hologram. The flexibility of speckle size adjustment in Fresnel DH ensures the accuracy of estimation result using DSP.

Description and Flight Test Results of the NASA F-8 Digital Fly-by-Wire Control System

NASA Technical Reports Server (NTRS)

1975-01-01

A NASA program to develop digital fly-by-wire (DFBW) technology for aircraft applications is discussed. Phase I of the program demonstrated the feasibility of using a digital fly-by-wire system for aircraft control through developing and flight testing a single channel system, which used Apollo hardware, in an F-8C airplane. The objective of Phase II of the program is to establish a technology base for designing practical DFBW systems. It will involve developing and flight testing a triplex digital fly-by-wire system using state-of-the-art airborne computers, system hardware, software, and redundancy concepts. The papers included in this report describe the Phase I system and its development and present results from the flight program. Man-rated flight software and the effects of lightning on digital flight control systems are also discussed.

Analog circuit for controlling acoustic transducer arrays

DOEpatents

Drumheller, Douglas S.

1991-01-01

A simplified ananlog circuit is presented for controlling electromechanical transducer pairs in an acoustic telemetry system. The analog circuit of this invention comprises a single electrical resistor which replaces all of the digital components in a known digital circuit. In accordance with this invention, a first transducer in a transducer pair of array is driven in series with the resistor. The voltage drop across this resistor is then amplified and used to drive the second transducer. The voltage drop across the resistor is proportional and in phase with the current to the transducer. This current is approximately 90 degrees out of phase with the driving voltage to the transducer. This phase shift replaces the digital delay required by the digital control circuit of the prior art.

Demonstration of holographic smart card system using the optical memory technology

NASA Astrophysics Data System (ADS)

Kim, JungHoi; Choi, JaeKwang; An, JunWon; Kim, Nam; Lee, KwonYeon; Jeon, SeckHee

2003-05-01

In this paper, we demonstrate the holographic smart card system using digital holographic memory technique that uses reference beam encrypted by the random phase mask to prevent unauthorized users from accessing the stored digital page. The input data that include document data, a picture of face, and a fingerprint for identification is encoded digitally and then coupled with the reference beam modulated by a random phase mask. Therefore, this proposed system can execute recording in the order of MB~GB and readout all personal information from just one card without any additional database system. Also, recorded digital holograms can't be reconstructed without a phase key and can't be copied by using computers, scanners, or photography.

FIR digital filter-based ZCDPLL for carrier recovery

NASA Astrophysics Data System (ADS)

Nasir, Qassim

2016-04-01

The objective of this work is to analyse the performance of the newly proposed two-tap FIR digital filter-based first-order zero-crossing digital phase-locked loop (ZCDPLL) in the absence or presence of additive white Gaussian noise (AWGN). The introduction of the two-tap FIR digital filter widens the lock range of a ZCDPLL and improves the loop's operation in the presence of AWGN. The FIR digital filter tap coefficients affect the loop convergence behaviour and appropriate selection of those gains should be taken into consideration. The new proposed loop has wider locking range and faster acquisition time and reduces the phase error variations in the presence of noise.

Linear-phase delay filters for ultra-low-power signal processing in neural recording implants.

PubMed

Gosselin, Benoit; Sawan, Mohamad; Kerherve, Eric

2010-06-01

We present the design and implementation of linear-phase delay filters for ultra-low-power signal processing in neural recording implants. We use these filters as low-distortion delay elements along with an automatic biopotential detector to perform integral waveform extraction and efficient power management. The presented delay elements are realized employing continuous-time OTA-C filters featuring 9th-order equiripple transfer functions with constant group delay. Such analog delay enables processing neural waveforms with reduced overhead compared to a digital delay since it does not requires sampling and digitization. It uses an allpass transfer function for achieving wider constant-delay bandwidth than all-pole does. Two filters realizations are compared for implementing the delay element: the Cascaded structure and the Inverse follow-the-leader feedback filter. Their respective strengths and drawbacks are assessed by modeling parasitics and non-idealities of OTAs, and by transistor-level simulations. A budget of 200 nA is used in both filters. Experimental measurements with the chosen filter topology are presented and discussed.

Design and implementation of a hybrid digital phase-locked loop with a TMS320C25: An application to a transponder receiver breadboard

NASA Technical Reports Server (NTRS)

Yeh, H.-G.; Nguyen, T. M.

1994-01-01

Design, modeling, analysis, and simulation of a phase-locked loop (PLL) with a digital loop filter are presented in this article. A TMS320C25 digital signal processor (DSP) is used to implement this digital loop filter. In order to keep the compatibility, the main design goal was to replace the analog PLL (APLL) of the Deep-Space Transponder (DST) receiver breadboard's loop filter with a digital loop filter without changing anything else. This replacement results in a hybrid digital PLL (HDPLL). Both the original APLL and the designed HDPLL are Type I second-order systems. The real-time performance of the HDPLL and the receiver is provided and evaluated.

Tile-Based Two-Dimensional Phase Unwrapping for Digital Holography Using a Modular Framework

PubMed Central

Antonopoulos, Georgios C.; Steltner, Benjamin; Heisterkamp, Alexander; Ripken, Tammo; Meyer, Heiko

2015-01-01

A variety of physical and biomedical imaging techniques, such as digital holography, interferometric synthetic aperture radar (InSAR), or magnetic resonance imaging (MRI) enable measurement of the phase of a physical quantity additionally to its amplitude. However, the phase can commonly only be measured modulo 2π, as a so called wrapped phase map. Phase unwrapping is the process of obtaining the underlying physical phase map from the wrapped phase. Tile-based phase unwrapping algorithms operate by first tessellating the phase map, then unwrapping individual tiles, and finally merging them to a continuous phase map. They can be implemented computationally efficiently and are robust to noise. However, they are prone to failure in the presence of phase residues or erroneous unwraps of single tiles. We tried to overcome these shortcomings by creating novel tile unwrapping and merging algorithms as well as creating a framework that allows to combine them in modular fashion. To increase the robustness of the tile unwrapping step, we implemented a model-based algorithm that makes efficient use of linear algebra to unwrap individual tiles. Furthermore, we adapted an established pixel-based unwrapping algorithm to create a quality guided tile merger. These original algorithms as well as previously existing ones were implemented in a modular phase unwrapping C++ framework. By examining different combinations of unwrapping and merging algorithms we compared our method to existing approaches. We could show that the appropriate choice of unwrapping and merging algorithms can significantly improve the unwrapped result in the presence of phase residues and noise. Beyond that, our modular framework allows for efficient design and test of new tile-based phase unwrapping algorithms. The software developed in this study is freely available. PMID:26599984

Tile-Based Two-Dimensional Phase Unwrapping for Digital Holography Using a Modular Framework.

PubMed

Antonopoulos, Georgios C; Steltner, Benjamin; Heisterkamp, Alexander; Ripken, Tammo; Meyer, Heiko

2015-01-01

A variety of physical and biomedical imaging techniques, such as digital holography, interferometric synthetic aperture radar (InSAR), or magnetic resonance imaging (MRI) enable measurement of the phase of a physical quantity additionally to its amplitude. However, the phase can commonly only be measured modulo 2π, as a so called wrapped phase map. Phase unwrapping is the process of obtaining the underlying physical phase map from the wrapped phase. Tile-based phase unwrapping algorithms operate by first tessellating the phase map, then unwrapping individual tiles, and finally merging them to a continuous phase map. They can be implemented computationally efficiently and are robust to noise. However, they are prone to failure in the presence of phase residues or erroneous unwraps of single tiles. We tried to overcome these shortcomings by creating novel tile unwrapping and merging algorithms as well as creating a framework that allows to combine them in modular fashion. To increase the robustness of the tile unwrapping step, we implemented a model-based algorithm that makes efficient use of linear algebra to unwrap individual tiles. Furthermore, we adapted an established pixel-based unwrapping algorithm to create a quality guided tile merger. These original algorithms as well as previously existing ones were implemented in a modular phase unwrapping C++ framework. By examining different combinations of unwrapping and merging algorithms we compared our method to existing approaches. We could show that the appropriate choice of unwrapping and merging algorithms can significantly improve the unwrapped result in the presence of phase residues and noise. Beyond that, our modular framework allows for efficient design and test of new tile-based phase unwrapping algorithms. The software developed in this study is freely available.

Superluminal Labview Code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wheat, Robert; Marksteiner, Quinn; Quenzer, Jonathan

2012-03-26

This labview code is used to set the phase and amplitudes on the 72 antenna of the superluminal machine, and to map out the radiation patter from the superluminal antenna.Each antenna radiates a modulated signal consisting of two separate frequencies, in the range of 2 GHz to 2.8 GHz. The phases and amplitudes from each antenna are controlled by a pair of AD8349 vector modulators (VMs). These VMs set the phase and amplitude of a high frequency signal using a set of four DC inputs, which are controlled by Linear Technologies LTC1990 digital to analog converters (DACs). The labview codemore » controls these DACs through an 8051 microcontroller.This code also monitors the phases and amplitudes of the 72 channels. Near each antenna, there is a coupler that channels a portion of the power into a binary network. Through a labview controlled switching array, any of the 72 coupled signals can be channeled in to the Tektronix TDS 7404 digital oscilloscope. Then the labview code takes an FFT of the signal, and compares it to the FFT of a reference signal in the oscilloscope to determine the magnitude and phase of each sideband of the signal. The code compensates for phase and amplitude errors introduced by differences in cable lengths.The labview code sets each of the 72 elements to a user determined phase and amplitude. For each element, the code runs an iterative procedure, where it adjusts the DACs until the correct phases and amplitudes have been reached.« less

Fast, externally triggered, digital phase controller for an optical lattice

NASA Astrophysics Data System (ADS)

Sadgrove, Mark; Nakagawa, Ken'ichi

2011-11-01

We present a method to control the phase of an optical lattice according to an external trigger signal. The method has a latency of less than 30 μs. Two phase locked digital synthesizers provide the driving signal for two acousto-optic modulators which control the frequency and phase of the counter-propagating beams which form a standing wave (optical lattice). A micro-controller with an external interrupt function is connected to the desired external signal, and updates the phase register of one of the synthesizers when the external signal changes. The standing wave (period λ/2 = 390 nm) can be moved by units of 49 nm with a mean jitter of 28 nm. The phase change is well known due to the digital nature of the synthesizer, and does not need calibration. The uses of the scheme include coherent control of atomic matter-wave dynamics.

Phase reconstruction using compressive two-step parallel phase-shifting digital holography

NASA Astrophysics Data System (ADS)

Ramachandran, Prakash; Alex, Zachariah C.; Nelleri, Anith

2018-04-01

The linear relationship between the sample complex object wave and its approximated complex Fresnel field obtained using single shot parallel phase-shifting digital holograms (PPSDH) is used in compressive sensing framework and an accurate phase reconstruction is demonstrated. It is shown that the accuracy of phase reconstruction of this method is better than that of compressive sensing adapted single exposure inline holography (SEOL) method. It is derived that the measurement model of PPSDH method retains both the real and imaginary parts of the Fresnel field but with an approximation noise and the measurement model of SEOL retains only the real part exactly equal to the real part of the complex Fresnel field and its imaginary part is completely not available. Numerical simulation is performed for CS adapted PPSDH and CS adapted SEOL and it is demonstrated that the phase reconstruction is accurate for CS adapted PPSDH and can be used for single shot digital holographic reconstruction.

End-to-end learning for digital hologram reconstruction

NASA Astrophysics Data System (ADS)

Xu, Zhimin; Zuo, Si; Lam, Edmund Y.

2018-02-01

Digital holography is a well-known method to perform three-dimensional imaging by recording the light wavefront information originating from the object. Not only the intensity, but also the phase distribution of the wavefront can then be computed from the recorded hologram in the numerical reconstruction process. However, the reconstructions via the traditional methods suffer from various artifacts caused by twin-image, zero-order term, and noise from image sensors. Here we demonstrate that an end-to-end deep neural network (DNN) can learn to perform both intensity and phase recovery directly from an intensity-only hologram. We experimentally show that the artifacts can be effectively suppressed. Meanwhile, our network doesn't need any preprocessing for initialization, and is comparably fast to train and test, in comparison with the recently published learning-based method. In addition, we validate that the performance improvement can be achieved by introducing a prior on sparsity.

Spectrally resolved digital holography using a white light LED

NASA Astrophysics Data System (ADS)

Claus, D.; Pedrini, G.; Buchta, D.; Osten, W.

2017-06-01

This paper introduces the concept of spectrally resolved digital holography. The measurement principle and the analysis of the data will be discussed in detail. The usefulness of spectrally resolved digital holography is demonstrated for colour imaging and optical metrology with regards to the recovery of modulus information and phase information, respectively. The phase information will be used to measure the shape of an object via the application of the dual wavelength method. Based on the large degree of data available, multiple speckle de-correlated dual wavelength phase maps can be obtained, which when averaged result in a signal to noise ratio improvement.

Multiple-access phased array antenna simulator for a digital beam-forming system investigation

NASA Technical Reports Server (NTRS)

Kerczewski, Robert J.; Yu, John; Walton, Joanne C.; Perl, Thomas D.; Andro, Monty; Alexovich, Robert E.

1992-01-01

Future versions of data relay satellite systems are currently being planned by NASA. Being given consideration for implementation are on-board digital beamforming techniques which will allow multiple users to simultaneously access a single S-band phased array antenna system. To investigate the potential performance of such a system, a laboratory simulator has been developed at NASA's Lewis Research Center. This paper describes the system simulator, and in particular, the requirements, design and performance of a key subsystem, the phased array antenna simulator, which provides realistic inputs to the digital processor including multiple signals, noise, and nonlinearities.

Multiple-access phased array antenna simulator for a digital beam forming system investigation

NASA Technical Reports Server (NTRS)

Kerczewski, Robert J.; Yu, John; Walton, Joanne C.; Perl, Thomas D.; Andro, Monty; Alexovich, Robert E.

1992-01-01

Future versions of data relay satellite systems are currently being planned by NASA. Being given consideration for implementation are on-board digital beamforming techniques which will allow multiple users to simultaneously access a single S-band phased array antenna system. To investigate the potential performance of such a system, a laboratory simulator has been developed at NASA's Lewis Research Center. This paper describes the system simulator, and in particular, the requirements, design, and performance of a key subsystem, the phased array antenna simulator, which provides realistic inputs to the digital processor including multiple signals, noise, and nonlinearities.

Development of Michelson interferometer based spatial phase-shift digital shearography

NASA Astrophysics Data System (ADS)

Xie, Xin

Digital shearography is a non-contact, full field, optical measurement method, which has the capability of directly measuring the gradient of deformation. For high measurement sensitivity, phase evaluation method has to be introduced into digital shearography by phase-shift technique. Catalog by phase-shift method, digital phase-shift shearography can be divided into Temporal Phase-Shift Digital Shearography (TPS-DS) and Spatial Phase-Shift Digital Shearography (SPS-DS). TPS-DS is the most widely used phase-shift shearography system, due to its simple algorithm, easy operation and good phase-map quality. However, the application of TPS-DS is only limited in static/step-by-step loading measurement situation, due to its multi-step shifting process. In order to measure the strain under dynamic/continuous loading situation, a SPS-DS system has to be developed. This dissertation aims to develop a series of Michelson Interferometer based SPS-DS measurement methods to achieve the strain measurement by using only a single pair of speckle pattern images. The Michelson Interferometer based SPS-DS systems utilize special designed optical setup to introduce extra carrier frequency into the laser wavefront. The phase information corresponds to the strain field can be separated on the Fourier domain using a Fourier Transform and can further be evaluated with a Windowed Inverse Fourier Transform. With different optical setups and carrier frequency arrangements, the Michelson Interferometer based SPS-DS method is capable to achieve a variety of measurement tasks using only single pair of speckle pattern images. Catalog by the aimed measurand, these capable measurement tasks can be divided into five categories: 1) measurement of out-of-plane strain field with small shearing amount; 2) measurement of relative out-of-plane deformation field with big shearing amount; 3) simultaneous measurement of relative out-of-plane deformation field and deformation gradient field by using multiple carrier frequencies; 4) simultaneous measurement of two directional strain field using dual measurement channels 5) measurement of pure in-plane strain and pure out-of-plane strain with multiple carrier frequencies. The basic theory, optical path analysis, preliminary studies, results analysis and research plan are shown in detail in this dissertation.

Power supply with air core transformer and seperated power supplies for high dynamic range

NASA Technical Reports Server (NTRS)

Orient, Otto (Inventor); Chutjian, Ara (Inventor); Aalami, Dean (Inventor); Darrach, Murray (Inventor)

2001-01-01

A power supply for a quadrupole mass spectrometer which operates using an RF signal. The RF signal is controllable via a feedback loop. The feedback loop is from the output, through a comparator, and compared to a digital signal. An air core transformer is used to minimize the weight. The air core transformer is driven via two out of phase sawtooth signals which drive opposite ends of the transformer.

Imaging and computational considerations for image computed permeability: Operating envelope of Digital Rock Physics

NASA Astrophysics Data System (ADS)

Saxena, Nishank; Hows, Amie; Hofmann, Ronny; Alpak, Faruk O.; Freeman, Justin; Hunter, Sander; Appel, Matthias

2018-06-01

This study defines the optimal operating envelope of the Digital Rock technology from the perspective of imaging and numerical simulations of transport properties. Imaging larger volumes of rocks for Digital Rock Physics (DRP) analysis improves the chances of achieving a Representative Elementary Volume (REV) at which flow-based simulations (1) do not vary with change in rock volume, and (2) is insensitive to the choice of boundary conditions. However, this often comes at the expense of image resolution. This trade-off exists due to the finiteness of current state-of-the-art imaging detectors. Imaging and analyzing digital rocks that sample the REV and still sufficiently resolve pore throats is critical to ensure simulation quality and robustness of rock property trends for further analysis. We find that at least 10 voxels are needed to sufficiently resolve pore throats for single phase fluid flow simulations. If this condition is not met, additional analyses and corrections may allow for meaningful comparisons between simulation results and laboratory measurements of permeability, but some cases may fall outside the current technical feasibility of DRP. On the other hand, we find that the ratio of field of view and effective grain size provides a reliable measure of the REV for siliciclastic rocks. If this ratio is greater than 5, the coefficient of variation for single-phase permeability simulations drops below 15%. These imaging considerations are crucial when comparing digitally computed rock flow properties with those measured in the laboratory. We find that the current imaging methods are sufficient to achieve both REV (with respect to numerical boundary conditions) and required image resolution to perform digital core analysis for coarse to fine-grained sandstones.

Blocker-tolerant and high-sensitivity $Δ$$\\!$$Σ$ correlation digitizer for radar and coherent receiver applications

DOE PAGES

Mincey, John S.; Silva-Martinez, Jose; Karsilayan, AydinIlker; ...

2017-03-17

In this study, a coherent subsampling digitizer for pulsed Doppler radar systems is proposed. Prior to transmission, the radar system modulates the RF pulse with a known pseudorandom binary phase shift keying (BPSK) sequence. Upon reception, the radar digitizer uses a programmable sample-and-hold circuit to multiply the received waveform by a properly time-delayed version of the known a priori BPSK sequence. This operation demodulates the desired echo signal while suppressing the spectrum of all in-band noncorrelated interferers, making them appear as noise in the frequency domain. The resulting demodulated narrowband Doppler waveform is then subsampled at the IF frequency bymore » a delta-sigma modulator. Because the digitization bandwidth within the delta-sigma feedback loop is much less than the input bandwidth to the digitizer, the thermal noise outside of the Doppler bandwidth is effectively filtered prior to quantization, providing an increase in signal-to-noise ratio (SNR) at the digitizer's output compared with the input SNR. In this demonstration, a delta-sigma correlation digitizer is fabricated in a 0.18-μm CMOS technology. The digitizer has a power consumption of 1.12 mW with an IIP3 of 7.5 dBm. The digitizer is able to recover Doppler tones in the presence of blockers up to 40 dBm greater than the Doppler tone.« less

Flexible digital modulation and coding synthesis for satellite communications

NASA Technical Reports Server (NTRS)

Vanderaar, Mark; Budinger, James; Hoerig, Craig; Tague, John

1991-01-01

An architecture and a hardware prototype of a flexible trellis modem/codec (FTMC) transmitter are presented. The theory of operation is built upon a pragmatic approach to trellis-coded modulation that emphasizes power and spectral efficiency. The system incorporates programmable modulation formats, variations of trellis-coding, digital baseband pulse-shaping, and digital channel precompensation. The modulation formats examined include (uncoded and coded) binary phase shift keying (BPSK), quatenary phase shift keying (QPSK), octal phase shift keying (8PSK), 16-ary quadrature amplitude modulation (16-QAM), and quadrature quadrature phase shift keying (Q squared PSK) at programmable rates up to 20 megabits per second (Mbps). The FTMC is part of the developing test bed to quantify modulation and coding concepts.

Phase aberration compensation of digital holographic microscopy based on least squares surface fitting

NASA Astrophysics Data System (ADS)

Di, Jianglei; Zhao, Jianlin; Sun, Weiwei; Jiang, Hongzhen; Yan, Xiaobo

2009-10-01

Digital holographic microscopy allows the numerical reconstruction of the complex wavefront of samples, especially biological samples such as living cells. In digital holographic microscopy, a microscope objective is introduced to improve the transverse resolution of the sample; however a phase aberration in the object wavefront is also brought along, which will affect the phase distribution of the reconstructed image. We propose here a numerical method to compensate for the phase aberration of thin transparent objects with a single hologram. The least squares surface fitting with points number less than the matrix of the original hologram is performed on the unwrapped phase distribution to remove the unwanted wavefront curvature. The proposed method is demonstrated with the samples of the cicada wings and epidermal cells of garlic, and the experimental results are consistent with that of the double exposure method.

The Influence of Internal Structures in Fused Deposition Modeling Method on Dimensional Accuracy of Components

NASA Astrophysics Data System (ADS)

Milde, Ján; Morovič, Ladislav

2016-09-01

The paper investigates the influence of infill (internal structures of components) in the Fused Deposition Modeling (FDM) method on dimensional and geometrical accuracy of components. The components in this case were real models of human mandible, which were obtained by Computed Tomography (CT) mostly used in medical applications. In the production phase, the device used for manufacturing, was a 3D printer Zortrax M200 based on the FDM technology. In the second phase, the mandibles made by the printer, were digitized using optical scanning device of GOM ATOS Triple Scan II. They were subsequently evaluated in the final phase. The practical part of this article describes the procedure of jaw model modification, the production of components using a 3D printer, the procedure of digitization of printed parts by optical scanning device and the procedure of comparison. The outcome of this article is a comparative analysis of individual printed parts, containing tables with mean deviations for individual printed parts, as well as tables for groups of printed parts with the same infill parameter.

Variable current speed controller for eddy current motors

DOEpatents

Gerth, H.L.; Bailey, J.M.; Casstevens, J.M.; Dixon, J.H.; Griffith, B.O.; Igou, R.E.

1982-03-12

A speed control system for eddy current motors is provided in which the current to the motor from a constant frequency power source is varied by comparing the actual motor speed signal with a setpoint speed signal to control the motor speed according to the selected setpoint speed. A three-phase variable voltage autotransformer is provided for controlling the voltage from a three-phase power supply. A corresponding plurality of current control resistors is provided in series with each phase of the autotransformer output connected to inputs of a three-phase motor. Each resistor is connected in parallel with a set of normally closed contacts of plurality of relays which are operated by control logic. A logic circuit compares the selected speed with the actual motor speed obtained from a digital tachometer monitoring the motor spindle speed and operated the relays to add or substract resistance equally in each phase of the motor input to vary the motor current to control the motor at the selected speed.

Quality assurance in the EORTC 22033-26033/CE5 phase III randomized trial for low grade glioma: the digital individual case review.

PubMed

Fairchild, Alysa; Weber, Damien C; Bar-Deroma, Raquel; Gulyban, Akos; Fenton, Paul A; Stupp, Roger; Baumert, Brigitta G

2012-06-01

The phase III EORTC 22033-26033/NCIC CE5 intergroup trial compares 50.4 Gy radiotherapy with up-front temozolomide in previously untreated low-grade glioma. We describe the digital EORTC individual case review (ICR) performed to evaluate protocol radiotherapy (RT) compliance. Fifty-eight institutions were asked to submit 1-2 randomly selected cases. Digital ICR datasets were uploaded to the EORTC server and accessed by three central reviewers. Twenty-seven parameters were analysed including volume delineation, treatment planning, organ at risk (OAR) dosimetry and verification. Consensus reviews were collated and summary statistics calculated. Fifty-seven of seventy-two requested datasets from forty-eight institutions were technically usable. 31/57 received a major deviation for at least one section. Relocation accuracy was according to protocol in 45. Just over 30% had acceptable target volumes. OAR contours were missing in an average of 25% of cases. Up to one-third of those present were incorrectly drawn while dosimetry was largely protocol compliant. Beam energy was acceptable in 97% and 48 patients had per protocol beam arrangements. Digital RT plan submission and review within the EORTC 22033-26033 ICR provide a solid foundation for future quality assurance procedures. Strict evaluation resulted in overall grades of minor and major deviation for 37% and 32%, respectively. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

The energetics of heterogeneous deformation in open-cell elastic foams

NASA Astrophysics Data System (ADS)

Gioia, Gustavo; Cuitino, Alberto

2002-03-01

We study the energetics of a model of elastic foams to show that the stretch heterogeneity observed in experiments stems from the lack of convexity of the governing energy functional. The predicted stretch distributions correspond to stratified mixtures of two configurational phases of the foam. Stretching occurs in the form of a phase transition, by growth of one of the phases at the expense of the other. We also compare the predicted mechanical response with experimental data for foams of different densities. Lastly, we perform displacement field measurements using the digital image correlation technique, and find the results to be in agreement with our predictions.

Linear least squares approach for evaluating crack tip fracture parameters using isochromatic and isoclinic data from digital photoelasticity

NASA Astrophysics Data System (ADS)

Patil, Prataprao; Vyasarayani, C. P.; Ramji, M.

2017-06-01

In this work, digital photoelasticity technique is used to estimate the crack tip fracture parameters for different crack configurations. Conventionally, only isochromatic data surrounding the crack tip is used for SIF estimation, but with the advent of digital photoelasticity, pixel-wise availability of both isoclinic and isochromatic data could be exploited for SIF estimation in a novel way. A linear least square approach is proposed to estimate the mixed-mode crack tip fracture parameters by solving the multi-parameter stress field equation. The stress intensity factor (SIF) is extracted from those estimated fracture parameters. The isochromatic and isoclinic data around the crack tip is estimated using the ten-step phase shifting technique. To get the unwrapped data, the adaptive quality guided phase unwrapping algorithm (AQGPU) has been used. The mixed mode fracture parameters, especially SIF are estimated for specimen configurations like single edge notch (SEN), center crack and straight crack ahead of inclusion using the proposed algorithm. The experimental SIF values estimated using the proposed method are compared with analytical/finite element analysis (FEA) results, and are found to be in good agreement.

Digital holographic microscopy combined with optical tweezers

NASA Astrophysics Data System (ADS)

Cardenas, Nelson; Yu, Lingfeng; Mohanty, Samarendra K.

2011-02-01

While optical tweezers have been widely used for the manipulation and organization of microscopic objects in three dimensions, observing the manipulated objects along axial direction has been quite challenging. In order to visualize organization and orientation of objects along axial direction, we report development of a Digital holographic microscopy combined with optical tweezers. Digital holography is achieved by use of a modified Mach-Zehnder interferometer with digital recording of interference pattern of the reference and sample laser beams by use of a single CCD camera. In this method, quantitative phase information is retrieved dynamically with high temporal resolution, only limited by frame rate of the CCD. Digital focusing, phase-unwrapping as well as online analysis and display of the quantitative phase images was performed on a software developed on LabView platform. Since phase changes observed in DHOT is very sensitive to optical thickness of trapped volume, estimation of number of particles trapped in the axial direction as well as orientation of non-spherical objects could be achieved with high precision. Since in diseases such as malaria and diabetics, change in refractive index of red blood cells occurs, this system can be employed to map such disease-specific changes in biological samples upon immobilization with optical tweezers.

Digital Filters for Digital Phase-locked Loops

NASA Technical Reports Server (NTRS)

Simon, M.; Mileant, A.

1985-01-01

An s/z hybrid model for a general phase locked loop is proposed. The impact of the loop filter on the stability, gain margin, noise equivalent bandwidth, steady state error and time response is investigated. A specific digital filter is selected which maximizes the overall gain margin of the loop. This filter can have any desired number of integrators. Three integrators are sufficient in order to track a phase jerk with zero steady state error at loop update instants. This filter has one zero near z = 1.0 for each integrator. The total number of poles of the filter is equal to the number of integrators plus two.

A simple second-order digital phase-locked loop.

NASA Technical Reports Server (NTRS)

Tegnelia, C. R.

1972-01-01

A simple second-order digital phase-locked loop has been designed for the Viking Orbiter 1975 command system. Excluding analog-to-digital conversion, implementation of the loop requires only an adder/subtractor, two registers, and a correctable counter with control logic. The loop considers only the polarity of phase error and corrects system clocks according to a filtered sequence of this polarity. The loop is insensitive to input gain variation, and therefore offers the advantage of stable performance over long life. Predictable performance is guaranteed by extreme reliability of acquisition, yet in the steady state the loop produces only a slight degradation with respect to analog loop performance.

[INVITED] Laser-induced forward transfer: A high resolution additive manufacturing technology

NASA Astrophysics Data System (ADS)

Delaporte, Philippe; Alloncle, Anne-Patricia

2016-04-01

Among the additive manufacturing techniques, laser-induced forward transfer addresses the challenges of printing thin films in solid phase or small volume droplets in liquid phase with very high resolution. This paper reviews the physics of this process and explores the pros and cons of this technology versus other digital printing technologies. The main field of applications are printed electronics, organic electronics and tissue engineering, and the most promising short terms ones concern digital laser printing of sensors and conductive tracks. Future directions and emerging areas of interest are discussed such as printing solid from a liquid phase and 3D digital nanomanufacturing.

Digital spiral-slit for bi-photon imaging

NASA Astrophysics Data System (ADS)

McLaren, Melanie; Forbes, Andrew

2017-04-01

Quantum ghost imaging using entangled photon pairs has become a popular field of investigation, highlighting the quantum correlation between the photon pairs. We introduce a technique using spatial light modulators encoded with digital holograms to recover both the amplitude and the phase of the digital object. Down-converted photon pairs are entangled in the orbital angular momentum basis, and are commonly measured using spiral phase holograms. Consequently, by encoding a spiral ring-slit hologram into the idler arm, and varying it radially we can simultaneously recover the phase and amplitude of the object in question. We demonstrate that a good correlation between the encoded field function and the reconstructed images exists.

Dual-channel in-line digital holographic double random phase encryption

PubMed Central

Das, Bhargab; Yelleswarapu, Chandra S; Rao, D V G L N

2012-01-01

We present a robust encryption method for the encoding of 2D/3D objects using digital holography and virtual optics. Using our recently developed dual-plane in-line digital holography technique, two in-line digital holograms are recorded at two different planes and are encrypted using two different double random phase encryption configurations, independently. The process of using two mutually exclusive encryption channels makes the system more robust against attacks since both the channels should be decrypted accurately in order to get a recognizable reconstruction. Results show that the reconstructed object is unrecognizable even when the portion of the correct phase keys used during decryption is close to 75%. The system is verified against blind decryptions by evaluating the SNR and MSE. Validation of the proposed method and sensitivities of the associated parameters are quantitatively analyzed and illustrated. PMID:23471012

Pile Driving

NASA Technical Reports Server (NTRS)

1987-01-01

Machine-oriented structural engineering firm TERA, Inc. is engaged in a project to evaluate the reliability of offshore pile driving prediction methods to eventually predict the best pile driving technique for each new offshore oil platform. Phase I Pile driving records of 48 offshore platforms including such information as blow counts, soil composition and pertinent construction details were digitized. In Phase II, pile driving records were statistically compared with current methods of prediction. Result was development of modular software, the CRIPS80 Software Design Analyzer System, that companies can use to evaluate other prediction procedures or other data bases.

Suppressing Transients In Digital Phase-Locked Loops

NASA Technical Reports Server (NTRS)

Thomas, J. B.

1993-01-01

Loop of arbitrary order starts in steady-state lock. Method for initializing variables of digital phase-locked loop reduces or eliminates transients in phase and frequency typically occurring during acquisition of lock on signal or when changes made in values of loop-filter parameters called "loop constants". Enables direct acquisition by third-order loop without prior acquisition by second-order loop of greater bandwidth, and eliminates those perturbations in phase and frequency lock occurring when loop constants changed by arbitrarily large amounts.

On higher order discrete phase-locked loops.

NASA Technical Reports Server (NTRS)

Gill, G. S.; Gupta, S. C.

1972-01-01

An exact mathematical model is developed for a discrete loop of a general order particularly suitable for digital computation. The deterministic response of the loop to the phase step and the frequency step is investigated. The design of the digital filter for the second-order loop is considered. Use is made of the incremental phase plane to study the phase error behavior of the loop. The model of the noisy loop is derived and the optimization of the loop filter for minimum mean-square error is considered.

Detection of digital FSK using a phase-locked loop

NASA Technical Reports Server (NTRS)

Lindsey, W. C.; Simon, M. K.

1975-01-01

A theory is presented for the design of a digital FSK receiver which employs a phase-locked loop to set up the desired matched filter as the arriving signal frequency switches. The developed mathematical model makes it possible to establish the error probability performance of systems which employ a class of digital FM modulations. The noise mechanism which accounts for decision errors is modeled on the basis of the Meyr distribution and renewal Markov process theory.

Restoration of singularities in reconstructed phase of crystal image in electron holography.

PubMed

Li, Wei; Tanji, Takayoshi

2014-12-01

Off-axis electron holography can be used to measure the inner potential of a specimen from its reconstructed phase image and is thus a powerful technique for materials scientists. However, abrupt reversals of contrast from white to black may sometimes occur in a digitally reconstructed phase image, which results in inaccurate information. Such phase distortion is mainly due to the digital reconstruction process and weak electron wave amplitude in some areas of the specimen. Therefore, digital image processing can be applied to the reconstruction and restoration of phase images. In this paper, fringe reconnection processing is applied to phase image restoration of a crystal structure image. The disconnection and wrong connection of interference fringes in the hologram that directly cause a 2π phase jump imperfection are correctly reconnected. Experimental results show that the phase distortion is significantly reduced after the processing. The quality of the reconstructed phase image was improved by the removal of imperfections in the final phase. © The Author 2014. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Phase unwrapping in digital holography based on non-subsampled contourlet transform

NASA Astrophysics Data System (ADS)

Zhang, Xiaolei; Zhang, Xiangchao; Xu, Min; Zhang, Hao; Jiang, Xiangqian

2018-01-01

In the digital holographic measurement of complex surfaces, phase unwrapping is a critical step for accurate reconstruction. The phases of the complex amplitudes calculated from interferometric holograms are disturbed by speckle noise, thus reliable unwrapping results are difficult to be obtained. Most of existing unwrapping algorithms implement denoising operations first to obtain noise-free phases and then conduct phase unwrapping pixel by pixel. This approach is sensitive to spikes and prone to unreliable results in practice. In this paper, a robust unwrapping algorithm based on the non-subsampled contourlet transform (NSCT) is developed. The multiscale and directional decomposition of NSCT enhances the boundary between adjacent phase levels and henceforth the influence of local noise can be eliminated in the transform domain. The wrapped phase map is segmented into several regions corresponding to different phase levels. Finally, an unwrapped phase map is obtained by elevating the phases of a whole segment instead of individual pixels to avoid unwrapping errors caused by local spikes. This algorithm is suitable for dealing with complex and noisy wavefronts. Its universality and superiority in the digital holographic interferometry have been demonstrated by both numerical analysis and practical experiments.

Study of signal-to-noise ratio in digital mammography

NASA Astrophysics Data System (ADS)

Kato, Yuri; Fujita, Naotoshi; Kodera, Yoshie

2009-02-01

Mammography techniques have recently advanced from those using analog systems (the screen-film system) to those using digital systems; for example, computed radiography (CR) and flat-panel detectors (FPDs) are nowadays used in mammography. Further, phase contrast mammography (PCM)-a digital technique by which images with a magnification of 1.75× can be obtained-is now available in the market. We studied the effect of the air gap in PCM and evaluated the effectiveness of an antiscatter x-ray grid in conventional mammography (CM) by measuring the scatter fraction ratio (SFR) and relative signal-to-noise ratio (rSNR) and comparing them between PCM and the digital CM. The results indicated that the SFRs for the CM images obtained with a grid were the lowest and that these ratios were almost the same as those for the PCM images. In contrast, the rSNRs for the PCM images were the highest, which means that the scattering of x-rays was sufficiently reduced by the air gap without the loss of primary x-rays.

A bunch to bucket phase detector for the RHIC LLRF upgrade platform

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, K.S.; Harvey, M.; Hayes, T.

2011-03-28

As part of the overall development effort for the RHIC LLRF Upgrade Platform [1,2,3], a generic four channel 16 bit Analog-to-Digital Converter (ADC) daughter module was developed to provide high speed, wide dynamic range digitizing and processing of signals from DC to several hundred megahertz. The first operational use of this card was to implement the bunch to bucket phase detector for the RHIC LLRF beam control feedback loops. This paper will describe the design and performance features of this daughter module as a bunch to bucket phase detector, and also provide an overview of its place within the overallmore » LLRF platform architecture as a high performance digitizer and signal processing module suitable to a variety of applications. In modern digital control and signal processing systems, ADCs provide the interface between the analog and digital signal domains. Once digitized, signals are then typically processed using algorithms implemented in field programmable gate array (FPGA) logic, general purpose processors (GPPs), digital signal processors (DSPs) or a combination of these. For the recently developed and commissioned RHIC LLRF Upgrade Platform, we've developed a four channel ADC daughter module based on the Linear Technology LTC2209 16 bit, 160 MSPS ADC and the Xilinx V5FX70T FPGA. The module is designed to be relatively generic in application, and with minimal analog filtering on board, is capable of processing signals from DC to 500 MHz or more. The module's first application was to implement the bunch to bucket phase detector (BTB-PD) for the RHIC LLRF system. The same module also provides DC digitizing of analog processed BPM signals used by the LLRF system for radial feedback.« less

Precision electronic speed controller for an alternating-current motor

DOEpatents

Bolie, V.W.

A high precision controller for an alternating-current multi-phase electrical motor that is subject to a large inertial load. The controller was developed for controlling, in a neutron chopper system, a heavy spinning rotor that must be rotated in phase-locked synchronism with a reference pulse train that is representative of an ac power supply signal having a meandering line frequency. The controller includes a shaft revolution sensor which provides a feedback pulse train representative of the actual speed of the motor. An internal digital timing signal generator provides a reference signal which is compared with the feedback signal in a computing unit to provide a motor control signal. The motor control signal is a weighted linear sum of a speed error voltage, a phase error voltage, and a drift error voltage, each of which is computed anew with each revolution of the motor shaft. The speed error signal is generated by a novel vernier-logic circuit which is drift-free and highly sensitive to small speed changes. The phase error is also computed by digital logic, with adjustable sensitivity around a 0 mid-scale value. The drift error signal, generated by long-term counting of the phase error, is used to compensate for any slow changes in the average friction drag on the motor. An auxillary drift-byte status sensor prevents any disruptive overflow or underflow of the drift-error counter. An adjustable clocked-delay unit is inserted between the controller and the source of the reference pulse train to permit phase alignment of the rotor to any desired offset angle. The stator windings of the motor are driven by two amplifiers which are provided with input signals having the proper quadrature relationship by an exciter unit consisting of a voltage controlled oscillator, a binary counter, a pair of read-only memories, and a pair of digital-to-analog converters.

Steady-state probability density function of the phase error for a DPLL with an integrate-and-dump device

NASA Technical Reports Server (NTRS)

Simon, M.; Mileant, A.

1986-01-01

The steady-state behavior of a particular type of digital phase-locked loop (DPLL) with an integrate-and-dump circuit following the phase detector is characterized in terms of the probability density function (pdf) of the phase error in the loop. Although the loop is entirely digital from an implementation standpoint, it operates at two extremely different sampling rates. In particular, the combination of a phase detector and an integrate-and-dump circuit operates at a very high rate whereas the loop update rate is very slow by comparison. Because of this dichotomy, the loop can be analyzed by hybrid analog/digital (s/z domain) techniques. The loop is modeled in such a general fashion that previous analyses of the Real-Time Combiner (RTC), Subcarrier Demodulator Assembly (SDA), and Symbol Synchronization Assembly (SSA) fall out as special cases.

Kilohertz binary phase modulator for pulsed laser sources using a digital micromirror device.

PubMed

Hoffmann, Maximilian; Papadopoulos, Ioannis N; Judkewitz, Benjamin

2018-01-01

The controlled modulation of an optical wavefront is required for aberration correction, digital phase conjugation, or patterned photostimulation. For most of these applications, it is desirable to control the wavefront modulation at the highest rates possible. The digital micromirror device (DMD) presents a cost-effective solution to achieve high-speed modulation and often exceeds the speed of the more conventional liquid crystal spatial light modulator but is inherently an amplitude modulator. Furthermore, spatial dispersion caused by DMD diffraction complicates its use with pulsed laser sources, such as those used in nonlinear microscopy. Here we introduce a DMD-based optical design that overcomes these limitations and achieves dispersion-free high-speed binary phase modulation. We show that this phase modulation can be used to switch through binary phase patterns at the rate of 20 kHz in two-photon excitation fluorescence applications.

Kilohertz binary phase modulator for pulsed laser sources using a digital micromirror device

NASA Astrophysics Data System (ADS)

Hoffmann, Maximilian; Papadopoulos, Ioannis N.; Judkewitz, Benjamin

2018-01-01

The controlled modulation of an optical wavefront is required for aberration correction, digital phase conjugation or patterned photostimulation. For most of these applications it is desirable to control the wavefront modulation at the highest rates possible. The digital micromirror device (DMD) presents a cost-effective solution to achieve high-speed modulation and often exceeds the speed of the more conventional liquid crystal spatial light modulator, but is inherently an amplitude modulator. Furthermore, spatial dispersion caused by DMD diffraction complicates its use with pulsed laser sources, such as those used in nonlinear microscopy. Here we introduce a DMD-based optical design that overcomes these limitations and achieves dispersion-free high-speed binary phase modulation. We show that this phase modulation can be used to switch through binary phase patterns at the rate of 20 kHz in two-photon excitation fluorescence applications.

Multi-scale imaging and elastic simulation of carbonates

NASA Astrophysics Data System (ADS)

Faisal, Titly Farhana; Awedalkarim, Ahmed; Jouini, Mohamed Soufiane; Jouiad, Mustapha; Chevalier, Sylvie; Sassi, Mohamed

2016-05-01

Digital Rock Physics (DRP) is an emerging technology that can be used to generate high quality, fast and cost effective special core analysis (SCAL) properties compared to conventional experimental techniques and modeling techniques. The primary workflow of DRP conssits of three elements: 1) image the rock sample using high resolution 3D scanning techniques (e.g. micro CT, FIB/SEM), 2) process and digitize the images by segmenting the pore and matrix phases 3) simulate the desired physical properties of the rocks such as elastic moduli and velocities of wave propagation. A Finite Element Method based algorithm, that discretizes the basic Hooke's Law equation of linear elasticity and solves it numerically using a fast conjugate gradient solver, developed by Garboczi and Day [1] is used for mechanical and elastic property simulations. This elastic algorithm works directly on the digital images by treating each pixel as an element. The images are assumed to have periodic constant-strain boundary condition. The bulk and shear moduli of the different phases are required inputs. For standard 1.5" diameter cores however the Micro-CT scanning reoslution (around 40 μm) does not reveal smaller micro- and nano- pores beyond the resolution. This results in an unresolved "microporous" phase, the moduli of which is uncertain. Knackstedt et al. [2] assigned effective elastic moduli to the microporous phase based on self-consistent theory (which gives good estimation of velocities for well cemented granular media). Jouini et al. [3] segmented the core plug CT scan image into three phases and assumed that micro porous phase is represented by a sub-extracted micro plug (which too was scanned using Micro-CT). Currently the elastic numerical simulations based on CT-images alone largely overpredict the bulk, shear and Young's modulus when compared to laboratory acoustic tests of the same rocks. For greater accuracy of numerical simulation prediction, better estimates of moduli inputs for this current unresolved phase is important. In this work we take a multi-scale imaging approach by first extracting a smaller 0.5" core and scanning at approx 13 µm, then further extracting a 5mm diameter core scanned at 5 μm. From this last scale, region of interests (containing unresolved areas) are identified for scanning at higher resolutions using Focalised Ion Beam (FIB/SEM) scanning technique reaching 50 nm resolution. Numerical simulation is run on such a small unresolved section to obtain a better estimate of the effective moduli which is then used as input for simulations performed using CT-images. Results are compared with expeirmental acoustic test moduli obtained also at two scales: 1.5" and 0.5" diameter cores.

A Fully Integrated Sensor SoC with Digital Calibration Hardware and Wireless Transceiver at 2.4 GHz

PubMed Central

Kim, Dong-Sun; Jang, Sung-Joon; Hwang, Tae-Ho

2013-01-01

A single-chip sensor system-on-a-chip (SoC) that implements radio for 2.4 GHz, complete digital baseband physical layer (PHY), 10-bit sigma-delta analog-to-digital converter and dedicated sensor calibration hardware for industrial sensing systems has been proposed and integrated in a 0.18-μm CMOS technology. The transceiver's building block includes a low-noise amplifier, mixer, channel filter, receiver signal-strength indicator, frequency synthesizer, voltage-controlled oscillator, and power amplifier. In addition, the digital building block consists of offset quadrature phase-shift keying (OQPSK) modulation, demodulation, carrier frequency offset compensation, auto-gain control, digital MAC function, sensor calibration hardware and embedded 8-bit microcontroller. The digital MAC function supports cyclic redundancy check (CRC), inter-symbol timing check, MAC frame control, and automatic retransmission. The embedded sensor signal processing block consists of calibration coefficient calculator, sensing data calibration mapper and sigma-delta analog-to-digital converter with digital decimation filter. The sensitivity of the overall receiver and the error vector magnitude (EVM) of the overall transmitter are −99 dBm and 18.14%, respectively. The proposed calibration scheme has a reduction of errors by about 45.4% compared with the improved progressive polynomial calibration (PPC) method and the maximum current consumption of the SoC is 16 mA. PMID:23698271

Input-output characterization of an ultrasonic testing system by digital signal analysis

NASA Technical Reports Server (NTRS)

Williams, J. H., Jr.; Lee, S. S.; Karagulle, H.

1986-01-01

Ultrasonic test system input-output characteristics were investigated by directly coupling the transmitting and receiving transducers face to face without a test specimen. Some of the fundamentals of digital signal processing were summarized. Input and output signals were digitized by using a digital oscilloscope, and the digitized data were processed in a microcomputer by using digital signal-processing techniques. The continuous-time test system was modeled as a discrete-time, linear, shift-invariant system. In estimating the unit-sample response and frequency response of the discrete-time system, it was necessary to use digital filtering to remove low-amplitude noise, which interfered with deconvolution calculations. A digital bandpass filter constructed with the assistance of a Blackman window and a rectangular time window were used. Approximations of the impulse response and the frequency response of the continuous-time test system were obtained by linearly interpolating the defining points of the unit-sample response and the frequency response of the discrete-time system. The test system behaved as a linear-phase bandpass filter in the frequency range 0.6 to 2.3 MHz. These frequencies were selected in accordance with the criterion that they were 6 dB below the maximum peak of the amplitude of the frequency response. The output of the system to various inputs was predicted and the results were compared with the corresponding measurements on the system.

Frequency control circuit for all-digital phase-lock loops

NASA Technical Reports Server (NTRS)

Anderson, T. O.

1973-01-01

Phase-lock loop references all its operations to fixed high-frequency service clock operating at highest speed which digital circuits permit. Wide-range control circuit provides linear control of frequency of reference signal. It requires only two counters in combination with control circuit consisting only of flip-flop and gate.

A note on the generation of phase plane plots on a digital computer. [for solution of nonlinear differential equations

NASA Technical Reports Server (NTRS)

Simon, M. K.

1980-01-01

A technique is presented for generating phase plane plots on a digital computer which circumvents the difficulties associated with more traditional methods of numerical solving nonlinear differential equations. In particular, the nonlinear differential equation of operation is formulated.

Digital phase-locked-loop speed sensor for accuracy improvement in analog speed controls. [feedback control and integrated circuits

NASA Technical Reports Server (NTRS)

Birchenough, A. G.

1975-01-01

A digital speed control that can be combined with a proportional analog controller is described. The stability and transient response of the analog controller were retained and combined with the long-term accuracy of a crystal-controlled integral controller. A relatively simple circuit was developed by using phase-locked-loop techniques and total error storage. The integral digital controller will maintain speed control accuracy equal to that of the crystal reference oscillator.

Phase retrieval without unwrapping by single-shot dual-wavelength digital holography

NASA Astrophysics Data System (ADS)

Min, Junwei; Yao, Baoli; Zhou, Meiling; Guo, Rongli; Lei, Ming; Yang, Yanlong; Dan, Dan; Yan, Shaohui; Peng, Tong

2014-12-01

A phase retrieval method by using single-shot dual-wavelength digital holography is proposed. Each single wavelength hologram is extracted from the color CCD recorded hologram at one exposure, and the unwrapped phase image of object can be reconstructed directly. Different from the traditional multiple wavelength phase unwrapping techniques, any single complex wave-fronts at different wavelengths have no need to be calculated any more. Thus, the phase retrieval is computationally fast and straightforward, and the limitations on the total optical path difference are significantly relaxed. The practicability of the proposed method is demonstrated by both simulated and experimental results.

Time-Dependent Traveling Wave Tube Model for Intersymbol Interference Investigations

NASA Technical Reports Server (NTRS)

Kory, Carol L.; Andro, Monty; Downey, Alan (Technical Monitor)

2001-01-01

For the first time, a computational model has been used to provide a direct description of the effects of the traveling wave tube (TWT) on modulated digital signals. The TWT model comprehensively takes into account the effects of frequency dependent AM/AM and AM/PM conversion, gain and phase ripple; drive-induced oscillations; harmonic generation; intermodulation products; and backward waves. Thus, signal integrity can be investigated in the presence of these sources of potential distortion as a function of the physical geometry of the high power amplifier and the operational digital signal. This method promises superior predictive fidelity compared to methods using TWT models based on swept-amplitude and/or swept-frequency data. The fully three-dimensional (3D), time-dependent, TWT interaction model using the electromagnetic code MAFIA is presented. This model is used to investigate assumptions made in TWT black-box models used in communication system level simulations. In addition, digital signal performance, including intersymbol interference (ISI), is compared using direct data input into the MAFIA model and using the system level analysis tool, SPW.

Intersymbol Interference Investigations Using a 3D Time-Dependent Traveling Wave Tube Model

NASA Technical Reports Server (NTRS)

Kory, Carol L.; Andro, Monty; Downey, Alan (Technical Monitor)

2001-01-01

For the first time, a physics based computational model has been used to provide a direct description of the effects of the TWT (Traveling Wave Tube) on modulated digital signals. The TWT model comprehensively takes into account the effects of frequency dependent AM/AM and AM/PM conversion; gain and phase ripple; drive-induced oscillations; harmonic generation; intermodulation products; and backward waves. Thus, signal integrity can be investigated in the presence of these sources of potential distortion as a function of the physical geometry of the high power amplifier and the operational digital signal. This method promises superior predictive fidelity compared to methods using TWT models based on swept amplitude and/or swept frequency data. The fully three-dimensional (3D), time-dependent, TWT interaction model using the electromagnetic code MAFIA is presented. This model is used to investigate assumptions made in TWT black box models used in communication system level simulations. In addition, digital signal performance, including intersymbol interference (ISI), is compared using direct data input into the MAFIA model and using the system level analysis tool, SPW (Signal Processing Worksystem).

CryoPAF4: a cryogenic phased array feed design

NASA Astrophysics Data System (ADS)

Locke, Lisa; Garcia, Dominic; Halman, Mark; Henke, Doug; Hovey, Gary; Jiang, Nianhua; Knee, Lewis; Lacy, Gordon; Loop, David; Rupen, Michael; Veidt, Bruce; Wierzbicki, Ramunas

2016-07-01

Phased array feed (PAF) receivers used on radio astronomy telescopes offer the promise of increased fields of view while maintaining the superlative performance attained with traditional single pixel feeds (SPFs). However, the much higher noise temperatures of room temperature PAFs compared to cryogenically-cooled SPFs have prevented their general adoption. Here we describe a conceptual design for a cryogenically cooled 2.8 - 5.18 GHz dual linear polarization PAF with estimated receiver temperature of 11 K. The cryogenic PAF receiver will comprise a 140 element Vivaldi antenna array and low-noise amplifiers housed in a 480 mm diameter cylindrical dewar covered with a RF transparent radome. A broadband two-section coaxial feed is integrated within each metal antenna element to withstand the cryogenic environment and to provide a 50 ohm impedance for connection to the rest of the receiver. The planned digital beamformer performs digitization, frequency band selection, beam forming and array covariance matrix calibration. Coupling to a 15 m offset Gregorian dual-reflector telescope, cryoPAF4 can expect to form 18 overlapping beams increasing the field of view by a factor of 8x compared to a single pixel receiver of equal system temperature.

MMIC linear-phase and digital modulators for deep space spacecraft X-band transponder applications

NASA Technical Reports Server (NTRS)

Mysoor, Narayan R.; Ali, Fazal

1991-01-01

The design concepts, analyses, and development of GaAs monolithic microwave integrated circuit (MMIC) linear-phase and digital modulators for the next generation of space-borne communications systems are summarized. The design approach uses a compact lumped element quadrature hybrid and Metal Semiconductor Field Effect Transistors (MESFET)-varactors to provide low loss and well-controlled phase performance for deep space transponder (DST) applications. The measured results of the MESFET-diode show a capacitance range of 2:1 under reverse bias, and a Q of 38 at 10 GHz. Three cascaded sections of hybrid-coupled reflection phase shifters were modeled and simulations performed to provide an X-band (8415 +/- 50 MHz) DST phase modulator with +/- 2.5 radians of peak phase deviation. The modulator will accommodate downlink signal modulation with composite telemetry and ranging data, with a deviation linearity tolerance of +/- 8 percent and insertion loss of less than 8 +/- 0.5 dB. The MMIC digital modulator is designed to provide greater than 10 Mb/s of bi-phase modulation at X-band.

A 45 ps time digitizer with a two-phase clock and dual-edge two-stage interpolation in a field programmable gate array device

NASA Astrophysics Data System (ADS)

Szplet, R.; Kalisz, J.; Jachna, Z.

2009-02-01

We present a time digitizer having 45 ps resolution, integrated in a field programmable gate array (FPGA) device. The time interval measurement is based on the two-stage interpolation method. A dual-edge two-phase interpolator is driven by the on-chip synthesized 250 MHz clock with precise phase adjustment. An improved dual-edge double synchronizer was developed to control the main counter. The nonlinearity of the digitizer's transfer characteristic is identified and utilized by the dedicated hardware code processor for the on-the-fly correction of the output data. Application of presented ideas has resulted in the measurement uncertainty of the digitizer below 70 ps RMS over the time interval ranging from 0 to 1 s. The use of the two-stage interpolation and a fast FIFO memory has allowed us to obtain the maximum measurement rate of five million measurements per second.

Deep-turbulence wavefront sensing using digital holography in the on-axis phase shifting recording geometry

NASA Astrophysics Data System (ADS)

Thornton, Douglas E.; Spencer, Mark F.; Perram, Glen P.

2017-09-01

The effects of deep turbulence in long-range imaging applications presents unique challenges to properly measure and correct for aberrations incurred along the atmospheric path. In practice, digital holography can detect the path-integrated wavefront distortions caused by deep turbulence, and di erent recording geometries offer different benefits depending on the application of interest. Previous studies have evaluated the performance of the off-axis image and pupil plane recording geometries for deep-turbulence sensing. This study models digital holography in the on-axis phase shifting recording geometry using wave optics simulations. In particular, the analysis models spherical-wave propagation through varying deep-turbulence conditions to estimate the complex optical field, and performance is evaluated by calculating the field-estimated Strehl ratio and RMS wavefront error. Altogether, the results show that digital holography in the on-axis phase shifting recording geometry is an effective wavefront-sensing method in the presence of deep turbulence.

Propagation phasor approach for holographic image reconstruction

PubMed Central

Luo, Wei; Zhang, Yibo; Göröcs, Zoltán; Feizi, Alborz; Ozcan, Aydogan

2016-01-01

To achieve high-resolution and wide field-of-view, digital holographic imaging techniques need to tackle two major challenges: phase recovery and spatial undersampling. Previously, these challenges were separately addressed using phase retrieval and pixel super-resolution algorithms, which utilize the diversity of different imaging parameters. Although existing holographic imaging methods can achieve large space-bandwidth-products by performing pixel super-resolution and phase retrieval sequentially, they require large amounts of data, which might be a limitation in high-speed or cost-effective imaging applications. Here we report a propagation phasor approach, which for the first time combines phase retrieval and pixel super-resolution into a unified mathematical framework and enables the synthesis of new holographic image reconstruction methods with significantly improved data efficiency. In this approach, twin image and spatial aliasing signals, along with other digital artifacts, are interpreted as noise terms that are modulated by phasors that analytically depend on the lateral displacement between hologram and sensor planes, sample-to-sensor distance, wavelength, and the illumination angle. Compared to previous holographic reconstruction techniques, this new framework results in five- to seven-fold reduced number of raw measurements, while still achieving a competitive resolution and space-bandwidth-product. We also demonstrated the success of this approach by imaging biological specimens including Papanicolaou and blood smears. PMID:26964671

Development of the Phase-up Technology of the Radio Telescopes: 6.7 GHz Methanol Maser Observations with Phased Hitachi 32 m and Takahagi 32 m Radio Telescopes

NASA Astrophysics Data System (ADS)

Takefuji, K.; Sugiyama, K.; Yonekura, Y.; Saito, T.; Fujisawa, K.; Kondo, T.

2017-11-01

For the sake of high-sensitivity 6.7 GHz methanol maser observations, we developed a new technology for coherently combining the two signals from the Hitachi 32 m radio telescope and the Takahagi 32 m radio telescope of the Japanese Very long baseline interferometer Network (JVN), where the two telescopes were separated by about 260 m. After the two telescopes were phased as a twofold larger single telescope, the mean signal-to-noise ratio (S/N) of the 6.7 GHz methanol masers observed by the phased telescopes was improved to 1.254-fold higher than that of the single dish, through a very long baseline interferometry (VLBI) experiment on the 50 km baseline of the Kashima 34 m telescope and the 1000 km baseline of the Yamaguchi 32 m telescope. Furthermore, we compared the S/Ns of the 6.7 GHz maser spectra for two methods. One is a VLBI method and the other is the newly developed digital position switching that is a similar technology to that used in noise-canceling headphones. Finally, we confirmed that the mean S/N of method of the digital position switching (ON-OFF) was 1.597-fold higher than that of the VLBI method.

A class of optimum digital phase locked loops

NASA Technical Reports Server (NTRS)

Kumar, R.; Hurd, W. J.

1986-01-01

This paper presents a class of optimum digital filters for digital phase locked loops, for the important case in which the maximum update rate of the loop filter and numerically controlled oscillator (NCO) is limited. This case is typical when the loop filter is implemented in a microprocessor. In these situations, pure delay is encountered in the loop transfer function and thus the stability and gain margin of the loop are of crucial interest. The optimum filters designed for such situations are evaluated in terms of their gain margin for stability, dynamic error, and steady-state error performance. For situations involving considerably high phase dynamics an adaptive and programmable implementation is also proposed to obtain an overall optimum strategy.

A second-order all-digital phase-locked loop

NASA Technical Reports Server (NTRS)

Holmes, J. K.; Tegnelia, C. R.

1974-01-01

A simple second-order digital phase-locked loop has been designed to synchronize itself to a square-wave subcarrier. Analysis and experimental performance are given for both acquisition behavior and steady-state phase error performance. In addition, the damping factor and the noise bandwidth are derived analytically. Although all the data are given for the square-wave subcarrier case, the results are applicable to arbitrary subcarriers that are odd symmetric about their transition region.

An image encryption algorithm based on 3D cellular automata and chaotic maps

NASA Astrophysics Data System (ADS)

Del Rey, A. Martín; Sánchez, G. Rodríguez

2015-05-01

A novel encryption algorithm to cipher digital images is presented in this work. The digital image is rendering into a three-dimensional (3D) lattice and the protocol consists of two phases: the confusion phase where 24 chaotic Cat maps are applied and the diffusion phase where a 3D cellular automata is evolved. The encryption method is shown to be secure against the most important cryptanalytic attacks.

Quantitative assessment of cancer cell morphology and motility using telecentric digital holographic microscopy and machine learning.

PubMed

Lam, Van K; Nguyen, Thanh C; Chung, Byung M; Nehmetallah, George; Raub, Christopher B

2018-03-01

The noninvasive, fast acquisition of quantitative phase maps using digital holographic microscopy (DHM) allows tracking of rapid cellular motility on transparent substrates. On two-dimensional surfaces in vitro, MDA-MB-231 cancer cells assume several morphologies related to the mode of migration and substrate stiffness, relevant to mechanisms of cancer invasiveness in vivo. The quantitative phase information from DHM may accurately classify adhesive cancer cell subpopulations with clinical relevance. To test this, cells from the invasive breast cancer MDA-MB-231 cell line were cultured on glass, tissue-culture treated polystyrene, and collagen hydrogels, and imaged with DHM followed by epifluorescence microscopy after staining F-actin and nuclei. Trends in cell phase parameters were tracked on the different substrates, during cell division, and during matrix adhesion, relating them to F-actin features. Support vector machine learning algorithms were trained and tested using parameters from holographic phase reconstructions and cell geometric features from conventional phase images, and used to distinguish between elongated and rounded cell morphologies. DHM was able to distinguish between elongated and rounded morphologies of MDA-MB-231 cells with 94% accuracy, compared to 83% accuracy using cell geometric features from conventional brightfield microscopy. This finding indicates the potential of DHM to detect and monitor cancer cell morphologies relevant to cell cycle phase status, substrate adhesion, and motility. © 2017 International Society for Advancement of Cytometry. © 2017 International Society for Advancement of Cytometry.

Optical design of cipher block chaining (CBC) encryption mode by using digital holography

NASA Astrophysics Data System (ADS)

Gil, Sang Keun; Jeon, Seok Hee; Jung, Jong Rae; Kim, Nam

2016-03-01

We propose an optical design of cipher block chaining (CBC) encryption by using digital holographic technique, which has higher security than the conventional electronic method because of the analog-type randomized cipher text with 2-D array. In this paper, an optical design of CBC encryption mode is implemented by 2-step quadrature phase-shifting digital holographic encryption technique using orthogonal polarization. A block of plain text is encrypted with the encryption key by applying 2-step phase-shifting digital holography, and it is changed into cipher text blocks which are digital holograms. These ciphered digital holograms with the encrypted information are Fourier transform holograms and are recorded on CCDs with 256 gray levels quantized intensities. The decryption is computed by these encrypted digital holograms of cipher texts, the same encryption key and the previous cipher text. Results of computer simulations are presented to verify that the proposed method shows the feasibility in the high secure CBC encryption system.

A class of optimum digital phase locked loops for the DSN advanced receiver

NASA Technical Reports Server (NTRS)

Hurd, W. J.; Kumar, R.

1985-01-01

A class of optimum digital filters for digital phase locked loop of the deep space network advanced receiver is discussed. The filter minimizes a weighted combination of the variance of the random component of the phase error and the sum square of the deterministic dynamic component of phase error at the output of the numerically controlled oscillator (NCO). By varying the weighting coefficient over a suitable range of values, a wide set of filters are obtained such that, for any specified value of the equivalent loop-noise bandwidth, there corresponds a unique filter in this class. This filter thus has the property of having the best transient response over all possible filters of the same bandwidth and type. The optimum filters are also evaluated in terms of their gain margin for stability and their steady-state error performance.

Novel Perspectives on the Characterization of Species-Dependent Optical Signatures of Bacterial Colonies by Digital Holography.

PubMed

Buzalewicz, Igor; Kujawińska, Małgorzata; Krauze, Wojciech; Podbielska, Halina

2016-01-01

The use of light diffraction for the microbiological diagnosis of bacterial colonies was a significant breakthrough with widespread implications for the food industry and clinical practice. We previously confirmed that optical sensors for bacterial colony light diffraction can be used for bacterial identification. This paper is focused on the novel perspectives of this method based on digital in-line holography (DIH), which is able to reconstruct the amplitude and phase properties of examined objects, as well as the amplitude and phase patterns of the optical field scattered/diffracted by the bacterial colony in any chosen observation plane behind the object from single digital hologram. Analysis of the amplitude and phase patterns inside a colony revealed its unique optical properties, which are associated with the internal structure and geometry of the bacterial colony. Moreover, on a computational level, it is possible to select the desired scattered/diffracted pattern within the entire observation volume that exhibits the largest amount of unique, differentiating bacterial features. These properties distinguish this method from the already proposed sensing techniques based on light diffraction/scattering of bacterial colonies. The reconstructed diffraction patterns have a similar spatial distribution as the recorded Fresnel patterns, previously applied for bacterial identification with over 98% accuracy, but they are characterized by both intensity and phase distributions. Our results using digital holography provide new optical discriminators of bacterial species revealed in one single step in form of new optical signatures of bacterial colonies: digital holograms, reconstructed amplitude and phase patterns, as well as diffraction patterns from all observation space, which exhibit species-dependent features. To the best of our knowledge, this is the first report on bacterial colony analysis via digital holography and our study represents an innovative approach to the subject.

Novel Perspectives on the Characterization of Species-Dependent Optical Signatures of Bacterial Colonies by Digital Holography

PubMed Central

Buzalewicz, Igor; Kujawińska, Małgorzata; Krauze, Wojciech; Podbielska, Halina

2016-01-01

The use of light diffraction for the microbiological diagnosis of bacterial colonies was a significant breakthrough with widespread implications for the food industry and clinical practice. We previously confirmed that optical sensors for bacterial colony light diffraction can be used for bacterial identification. This paper is focused on the novel perspectives of this method based on digital in-line holography (DIH), which is able to reconstruct the amplitude and phase properties of examined objects, as well as the amplitude and phase patterns of the optical field scattered/diffracted by the bacterial colony in any chosen observation plane behind the object from single digital hologram. Analysis of the amplitude and phase patterns inside a colony revealed its unique optical properties, which are associated with the internal structure and geometry of the bacterial colony. Moreover, on a computational level, it is possible to select the desired scattered/diffracted pattern within the entire observation volume that exhibits the largest amount of unique, differentiating bacterial features. These properties distinguish this method from the already proposed sensing techniques based on light diffraction/scattering of bacterial colonies. The reconstructed diffraction patterns have a similar spatial distribution as the recorded Fresnel patterns, previously applied for bacterial identification with over 98% accuracy, but they are characterized by both intensity and phase distributions. Our results using digital holography provide new optical discriminators of bacterial species revealed in one single step in form of new optical signatures of bacterial colonies: digital holograms, reconstructed amplitude and phase patterns, as well as diffraction patterns from all observation space, which exhibit species-dependent features. To the best of our knowledge, this is the first report on bacterial colony analysis via digital holography and our study represents an innovative approach to the subject. PMID:26943121

Vocal Fold Phase Asymmetries in Patients with Voice Disorders: A Study across Visualization Techniques

ERIC Educational Resources Information Center

Bonilha, Heather Shaw; Deliyski, Dimitar D.; Whiteside, Joanna Piasecki; Gerlach, Terri Treman

2012-01-01

Purpose: To examine differences in vocal fold vibratory phase asymmetry judged from stroboscopy, high-speed videoendoscopy (HSV), and the HSV-derived playbacks of mucosal wave kymography, digital kymography, and a static medial digital kymography image of persons with hypofunctional and hyperfunctional voice disorders. Differences between the…

Direct-phase and amplitude digitalization based on free-space interferometry

NASA Astrophysics Data System (ADS)

Kleiner, Vladimir; Rudnitsky, Arkady; Zalevsky, Zeev

2017-12-01

A novel ADC configuration that can be characterized as a photonic-domain flash analog-to-digital convertor operating based upon free-space interferometry is proposed and analysed. The structure can be used as the front-end of a coherent receiver as well as for other applications. Two configurations are considered: the first, ‘direct free-space interference’, allows simultaneous measuring of the optical phase and amplitude; the second, ‘extraction of the ac component of interference by means of pixel-by-pixel balanced photodetection’, allows only phase digitization but with significantly higher sensitivity. For both proposed configurations, we present Monte Carlo estimations of the performance limitations, due to optical noise and photo-current noise, at sampling rates of 60 giga-samples per second. In terms of bit resolution, we simulated multiple cases with growing complexity of up to 4 bits for the amplitude and up to 6 bits for the phase. The simulations show that the digitization errors in the optical domain can be reduced to levels close to the quantization noise limits. Preliminary experimental results validate the fundamentals of the proposed idea.

Thermal residual stress evaluation based on phase-shift lateral shearing interferometry

NASA Astrophysics Data System (ADS)

Dai, Xiangjun; Yun, Hai; Shao, Xinxing; Wang, Yanxia; Zhang, Donghuan; Yang, Fujun; He, Xiaoyuan

2018-06-01

An interesting phase-shift lateral shearing interferometry system was proposed to evaluate the thermal residual stress distribution in transparent specimen. The phase-shift interferograms was generated by moving a parallel plane plate. Based on analyzing the fringes deflected by deformation and refractive index change, the stress distribution can be obtained. To verify the validity of the proposed method, a typical experiment was elaborately designed to determine thermal residual stresses of a transparent PMMA plate subjected to the flame of a lighter. The sum of in-plane stress distribution was demonstrated. The experimental data were compared with values measured by digital gradient sensing method. Comparison of the results reveals the effectiveness and feasibility of the proposed method.

Neural Networks For Demodulation Of Phase-Modulated Signals

NASA Technical Reports Server (NTRS)

Altes, Richard A.

1995-01-01

Hopfield neural networks proposed for demodulating quadrature phase-shift-keyed (QPSK) signals carrying digital information. Networks solve nonlinear integral equations prior demodulation circuits cannot solve. Consists of set of N operational amplifiers connected in parallel, with weighted feedback from output terminal of each amplifier to input terminals of other amplifiers. Used to solve signal processing problems. Implemented as analog very-large-scale integrated circuit that achieves rapid convergence. Alternatively, implemented as digital simulation of such circuit. Also used to improve phase estimation performance over that of phase-locked loop.

Retrieval of phase-derivative discontinuities in digital speckle pattern interferometry fringes using the Wigner-Ville distribution

NASA Astrophysics Data System (ADS)

Federico, Alejandro; Kaufmann, Guillermo H.

2004-08-01

We evaluate the application of the Wigner-Ville distribution (WVD) to measure phase gradient maps in digital speckle pattern interferometry (DSPI), when the generated correlation fringes present phase discontinuities. The performance of the WVD method is evaluated using computer-simulated fringes. The influence of the filtering process to smooth DSPI fringes and additional drawbacks that emerge when this method is applied are discussed. A comparison with the conventional method based on the continuous wavelet transform in the stationary phase approximation is also presented.

Pulsed spatial phase-shifting digital shearography based on a micropolarizer camera

NASA Astrophysics Data System (ADS)

Aranchuk, Vyacheslav; Lal, Amit K.; Hess, Cecil F.; Trolinger, James Davis; Scott, Eddie

2018-02-01

We developed a pulsed digital shearography system that utilizes the spatial phase-shifting technique. The system employs a commercial micropolarizer camera and a double pulse laser, which allows for instantaneous phase measurements. The system can measure dynamic deformation of objects as large as 1 m at a 2-m distance during the time between two laser pulses that range from 30 μs to 30 ms. The ability of the system to measure dynamic deformation was demonstrated by obtaining phase wrapped and unwrapped shearograms of a vibrating object.

Optical encryption interface

NASA Technical Reports Server (NTRS)

Jackson, Deborah J. (Inventor)

1998-01-01

An analog optical encryption system based on phase scrambling of two-dimensional optical images and holographic transformation for achieving large encryption keys and high encryption speed. An enciphering interface uses a spatial light modulator for converting a digital data stream into a two dimensional optical image. The optical image is further transformed into a hologram with a random phase distribution. The hologram is converted into digital form for transmission over a shared information channel. A respective deciphering interface at a receiver reverses the encrypting process by using a phase conjugate reconstruction of the phase scrambled hologram.

Digital phase demodulation for low-coherence interferometry-based fiber-optic sensors

NASA Astrophysics Data System (ADS)

Liu, Y.; Strum, R.; Stiles, D.; Long, C.; Rakhman, A.; Blokland, W.; Winder, D.; Riemer, B.; Wendel, M.

2018-03-01

We describe a digital phase demodulation scheme for low-coherence interferometry-based fiber-optic sensors by employing a simple generation of phase-shifted signals at the interrogation interferometer. The scheme allows a real-time calibration process and offers capability of measuring large variations (up to the coherence of the light source) at the bandwidth that is only limited by the data acquisition system. The proposed phase demodulation method is analytically derived and its validity and performance are experimentally verified using fiber-optic Fabry-Perot sensors for measurement of strains and vibrations.

Dual-wavelength phase-shifting digital holography selectively extracting wavelength information from wavelength-multiplexed holograms.

PubMed

Tahara, Tatsuki; Mori, Ryota; Kikunaga, Shuhei; Arai, Yasuhiko; Takaki, Yasuhiro

2015-06-15

Dual-wavelength phase-shifting digital holography that selectively extracts wavelength information from five wavelength-multiplexed holograms is presented. Specific phase shifts for respective wavelengths are introduced to remove the crosstalk components and extract only the object wave at the desired wavelength from the holograms. Object waves in multiple wavelengths are selectively extracted by utilizing 2π ambiguity and the subtraction procedures based on phase-shifting interferometry. Numerical results show the validity of the proposed technique. The proposed technique is also experimentally demonstrated.

Improvement of the GERDA Ge Detectors Energy Resolution by an Optimized Digital Signal Processing

NASA Astrophysics Data System (ADS)

Benato, G.; D'Andrea, V.; Cattadori, C.; Riboldi, S.

GERDA is a new generation experiment searching for neutrinoless double beta decay of 76Ge, operating at INFN Gran Sasso Laboratories (LNGS) since 2010. Coaxial and Broad Energy Germanium (BEGe) Detectors have been operated in liquid argon (LAr) in GERDA Phase I. In the framework of the second GERDA experimental phase, both the contacting technique, the connection to and the location of the front end readout devices are novel compared to those previously adopted, and several tests have been performed. In this work, starting from considerations on the energy scale stability of the GERDA Phase I calibrations and physics data sets, an optimized pulse filtering method has been developed and applied to the Phase II pilot tests data sets, and to few GERDA Phase I data sets. In this contribution the detector performances in term of energy resolution and time stability are here presented. The improvement of the energy resolution, compared to standard Gaussian shaping adopted for Phase I data analysis, is discussed and related to the optimized noise filtering capability. The result is an energy resolution better than 0.1% at 2.6 MeV for the BEGe detectors operated in the Phase II pilot tests and an improvement of the energy resolution in LAr of about 8% achieved on the GERDA Phase I calibration runs, compared to previous analysis algorithms.

A hybrid analog-digital phase-locked loop for frequency mode non-contact scanning probe microscopy.

PubMed

Mehta, M M; Chandrasekhar, V

2014-01-01

Non-contact scanning probe microscopy (SPM) has developed into a powerful technique to image many different properties of samples. The conventional method involves monitoring the amplitude, phase, or frequency of a cantilever oscillating at or near its resonant frequency as it is scanned across the surface of a sample. For high Q factor cantilevers, monitoring the resonant frequency is the preferred method in order to obtain reasonable scan times. This can be done by using a phase-locked-loop (PLL). PLLs can be obtained as commercial integrated circuits, but these do not have the frequency resolution required for SPM. To increase the resolution, all-digital PLLs requiring sophisticated digital signal processors or field programmable gate arrays have also been implemented. We describe here a hybrid analog/digital PLL where most of the components are implemented using discrete analog integrated circuits, but the frequency resolution is provided by a direct digital synthesis chip controlled by a simple peripheral interface controller (PIC) microcontroller. The PLL has excellent frequency resolution and noise, and can be controlled and read by a computer via a universal serial bus connection.

A hybrid analog-digital phase-locked loop for frequency mode non-contact scanning probe microscopy

NASA Astrophysics Data System (ADS)

Mehta, M. M.; Chandrasekhar, V.

2014-01-01

Non-contact scanning probe microscopy (SPM) has developed into a powerful technique to image many different properties of samples. The conventional method involves monitoring the amplitude, phase, or frequency of a cantilever oscillating at or near its resonant frequency as it is scanned across the surface of a sample. For high Q factor cantilevers, monitoring the resonant frequency is the preferred method in order to obtain reasonable scan times. This can be done by using a phase-locked-loop (PLL). PLLs can be obtained as commercial integrated circuits, but these do not have the frequency resolution required for SPM. To increase the resolution, all-digital PLLs requiring sophisticated digital signal processors or field programmable gate arrays have also been implemented. We describe here a hybrid analog/digital PLL where most of the components are implemented using discrete analog integrated circuits, but the frequency resolution is provided by a direct digital synthesis chip controlled by a simple peripheral interface controller (PIC) microcontroller. The PLL has excellent frequency resolution and noise, and can be controlled and read by a computer via a universal serial bus connection.

Double closed-loop resonant micro optic gyro using hybrid digital phase modulation.

PubMed

Ma, Huilian; Zhang, Jianjie; Wang, Linglan; Jin, Zhonghe

2015-06-15

It is well-known that the closed-loop operation in optical gyros offers wider dynamic range and better linearity. By adding a stair-like digital serrodyne wave to a phase modulator can be used as a frequency shifter. The width of one stair in this stair-like digital serrodyne wave should be set equal to the optical transmission time in the resonator, which is relaxed in the hybrid digital phase modulation (HDPM) scheme. The physical mechanism for this relaxation is firstly indicated in this paper. Detailed theoretical and experimental investigations are presented for the HDPM. Simulation and experimental results show that the width of one stair is not restricted by the optical transmission time, however, it should be optimized according to the rise time of the output of the digital-to-analogue converter. Based on the optimum parameters of the HDPM, a bias stability of 0.05°/s for the integration time of 400 seconds in 1 h has been carried out in an RMOG with a waveguide ring resonator with a length of 7.9 cm and a diameter of 2.5 cm.

Digital quadrature phase detection

DOEpatents

Smith, James A.; Johnson, John A.

1992-01-01

A system for detecting the phase of a frequency of phase modulated signal that includes digital quadrature sampling of the frequency or phase modulated signal at two times that are one quarter of a cycle of a reference signal apart, determination of the arctangent of the ratio of a first sampling of the frequency or phase modulated signal to the second sampling of the frequency or phase modulated signal, and a determination of quadrant in which the phase determination is increased by 2.pi. when the quadrant changes from the first quadrant to the fourth quadrant and decreased by 2.pi. when the quadrant changes from the fourth quadrant to the first quadrant whereby the absolute phase of the frequency or phase modulated signal can be determined using an arbitrary reference convention.

Digital quadrature phase detection

DOEpatents

Smith, J.A.; Johnson, J.A.

1992-05-26

A system for detecting the phase of a frequency or phase modulated signal that includes digital quadrature sampling of the frequency or phase modulated signal at two times that are one quarter of a cycle of a reference signal apart, determination of the arctangent of the ratio of a first sampling of the frequency or phase modulated signal to the second sampling of the frequency or phase modulated signal, and a determination of quadrant in which the phase determination is increased by 2[pi] when the quadrant changes from the first quadrant to the fourth quadrant and decreased by 2[pi] when the quadrant changes from the fourth quadrant to the first quadrant whereby the absolute phase of the frequency or phase modulated signal can be determined using an arbitrary reference convention. 6 figs.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jacobina, C.B.; Silva, E.R.C. da; Lima, A.M.N.

This paper investigates the PWM operation of a four switch three phase inverter (FSTPI), in the case of digital implementation. Different switching sequence strategies for vector control are described and a digital scalar method is also presented. The influence of different switching patterns on the output voltage symmetry, current waveform and switching frequency are examined. The results obtained by employing the vector and scalar strategies are compared and a relationship between them is established. This comparison is based on analytical study and is corroborated either by the computer simulations and by the experimental results. The vector approach makes ease themore » understanding and analysis of the FSTPI, as well the choice of a PWM pattern. However, similar results may be obtained through the scalar approach, which has a simpler implementation. The experimental results of the use of the FSTPI and digital PWM to control an induction motor are presented.« less

Direct bit detection receiver noise performance analysis for 32-PSK and 64-PSK modulated signals

NASA Astrophysics Data System (ADS)

Ahmed, Iftikhar

1987-12-01

Simple two channel receivers for 32-PSK and 64-PSK modulated signals have been proposed which allow digital data (namely bits), to be recovered directly instead of the traditional approach of symbol detection followed by symbol to bit mappings. This allows for binary rather than M-ary receiver decisions, reduces the amount of signal processing operations and permits parallel recovery of the bits. The noise performance of these receivers quantified by the Bit Error Rate (BER) assuming an Additive White Gaussian Noise interference model is evaluated as a function of Eb/No, the signal to noise ratio, and transmitted phase angles of the signals. The performance results of the direct bit detection receivers (DBDR) when compared to that of convectional phase measurement receivers demonstrate that DBDR's are optimum in BER sense. The simplicity of the receiver implementations and the BER of the delivered data make DBDR's attractive for high speed, spectrally efficient digital communication systems.

Direct Measurement of Large, Diffuse, Optical Structures

NASA Technical Reports Server (NTRS)

Saif, Babak N.; Keski-Kuha, Ritva; Feinberg, Lee; Wyant, J. C.; Atkinson, C.

2004-01-01

Digital Speckle Pattern Interferometry (DSPI) is a well-established method for the measurement of diffuse objects in experimental mechanics. DSPIs are phase shifting interferometers. Three or four bucket temporal phase shifting algorithms are commonly used to provide phase shifting. These algorithms are sensitive to vibrations and can not be used to measure large optical structures far away from the interferometer. In this research a simultaneous phase shifted interferometer, PhaseCam product of 4D Technology Corporation in Tucson Arizona, is modified to be a Simultaneous phase shifted Digital Speckle Pattern Interferometer (SDSPI). Repeatability, dynamic range, and accuracy of the SDSPI are characterized by measuring a 5 cm x 5 cm carbon fiber coupon.

Multi-speed multi-phase resolver converter

NASA Technical Reports Server (NTRS)

Alhorn, Dean (Inventor); Howard, David (Inventor)

1994-01-01

A multiphase converter circuit generates a plurality of sinusoidal outputs of displaced phase and given speed value from the output of an angular resolver system attachable to a motor excited by these multi-phase outputs, the resolver system having a lower speed value than that of the motor. The angular resolver system provides in parallel format sequential digital numbers indicative of the amount of rotation of the shaft of an angular position sensor associated with the angular resolver system. These numbers are used to excite simultaneously identical addresses of a plurality of addressable memory systems, each memory system having stored therein at sequential addresses sequential values of a sinusoidal wavetrain of a given number of sinusoids. The stored wavetrain values represent sinusoids displaced from each other in phase according to the number of output phases desired. A digital-to-analog converter associated with each memory system converts each accessed word to a corresponding analog value to generate attendant to rotation of the angular resolver a sinusoidal wave of proper phase at each of the plurality of outputs. By properly orienting the angular resolver system with respect to the rotor of the motor, essentially ripple-free torque is supplied to the rotor. The angular resolver system may employ an analog resolver feeding an integrated circuit resolver-to-digital converter to produce the requisite digital values serving as addresses. Alternative versions employing incremental or absolute encoders are also described.

Multi-speed multi-phase resolver converter

NASA Technical Reports Server (NTRS)

Alhorn, Dean C. (Inventor); Howard, David E. (Inventor)

1995-01-01

A multiphase converter circuit generates a plurality of sinusoidal outputs of displaced phase and given speed value from the output of an angular resolver system attachable to a motor excited by these multi-phase outputs, the resolver system having a lower speed value than that of the motor. The angular resolver system provides in parallel format sequential digital numbers indicative of the amount of rotation of the shaft of an angular position sensor associated with the angular resolver system. These numbers are used to excite simultaneously identical addresses of a plurality of addressable memory systems, each memory system having stored therein at sequential addresses sequential values of a sinusoidal wavetrain of a given number of sinusoids. The stored wavetrain values represent sinusoids displaced from each other in phase according to the number of output phases desired. A digital-to-analog converter associated with each memory system converts each accessed word to a corresponding analog value to generate attendant to rotation of the angular resolver a sinusoidal wave of proper phase at each of the plurality of outputs. By properly orienting the angular resolver system with respect to the rotor of the motor, essentially ripple-free torque is supplied to the rotor. The angular resolver system may employ an analog resolver feeding an integrated circuit resolver-to-digital converter to produce the requisite digital values serving as addresses. Alternative versions employing incremental or absolute encoders are also described.

Frequency transfer via a two-way optical phase comparison on a multiplexed fiber network.

PubMed

Calosso, C E; Bertacco, E; Calonico, D; Clivati, C; Costanzo, G A; Frittelli, M; Levi, F; Mura, A; Godone, A

2014-03-01

We performed a two-way remote optical phase comparison on optical fiber. Two optical frequency signals were launched in opposite directions in an optical fiber and their phases were simultaneously measured at the other end. In this technique, the fiber noise is passively canceled, and we compared two optical frequencies at the ultimate 10(-21) stability level. The experiment was performed on a 47 km fiber that is part of the metropolitan network for Internet traffic. The technique relies on the synchronous measurement of the optical phases at the two ends of the link, which is here performed by digital electronics. This scheme offers some advantages with respect to active noise cancellation schemes, as the light travels only once in the fiber.

D Digitization of AN Heritage Masterpiece - a Critical Analysis on Quality Assessment

NASA Astrophysics Data System (ADS)

Menna, F.; Nocerino, E.; Remondino, F.; Dellepiane, M.; Callieri, M.; Scopigno, R.

2016-06-01

Despite being perceived as interchangeable when properly applied, close-range photogrammetry and range imaging have both their pros and limitations that can be overcome using suitable procedures. Even if the two techniques have been frequently cross-compared, critical analysis discussing all sub-phases of a complex digitization project are quite rare. Comparisons taking into account the digitization of a cultural masterpiece, such as the Etruscan Sarcophagus of the Spouses (Figure 1) discussed in this paper, are even less common. The final 3D model of the Sarcophagus shows impressive spatial and texture resolution, in the order of tenths of millimetre for both digitization techniques, making it a large 3D digital model even though the physical size of the artwork is quite limited. The paper presents the survey of the Sarcophagus, a late 6th century BC Etruscan anthropoid Sarcophagus. Photogrammetry and laser scanning were used for its 3D digitization in two different times only few days apart from each other. The very short time available for the digitization was a crucial constraint for the surveying operations (due to constraints imposed us by the museum curators). Despite very high-resolution and detailed 3D models have been produced, a metric comparison between the two models shows intrinsic limitations of each technique that should be overcome through suitable onsite metric verification procedures as well as a proper processing workflow.

Experimental demonstration of quantum digital signatures over 43 dB channel loss using differential phase shift quantum key distribution.

PubMed

Collins, Robert J; Amiri, Ryan; Fujiwara, Mikio; Honjo, Toshimori; Shimizu, Kaoru; Tamaki, Kiyoshi; Takeoka, Masahiro; Sasaki, Masahide; Andersson, Erika; Buller, Gerald S

2017-06-12

Ensuring the integrity and transferability of digital messages is an important challenge in modern communications. Although purely mathematical approaches exist, they usually rely on the computational complexity of certain functions, in which case there is no guarantee of long-term security. Alternatively, quantum digital signatures offer security guaranteed by the physical laws of quantum mechanics. Prior experimental demonstrations of quantum digital signatures in optical fiber have typically been limited to operation over short distances and/or operated in a laboratory environment. Here we report the experimental transmission of quantum digital signatures over channel losses of up to 42.8 ± 1.2 dB in a link comprised of 90 km of installed fiber with additional optical attenuation introduced to simulate longer distances. The channel loss of 42.8 ± 1.2 dB corresponds to an equivalent distance of 134.2 ± 3.8 km and this represents the longest effective distance and highest channel loss that quantum digital signatures have been shown to operate over to date. Our theoretical model indicates that this represents close to the maximum possible channel attenuation for this quantum digital signature protocol, defined as the loss for which the signal rate is comparable to the dark count rate of the detectors.

Precision electronic speed controller for an alternating-current

DOEpatents

Bolie, Victor W.

1988-01-01

A high precision controller for an alternating-current multi-phase electrical motor that is subject to a large inertial load. The controller was developed for and is particularly suitable for controlling, in a neutron chopper system, a heavy spinning rotor that must be rotated in phase-locked synchronism with a reference pulse train that is representative of an ac power supply signal having a meandering line frequency. The controller includes a shaft revolution sensor which provides a feedback pulse train representative of the actual speed of the motor. An internal digital timing signal generator provides a reference signal which is compared with the feedback signal in a computing unit to provide a motor control signal. In the preferred embodiment, the motor control signal is a weighted linear sum of a speed error voltage, a phase error voltage, and a drift error voltage, each of which is computed anew with each revolution of the motor shaft. The stator windings of the motor are driven by two amplifiers which are provided with input signals having the proper quadrature relationship by an exciter unit consisting of a voltage controlled oscillator, a binary counter, a pair of readonly memories, and a pair of digital-to-analog converters.

Effects of digital phase-conjugate light intensity on time-reversal imaging through animal tissue.

PubMed

Toda, Sogo; Kato, Yuji; Kudo, Nobuki; Shimizu, Koichi

2018-04-01

For transillumination imaging of animal tissues, we have attempted to suppress the scattering effect in a turbid medium using the time-reversal principle of phase-conjugate light. We constructed a digital phase-conjugate system to enable intensity modulation and phase modulation. Using this system, we clarified the effectiveness of the intensity information for restoration of the original light distribution through a turbid medium. By varying the scattering coefficient of the medium, we clarified the limit of time-reversal ability with intensity information of the phase-conjugate light. Experiment results demonstrated the applicability of the proposed technique to animal tissue.

A second-order frequency-aided digital phase-locked loop for Doppler rate tracking

NASA Astrophysics Data System (ADS)

Chie, C. M.

1980-08-01

A second-order digital phase-locked loop (DPLL) has a finite lock range which is a function of the frequency of the incoming signal to be tracked. For this reason, it is not capable of tracking an input with Doppler rate for an indefinite period of time. In this correspondence, an analytical expression for the hold-in time is derived. In addition, an all-digital scheme to alleviate this problem is proposed based on the information obtained from estimating the input signal frequency.

Interference mitigation for simultaneous transmit and receive applications on digital phased array systems

NASA Astrophysics Data System (ADS)

Snow, Trevor M.

As analog-to-digital (ADC) and digital-to-analog conversion (DAC) technologies become cheaper and digital processing capabilities improve, phased array systems with digital transceivers at every element will become more commonplace. These architectures offer greater capability over traditional analog systems and enable advanced applications such as multiple-input, multiple-output (MIMO) communications, adaptive beamforming, space-time adaptive processing (STAP), and MIMO for radar. Capabilities for such systems are still limited by the need for isolating self-interference from transmitters at co-located receivers. The typical approach of time-sharing the antenna aperture between transmitters and receivers works but leaves the receivers blind for a period of time. For full-duplex operation, some systems use separate frequency bands for transmission and reception, but these require fixed filtering which reduces the system's ability to adapt to its environment and is also an inefficient use of spectral resources. To that end, tunable, high quality-factor filters are used for sub-band isolation and protect receivers while allowing open reception at other frequencies. For more flexibility, another emergent area of related research has focused on co-located spatial isolation using multiple antennas and direct injection of interference cancellation signals into receivers, which enables same-frequency full-duplex operation. With all these methods, self-interference must be reduced by an amount that prevents saturation of the ADC. Intermodulation products generated in the receiver in this process can potentially be problematic, as certain intermodulation products may appear to come from a particular angle and cohere in the beamformer. This work explores various digital phased array architectures and the how the flexibility afforded by an all-digital beamforming architecture, layered with other methods of isolation, can be used to reduce self-interference within the system. Specifically, digital control of coupled energy into receiving elements for planar and cylindrical array symmetries can be significantly reduced using near-field nulling, optimization of transmission frequencies for particular steering angles, and optimization of phase weights over restricted sets, without major impacts to the far-field performance of the system. Finally, a method for reducing in-band intermodulation that would ordinarily cohere in a system's receive beamformer is demonstrated using parallel cross-linearization of adjacent digital receivers in a phased array.

Fluorescence lifetime measurements in flow cytometry

NASA Astrophysics Data System (ADS)

Beisker, Wolfgang; Klocke, Axel

1997-05-01

Fluorescence lifetime measurements provide insights int eh dynamic and structural properties of dyes and their micro- environment. The implementation of fluorescence lifetime measurements in flow cytometric systems allows to monitor large cell and particle populations with high statistical significance. In our system, a modulated laser beam is used for excitation and the phase shift of the fluorescence signal recorded with a fast computer controlled digital oscilloscope is processed digitally to determine the phase shift with respect to a reference beam by fast fourier transform. Total fluorescence intensity as well as other parameters can be determined simultaneously from the same fluorescence signal. We use the epi-illumination design to allow the use of high numerical apertures to collect as much light as possible to ensure detection of even weak fluorescence. Data storage and processing is done comparable to slit-scan flow cytometric data using data analysis system. The results are stored, displayed, combined with other parameters and analyzed as normal listmode data. In our report we discuss carefully the signal to noise ratio for analog and digital processed lifetime signals to evaluate the theoretical minimum fluorescence intensity for lifetime measurements. Applications to be presented include DNA staining, parameters of cell functions as well as different applications in non-mammalian cells such as algae.

Image fidelity improvement in digital holographic microscopy using optical phase conjugation

NASA Astrophysics Data System (ADS)

Chan, Huang-Tian; Chew, Yang-Kun; Shiu, Min-Tzung; Chang, Chi-Ching

2018-01-01

With respect to digital holography, techniques in suppressing noises derived from reference arm are maturely developed. However, techniques for the object counterpart are not being well developed. Optical phase conjugation technique was believed to be a promising method for this interest. A 0°-cut BaTiO3 photorefractive crystal was involved in self-pumped phase conjugation scheme, and was employed to in-line digital holographic microscopy, in both transmission-type and reflection-type configuration. On pure physical compensation basis, results revealed that the image fidelity was improved substantially with 2.9096 times decrease in noise level and 3.5486 times increase in the ability to discriminate noise on average, by suppressing the scattering noise prior to recording stage.

Total internal reflection holographic microscopy (TIRHM) for quantitative phase characterization of cell-substrate adhesion

NASA Astrophysics Data System (ADS)

Ash, William Mason, III

Total Internal Reflection Holographic Microscopy (TIRHM) combines near-field microscopy with digital holography to produce a new form of near-field phase microscopy. Using a prism in TIR as a near-field imager, the presence of microscopic organisms, cell-substrate interfaces, and adhesions, causes relative refractive index (RRI) and frustrated TIR (f-TIR) to modulate the object beam's evanescent wave phase front. Quantitative phase images of test specimens such as Amoeba proteus, Dictyostelium Discoideum and cells such as SKOV-3 ovarian cancer and 3T3 fibroblasts are produced without the need to introduce stains or fluorophores. The angular spectrum method of digital holography to compensate for tilt anamorphism due to the inclined TIR plane is also discussed. The results of this work conclusively demonstrate, for the first time, the integration of near-field microscopy with digital holography. The cellular images presented show a correlation between the physical extent of the Amoeba proteus plasma membrane and the adhesions that are quantitatively profiled by phase cross-sectioning of the holographic images obtained by digital holography. With its ability to quantitatively characterise cellular adhesion and motility, it is anticipated that TIRHM can be a tool for characterizing and combating cancer metastasis, as well as improving our understanding of morphogenesis and embryogenesis itself.

Review of quantitative phase-digital holographic microscopy: promising novel imaging technique to resolve neuronal network activity and identify cellular biomarkers of psychiatric disorders

PubMed Central

Marquet, Pierre; Depeursinge, Christian; Magistretti, Pierre J.

2014-01-01

Abstract. Quantitative phase microscopy (QPM) has recently emerged as a new powerful quantitative imaging technique well suited to noninvasively explore a transparent specimen with a nanometric axial sensitivity. In this review, we expose the recent developments of quantitative phase-digital holographic microscopy (QP-DHM). Quantitative phase-digital holographic microscopy (QP-DHM) represents an important and efficient quantitative phase method to explore cell structure and dynamics. In a second part, the most relevant QPM applications in the field of cell biology are summarized. A particular emphasis is placed on the original biological information, which can be derived from the quantitative phase signal. In a third part, recent applications obtained, with QP-DHM in the field of cellular neuroscience, namely the possibility to optically resolve neuronal network activity and spine dynamics, are presented. Furthermore, potential applications of QPM related to psychiatry through the identification of new and original cell biomarkers that, when combined with a range of other biomarkers, could significantly contribute to the determination of high risk developmental trajectories for psychiatric disorders, are discussed. PMID:26157976

Review of quantitative phase-digital holographic microscopy: promising novel imaging technique to resolve neuronal network activity and identify cellular biomarkers of psychiatric disorders.

PubMed

Marquet, Pierre; Depeursinge, Christian; Magistretti, Pierre J

2014-10-01

Quantitative phase microscopy (QPM) has recently emerged as a new powerful quantitative imaging technique well suited to noninvasively explore a transparent specimen with a nanometric axial sensitivity. In this review, we expose the recent developments of quantitative phase-digital holographic microscopy (QP-DHM). Quantitative phase-digital holographic microscopy (QP-DHM) represents an important and efficient quantitative phase method to explore cell structure and dynamics. In a second part, the most relevant QPM applications in the field of cell biology are summarized. A particular emphasis is placed on the original biological information, which can be derived from the quantitative phase signal. In a third part, recent applications obtained, with QP-DHM in the field of cellular neuroscience, namely the possibility to optically resolve neuronal network activity and spine dynamics, are presented. Furthermore, potential applications of QPM related to psychiatry through the identification of new and original cell biomarkers that, when combined with a range of other biomarkers, could significantly contribute to the determination of high risk developmental trajectories for psychiatric disorders, are discussed.

Simple and fast spectral domain algorithm for quantitative phase imaging of living cells with digital holographic microscopy

NASA Astrophysics Data System (ADS)

Min, Junwei; Yao, Baoli; Ketelhut, Steffi; Kemper, Björn

2017-02-01

The modular combination of optical microscopes with digital holographic microscopy (DHM) has been proven to be a powerful tool for quantitative live cell imaging. The introduction of condenser and different microscope objectives (MO) simplifies the usage of the technique and makes it easier to measure different kinds of specimens with different magnifications. However, the high flexibility of illumination and imaging also causes variable phase aberrations that need to be eliminated for high resolution quantitative phase imaging. The existent phase aberrations compensation methods either require add additional elements into the reference arm or need specimen free reference areas or separate reference holograms to build up suitable digital phase masks. These inherent requirements make them unpractical for usage with highly variable illumination and imaging systems and prevent on-line monitoring of living cells. In this paper, we present a simple numerical method for phase aberration compensation based on the analysis of holograms in spatial frequency domain with capabilities for on-line quantitative phase imaging. From a single shot off-axis hologram, the whole phase aberration can be eliminated automatically without numerical fitting or pre-knowledge of the setup. The capabilities and robustness for quantitative phase imaging of living cancer cells are demonstrated.

Calibration Test Set for a Phase-Comparison Digital Tracker

NASA Technical Reports Server (NTRS)

Boas, Amy; Li, Samuel; McMaster, Robert

2007-01-01

An apparatus that generates four signals at a frequency of 7.1 GHz having precisely controlled relative phases and equal amplitudes has been designed and built. This apparatus is intended mainly for use in computer-controlled automated calibration and testing of a phase-comparison digital tracker (PCDT) that measures the relative phases of replicas of the same X-band signal received by four antenna elements in an array. (The relative direction of incidence of the signal on the array is then computed from the relative phases.) The present apparatus can also be used to generate precisely phased signals for steering a beam transmitted from a phased antenna array. The apparatus (see figure) includes a 7.1-GHz signal generator, the output of which is fed to a four-way splitter. Each of the four splitter outputs is attenuated by 10 dB and fed as input to a vector modulator, wherein DC bias voltages are used to control the in-phase (I) and quadrature (Q) signal components. The bias voltages are generated by digital-to-analog- converter circuits on a control board that receives its digital control input from a computer running a LabVIEW program. The outputs of the vector modulators are further attenuated by 10 dB, then presented at high-grade radio-frequency connectors. The attenuation reduces the effects of changing mismatch and reflections. The apparatus was calibrated in a process in which the bias voltages were first stepped through all possible IQ settings. Then in a reverse interpolation performed by use of MATLAB software, a lookup table containing 3,600 IQ settings, representing equal amplitude and phase increments of 0.1 , was created for each vector modulator. During operation of the apparatus, these lookup tables are used in calibrating the PCDT.

A digital optical phase-locked loop for diode lasers based on field programmable gate array.

PubMed

Xu, Zhouxiang; Zhang, Xian; Huang, Kaikai; Lu, Xuanhui

2012-09-01

We have designed and implemented a highly digital optical phase-locked loop (OPLL) for diode lasers in atom interferometry. The three parts of controlling circuit in this OPLL, including phase and frequency detector (PFD), loop filter and proportional integral derivative (PID) controller, are implemented in a single field programmable gate array chip. A structure type compatible with the model MAX9382∕MCH12140 is chosen for PFD and pipeline and parallelism technology have been adapted in PID controller. Especially, high speed clock and twisted ring counter have been integrated in the most crucial part, the loop filter. This OPLL has the narrow beat note line width below 1 Hz, residual mean-square phase error of 0.14 rad(2) and transition time of 100 μs under 10 MHz frequency step. A main innovation of this design is the completely digitalization of the whole controlling circuit in OPLL for diode lasers.

A digital optical phase-locked loop for diode lasers based on field programmable gate array

NASA Astrophysics Data System (ADS)

Xu, Zhouxiang; Zhang, Xian; Huang, Kaikai; Lu, Xuanhui

2012-09-01

We have designed and implemented a highly digital optical phase-locked loop (OPLL) for diode lasers in atom interferometry. The three parts of controlling circuit in this OPLL, including phase and frequency detector (PFD), loop filter and proportional integral derivative (PID) controller, are implemented in a single field programmable gate array chip. A structure type compatible with the model MAX9382/MCH12140 is chosen for PFD and pipeline and parallelism technology have been adapted in PID controller. Especially, high speed clock and twisted ring counter have been integrated in the most crucial part, the loop filter. This OPLL has the narrow beat note line width below 1 Hz, residual mean-square phase error of 0.14 rad2 and transition time of 100 μs under 10 MHz frequency step. A main innovation of this design is the completely digitalization of the whole controlling circuit in OPLL for diode lasers.

Fiber-optic extrinsic Fabry-Perot interferometer strain sensor with <50 pm displacement resolution using three-wavelength digital phase demodulation.

PubMed

Schmidt, M; Werther, B; Fuerstenau, N; Matthias, M; Melz, T

2001-04-09

A fiber-optic extrinsic Fabry-Perot interferometer strain sensor (EFPI-S) of ls = 2.5 cm sensor length using three-wavelength digital phase demodulation is demonstrated to exhibit <50 pm displacement resolution (<2nm/m strain resolution) when measuring the cross expansion of a PZT-ceramic plate. The sensing (single-mode downlead-) and reflecting fibers are fused into a 150/360 microm capillary fiber where the fusion points define the sensor length. Readout is performed using an improved version of the previously described three-wavelength digital phase demodulation method employing an arctan-phase stepping algorithm. In the resent experiments the strain sensitivity was varied via the mapping of the arctan - lookup table to the 16-Bit DA-converter range from 188.25 k /V (6 Volt range 1130 k ) to 11.7 k /Volt (range 70 k ).

Improving the Mechanical Properties of the Fusion Zone in Electron-Beam Welded Ti-5Al-5Mo-5V-3Cr Alloys

NASA Astrophysics Data System (ADS)

Marvel, Christopher J.; Sabol, Joseph C.; Pasang, Timotius; Watanabe, Masashi; Misiolek, Wojciech Z.

2017-04-01

It is well-known that ω-phase precipitates embrittle Ti-5553 alloys and that ω-phase embrittlement can be overcome with appropriate heat treatments. However, the microstructural evolution of electron-beam welded Ti-5553 is not as understood as compared to the cast or wrought material. This study compared the microstructures of as-welded and post-weld heat-treated specimens by scanning and transmission electron microscopy, and similarly compared the localized mechanical behavior of the fusion zones with microhardness testing and digital image correlation coupled tensile testing. The primary observations were that the embrittling ω-phase precipitates formed upon cooling, and could not be fully solutionized in a single-step treatment of 1077 K (804 °C) for 1 hour. It was also discovered that nanoscale α-phase precipitates nucleated after the single-step treatment, although they were small in number and sparsely distributed. However, a two-step heat treatment of 1077 K (804 °C) for 1 hour and 873 K (600 °C) for 4 hours completely solutionized the ω-phase and produced a dense network of 2- μm-wide α-phase plates, which significantly improved the mechanical properties. Overall, this study has shown that post-weld heat treatments improve the strength and ductility of electron-beam welded Ti-5553 alloys by controlling ω- and α-phase evolution.

Digital phase-locked loop speed control for a brushless dc motor

NASA Astrophysics Data System (ADS)

Wise, M. G.

1985-06-01

Speed control of d.c. motors by phase-locked loops (PLL) is becoming increasingly popular. Primary interest has been in employing PLL for constant speed control. This thesis investigates the theory and techniques of digital PLL to speed control of a brushless d.c. motor with a variable speed of operation. Addition of logic controlled count enable/disable to a synchronous up/down counter, used as a phase-frequency detector, is shown to improve the performance of previously proposed PLL control schemes.

Performance evaluation of the time delay digital tanlock loop architectures

NASA Astrophysics Data System (ADS)

Al-Kharji Al-Ali, Omar; Anani, Nader; Al-Qutayri, Mahmoud; Al-Araji, Saleh; Ponnapalli, Prasad

2016-01-01

This article presents the architectures, theoretical analyses and testing results of modified time delay digital tanlock loop (TDTLs) system. The modifications to the original TDTL architecture were introduced to overcome some of the limitations of the original TDTL and to enhance the overall performance of the particular systems. The limitations addressed in this article include the non-linearity of the phase detector, the restricted width of the locking range and the overall system acquisition speed. Each of the modified architectures was tested by subjecting the system to sudden positive and negative frequency steps and comparing its response with that of the original TDTL. In addition, the performance of all the architectures was evaluated under noise-free as well as noisy environments. The extensive simulation results using MATLAB/SIMULINK demonstrate that the new architectures overcome the limitations they addressed and the overall results confirmed significant improvements in performance compared to the conventional TDTL system.

LANDSAT data for state planning. [of transportation for Georgia

NASA Technical Reports Server (NTRS)

Faust, N. L.; Spann, G. W.

1975-01-01

The results of an effort to generate and apply automated classification of LANDSAT digital data to state of Georgia problems are presented. This phase centers on an analysis of the usefulness of LANDSAT digital data to provide land-use data for transportation planning. Hall County, Georgia was chosen as a test site because it is part of a seventeen county area for which the Georgia Department of Transportation is currently designing a Transportation Planning Land-Use Simulation Model. The land-cover information derived from this study was compared to several other existing sources of land-use data for Hall County and input into this simulation. The results indicate that there is difficulty comparing LANDSAT derived land-cover information with previous land-use information since the LANDSAT data are acquired on an acre by acre grid basis while all previous land-use surveys for Hall County used land-use data on a parcel basis.

Parallel phase-shifting self-interference digital holography with faithful reconstruction using compressive sensing

NASA Astrophysics Data System (ADS)

Wan, Yuhong; Man, Tianlong; Wu, Fan; Kim, Myung K.; Wang, Dayong

2016-11-01

We present a new self-interference digital holographic approach that allows single-shot capturing three-dimensional intensity distribution of the spatially incoherent objects. The Fresnel incoherent correlation holographic microscopy is combined with parallel phase-shifting technique to instantaneously obtain spatially multiplexed phase-shifting holograms. The compressive-sensing-based reconstruction algorithm is implemented to reconstruct the original object from the under sampled demultiplexed holograms. The scheme is verified with simulations. The validity of the proposed method is experimentally demonstrated in an indirectly way by simulating the use of specific parallel phase-shifting recording device.

Digital phase demodulation for low-coherence interferometry-based fiber-optic sensors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Y.; Strum, R.; Stiles, D.

In this paper, we describe a digital phase demodulation scheme for low-coherence interferometry-based fiber-optic sensors by employing a simple generation of phase-shifted signals at the interrogation interferometer. The scheme allows a real-time calibration process and offers capability of measuring large variations (up to the coherence of the light source) at the bandwidth that is only limited by the data acquisition system. Finally, the proposed phase demodulation method is analytically derived and its validity and performance are experimentally verified using fiber-optic Fabry–Perot sensors for measurement of strains and vibrations.

Digital phase demodulation for low-coherence interferometry-based fiber-optic sensors

DOE PAGES

Liu, Y.; Strum, R.; Stiles, D.; ...

2017-11-20

In this paper, we describe a digital phase demodulation scheme for low-coherence interferometry-based fiber-optic sensors by employing a simple generation of phase-shifted signals at the interrogation interferometer. The scheme allows a real-time calibration process and offers capability of measuring large variations (up to the coherence of the light source) at the bandwidth that is only limited by the data acquisition system. Finally, the proposed phase demodulation method is analytically derived and its validity and performance are experimentally verified using fiber-optic Fabry–Perot sensors for measurement of strains and vibrations.

[The extraction and analysis of a- and b- wave from electroretinogram in human].

PubMed

Chen, Zi-he; Zheng, Chang-wei; Lei, Bo

2013-12-01

To determine the frequency range of a-b wave complex in the dark- and light-adapted electroretinogram (ERG) and to isolate the pure a- and b- waves. Case series study. Full-field ERGs were recorded in 16 eyes of 8 normal volunteers from October to November 2011. Digital filtering technique was used to extract the a- and b-waves from dark- and light-adapted ERG responses. The timings of a- and b-wave were measured to determine the frequency range of a-b wave complex. Major frequency components were determined from power spectra using fast Fourier transform (FFT). The effect of different order settings in the digital filter were compared to investigate the optimum condition, where the oscillatory potential (OP) was completely removed while the amplitudes and phases of the a- and b- waves were less affected. The Student-t test was used to compare the frequency range of a-b wave complex in dark- and light-adapted ERG. The averaged frequency range of the dark-adapted a-b wave complex was from (14.99 ± 2.39) to (25.35 ± 3.77) Hz, compared with (25.22 ± 6.56) to (32.47 ± 3.68) Hz for the light-adapted a-b wave complex, respectively, indicating the frequency range of the dark-adapted a-b wave complex was significantly less than the light-adapted a-b wave complex (t = 7.910, 7.693; both P < 0.01). The third order of the digital filter and a passband of 1 to 45 Hz was the best choice in term of removing the high frequency OP from the waveform of ERG and keeping the amplitude and phase of the a- and b- waves. The frequency of a-b wave complex is lower than that of OP. Therefore the a- and b- waves can be isolated from OP using different digital filter settings in human ERG. A third order and a passband of 1 to 45 Hz is the best choice to extract pure a- and b- waves from the original ERG.

Setup calibration and optimization for comparative digital holography

NASA Astrophysics Data System (ADS)

Baumbach, Torsten; Osten, Wolfgang; Kebbel, Volker; von Kopylow, Christoph; Jueptner, Werner

2004-08-01

With increasing globalization many enterprises decide to produce the components of their products at different locations all over the world. Consequently, new technologies and strategies for quality control are required. In this context the remote comparison of objects with regard to their shape or response on certain loads is getting more and more important for a variety of applications. For such a task the novel method of comparative digital holography is a suitable tool with interferometric sensitivity. With this technique the comparison in shape or deformation of two objects does not require the presence of both objects at the same place. In contrast to the well known incoherent techniques based on inverse fringe projection this new approach uses a coherent mask for the illumination of the sample object. The coherent mask is created by digital holography to enable the instant access to the complete optical information of the master object at any wanted place. The reconstruction of the mask is done by a spatial light modulator (SLM). The transmission of the digital master hologram to the place of comparison can be done via digital telecommunication networks. Contrary to other interferometric techniques this method enables the comparison of objects with different microstructure. In continuation of earlier reports our investigations are focused here on the analysis of the constraints of the setup with respect to the quality of the hologram reconstruction with a spatial light modulator. For successful measurements the selection of the appropriate reconstruction method and the adequate optical set-up is mandatory. In addition, the use of a SLM for the reconstruction requires the knowledge of its properties for the accomplishment of this method. The investigation results for the display properties such as display curvature, phase shift and the consequences for the technique will be presented. The optimization and the calibration of the set-up and its components lead to improved results in comparative digital holography with respect to the resolution. Examples of measurements before and after the optimization and calibration will be presented.

Preliminary design and implementation of the baseline digital baseband architecture for advanced deep space transponders

NASA Technical Reports Server (NTRS)

Nguyen, T. M.; Yeh, H.-G.

1993-01-01

The baseline design and implementation of the digital baseband architecture for advanced deep space transponders is investigated and identified. Trade studies on the selection of the number of bits for the analog-to-digital converter (ADC) and optimum sampling schemes are presented. In addition, the proposed optimum sampling scheme is analyzed in detail. Descriptions of possible implementations for the digital baseband (or digital front end) and digital phase-locked loop (DPLL) for carrier tracking are also described.

Incoherent digital holograms acquired by interferenceless coded aperture correlation holography system without refractive lenses.

PubMed

Kumar, Manoj; Vijayakumar, A; Rosen, Joseph

2017-09-14

We present a lensless, interferenceless incoherent digital holography technique based on the principle of coded aperture correlation holography. The acquired digital hologram by this technique contains a three-dimensional image of some observed scene. Light diffracted by a point object (pinhole) is modulated using a random-like coded phase mask (CPM) and the intensity pattern is recorded and composed as a point spread hologram (PSH). A library of PSHs is created using the same CPM by moving the pinhole to all possible axial locations. Intensity diffracted through the same CPM from an object placed within the axial limits of the PSH library is recorded by a digital camera. The recorded intensity this time is composed as the object hologram. The image of the object at any axial plane is reconstructed by cross-correlating the object hologram with the corresponding component of the PSH library. The reconstruction noise attached to the image is suppressed by various methods. The reconstruction results of multiplane and thick objects by this technique are compared with regular lens-based imaging.

Digital adaptive optics confocal microscopy based on iterative retrieval of optical aberration from a guidestar hologram

PubMed Central

Liu, Changgeng; Thapa, Damber; Yao, Xincheng

2017-01-01

Guidestar hologram based digital adaptive optics (DAO) is one recently emerging active imaging modality. It records each complex distorted line field reflected or scattered from the sample by an off-axis digital hologram, measures the optical aberration from a separate off-axis digital guidestar hologram, and removes the optical aberration from the distorted line fields by numerical processing. In previously demonstrated DAO systems, the optical aberration was directly retrieved from the guidestar hologram by taking its Fourier transform and extracting the phase term. For the direct retrieval method (DRM), when the sample is not coincident with the guidestar focal plane, the accuracy of the optical aberration retrieved by DRM undergoes a fast decay, leading to quality deterioration of corrected images. To tackle this problem, we explore here an image metrics-based iterative method (MIM) to retrieve the optical aberration from the guidestar hologram. Using an aberrated objective lens and scattering samples, we demonstrate that MIM can improve the accuracy of the retrieved aberrations from both focused and defocused guidestar holograms, compared to DRM, to improve the robustness of the DAO. PMID:28380937

Research on phase locked loop in optical memory servo system

NASA Astrophysics Data System (ADS)

Qin, Liqin; Ma, Jianshe; Zhang, Jianyong; Pan, Longfa; Deng, Ming

2005-09-01

Phase locked loop (PLL) is a closed loop automatic control system, which can track the phase of input signal. It widely applies in each area of electronic technology. This paper research the phase locked loop in optical memory servo area. This paper introduces the configuration of digital phase locked loop (PLL) and phase locked servo system, the control theory, and analyses system's stability. It constructs the phase locked loop experiment system of optical disk spindle servo, which based on special chip. DC motor is main object, this system adopted phase locked servo technique and digital signal processor (DSP) to achieve constant linear velocity (CLV) in controlling optical spindle motor. This paper analyses the factors that affect the stability of phase locked loop in spindle servo system, and discusses the affection to the optical disk readout signal and jitter due to the stability of phase locked loop.

Programmable rate modem utilizing digital signal processing techniques

NASA Technical Reports Server (NTRS)

Bunya, George K.; Wallace, Robert L.

1989-01-01

The engineering development study to follow was written to address the need for a Programmable Rate Digital Satellite Modem capable of supporting both burst and continuous transmission modes with either binary phase shift keying (BPSK) or quadrature phase shift keying (QPSK) modulation. The preferred implementation technique is an all digital one which utilizes as much digital signal processing (DSP) as possible. Here design tradeoffs in each portion of the modulator and demodulator subsystem are outlined, and viable circuit approaches which are easily repeatable, have low implementation losses and have low production costs are identified. The research involved for this study was divided into nine technical papers, each addressing a significant region of concern in a variable rate modem design. Trivial portions and basic support logic designs surrounding the nine major modem blocks were omitted. In brief, the nine topic areas were: (1) Transmit Data Filtering; (2) Transmit Clock Generation; (3) Carrier Synthesizer; (4) Receive AGC; (5) Receive Data Filtering; (6) RF Oscillator Phase Noise; (7) Receive Carrier Selectivity; (8) Carrier Recovery; and (9) Timing Recovery.

X-ray phase contrast tomography by tracking near field speckle

PubMed Central

Wang, Hongchang; Berujon, Sebastien; Herzen, Julia; Atwood, Robert; Laundy, David; Hipp, Alexander; Sawhney, Kawal

2015-01-01

X-ray imaging techniques that capture variations in the x-ray phase can yield higher contrast images with lower x-ray dose than is possible with conventional absorption radiography. However, the extraction of phase information is often more difficult than the extraction of absorption information and requires a more sophisticated experimental arrangement. We here report a method for three-dimensional (3D) X-ray phase contrast computed tomography (CT) which gives quantitative volumetric information on the real part of the refractive index. The method is based on the recently developed X-ray speckle tracking technique in which the displacement of near field speckle is tracked using a digital image correlation algorithm. In addition to differential phase contrast projection images, the method allows the dark-field images to be simultaneously extracted. After reconstruction, compared to conventional absorption CT images, the 3D phase CT images show greatly enhanced contrast. This new imaging method has advantages compared to other X-ray imaging methods in simplicity of experimental arrangement, speed of measurement and relative insensitivity to beam movements. These features make the technique an attractive candidate for material imaging such as in-vivo imaging of biological systems containing soft tissue. PMID:25735237

Fringe pattern demodulation with a two-dimensional digital phase-locked loop algorithm.

PubMed

Gdeisat, Munther A; Burton, David R; Lalor, Michael J

2002-09-10

A novel technique called a two-dimensional digital phase-locked loop (DPLL) for fringe pattern demodulation is presented. This algorithm is more suitable for demodulation of fringe patterns with varying phase in two directions than the existing DPLL techniques that assume that the phase of the fringe patterns varies only in one direction. The two-dimensional DPLL technique assumes that the phase of a fringe pattern is continuous in both directions and takes advantage of the phase continuity; consequently, the algorithm has better noise performance than the existing DPLL schemes. The two-dimensional DPLL algorithm is also suitable for demodulation of fringe patterns with low sampling rates, and it outperforms the Fourier fringe analysis technique in this aspect.

Wavefront sensing with all-digital Stokes measurements

NASA Astrophysics Data System (ADS)

Dudley, Angela; Milione, Giovanni; Alfano, Robert R.; Forbes, Andrew

2014-09-01

A long-standing question in optics has been to efficiently measure the phase (or wavefront) of an optical field. This has led to numerous publications and commercial devices such as phase shift interferometry, wavefront reconstruction via modal decomposition and Shack-Hartmann wavefront sensors. In this work we develop a new technique to extract the phase which in contrast to previously mentioned methods is based on polarization (or Stokes) measurements. We outline a simple, all-digital approach using only a spatial light modulator and a polarization grating to exploit the amplitude and phase relationship between the orthogonal states of polarization to determine the phase of an optical field. We implement this technique to reconstruct the phase of static and propagating optical vortices.

Single-shot digital holography by use of the fractional Talbot effect.

PubMed

Martínez-León, Lluís; Araiza-E, María; Javidi, Bahram; Andrés, Pedro; Climent, Vicent; Lancis, Jesús; Tajahuerce, Enrique

2009-07-20

We present a method for recording in-line single-shot digital holograms based on the fractional Talbot effect. In our system, an image sensor records the interference between the light field scattered by the object and a properly codified parallel reference beam. A simple binary two-dimensional periodic grating is used to codify the reference beam generating a periodic three-step phase distribution over the sensor plane by fractional Talbot effect. This provides a method to perform single-shot phase-shifting interferometry at frame rates only limited by the sensor capabilities. Our technique is well adapted for dynamic wavefront sensing applications. Images of the object are digitally reconstructed from the digital hologram. Both computer simulations and experimental results are presented.

Quantitative photothermal phase imaging of red blood cells using digital holographic photothermal microscope.

PubMed

Vasudevan, Srivathsan; Chen, George C K; Lin, Zhiping; Ng, Beng Koon

2015-05-10

Photothermal microscopy (PTM), a noninvasive pump-probe high-resolution microscopy, has been applied as a bioimaging tool in many biomedical studies. PTM utilizes a conventional phase contrast microscope to obtain highly resolved photothermal images. However, phase information cannot be extracted from these photothermal images, as they are not quantitative. Moreover, the problem of halos inherent in conventional phase contrast microscopy needs to be tackled. Hence, a digital holographic photothermal microscopy technique is proposed as a solution to obtain quantitative phase images. The proposed technique is demonstrated by extracting phase values of red blood cells from their photothermal images. These phase values can potentially be used to determine the temperature distribution of the photothermal images, which is an important study in live cell monitoring applications.

Response of an all digital phase-locked loop

NASA Technical Reports Server (NTRS)

Garodnick, J.; Greco, J.; Schilling, D. L.

1974-01-01

An all digital phase-locked loop (DPLL) is designed, analyzed, and tested. Three specific configurations are considered, generating first, second, and third order DPLL's; and it is found, using a computer simulation of a noise spike, and verified experimentally, that of these configurations the second-order system is optimum from the standpoint of threshold extension. This substantiates results obtained for analog PLL's.

Understanding University Students' Thoughts and Practices about Digital Citizenship: A Mixed Methods Study

ERIC Educational Resources Information Center

Kara, Nuri

2018-01-01

The purpose of this study was to investigate university students' thoughts and practices concerning digital citizenship. An explanatory mixed methods design was used, and it involved collecting qualitative data after a quantitative phase in order to follow up on the quantitative data in more depth. In the first quantitative phase of the study, a…

The Effect of a Digital Learning Environment on Children's Conceptions about the Protection of Endemic Plants

ERIC Educational Resources Information Center

Petrou, Stella; Korfiatis, Konstantinos

2013-01-01

This study presents the results of a pilot learning intervention for improving children's ideas about plant protection. The research was executed in two phases. The first phase aimed at exploring children's ideas about plant protection. These ideas were taken into account for the design and development of a digital learning environment. The second…

Method and apparatus for spur-reduced digital sinusoid synthesis

NASA Technical Reports Server (NTRS)

Zimmerman, George A. (Inventor); Flanagan, Michael J. (Inventor)

1995-01-01

A technique for reducing the spurious signal content in digital sinusoid synthesis is presented. Spur reduction is accomplished through dithering both amplitude and phase values prior to word-length reduction. The analytical approach developed for analog quantization is used to produce new bounds on spur performance in these dithered systems. Amplitude dithering allows output word-length reduction without introducing additional spurs. Effects of periodic dither similar to that produced by a pseudo-noise (PN) generator are analyzed. This phase dithering method provides a spur reduction of 6(M + 1) dB per phase bit when the dither consists of M uniform variates. While the spur reduction is at the expense of an increase in system noise, the noise power can be made white, making the power spectral density small. This technique permits the use of a smaller number of phase bits addressing sinusoid look-up tables, resulting in an exponential decrease in system complexity. Amplitude dithering allows the use of less complicated multipliers and narrower data paths in purely digital applications, as well as the use of coarse-resolution, highly-linear digital-to-analog converters (DAC's) to obtain spur performance limited by the DAC linearity rather than its resolution.

Development of a Digital Control for the Phase Contrast Imaging Alignment Feedback System

NASA Astrophysics Data System (ADS)

Hirata, M.; Marinoni, A.; Rost, J. C.; Davis, E. M.; Porkolab, M.

2016-10-01

The Phase Contrast Imaging diagnostic is an internal reference interferometer that images density fluctuations on a 32-element linear detector array. Since proper operation of the system requires accurate alignment of a CO2 laser beam on a phase plate, beam motion due to vibrations of the DIII-D vessel need to be compensated up to 1 kHz. The feedback network controlling the steering mirrors currently uses a linear analog controller, but a digital controller can provide improved stability performance and flexibility. A prototype was developed using an Arduino Due, a low-cost microcontroller, to assess performance capabilities. Digital control parameters will be developed based on the measured frequency and phase response of the physical components. Finally, testing of the digital feedback system and the required revisions will be done to achieve successful performance. This upgrade to the linear analog controller is expected to be used routinely on similar diagnostics in fusion devices, especially in view of restricted access to the machine hall. Work supported in part by the US Department of Energy under DE-FG02-94ER54235, DE-FC02-04ER54698, and the Science Undergraduate Laboratory Internships Program (SULI).

Algorithms for image recovery calculation in extended single-shot phase-shifting digital holography

NASA Astrophysics Data System (ADS)

Hasegawa, Shin-ya; Hirata, Ryo

2018-04-01

The single-shot phase-shifting method of image recovery using an inclined reference wave has the advantages of reducing the effects of vibration, being capable of operating in real time, and affording low-cost sensing. In this method, relatively low reference angles compared with that in the conventional method using phase shift between three or four pixels has been required. We propose an extended single-shot phase-shifting technique which uses the multiple-step phase-shifting algorithm and the corresponding multiple pixels which are the same as that of the period of an interference fringe. We have verified the theory underlying this recovery method by means of Fourier spectral analysis and its effectiveness by evaluating the visibility of the image using a high-resolution pattern. Finally, we have demonstrated high-contrast image recovery experimentally using a resolution chart. This method can be used in a variety of applications such as color holographic interferometry.

Evaluation of vocal fold vibration with an assessment form for high-speed digital imaging: comparative study between healthy young and elderly subjects.

PubMed

Yamauchi, Akihito; Imagawa, Hiroshi; Yokonishi, Hisayuki; Nito, Takaharu; Yamasoba, Tatsuya; Goto, Takao; Takano, Shingo; Sakakibara, Ken-Ichi; Tayama, Niro

2012-11-01

We conducted a prospective study with a subjective assessment form for high-speed digital imaging (HSDI) to elucidate the features of vocal fold vibrations in vocally healthy subjects and to clarify gender- and age-related differences. Healthy adult volunteers participated in this study. They were divided into young (aged 35 and younger) and elderly (aged 65 and older) groups, and the scores of an assessment form for HSDI characteristics elaborated at our institution were statistically analyzed. Twenty-six young subjects (males: 9, females: 17; mean age: 27 years) and 20 elderly subjects (males: 8, females: 12; mean age: 72 years) were assigned to our study. Posterior gap and posterior-to-anterior longitudinal phase difference were characteristic to young females, whereas in young males, mucosal wave, anterior-to-posterior longitudinal phase difference, and supraglottic hyperactivity were frequent. In elderly males, axis shift, asymmetry, supraglottic hyperactivity, increased mucosal wave, lateral phase difference, and anterior-to-posterior longitudinal phase difference were frequent; and in elderly females, high incidence of lateral phase difference, atrophic change, anterior gap, and asymmetry were observed. The results show that the behaviors of vocal fold vibrations were diverse even in healthy subjects with no vocal complaints or history of laryngeal diseases, and hence, the diversity of vocal fold vibrations in normal subjects must be taken into account in evaluating vocal fold vibrations. Copyright © 2012 The Voice Foundation. Published by Mosby, Inc. All rights reserved.

All-digital radar architecture

NASA Astrophysics Data System (ADS)

Molchanov, Pavlo A.

2014-10-01

All digital radar architecture requires exclude mechanical scan system. The phase antenna array is necessarily large because the array elements must be co-located with very precise dimensions and will need high accuracy phase processing system for aggregate and distribute T/R modules data to/from antenna elements. Even phase array cannot provide wide field of view. New nature inspired all digital radar architecture proposed. The fly's eye consists of multiple angularly spaced sensors giving the fly simultaneously thee wide-area visual coverage it needs to detect and avoid the threats around him. Fly eye radar antenna array consist multiple directional antennas loose distributed along perimeter of ground vehicle or aircraft and coupled with receiving/transmitting front end modules connected by digital interface to central processor. Non-steering antenna array allows creating all-digital radar with extreme flexible architecture. Fly eye radar architecture provides wide possibility of digital modulation and different waveform generation. Simultaneous correlation and integration of thousands signals per second from each point of surveillance area allows not only detecting of low level signals ((low profile targets), but help to recognize and classify signals (targets) by using diversity signals, polarization modulation and intelligent processing. Proposed all digital radar architecture with distributed directional antenna array can provide a 3D space vector to the jammer by verification direction of arrival for signals sources and as result jam/spoof protection not only for radar systems, but for communication systems and any navigation constellation system, for both encrypted or unencrypted signals, for not limited number or close positioned jammers.

Are forward and backward recall the same? A dual-task study of digit recall.

PubMed

St Clair-Thompson, Helen L; Allen, Richard J

2013-05-01

There is some debate surrounding the cognitive resources underlying backward digit recall. Some researchers consider it to differ from forward digit recall due to the involvement of executive control, while others suggest that backward recall involves visuospatial resources. Five experiments therefore investigated the role of executive-attentional and visuospatial resources in both forward and backward digit recall. In the first, participants completed visuospatial 0-back and 2-back tasks during the encoding of information to be remembered. The concurrent tasks did not differentially disrupt performance on backward digit recall, relative to forward digit recall. Experiment 2 shifted concurrent load to the recall phase instead and, in this case, revealed a larger effect of both tasks on backward recall, relative to forwards recall, suggesting that backward recall may draw on additional resources during the recall phase and that these resources are visuospatial in nature. Experiments 3 and 4 then further investigated the role of visual processes in forward and backward recall using dynamic visual noise (DVN). In Experiment 3, DVN was presented during encoding of information to be remembered and had no effect upon performance. However, in Experiment 4, it was presented during the recall phase, and the results provided evidence of a role for visual imagery in backward digit recall. These results were replicated in Experiment 5, in which the same list length was used for forward and backward recall tasks. The findings are discussed in terms of both theoretical and practical implications.

Spatiotemporal distribution of location and object effects in reach-to-grasp kinematics

PubMed Central

Rouse, Adam G.

2015-01-01

In reaching to grasp an object, the arm transports the hand to the intended location as the hand shapes to grasp the object. Prior studies that tracked arm endpoint and grip aperture have shown that reaching and grasping, while proceeding in parallel, are interdependent to some degree. Other studies of reaching and grasping that have examined the joint angles of all five digits as the hand shapes to grasp various objects have not tracked the joint angles of the arm as well. We, therefore, examined 22 joint angles from the shoulder to the five digits as monkeys reached, grasped, and manipulated in a task that dissociated location and object. We quantified the extent to which each angle varied depending on location, on object, and on their interaction, all as a function of time. Although joint angles varied depending on both location and object beginning early in the movement, an early phase of location effects in joint angles from the shoulder to the digits was followed by a later phase in which object effects predominated at all joint angles distal to the shoulder. Interaction effects were relatively small throughout the reach-to-grasp. Whereas reach trajectory was influenced substantially by the object, grasp shape was comparatively invariant to location. Our observations suggest that neural control of reach-to-grasp may occur largely in two sequential phases: the first determining the location to which the arm transports the hand, and the second shaping the entire upper extremity to grasp and manipulate the object. PMID:26445870

Using digital time-lapse cameras to monitor species-specific understorey and overstorey phenology in support of wildlife habitat assessment.

PubMed

Bater, Christopher W; Coops, Nicholas C; Wulder, Michael A; Hilker, Thomas; Nielsen, Scott E; McDermid, Greg; Stenhouse, Gordon B

2011-09-01

Critical to habitat management is the understanding of not only the location of animal food resources, but also the timing of their availability. Grizzly bear (Ursus arctos) diets, for example, shift seasonally as different vegetation species enter key phenological phases. In this paper, we describe the use of a network of seven ground-based digital camera systems to monitor understorey and overstorey vegetation within species-specific regions of interest. Established across an elevation gradient in western Alberta, Canada, the cameras collected true-colour (RGB) images daily from 13 April 2009 to 27 October 2009. Fourth-order polynomials were fit to an RGB-derived index, which was then compared to field-based observations of phenological phases. Using linear regression to statistically relate the camera and field data, results indicated that 61% (r (2) = 0.61, df = 1, F = 14.3, p = 0.0043) of the variance observed in the field phenological phase data is captured by the cameras for the start of the growing season and 72% (r (2) = 0.72, df = 1, F = 23.09, p = 0.0009) of the variance in length of growing season. Based on the linear regression models, the mean absolute differences in residuals between predicted and observed start of growing season and length of growing season were 4 and 6 days, respectively. This work extends upon previous research by demonstrating that specific understorey and overstorey species can be targeted for phenological monitoring in a forested environment, using readily available digital camera technology and RGB-based vegetation indices.

Blind phase error suppression for color-encoded digital fringe projection profilometry

NASA Astrophysics Data System (ADS)

Ma, S.; Zhu, R.; Quan, C.; Li, B.; Tay, C. J.; Chen, L.

2012-04-01

Color-encoded digital fringe projection profilometry (CDFPP) has the advantage of fast speed, non-contact and full-field testing. It is one of the most important dynamic three-dimensional (3D) profile measurement techniques. However, due to factors such as color cross-talk and gamma distortion of electro-optical devices, phase errors arise when conventional phase-shifting algorithms with fixed phase shift values are utilized to retrieve phases. In this paper, a simple and effective blind phase error suppression approach based on isotropic n-dimensional fringe pattern normalization (INFPN) and carrier squeezing interferometry (CSI) is proposed. It does not require pre-calibration for the gamma and color-coupling coefficients or the phase shift values. Simulation and experimental works show that our proposed approach is able to effectively suppress phase errors and achieve accurate measurement results in CDFPP.

Investigation to realize a computationally efficient implementation of the high-order instantaneous-moments-based fringe analysis method

NASA Astrophysics Data System (ADS)

Gorthi, Sai Siva; Rajshekhar, Gannavarpu; Rastogi, Pramod

2010-06-01

Recently, a high-order instantaneous moments (HIM)-operator-based method was proposed for accurate phase estimation in digital holographic interferometry. The method relies on piece-wise polynomial approximation of phase and subsequent evaluation of the polynomial coefficients from the HIM operator using single-tone frequency estimation. The work presents a comparative analysis of the performance of different single-tone frequency estimation techniques, like Fourier transform followed by optimization, estimation of signal parameters by rotational invariance technique (ESPRIT), multiple signal classification (MUSIC), and iterative frequency estimation by interpolation on Fourier coefficients (IFEIF) in HIM-operator-based methods for phase estimation. Simulation and experimental results demonstrate the potential of the IFEIF technique with respect to computational efficiency and estimation accuracy.

Radiation Tolerant, Low Noise Phase Locked Loops in 65 nm CMOS Technology

NASA Astrophysics Data System (ADS)

Prinzie, Jeffrey; Christiansen, Jorgen; Moreira, Paulo; Steyaert, Michiel; Leroux, Paul

2018-04-01

This work presents an introduction to radiation hardened Phase Locked Loops (PLLs) for nuclear and high-energy physics application. An experimental circuit has been fabricated and irradiated with Xrays up to 600 Mrad. Heavy ions with an LET between 3.2 and 69.2 MeV.cm2/mg were used to verify the SEU cross section of the devices. A Two-photon Absorption (TPA) laser facility has been used to provide detailed results on the SEU sensitivity. The presented circuit employs TMR in the digital logic and an asynchronous phase-frequency detector (PFD) is presented. The PLL has a ringand LC-oscillator to be compared experimentally. The circuit has been fabricated in a 65 nm CMOS technology.

Single and two-shot quantitative phase imaging using Hilbert-Huang Transform based fringe pattern analysis

NASA Astrophysics Data System (ADS)

Trusiak, Maciej; Micó, Vicente; Patorski, Krzysztof; García-Monreal, Javier; Sluzewski, Lukasz; Ferreira, Carlos

2016-08-01

In this contribution we propose two Hilbert-Huang Transform based algorithms for fast and accurate single-shot and two-shot quantitative phase imaging applicable in both on-axis and off-axis configurations. In the first scheme a single fringe pattern containing information about biological phase-sample under study is adaptively pre-filtered using empirical mode decomposition based approach. Further it is phase demodulated by the Hilbert Spiral Transform aided by the Principal Component Analysis for the local fringe orientation estimation. Orientation calculation enables closed fringes efficient analysis and can be avoided using arbitrary phase-shifted two-shot Gram-Schmidt Orthonormalization scheme aided by Hilbert-Huang Transform pre-filtering. This two-shot approach is a trade-off between single-frame and temporal phase shifting demodulation. Robustness of the proposed techniques is corroborated using experimental digital holographic microscopy studies of polystyrene micro-beads and red blood cells. Both algorithms compare favorably with the temporal phase shifting scheme which is used as a reference method.

Motion compensation and noise tolerance in phase-shifting digital in-line holography.

PubMed

Stenner, Michael D; Neifeld, Mark A

2006-05-15

We present a technique for phase-shifting digital in-line holography which compensates for lateral object motion. By collecting two frames of interference between object and reference fields with identical reference phase, one can estimate the lateral motion that occurred between frames using the cross-correlation. We also describe a very general linear framework for phase-shifting holographic reconstruction which minimizes additive white Gaussian noise (AWGN) for an arbitrary set of reference field amplitudes and phases. We analyze the technique's sensitivity to noise (AWGN, quantization, and shot), errors in the reference fields, errors in motion estimation, resolution, and depth of field. We also present experimental motion-compensated images achieving the expected resolution.

Digital Interface Board to Control Phase and Amplitude of Four Channels

NASA Technical Reports Server (NTRS)

Smith, Amy E.; Cook, Brian M.; Khan, Abdur R.; Lux, James P.

2011-01-01

An increasing number of parts are designed with digital control interfaces, including phase shifters and variable attenuators. When designing an antenna array in which each antenna has independent amplitude and phase control, the number of digital control lines that must be set simultaneously can grow very large. Use of a parallel interface would require separate line drivers, more parts, and thus additional failure points. A convenient form of control where single-phase shifters or attenuators could be set or the whole set could be programmed with an update rate of 100 Hz is needed to solve this problem. A digital interface board with a field-programmable gate array (FPGA) can simultaneously control an essentially arbitrary number of digital control lines with a serial command interface requiring only three wires. A small set of short, high-level commands provides a simple programming interface for an external controller. Parity bits are used to validate the control commands. Output timing is controlled within the FPGA to allow for rapid update rates of the phase shifters and attenuators. This technology has been used to set and monitor eight 5-bit control signals via a serial UART (universal asynchronous receiver/transmitter) interface. The digital interface board controls the phase and amplitude of the signals for each element in the array. A host computer running Agilent VEE sends commands via serial UART connection to a Xilinx VirtexII FPGA. The commands are decoded, and either outputs are set or telemetry data is sent back to the host computer describing the status and the current phase and amplitude settings. This technology is an integral part of a closed-loop system in which the angle of arrival of an X-band uplink signal is detected and the appropriate phase shifts are applied to the Ka-band downlink signal to electronically steer the array back in the direction of the uplink signal. It will also be used in the non-beam-steering case to compensate for phase shift variations through power amplifiers. The digital interface board can be used to set four 5-bit phase shifters and four 5-bit attenuators and monitor their current settings. Additionally, it is useful outside of the closed-loop system for beamsteering alone. When the VEE program is started, it prompts the user to initialize variables (to zero) or skip initialization. After that, the program enters into a continuous loop waiting for the telemetry period to elapse or a button to be pushed. A telemetry request is sent when the telemetry period is elapsed (every five seconds). Pushing one of the set or reset buttons will send the appropriate command. When a command is sent, the interface status is returned, and the user will be notified by a pop-up window if any error has occurred. The program runs until the End Program button is depressed.

Real Time Phase Noise Meter Based on a Digital Signal Processor

NASA Technical Reports Server (NTRS)

Angrisani, Leopoldo; D'Arco, Mauro; Greenhall, Charles A.; Schiano Lo Morille, Rosario

2006-01-01

A digital signal-processing meter for phase noise measurement on sinusoidal signals is dealt with. It enlists a special hardware architecture, made up of a core digital signal processor connected to a data acquisition board, and takes advantage of a quadrature demodulation-based measurement scheme, already proposed by the authors. Thanks to an efficient measurement process and an optimized implementation of its fundamental stages, the proposed meter succeeds in exploiting all hardware resources in such an effective way as to gain high performance and real-time operation. For input frequencies up to some hundreds of kilohertz, the meter is capable both of updating phase noise power spectrum while seamlessly capturing the analyzed signal into its memory, and granting as good frequency resolution as few units of hertz.

High resolution quantitative phase imaging of live cells with constrained optimization approach

NASA Astrophysics Data System (ADS)

Pandiyan, Vimal Prabhu; Khare, Kedar; John, Renu

2016-03-01

Quantitative phase imaging (QPI) aims at studying weakly scattering and absorbing biological specimens with subwavelength accuracy without any external staining mechanisms. Use of a reference beam at an angle is one of the necessary criteria for recording of high resolution holograms in most of the interferometric methods used for quantitative phase imaging. The spatial separation of the dc and twin images is decided by the reference beam angle and Fourier-filtered reconstructed image will have a very poor resolution if hologram is recorded below a minimum reference angle condition. However, it is always inconvenient to have a large reference beam angle while performing high resolution microscopy of live cells and biological specimens with nanometric features. In this paper, we treat reconstruction of digital holographic microscopy images as a constrained optimization problem with smoothness constraint in order to recover only complex object field in hologram plane even with overlapping dc and twin image terms. We solve this optimization problem by gradient descent approach iteratively and the smoothness constraint is implemented by spatial averaging with appropriate size. This approach will give excellent high resolution image recovery compared to Fourier filtering while keeping a very small reference angle. We demonstrate this approach on digital holographic microscopy of live cells by recovering the quantitative phase of live cells from a hologram recorded with nearly zero reference angle.

Development strategy and process models for phased automation of design and digital manufacturing electronics

NASA Astrophysics Data System (ADS)

Korshunov, G. I.; Petrushevskaya, A. A.; Lipatnikov, V. A.; Smirnova, M. S.

2018-03-01

The strategy of quality of electronics insurance is represented as most important. To provide quality, the processes sequence is considered and modeled by Markov chain. The improvement is distinguished by simple database means of design for manufacturing for future step-by-step development. Phased automation of design and digital manufacturing electronics is supposed. The MatLab modelling results showed effectiveness increase. New tools and software should be more effective. The primary digital model is proposed to represent product in the processes sequence from several processes till the whole life circle.

Examination of rapid phase change in copper wires to improve material models and understanding of burst

NASA Astrophysics Data System (ADS)

Olles, Joseph; Garasi, Christopher; Ball, J. Patrick

2017-11-01

Electrically-pulsed wires undergo multiple phase changes including a postulated metastable phase resulting in explosive wire growth. Simulations using the MHD approximation attempt to account for the governing physics, but lack the material properties (equations-of-state and electrical conductivity) to accurately predict the phase evolution of the exploding (bursting) wire. To explore the dynamics of an exploding copper wire (in water), we employ a digital micro-Schlieren streak photography technique. This imaging quantifies wire expansion and shock waves emitted from the wire during phase changes. Using differential voltage probes, a Rogowski coil, and timing fiducials, the phase change of the wire is aligned with electrical power and energy deposition. Time-correlated electrical diagnostics and imaging allow for detailed validation of MHD simulations, comparing observed phases with phase change details found in the material property descriptions. In addition to streak imaging, a long exposure image is taken to capture axial striations along the length of the wire. These images are used to compare with results from 3D MHD simulations which propose that these perturbations impact the rate of wire expansion and temporal change in phases. If successful, the experimental data will identify areas for improvement in the material property models, and modeling results will provide insight into the details of phase change in the wire with correlation to variations in the electrical signals.

Design and verification of the miniature optical system for small object surface profile fast scanning

NASA Astrophysics Data System (ADS)

Chi, Sheng; Lee, Shu-Sheng; Huang, Jen, Jen-Yu; Lai, Ti-Yu; Jan, Chia-Ming; Hu, Po-Chi

2016-04-01

As the progress of optical technologies, different commercial 3D surface contour scanners are on the market nowadays. Most of them are used for reconstructing the surface profile of mold or mechanical objects which are larger than 50 mm×50 mm× 50 mm, and the scanning system size is about 300 mm×300 mm×100 mm. There are seldom optical systems commercialized for surface profile fast scanning for small object size less than 10 mm×10 mm×10 mm. Therefore, a miniature optical system has been designed and developed in this research work for this purpose. Since the most used scanning method of such system is line scan technology, we have developed pseudo-phase shifting digital projection technology by adopting projecting fringes and phase reconstruction method. A projector was used to project a digital fringe patterns on the object, and the fringes intensity images of the reference plane and of the sample object were recorded by a CMOS camera. The phase difference between the plane and object can be calculated from the fringes images, and the surface profile of the object was reconstructed by using the phase differences. The traditional phase shifting method was accomplished by using PZT actuator or precisely controlled motor to adjust the light source or grating and this is one of the limitations for high speed scanning. Compared with the traditional optical setup, we utilized a micro projector to project the digital fringe patterns on the sample. This diminished the phase shifting processing time and the controlled phase differences between the shifted phases become more precise. Besides, the optical path design based on a portable device scanning system was used to minimize the size and reduce the number of the system components. A screwdriver section about 7mm×5mm×5mm has been scanned and its surface profile was successfully restored. The experimental results showed that the measurement area of our system can be smaller than 10mm×10mm, the precision reached to +/-10μm, and the scanning time for each surface of an object was less than 15 seconds. This has proved that our system own the potential to be a fast scanning scanner for small object surface profile scanning.

Movies of cellular and sub-cellular motion by digital holographic microscopy.

PubMed

Mann, Christopher J; Yu, Lingfeng; Kim, Myung K

2006-03-23

Many biological specimens, such as living cells and their intracellular components, often exhibit very little amplitude contrast, making it difficult for conventional bright field microscopes to distinguish them from their surroundings. To overcome this problem phase contrast techniques such as Zernike, Normarsky and dark-field microscopies have been developed to improve specimen visibility without chemically or physically altering them by the process of staining. These techniques have proven to be invaluable tools for studying living cells and furthering scientific understanding of fundamental cellular processes such as mitosis. However a drawback of these techniques is that direct quantitative phase imaging is not possible. Quantitative phase imaging is important because it enables determination of either the refractive index or optical thickness variations from the measured optical path length with sub-wavelength accuracy. Digital holography is an emergent phase contrast technique that offers an excellent approach in obtaining both qualitative and quantitative phase information from the hologram. A CCD camera is used to record a hologram onto a computer and numerical methods are subsequently applied to reconstruct the hologram to enable direct access to both phase and amplitude information. Another attractive feature of digital holography is the ability to focus on multiple focal planes from a single hologram, emulating the focusing control of a conventional microscope. A modified Mach-Zender off-axis setup in transmission is used to record and reconstruct a number of holographic amplitude and phase images of cellular and sub-cellular features. Both cellular and sub-cellular features are imaged with sub-micron, diffraction-limited resolution. Movies of holographic amplitude and phase images of living microbes and cells are created from a series of holograms and reconstructed with numerically adjustable focus, so that the moving object can be accurately tracked with a reconstruction rate of 300ms for each hologram. The holographic movies show paramecium swimming among other microbes as well as displaying some of their intracellular processes. A time lapse movie is also shown for fibroblast cells in the process of migration. Digital holography and movies of digital holography are seen to be useful new tools for visualization of dynamic processes in biological microscopy. Phase imaging digital holography is a promising technique in terms of the lack of coherent noise and the precision with which the optical thickness of a sample can be profiled, which can lead to images with an axial resolution of a few nanometres.

Association between finger tapping, attention, memory, and cognitive diagnosis in elderly patients.

PubMed

Rabinowitz, Israel; Lavner, Yizhar

2014-08-01

This study examined the association between spontaneous finger tapping and cognitive function, with a detailed analysis of the two main phases of finger tapping, the touch-phase and the off-phase. 170 elderly patients (83 men, 87 women; M age = 82.1 yr., SD = 6.2) underwent cognitive assessment including the Mini-Mental State Examination, a forward digit span test, and 15 sec. of finger tapping. Results indicated a significant increase in the length and variability of the finger-touch phase among participants with mild cognitive impairment or dementia compared to participants with no cognitive impairment, suggesting a relationship between finger tapping and attention, short-term memory, and cognitive diagnosis. Pattern classification analyses on the finger tapping parameters indicated a specificity of 0.91 and sensitivity of 0.52 for ruling out cognitive impairment.

Low speed phaselock speed control system. [for brushless dc motor

NASA Technical Reports Server (NTRS)

Fulcher, R. W.; Sudey, J. (Inventor)

1975-01-01

A motor speed control system for an electronically commutated brushless dc motor is provided which includes a phaselock loop with bidirectional torque control for locking the frequency output of a high density encoder, responsive to actual speed conditions, to a reference frequency signal, corresponding to the desired speed. The system includes a phase comparator, which produces an output in accordance with the difference in phase between the reference and encoder frequency signals, and an integrator-digital-to-analog converter unit, which converts the comparator output into an analog error signal voltage. Compensation circuitry, including a biasing means, is provided to convert the analog error signal voltage to a bidirectional error signal voltage which is utilized by an absolute value amplifier, rotational decoder, power amplifier-commutators, and an arrangement of commutation circuitry.

Photonic Analog-to-Digital Converters

DTIC Science & Technology

2006-03-01

Edward W. Taylor, “Gamma-Ray Induced Damage and Recovery Behavior in an Erbium-Doped Fiber Laser ”, SPIE Proceedings, Vol. 4547, Sep. 2001, pp.126-133...requirements. The center frequency of the bandpass filter determined the laser mode-locked frequency. SNDP’s COEO had an operating frequency of... laser . Better filters and amplifiers were needed to improve operation and to reduce the phase noise to a level comparable with Delfyett’s actively

Higher Order Modulation Intersymbol Interference Caused by Traveling-wave Tube Amplifiers

NASA Technical Reports Server (NTRS)

Kory, Carol L.; Andro, Monty; Williams, W. D. (Technical Monitor)

2002-01-01

For the first time, a time-dependent, physics-based computational model has been used to provide a direct description of the effects of the traveling wave tube amplifier (TWTA) on modulated digital signals. The TWT model comprehensively takes into account the effects of frequency dependent AM/AM and AM/PM conversion; gain and phase ripple; drive-induced oscillations; harmonic generation; intermodulation products; and backward waves, Thus, signal integrity can be investigated in the presence of these sources of potential distortion as a function of the physical geometry and operating characteristics of the high power amplifier and the operational digital signal. This method promises superior predictive fidelity compared to methods using TWT models based on swept-amplitude and/or swept-frequency data. First, the TWT model using the three dimensional (3D) electromagnetic code MAFIA is presented. Then, this comprehensive model is used to investigate approximations made in conventional TWT black-box models used in communication system level simulations, To quantitatively demonstrate the effects these approximations have on digital signal performance predictions, including intersymbol interference (ISI), the MAFIA results are compared to the system level analysis tool, Signal Processing, Workstation (SPW), using high order modulation schemes including 16 and 64-QAM.

Intersymbol Interference Investigations Using a 3D Time-Dependent Traveling Wave Tube Model

NASA Technical Reports Server (NTRS)

Kory, Carol L.; Andro, Monty

2002-01-01

For the first time, a time-dependent, physics-based computational model has been used to provide a direct description of the effects of the traveling wave tube amplifier (TWTA) on modulated digital signals. The TWT model comprehensively takes into account the effects of frequency dependent AM/AM and AM/PM conversion; gain and phase ripple; drive-induced oscillations; harmonic generation; intermodulation products; and backward waves. Thus, signal integrity can be investigated in the presence of these sources of potential distortion as a function of the physical geometry and operating characteristics of the high power amplifier and the operational digital signal. This method promises superior predictive fidelity compared to methods using TWT models based on swept- amplitude and/or swept-frequency data. First, the TWT model using the three dimensional (3D) electromagnetic code MAFIA is presented. Then, this comprehensive model is used to investigate approximations made in conventional TWT black-box models used in communication system level simulations. To quantitatively demonstrate the effects these approximations have on digital signal performance predictions, including intersymbol interference (ISI), the MAFIA results are compared to the system level analysis tool, Signal Processing Workstation (SPW), using high order modulation schemes including 16 and 64-QAM.

High quality digital holographic reconstruction on analog film

NASA Astrophysics Data System (ADS)

Nelsen, B.; Hartmann, P.

2017-05-01

High quality real-time digital holographic reconstruction, i.e. at 30 Hz frame rates, has been at the forefront of research and has been hailed as the holy grail of display systems. While these efforts have produced a fascinating array of computer algorithms and technology, many applications of reconstructing high quality digital holograms do not require such high frame rates. In fact, applications such as 3D holographic lithography even require a stationary mask. Typical devices used for digital hologram reconstruction are based on spatial-light-modulator technology and this technology is great for reconstructing arbitrary holograms on the fly; however, it lacks the high spatial resolution achievable by its analog counterpart, holographic film. Analog holographic film is therefore the method of choice for reconstructing highquality static holograms. The challenge lies in taking a static, high-quality digitally calculated hologram and effectively writing it to holographic film. We have developed a theoretical system based on a tunable phase plate, an intensity adjustable high-coherence laser and a slip-stick based piezo rotation stage to effectively produce a digitally calculated hologram on analog film. The configuration reproduces the individual components, both the amplitude and phase, of the hologram in the Fourier domain. These Fourier components are then individually written on the holographic film after interfering with a reference beam. The system is analogous to writing angularly multiplexed plane waves with individual component phase control.

Doppler extraction with a digital VCO

NASA Technical Reports Server (NTRS)

Starner, E. R.; Nossen, E. J.

1977-01-01

Digitally controlled oscillator in phased-locked loop may be useful for data communications systems, or may be modified to serve as information extraction component of microwave or optical system for collision avoidance or automatic braking. Instrument is frequency-synthesizing device with output specified precisely by digital number programmed into frequency register.

Beyond Preservation: New Directions for Technological Innovation through Intangible Cultural Heritage

ERIC Educational Resources Information Center

Robbins, Christopher

2010-01-01

While many digitization projects are currently underway, to help preserve Indigenous traditions, few explore the full potential of the development of digital media and networked technology through Indigenous cultures. This paper outlines the three phases necessary for a robust digital preservation, promotion and growth project: 1) Straightforward…

Improvement of the energy resolution via an optimized digital signal processing in GERDA Phase I

DOE PAGES

Agostini, M.; Allardt, M.; Bakalyarov, A. M.; ...

2015-06-09

An optimized digital shaping filter has been developed for the Gerda experiment which searches for neutrinoless double beta decay inmore » $$^{76}$$Ge. The Gerda Phase I energy calibration data have been reprocessed and an average improvement of 0.3 keV in energy resolution (FWHM) corresponding to 10% at the $Q$ value for $$0\

Using convolutional decoding to improve time delay and phase estimation in digital communications

DOEpatents

Ormesher, Richard C [Albuquerque, NM; Mason, John J [Albuquerque, NM

2010-01-26

The time delay and/or phase of a communication signal received by a digital communication receiver can be estimated based on a convolutional decoding operation that the communication receiver performs on the received communication signal. If the original transmitted communication signal has been spread according to a spreading operation, a corresponding despreading operation can be integrated into the convolutional decoding operation.

Demodulation of moire fringes in digital holographic interferometry using an extended Kalman filter.

PubMed

Ramaiah, Jagadesh; Rastogi, Pramod; Rajshekhar, Gannavarpu

2018-03-10

This paper presents a method for extracting multiple phases from a single moire fringe pattern in digital holographic interferometry. The method relies on component separation using singular value decomposition and an extended Kalman filter for demodulating the moire fringes. The Kalman filter is applied by modeling the interference field locally as a multi-component polynomial phase signal and extracting the associated multiple polynomial coefficients using the state space approach. In addition to phase, the corresponding multiple phase derivatives can be simultaneously extracted using the proposed method. The applicability of the proposed method is demonstrated using simulation and experimental results.

Digital disaster evaluation and its application to 2015 Ms 8.1 Nepal Earthquake

NASA Astrophysics Data System (ADS)

WANG, Xiaoqing; LV, Jinxia; DING, Xiang; DOU, Aixia

2016-11-01

The purpose of the article is to probe the technique resolution of disaster information extraction and evaluation from the digital RS images based on the internet environment and aided by the social and geographic information. The solution is composed with such methods that the fast post-disaster assessment system will assess automatically the disaster area and grade, the multi-phase satellite and airborne high resolution digital RS images will provide the basis to extract the disaster areas or spots, assisted by the fast position of potential serious damage risk targets according to the geographic, administrative, population, buildings and other information in the estimated disaster region, the 2D digital map system or 3D digital earth system will provide platforms to interpret cooperatively the damage information in the internet environment, and further to estimate the spatial distribution of damage index or intensity, casualties or economic losses, which are very useful for the decision-making of emergency rescue and disaster relief, resettlement and reconstruction. The spatial seismic damage distribution of 2015 Ms 8.1 Nepal earthquake, as an example of the above solution, is evaluated by using the high resolution digital RS images, auxiliary geographic information and ground survey. The results are compared with the statistical disaster information issued by the ground truth by field surveying, and show good consistency.

An Improved Model Predictive Current Controller of Switched Reluctance Machines Using Time-Multiplexed Current Sensor

PubMed Central

Li, Bingchu; Ling, Xiao; Huang, Yixiang; Gong, Liang; Liu, Chengliang

2017-01-01

This paper presents a fixed-switching-frequency model predictive current controller using multiplexed current sensor for switched reluctance machine (SRM) drives. The converter was modified to distinguish currents from simultaneously excited phases during the sampling period. The only current sensor installed in the converter was time division multiplexing for phase current sampling. During the commutation stage, the control steps of adjacent phases were shifted so that sampling time was staggered. The maximum and minimum duty ratio of pulse width modulation (PWM) was limited to keep enough sampling time for analog-to-digital (A/D) conversion. Current sensor multiplexing was realized without complex adjustment of either driver circuit nor control algorithms, while it helps to reduce the cost and errors introduced in current sampling due to inconsistency between sensors. The proposed controller is validated by both simulation and experimental results with a 1.5 kW three-phase 12/8 SRM. Satisfied current sampling is received with little difference compared with independent phase current sensors for each phase. The proposed controller tracks the reference current profile as accurately as the model predictive current controller with independent phase current sensors, while having minor tracking errors compared with a hysteresis current controller. PMID:28513554

Designing, Prototyping and Evaluating Digital Mindfulness Applications: A Case Study of Mindful Breathing for Stress Reduction

PubMed Central

Hedman, Anders; Feng, Shuo; Li, Haibo; Osika, Walter

2017-01-01

Background During the past decade, there has been a rapid increase of interactive apps designed for health and well-being. Yet, little research has been published on developing frameworks for design and evaluation of digital mindfulness facilitating technologies. Moreover, many existing digital mindfulness applications are purely software based. There is room for further exploration and assessment of designs that make more use of physical qualities of artifacts. Objective The study aimed to develop and test a new physical digital mindfulness prototype designed for stress reduction. Methods In this case study, we designed, developed, and evaluated HU, a physical digital mindfulness prototype designed for stress reduction. In the first phase, we used vapor and light to support mindful breathing and invited 25 participants through snowball sampling to test HU. In the second phase, we added sonification. We deployed a package of probes such as photos, diaries, and cards to collect data from users who explored HU in their homes. Thereafter, we evaluated our installation using both self-assessed stress levels and heart rate (HR) and heart rate variability (HRV) measures in a pilot study, in order to measure stress resilience effects. After the experiment, we performed a semistructured interview to reflect on HU and investigate the design of digital mindfulness apps for stress reduction. Results The results of the first phase showed that 22 of 25 participants (88%) claimed vapor and light could be effective ways of promoting mindful breathing. Vapor could potentially support mindful breathing better than light (especially for mindfulness beginners). In addition, a majority of the participants mentioned sound as an alternative medium. In the second phase, we found that participants thought that HU could work well for stress reduction. We compared the effect of silent HU (using light and vapor without sound) and sonified HU on 5 participants. Subjective stress levels were statistically improved with both silent and sonified HU. The mean value of HR using silent HU was significantly lower than resting baseline and sonified HU. The mean value of root mean square of differences (RMSSD) using silent HU was significantly higher than resting baseline. We found that the differences between our objective and subjective assessments were intriguing and prompted us to investigate them further. Conclusions Our evaluation of HU indicated that HU could facilitate relaxed breathing and stress reduction. There was a difference in outcome between the physiological measures of stress and the subjective reports of stress, as well as a large intervariability among study participants. Our conclusion is that the use of stress reduction tools should be customized and that the design work of mindfulness technology for stress reduction is a complex process, which requires cooperation of designers, HCI (Human-Computer Interaction) experts and clinicians. PMID:28615157

Analysis and design of a second-order digital phase-locked loop

NASA Technical Reports Server (NTRS)

Blasche, P. R.

1979-01-01

A specific second-order digital phase-locked loop (DPLL) was modeled as a first-order Markov chain with alternatives. From the matrix of transition probabilities of the Markov chain, the steady-state phase error of the DPLL was determined. In a similar manner the loop's response was calculated for a fading input. Additionally, a hardware DPLL was constructed and tested to provide a comparison to the results obtained from the Markov chain model. In all cases tested, good agreement was found between the theoretical predictions and the experimental data.

Correction of I/Q channel errors without calibration

DOEpatents

Doerry, Armin W.; Tise, Bertice L.

2002-01-01

A method of providing a balanced demodular output for a signal such as a Doppler radar having an analog pulsed input; includes adding a variable phase shift as a function of time to the input signal, applying the phase shifted input signal to a demodulator; and generating a baseband signal from the input signal. The baseband signal is low-pass filtered and converted to a digital output signal. By removing the variable phase shift from the digital output signal, a complex data output is formed that is representative of the output of a balanced demodulator.

Multichannel Phase and Power Detector

NASA Technical Reports Server (NTRS)

Li, Samuel; Lux, James; McMaster, Robert; Boas, Amy

2006-01-01

An electronic signal-processing system determines the phases of input signals arriving in multiple channels, relative to the phase of a reference signal with which the input signals are known to be coherent in both phase and frequency. The system also gives an estimate of the power levels of the input signals. A prototype of the system has four input channels that handle signals at a frequency of 9.5 MHz, but the basic principles of design and operation are extensible to other signal frequencies and greater numbers of channels. The prototype system consists mostly of three parts: An analog-to-digital-converter (ADC) board, which coherently digitizes the input signals in synchronism with the reference signal and performs some simple processing; A digital signal processor (DSP) in the form of a field-programmable gate array (FPGA) board, which performs most of the phase- and power-measurement computations on the digital samples generated by the ADC board; and A carrier board, which allows a personal computer to retrieve the phase and power data. The DSP contains four independent phase-only tracking loops, each of which tracks the phase of one of the preprocessed input signals relative to that of the reference signal (see figure). The phase values computed by these loops are averaged over intervals, the length of which is chosen to obtain output from the DSP at a desired rate. In addition, a simple sum of squares is computed for each channel as an estimate of the power of the signal in that channel. The relative phases and the power level estimates computed by the DSP could be used for diverse purposes in different settings. For example, if the input signals come from different elements of a phased-array antenna, the phases could be used as indications of the direction of arrival of a received signal and/or as feedback for electronic or mechanical beam steering. The power levels could be used as feedback for automatic gain control in preprocessing of incoming signals. For another example, the system could be used to measure the phases and power levels of outputs of multiple power amplifiers to enable adjustment of the amplifiers for optimal power combining.

Quantitative phase-contrast digital holographic microscopy for cell dynamic evaluation

NASA Astrophysics Data System (ADS)

Yu, Lingfeng; Mohanty, Samarendra; Berns, Michael W.; Chen, Zhongping

2009-02-01

The laser microbeam uses lasers to alter and/or to ablate intracellular organelles and cellular and tissue samples, and, today, has become an important tool for cell biologists to study the molecular mechanism of complex biological systems by removing individual cells or sub-cellular organelles. However, absolute quantitation of the localized alteration/damage to transparent phase objects, such as the cell membrane or chromosomes, was not possible using conventional phase-contrast or differential interference contrast microscopy. We report the development of phase-contrast digital holographic microscopy for quantitative evaluation of cell dynamic changes in real time during laser microsurgery. Quantitative phase images are recorded during the process of laser microsurgery and thus, the dynamic change in phase can be continuously evaluated. Out-of-focus organelles are re-focused by numerical reconstruction algorithms.

Holographic fluorescence microscopy with incoherent digital holographic adaptive optics

NASA Astrophysics Data System (ADS)

Jang, Changwon; Kim, Jonghyun; Clark, David C.; Lee, Seungjae; Lee, Byoungho; Kim, Myung K.

2015-11-01

Introduction of adaptive optics technology into astronomy and ophthalmology has made great contributions in these fields, allowing one to recover images blurred by atmospheric turbulence or aberrations of the eye. Similar adaptive optics improvement in microscopic imaging is also of interest to researchers using various techniques. Current technology of adaptive optics typically contains three key elements: a wavefront sensor, wavefront corrector, and controller. These hardware elements tend to be bulky, expensive, and limited in resolution, involving, for example, lenslet arrays for sensing or multiactuator deformable mirrors for correcting. We have previously introduced an alternate approach based on unique capabilities of digital holography, namely direct access to the phase profile of an optical field and the ability to numerically manipulate the phase profile. We have also demonstrated that direct access and compensation of the phase profile are possible not only with conventional coherent digital holography, but also with a new type of digital holography using incoherent light: self­interference incoherent digital holography (SIDH). The SIDH generates a complex-i.e., amplitude plus phase-hologram from one or several interferograms acquired with incoherent light, such as LEDs, lamps, sunlight, or fluorescence. The complex point spread function can be measured using guide star illumination and it allows deterministic deconvolution of the full-field image. We present experimental demonstration of aberration compensation in holographic fluorescence microscopy using SIDH. Adaptive optics by SIDH provides new tools for improved cellular fluorescence microscopy through intact tissue layers or other types of aberrant media.

Holographic fluorescence microscopy with incoherent digital holographic adaptive optics

NASA Astrophysics Data System (ADS)

Jang, Changwon; Kim, Jonghyun; Clark, David C.; Lee, Byoungho; Kim, Myung K.

2015-03-01

Introduction of adaptive optics technology into astronomy and ophthalmology has made great contributions in these fields, allowing one to recover images blurred by atmospheric turbulence or aberrations of the eye. Similar adaptive optics improvement in microscopic imaging is also of interest to researchers using various techniques. Current technology of adaptive optics typically contains three key elements: wavefront sensor, wavefront corrector and controller. These hardware elements tend to be bulky, expensive, and limited in resolution, involving, e.g., lenslet arrays for sensing or multi-acuator deformable mirrors for correcting. We have previously introduced an alternate approach to adaptive optics based on unique capabilities of digital holography, namely direct access to the phase profile of an optical field and the ability to numerically manipulate the phase profile. We have also demonstrated that direct access and compensation of the phase profile is possible not only with the conventional coherent type of digital holography, but also with a new type of digital holography using incoherent light: self-interference incoherent digital holography (SIDH). The SIDH generates complex - i.e. amplitude plus phase - hologram from one or several interferograms acquired with incoherent light, such as LEDs, lamps, sunlight, or fluorescence. The complex point spread function can be measured using a guide star illumination and it allows deterministic deconvolution of the full-field image. We present experimental demonstration of aberration compensation in holographic fluorescence microscopy using SIDH. The adaptive optics by SIDH provides new tools for improved cellular fluorescence microscopy through intact tissue layers or other types of aberrant media.

Parallel-quadrature phase-shifting digital holographic microscopy using polarization beam splitter

PubMed Central

Das, Bhargab; Yelleswarapu, Chandra S; Rao, DVGLN

2012-01-01

We present a digital holography microscopy technique based on parallel-quadrature phase-shifting method. Two π/2 phase-shifted holograms are recorded simultaneously using polarization phase-shifting principle, slightly off-axis recording geometry, and two identical CCD sensors. The parallel phase-shifting is realized by combining circularly polarized object beam with a 45° degree polarized reference beam through a polarizing beam splitter. DC term is eliminated by subtracting the two holograms from each other and the object information is reconstructed after selecting the frequency spectrum of the real image. Both amplitude and phase object reconstruction results are presented. Simultaneous recording eliminates phase errors caused by mechanical vibrations and air turbulences. The slightly off-axis recording geometry with phase-shifting allows a much larger dimension of the spatial filter for reconstruction of the object information. This leads to better reconstruction capability than traditional off-axis holography. PMID:23109732

A digital optical phase-locked loop for diode lasers based on field programmable gate array

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu Zhouxiang; Zhang Xian; Huang Kaikai

2012-09-15

We have designed and implemented a highly digital optical phase-locked loop (OPLL) for diode lasers in atom interferometry. The three parts of controlling circuit in this OPLL, including phase and frequency detector (PFD), loop filter and proportional integral derivative (PID) controller, are implemented in a single field programmable gate array chip. A structure type compatible with the model MAX9382/MCH12140 is chosen for PFD and pipeline and parallelism technology have been adapted in PID controller. Especially, high speed clock and twisted ring counter have been integrated in the most crucial part, the loop filter. This OPLL has the narrow beat notemore » line width below 1 Hz, residual mean-square phase error of 0.14 rad{sup 2} and transition time of 100 {mu}s under 10 MHz frequency step. A main innovation of this design is the completely digitalization of the whole controlling circuit in OPLL for diode lasers.« less

Real-time phase correlation based integrated system for seizure detection

NASA Astrophysics Data System (ADS)

Romaine, James B.; Delgado-Restituto, Manuel; Leñero-Bardallo, Juan A.; Rodríguez-Vázquez, Ángel

2017-05-01

This paper reports a low area, low power, integer-based digital processor for the calculation of phase synchronization between two neural signals. The processor calculates the phase-frequency content of a signal by identifying the specific time periods associated with two consecutive minima. The simplicity of this phase-frequency content identifier allows for the digital processor to utilize only basic digital blocks, such as registers, counters, adders and subtractors, without incorporating any complex multiplication and or division algorithms. In fact, the processor, fabricated in a 0.18μm CMOS process, only occupies an area of 0.0625μm2 and consumes 12.5nW from a 1.2V supply voltage when operated at 128kHz. These low-area, low-power features make the proposed processor a valuable computing element in closed loop neural prosthesis for the treatment of neural diseases, such as epilepsy, or for extracting functional connectivity maps between different recording sites in the brain.

Timing performance of phased-locked loops in optical pulse position modulation communication systems

NASA Technical Reports Server (NTRS)

Lafaw, D. A.; Gardner, C. S.

1984-01-01

An optical digital communication system requires that an accurate clock signal be available at the receiver for proper synchronization with the transmitted signal. Phase synchronization is especially critical in M-ary pulse position modulation (PPM) systems where the optimum decision scheme is an energy detector which compares the energy in each of M time slots to decide which of M possible words was sent. Timing errors cause energy spillover into adjacent time slots (a form of intersymbol interference) so that only a portion of the signal energy may be attributed to the correct time slot. This effect decreases the effective signal, increases the effective noise, and increases the probability of error. A timing subsystem for a satellite-to-satellite optical PPM communication link is simulated. The receiver employs direct photodetection, preprocessing of the detected signal, and a phase-locked loop for timing synchronization. The variance of the relative phase error is examined under varying signal strength conditions as an indication of loop performance, and simulation results are compared to theoretical calculations.

Timing performance of phased-locked loops in optical pulse position modulation communication systems

NASA Astrophysics Data System (ADS)

Lafaw, D. A.; Gardner, C. S.

1984-08-01

An optical digital communication system requires that an accurate clock signal be available at the receiver for proper synchronization with the transmitted signal. Phase synchronization is especially critical in M-ary pulse position modulation (PPM) systems where the optimum decision scheme is an energy detector which compares the energy in each of M time slots to decide which of M possible words was sent. Timing errors cause energy spillover into adjacent time slots (a form of intersymbol interference) so that only a portion of the signal energy may be attributed to the correct time slot. This effect decreases the effective signal, increases the effective noise, and increases the probability of error. A timing subsystem for a satellite-to-satellite optical PPM communication link is simulated. The receiver employs direct photodetection, preprocessing of the detected signal, and a phase-locked loop for timing synchronization. The variance of the relative phase error is examined under varying signal strength conditions as an indication of loop performance, and simulation results are compared to theoretical calculations.

Optical phase nanoscopy in red blood cells using low-coherence spectroscopy.

PubMed

Shock, Itay; Barbul, Alexander; Girshovitz, Pinhas; Nevo, Uri; Korenstein, Rafi; Shaked, Natan T

2012-10-01

We propose a low-coherence spectral-domain phase microscopy (SDPM) system for accurate quantitative phase measurements in red blood cells (RBCs) for the prognosis and monitoring of disease conditions that affect the visco-elastic properties of RBCs. Using the system, we performed time-recordings of cell membrane fluctuations, and compared the nano-scale fluctuation dynamics of healthy and glutaraldehyde-treated RBCs. Glutaraldehyde-treated RBCs possess lower amplitudes of fluctuations, reflecting an increased membrane stiffness. To demonstrate the ability of our system to measure fluctuations of lower amplitudes than those measured by the commonly used holographic phase microscopy techniques, we also constructed wide-field digital interferometry (WFDI) system and compared the performances of both systems. Due to its common-path geometry, the optical-path-delay stability of SDPM was found to be less than 0.3 nm in liquid environment, at least three times better than WFDI under the same conditions. In addition, due to the compactness of SDPM and its inexpensive and robust design, the system possesses a high potential for clinical applications.

Digital PCM bit synchronizer and detector

NASA Astrophysics Data System (ADS)

Moghazy, A. E.; Maral, G.; Blanchard, A.

1980-08-01

A theoretical analysis of a digital self-bit synchronizer and detector is presented and supported by the implementation of an experimental model that utilizes standard TTL logic circuits. This synchronizer is based on the generation of spectral line components by nonlinear filtering of the received bit stream, and extracting the line by a digital phase-locked loop (DPLL). The extracted reference signal instructs a digital matched filter (DMF) data detector. This realization features a short acquisition time and an all-digital structure.

Patient engagement and the design of digital health

PubMed Central

Birnbaum, Faith; Lewis, Dana M.; Rosen, Rochelle; Ranney, Megan L.

2015-01-01

Digital health is an area of growing interest for physicians, patients, and technology companies alike. It promises the ability to engage patients in their care, before, during, and after an emergency department visit. Current efforts to create, study, and disseminate digital health have been limited by lack of user engagement. In this commentary, we outline the imperative for engaging end-users in each phase of digital health design, as well as a few techniques to facilitate better digital health design and implementation. PMID:25997375

Low photon count based digital holography for quadratic phase cryptography.

PubMed

Muniraj, Inbarasan; Guo, Changliang; Malallah, Ra'ed; Ryle, James P; Healy, John J; Lee, Byung-Geun; Sheridan, John T

2017-07-15

Recently, the vulnerability of the linear canonical transform-based double random phase encryption system to attack has been demonstrated. To alleviate this, we present for the first time, to the best of our knowledge, a method for securing a two-dimensional scene using a quadratic phase encoding system operating in the photon-counted imaging (PCI) regime. Position-phase-shifting digital holography is applied to record the photon-limited encrypted complex samples. The reconstruction of the complex wavefront involves four sparse (undersampled) dataset intensity measurements (interferograms) at two different positions. Computer simulations validate that the photon-limited sparse-encrypted data has adequate information to authenticate the original data set. Finally, security analysis, employing iterative phase retrieval attacks, has been performed.

Multiwavelength digital holography with wavelength-multiplexed holograms and arbitrary symmetric phase shifts.

PubMed

Tahara, Tatsuki; Otani, Reo; Omae, Kaito; Gotohda, Takuya; Arai, Yasuhiko; Takaki, Yasuhiro

2017-05-15

We propose multiwavelength in-line digital holography with wavelength-multiplexed phase-shifted holograms and arbitrary symmetric phase shifts. We use phase-shifting interferometry selectively extracting wavelength information to reconstruct multiwavelength object waves separately from wavelength-multiplexed monochromatic images. The proposed technique obtains systems of equations for real and imaginary parts of multiwavelength object waves from the holograms by introducing arbitrary symmetric phase shifts. Then, the technique derives each complex amplitude distribution of each object wave selectively and analytically by solving the two systems of equations. We formulate the algorithm in the case of an arbitrary number of wavelengths and confirm its validity numerically and experimentally in the cases where the number of wavelengths is two and three.

Threshold automatic selection hybrid phase unwrapping algorithm for digital holographic microscopy

NASA Astrophysics Data System (ADS)

Zhou, Meiling; Min, Junwei; Yao, Baoli; Yu, Xianghua; Lei, Ming; Yan, Shaohui; Yang, Yanlong; Dan, Dan

2015-01-01

Conventional quality-guided (QG) phase unwrapping algorithm is hard to be applied to digital holographic microscopy because of the long execution time. In this paper, we present a threshold automatic selection hybrid phase unwrapping algorithm that combines the existing QG algorithm and the flood-filled (FF) algorithm to solve this problem. The original wrapped phase map is divided into high- and low-quality sub-maps by selecting a threshold automatically, and then the FF and QG unwrapping algorithms are used in each level to unwrap the phase, respectively. The feasibility of the proposed method is proved by experimental results, and the execution speed is shown to be much faster than that of the original QG unwrapping algorithm.

The application of digital image plane holography technology to identify Chinese herbal medicine

NASA Astrophysics Data System (ADS)

Wang, Huaying; Guo, Zhongjia; Liao, Wei; Zhang, Zhihui

2012-03-01

In this paper, the imaging technology of digital image plane holography to identify the Chinese herbal medicine is studied. The optical experiment system of digital image plane holography which is the special case of pre-magnification digital holography was built. In the record system, one is an object light by using plane waves which illuminates the object, and the other one is recording hologram by using spherical light wave as reference light. There is a Micro objective lens behind the object. The second phase factor which caus ed by the Micro objective lens can be eliminated by choosing the proper position of the reference point source when digital image plane holography is recorded by spherical light. In this experiment, we use the Lygodium cells and Onion cells as the object. The experiment results with Lygodium cells and Onion cells show that digital image plane holography avoid the process of finding recording distance by using auto-focusing approach, and the phase information of the object can be reconstructed more accurately. The digital image plane holography is applied to the microscopic imaging of cells more effectively, and it is suit to apply for the identify of Chinese Herbal Medicine. And it promotes the application of digital holographic in practice.

Modeling and system design for the LOFAR station digital processing

NASA Astrophysics Data System (ADS)

Alliot, Sylvain; van Veelen, Martijn

2004-09-01

In the context of the LOFAR preliminary design phase and in particular for the specification of the Station Digital Processing (SDP), a performance/cost model of the system was used. We present here the framework and the trajectory followed in this phase when going from requirements to specification. In the phased array antenna concepts for the next generation of radio telescopes (LOFAR, ATA, SKA) signal processing (multi-beaming and RFI mitigation) replaces the large antenna dishes. The embedded systems for these telescopes are major infrastructure cost items. Moreover, the flexibility and overall performance of the instrument depend greatly on them, therefore alternative solutions need to be investigated. In particular, the technology and the various data transport selections play a fundamental role in the optimization of the architecture. We proposed a formal method [1] of exploring these alternatives that has been followed during the SDP developments. Different scenarios were compared for the specification of the application (selection of the algorithms as well as detailed signal processing techniques) and in the specification of the system architecture (selection of high level topologies, platforms and components). It gave us inside knowledge on the possible trade-offs in the application and architecture domains. This was successful in providing firm basis for the design choices that are demanded by technical review committees.

Phase in Optical Image Processing

NASA Astrophysics Data System (ADS)

Naughton, Thomas J.

2010-04-01

The use of phase has a long standing history in optical image processing, with early milestones being in the field of pattern recognition, such as VanderLugt's practical construction technique for matched filters, and (implicitly) Goodman's joint Fourier transform correlator. In recent years, the flexibility afforded by phase-only spatial light modulators and digital holography, for example, has enabled many processing techniques based on the explicit encoding and decoding of phase. One application area concerns efficient numerical computations. Pushing phase measurement to its physical limits, designs employing the physical properties of phase have ranged from the sensible to the wonderful, in some cases making computationally easy problems easier to solve and in other cases addressing mathematics' most challenging computationally hard problems. Another application area is optical image encryption, in which, typically, a phase mask modulates the fractional Fourier transformed coefficients of a perturbed input image, and the phase of the inverse transform is then sensed as the encrypted image. The inherent linearity that makes the system so elegant mitigates against its use as an effective encryption technique, but we show how a combination of optical and digital techniques can restore confidence in that security. We conclude with the concept of digital hologram image processing, and applications of same that are uniquely suited to optical implementation, where the processing, recognition, or encryption step operates on full field information, such as that emanating from a coherently illuminated real-world three-dimensional object.

Portable digital lock-in instrument to determine chemical constituents with single-color absorption measurements for Global Health Initiatives

NASA Astrophysics Data System (ADS)

Vacas-Jacques, Paulino; Linnes, Jacqueline; Young, Anna; Gerrard, Victoria; Gomez-Marquez, Jose

2014-03-01

Innovations in international health require the use of state-of-the-art technology to enable clinical chemistry for diagnostics of bodily fluids. We propose the implementation of a portable and affordable lock-in amplifier-based instrument that employs digital technology to perform biochemical diagnostics on blood, urine, and other fluids. The digital instrument is composed of light source and optoelectronic sensor, lock-in detection electronics, microcontroller unit, and user interface components working with either power supply or batteries. The instrument performs lock-in detection provided that three conditions are met. First, the optoelectronic signal of interest needs be encoded in the envelope of an amplitude-modulated waveform. Second, the reference signal required in the demodulation channel has to be frequency and phase locked with respect to the optoelectronic carrier signal. Third, the reference signal should be conditioned appropriately. We present three approaches to condition the signal appropriately: high-pass filtering the reference signal, precise offset tuning the reference level by low-pass filtering, and by using a voltage divider network. We assess the performance of the lock-in instrument by comparing it to a benchmark device and by determining protein concentration with single-color absorption measurements. We validate the concentration values obtained with the proposed instrument using chemical concentration measurements. Finally, we demonstrate that accurate retrieval of phase information can be achieved by using the same instrument.

A high performance DAC /DDS daughter module for the RHIC LLRF platform

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hayes, T.; Harvey, M.; Narayan, G.

The RHIC LLRF upgrade is a flexible, modular system. Output signals are generated by a custom designed XMC card with 4 high speed digital to analog (DAC) converters interfaced to a high performance field programmable gate array (FPGA). This paper discusses the hardware details of the XMC DAC board as well as the implementation of a low noise rf synthesizer with digital IQ modulation. This synthesizer also provides injection phase cogging and frequency hop rebucketing capabilities. A new modular RHIC LLRF system was recently designed and commissioned based on custom designed XMC cards. As part of that effort a highmore » speed, four channel DAC board was designed. The board uses Maxim MAX5891 16 bit DACs with a maximum update rate of 600 Msps. Since this module is intended to be used for many different systems throughout the Collider Accelerator complex, it was designed to be as generic as possible. One major application of this DAC card is to implement digital synthesizers to provide drive signals to the various cavities at RHIC. Since RHIC is a storage ring with stores that typically last many hours, extremely low RF noise is a critical requirement. Synchrotron frequencies at RHIC range from a few hertz to several hundred hertz depending on the species and point in the acceleration cycle so close in phase noise is a major concern. The RHIC LLRF system uses the Update Link, a deterministic, high speed data link that broadcasts the revolution frequency and the synchronous phase angle. The digital synthesizers use this data to generate a properly phased analog drive signal. The synthesizers must also provide smooth phase shifts for cogging and support frequency shift rebucketing. One additional feature implemented in the FPGA is a digital waveform generator (WFG) that generates I and Q data pairs based on a user selected amplitude and phase profile as a function of time.« less

Digital simulation of hybrid loop operation in RFI backgrounds.

NASA Technical Reports Server (NTRS)

Ziemer, R. E.; Nelson, D. R.

1972-01-01

A digital computer model for Monte-Carlo simulation of an imperfect second-order hybrid phase-locked loop (PLL) operating in radio-frequency interference (RFI) and Gaussian noise backgrounds has been developed. Characterization of hybrid loop performance in terms of cycle slipping statistics and phase error variance, through computer simulation, indicates that the hybrid loop has desirable performance characteristics in RFI backgrounds over the conventional PLL or the costas loop.

Subpicosecond Optical Digital Computation Using Conjugate Parametric Generators

DTIC Science & Technology

1989-03-31

Using Phase Conjugate Farametric Generators ..... 12. PERSONAL AUTHOR(S) Alfano, Robert- Eichmann . George; Dorsinville. Roger! Li. Yao 13a. TYPE OF...conjugation-based optical residue arithmetic processor," Y. Li, G. Eichmann , R. Dorsinville, and R. R. Alfano, Opt. Lett. 13, (1988). [2] "Parallel ultrafast...optical digital and symbolic computation via optical phase conjugation," Y. Li, G. Eichmann , R. Dorsinville, Appl. Opt. 27, 2025 (1988). [3

Digital Holographic Interferometry and Speckle Correlation

NASA Astrophysics Data System (ADS)

Yamaguchi, Ichirou

2010-04-01

Relations and combinations between holographic interferometry and speckle correlation in contouring by phase-shifting digital holography are discussed. Three-dimensional distributions of correlations of the complex amplitudes and intensities before and after the laser wavelength shift are calculated in numerical simulations where a rough surface is modeled with random numbers. Fringe localization related to speckle displacement as well as speckle suppression in phase analysis are demonstrated for general surface shape and recording conditions.

Compact wavelength-selective optical switch based on digital optical phase conjugation.

PubMed

Li, Zhiyang; Claver, Havyarimana

2013-11-15

In this Letter, we show that digital optical phase conjugation might be utilized to construct a new kind of wavelength-selective switches. When incorporated with a multimode interferometer, these switches have wide bandwidth, high tolerance for fabrication error, and low polarization dependency. They might help to build large-scale multiwavelength nonblocking switching systems, or even to fabricate an optical cross-connecting or routing system on a chip.

"Digital Futures in Teacher Education": Exploring Open Approaches towards Digital Literacy

ERIC Educational Resources Information Center

Gruszczynska, Anna; Merchant, Guy; Pountney, Richard,

2013-01-01

This paper reports the findings of a project "Digital Futures in Teacher Education" (DeFT) undertaken as part of the third phase of the Joint Information Systems Committee (JISC) UK Open Educational Resources (OER) programme. It builds on previous work (Gruszczynska and Pountney, 2012, 2013) that has addressed attempts to embed OER…

Generating nonlinear FM chirp radar signals by multiple integrations

DOEpatents

Doerry, Armin W [Albuquerque, NM

2011-02-01

A phase component of a nonlinear frequency modulated (NLFM) chirp radar pulse can be produced by performing digital integration operations over a time interval defined by the pulse width. Each digital integration operation includes applying to a respectively corresponding input parameter value a respectively corresponding number of instances of digital integration.

Coherent Optical Communications: Historical Perspectives and Future Directions

NASA Astrophysics Data System (ADS)

Kikuchi, Kazuro

Coherent optical fiber communications were studied extensively in the 1980s mainly because high sensitivity of coherent receivers could elongate the unrepeated transmission distance; however, their research and development have been interrupted for nearly 20 years behind the rapid progress in high-capacity wavelength-division multiplexed (WDM) systems using erbium-doped fiber amplifiers (EDFAs). In 2005, the demonstration of digital carrier phase estimation in coherent receivers has stimulated a widespread interest in coherent optical communications again. This is due to the fact that the digital coherent receiver enables us to employ a variety of spectrally efficient modulation formats such as M-ary phase-shift keying (PSK) and quadrature amplitude modulation (QAM) without relying upon a rather complicated optical phase-locked loop. In addition, since the phase information is preserved after detection, we can realize electrical post-processing functions such as compensation for chromatic dispersion and polarization-mode dispersion in the digital domain. These advantages of the born-again coherent receiver have enormous potential for innovating existing optical communication systems. In this chapter, after reviewing the 20-year history of coherent optical communication systems, we describe the principle of operation of coherent detection, the concept of the digital coherent receiver, and its performance evaluation. Finally, challenges for the future are summarized.

Geometric phase coded metasurface: from polarization dependent directive electromagnetic wave scattering to diffusion-like scattering.

PubMed

Chen, Ke; Feng, Yijun; Yang, Zhongjie; Cui, Li; Zhao, Junming; Zhu, Bo; Jiang, Tian

2016-10-24

Ultrathin metasurface compromising various sub-wavelength meta-particles offers promising advantages in controlling electromagnetic wave by spatially manipulating the wavefront characteristics across the interface. The recently proposed digital coding metasurface could even simplify the design and optimization procedures due to the digitalization of the meta-particle geometry. However, current attempts to implement the digital metasurface still utilize several structural meta-particles to obtain certain electromagnetic responses, and requiring time-consuming optimization especially in multi-bits coding designs. In this regard, we present herein utilizing geometric phase based single structured meta-particle with various orientations to achieve either 1-bit or multi-bits digital metasurface. Particular electromagnetic wave scattering patterns dependent on the incident polarizations can be tailored by the encoded metasurfaces with regular sequences. On the contrast, polarization insensitive diffusion-like scattering can also been successfully achieved by digital metasurface encoded with randomly distributed coding sequences leading to substantial suppression of backward scattering in a broadband microwave frequency. The proposed digital metasurfaces provide simple designs and reveal new opportunities for controlling electromagnetic wave scattering with or without polarization dependence.

Geometric phase coded metasurface: from polarization dependent directive electromagnetic wave scattering to diffusion-like scattering

PubMed Central

Chen, Ke; Feng, Yijun; Yang, Zhongjie; Cui, Li; Zhao, Junming; Zhu, Bo; Jiang, Tian

2016-01-01

Ultrathin metasurface compromising various sub-wavelength meta-particles offers promising advantages in controlling electromagnetic wave by spatially manipulating the wavefront characteristics across the interface. The recently proposed digital coding metasurface could even simplify the design and optimization procedures due to the digitalization of the meta-particle geometry. However, current attempts to implement the digital metasurface still utilize several structural meta-particles to obtain certain electromagnetic responses, and requiring time-consuming optimization especially in multi-bits coding designs. In this regard, we present herein utilizing geometric phase based single structured meta-particle with various orientations to achieve either 1-bit or multi-bits digital metasurface. Particular electromagnetic wave scattering patterns dependent on the incident polarizations can be tailored by the encoded metasurfaces with regular sequences. On the contrast, polarization insensitive diffusion-like scattering can also been successfully achieved by digital metasurface encoded with randomly distributed coding sequences leading to substantial suppression of backward scattering in a broadband microwave frequency. The proposed digital metasurfaces provide simple designs and reveal new opportunities for controlling electromagnetic wave scattering with or without polarization dependence. PMID:27775064

Fiber-optic projected-fringe digital interferometry

NASA Technical Reports Server (NTRS)

Mercer, Carolyn R.; Beheim, Glenn

1990-01-01

A phase-stepped projected-fringe interferometer was developed which uses a closed-loop fiber-optic phase-control system to make very accurate surface profile measurements. The closed-loop phase-control system greatly reduces phase-stepping error, which is frequently the dominant source of error in digital interferometers. Two beams emitted from a fiber-optic coupler are combined to form an interference fringe pattern on a diffusely reflecting object. Reflections off of the fibers' output faces are used to create a phase-indicating signal for the closed-loop optical phase controller. The controller steps the phase difference between the two beams by pi/2 radians in order to determine the object's surface profile using a solid-state camera and a computer. The system combines the ease of alignment and automated data reduction of phase-stepping projected-fringe interferometry with the greatly improved phase-stepping accuracy of our closed-loop phase-controller. The system is demonstrated by measuring the profile of a plate containing several convex surfaces whose heights range from 15 to 25 micron high.

Digital Doppler measurement with spacecraft

NASA Technical Reports Server (NTRS)

Kinman, Peter W.; Hinedi, Sami M.; Labelle, Remi C.; Bevan, Roland P.; Del Castillo, Hector M.; Chong, Dwayne C.

1991-01-01

Digital and analog phase-locked loop (PLL) receivers were operated in parallel, each tracking the residual carrier from a spacecraft. The PLL tracked the downlink carrier and measured its instantaneous phase. This information, combined with a knowledge of the uplink carrier and the transponder ratio, permitted the computation of a Doppler observable. In this way, two separate Doppler measurements were obtained for one observation window. The two receivers agreed on the magnitude of the Doppler effect to within 1 mHz. There was less jitter on the data from the digital receiver. This was due to its smaller noise bandwidth. The demonstration and its results are described.

Digitally Enhanced Heterodyne Interferometry

NASA Technical Reports Server (NTRS)

Shaddock, Daniel; Ware, Brent; Lay, Oliver; Dubovitsky, Serge

2010-01-01

Spurious interference limits the performance of many interferometric measurements. Digitally enhanced interferometry (DEI) improves measurement sensitivity by augmenting conventional heterodyne interferometry with pseudo-random noise (PRN) code phase modulation. DEI effectively changes the measurement problem from one of hardware (optics, electronics), which may deteriorate over time, to one of software (modulation, digital signal processing), which does not. DEI isolates interferometric signals based on their delay. Interferometric signals are effectively time-tagged by phase-modulating the laser source with a PRN code. DEI improves measurement sensitivity by exploiting the autocorrelation properties of the PRN to isolate only the signal of interest and reject spurious interference. The properties of the PRN code determine the degree of isolation.

Multilevel recording of complex amplitude data pages in a holographic data storage system using digital holography.

PubMed

Nobukawa, Teruyoshi; Nomura, Takanori

2016-09-05

A holographic data storage system using digital holography is proposed to record and retrieve multilevel complex amplitude data pages. Digital holographic techniques are capable of modulating and detecting complex amplitude distribution using current electronic devices. These techniques allow the development of a simple, compact, and stable holographic storage system that mainly consists of a single phase-only spatial light modulator and an image sensor. As a proof-of-principle experiment, complex amplitude data pages with binary amplitude and four-level phase are recorded and retrieved. Experimental results show the feasibility of the proposed holographic data storage system.

Development of Shunt-Type Three-Phase Active Power Filter with Novel Adaptive Control for Wind Generators

PubMed Central

2015-01-01

This paper proposes a new adaptive filter for wind generators that combines instantaneous reactive power compensation technology and current prediction controller, and therefore this system is characterized by low harmonic distortion, high power factor, and small DC-link voltage variations during load disturbances. The performance of the system was first simulated using MATLAB/Simulink, and the possibility of an adaptive digital low-pass filter eliminating current harmonics was confirmed in steady and transient states. Subsequently, a digital signal processor was used to implement an active power filter. The experimental results indicate, that for the rated operation of 2 kVA, the system has a total harmonic distortion of current less than 5.0% and a power factor of 1.0 on the utility side. Thus, the transient performance of the adaptive filter is superior to the traditional digital low-pass filter and is more economical because of its short computation time compared with other types of adaptive filters. PMID:26451391

Development of Shunt-Type Three-Phase Active Power Filter with Novel Adaptive Control for Wind Generators.

PubMed

Chen, Ming-Hung

2015-01-01

This paper proposes a new adaptive filter for wind generators that combines instantaneous reactive power compensation technology and current prediction controller, and therefore this system is characterized by low harmonic distortion, high power factor, and small DC-link voltage variations during load disturbances. The performance of the system was first simulated using MATLAB/Simulink, and the possibility of an adaptive digital low-pass filter eliminating current harmonics was confirmed in steady and transient states. Subsequently, a digital signal processor was used to implement an active power filter. The experimental results indicate, that for the rated operation of 2 kVA, the system has a total harmonic distortion of current less than 5.0% and a power factor of 1.0 on the utility side. Thus, the transient performance of the adaptive filter is superior to the traditional digital low-pass filter and is more economical because of its short computation time compared with other types of adaptive filters.

Effects of analog and digital filtering on auditory middle latency responses in adults and young children.

PubMed

Suzuki, T; Hirabayashi, M; Kobayashi, K

1984-01-01

Effects of analog high pass (HP) filtering were compared with those of zero phase-shift digital filtering on the auditory middle latency responses (MLR) from nine adults and 16 young children with normal hearing. Analog HP filtering exerted several prominent effects on the MLR waveforms in both adults and young children, such as suppression of Po (ABR), enhancement of Nb, enhancement or emergence of Pb, and latency decrements for Pa and the later components. Analog HP filtering at 20 Hz produced more pronounced waveform distortions in the responses from young children than from adults. Much greater latency decrements for Pa and Nb were observed for young children than for adults in the analog HP-filtered responses at 20 Hz. A large positive peak (Pb) emerged at about 65 ms after the stimulus onset. From these results, the use of digital HP filtering at 20 Hz is strongly recommended for obtaining unbiased and stable MLR in young children.

Design and theoretical investigation of a digital x-ray detector with large area and high spatial resolution

NASA Astrophysics Data System (ADS)

Gui, Jianbao; Guo, Jinchuan; Yang, Qinlao; Liu, Xin; Niu, Hanben

2007-05-01

X-ray phase contrast imaging is a promising new technology today, but the requirements of a digital detector with large area, high spatial resolution and high sensitivity bring forward a large challenge to researchers. This paper is related to the design and theoretical investigation of an x-ray direct conversion digital detector based on mercuric iodide photoconductive layer with the latent charge image readout by photoinduced discharge (PID). Mercuric iodide has been verified having a good imaging performance (high sensitivity, low dark current, low voltage operation and good lag characteristics) compared with the other competitive materials (α-Se,PbI II,CdTe,CdZnTe) and can be easily deposited on large substrates in the manner of polycrystalline. By use of line scanning laser beam and parallel multi-electrode readout make the system have high spatial resolution and fast readout speed suitable for instant general radiography and even rapid sequence radiography.

Sildenafil increases digital skin blood flow during all phases of local cooling in primary Raynaud's phenomenon

PubMed Central

Roustit, Matthieu; Hellmann, Marcin; Cracowski, Claire; Blaise, Sophie; Cracowski, Jean-Luc

2012-01-01

Digital skin vasoconstriction on local cooling is exaggerated in primary Raynaud’s phenomenon (RP) compared to controls. A significant part of such vasoconstriction relies on the nitric oxide (NO) pathway inhibition. We tested the effect of PDE5 inhibitor sildenafil, which potentiates the effect of NO, on skin blood flow. We recruited 15 patients with primary RP, performing local cooling without sildenafil (day 1), after a single 50 mg oral dose (day 2), and 100 mg (day 3). Skin blood flow, skin temperature and arterial pressure were recorded, and data were expressed as cutaneous vascular conductance (CVC). Sildenafil at 100 mg, but not 50 mg, significantly lessened the cooling-induced decrease in CVC. It also increased resting CVC and skin temperature. These data suggest that 100 mg sildenafil improves digital skin blood flow to local cooling in primary RP. The benefit of sildenafil “as required” should be confirmed in a randomized controlled trial. PMID:22453196

Probing orientation and rotation of red blood cells in optical tweezers by digital holographic microscopy

NASA Astrophysics Data System (ADS)

Cardenas, Nelson; Yu, Lingfeng; Mohanty, Samarendra K.

2011-03-01

Interaction of red blood cells (RBC) with optical tweezers has been found to differ under varied physiological and pathological conditions as compared to its normal conditions. Earlier, we reported difference in rotation of trapped RBC in hypertonic conditions for detection of malaria infection. Disk-like RBC when trapped in optical tweezers get oriented in the vertical plane to maximize interaction with trapping beam. However, classical bright field, phase contrast or epifluorescence microscopy cannot confirm its orientation, thus leading to ambiguous conclusions such as folding of RBC during trapping by some researchers. Now, with use of digital holographic microscopy (DHM), we achieved high axial sensitivity that confirmed orientation of trapped red blood cell. Further, DHM enabled quantitative phase imaging of RBC under hypertonic condition. Dynamic changes of rotating RBC under optical tweezers at different trapping laser power were evaluated by the use of DHM. The deviation from linear dependence of rotation speed of RBC on laser power, was attributed towards deformation of RBC shape due to higher laser power (or speed).

Methods for using a biometric parameter in the identification of persons

DOEpatents

Hively, Lee M [Philadelphia, TN

2011-11-22

Brain waves are used as a biometric parameter to provide for authentication and identification of personnel. The brain waves are sampled using EEG equipment and are processed using phase-space distribution functions to compare digital signature data from enrollment of authorized individuals to data taken from a test subject to determine if the data from the test subject matches the signature data to a degree to support positive identification.

Measurement of in-plane displacements using the phase singularities generated by directional wavelet transforms of speckle pattern images.

PubMed

Vadnjal, Ana Laura; Etchepareborda, Pablo; Federico, Alejandro; Kaufmann, Guillermo H

2013-03-20

We present a method to determine micro and nano in-plane displacements based on the phase singularities generated by application of directional wavelet transforms to speckle pattern images. The spatial distribution of the obtained phase singularities by the wavelet transform configures a network, which is characterized by two quasi-orthogonal directions. The displacement value is determined by identifying the intersection points of the network before and after the displacement produced by the tested object. The performance of this method is evaluated using simulated speckle patterns and experimental data. The proposed approach is compared with the optical vortex metrology and digital image correlation methods in terms of performance and noise robustness, and the advantages and limitations associated to each method are also discussed.

MULTIPLE INPUT BINARY ADDER EMPLOYING MAGNETIC DRUM DIGITAL COMPUTING APPARATUS

DOEpatents

Cooke-Yarborough, E.H.

1960-12-01

A digital computing apparatus is described for adding a plurality of multi-digit binary numbers. The apparatus comprises a rotating magnetic drum, a recording head, first and second reading heads disposed adjacent to the first and second recording tracks, and a series of timing signals recorded on the first track. A series of N groups of digit-representing signals is delivered to the recording head at time intervals corresponding to the timing signals, each group consisting of digits of the same significance in the numbers, and the signal series is recorded on the second track of the drum in synchronism with the timing signals on the first track. The multistage registers are stepped cyclically through all positions, and each of the multistage registers is coupled to the control lead of a separate gate circuit to open the corresponding gate at only one selected position in each cycle. One of the gates has its input coupled to the bistable element to receive the sum digit, and the output lead of this gate is coupled to the recording device. The inputs of the other gates receive the digits to be added from the second reading head, and the outputs of these gates are coupled to the adding register. A phase-setting pulse source is connected to each of the multistage registers individually to step the multistage registers to different initial positions in the cycle, and the phase-setting pulse source is actuated each N time interval to shift a sum digit to the bistable element, where the multistage register coupled to bistable element is operated by the phase- setting pulse source to that position in its cycle N steps before opening the first gate, so that this gate opens in synchronism with each of the shifts to pass the sum digits to the recording head.

Digital multi-channel stabilization of four-mode phase-sensitive parametric multicasting.

PubMed

Liu, Lan; Tong, Zhi; Wiberg, Andreas O J; Kuo, Bill P P; Myslivets, Evgeny; Alic, Nikola; Radic, Stojan

2014-07-28

Stable four-mode phase-sensitive (4MPS) process was investigated as a means to enhance two-pump driven parametric multicasting conversion efficiency (CE) and signal to noise ratio (SNR). Instability of multi-beam, phase sensitive (PS) device that inherently behaves as an interferometer, with output subject to ambient induced fluctuations, was addressed theoretically and experimentally. A new stabilization technique that controls phases of three input waves of the 4MPS multicaster and maximizes CE was developed and described. Stabilization relies on digital phase-locked loop (DPLL) specifically was developed to control pump phases to guarantee stable 4MPS operation that is independent of environmental fluctuations. The technique also controls a single (signal) input phase to optimize the PS-induced improvement of the CE and SNR. The new, continuous-operation DPLL has allowed for fully stabilized PS parametric broadband multicasting, demonstrating CE improvement over 20 signal copies in excess of 10 dB.

A fast-locking PLL with all-digital locked-aid circuit

NASA Astrophysics Data System (ADS)

Kao, Shao-Ku; Hsieh, Fu-Jen

2013-02-01

In this article, a fast-locking phase-locked loop (PLL) with an all-digital locked-aid circuit is proposed and analysed. The proposed topology is based on two tuning loops: frequency and phase detections. A frequency detection loop is used to accelerate frequency locking time, and a phase detection loop is used to adjust fine phase errors between the reference and feedback clocks. The proposed PLL circuit is designed based on the 0.35 µm CMOS process with a 3.3 V supply voltage. Experimental results show that the locking time of the proposed PLL achieves a 87.5% reduction from that of a PLL without the locked-aid circuit.

Considerations of digital phase modulation for narrowband satellite mobile communication

NASA Technical Reports Server (NTRS)

Grythe, Knut

1990-01-01

The Inmarsat-M system for mobile satellite communication is specified as a frequency division multiple access (FDMA) system, applying Offset Quadrature Phase Shift Keying (QPSK) for transmitting 8 kbit/sec in 10 kHz user channel bandwidth. We consider Digital Phase Modulation (DPM) as an alternative modulation format for INMARSAT-M. DPM is similar to Continuous Phase Modulation (CPM) except that DPM has a finite memory in the premodular filter with a continuous varying modulation index. It is shown that DPM with 64 states in the VA obtains a lower bit error rate (BER). Results for a 5 kHz system, with the same 8 kbit/sec transmitted bitstream, is also presented.

Usage Analysis for the Identification of Research Trends in Digital Libraries; Keepers of the Crumbling Culture: What Digital Preservation Can Learn from Library History; Patterns of Journal Use by Scientists through Three Evolutionary Phases; Developing a Content Management System-Based Web Site; Exploring Charging Models for Digital Cultural Heritage in Europe; Visions: The Academic Library in 2012.

ERIC Educational Resources Information Center

Bollen, Johan; Vemulapalli, Soma Sekara; Xu, Weining; Luce, Rick; Marcum, Deanna; Friedlander, Amy; Tenopir, Carol; Grayson, Matt; Zhang, Yan; Ebuen, Mercy; King, Donald W.; Boyce, Peter; Rogers, Clare; Kirriemuir, John; Tanner, Simon; Deegan, Marilyn; Marcum, James W.

2003-01-01

Includes six articles that discuss use analysis and research trends in digital libraries; library history and digital preservation; journal use by scientists; a content management system-based Web site for higher education in the United Kingdom; cost studies for transitioning to digitized collections in European cultural institutions; and the…

360-degrees profilometry using strip-light projection coupled to Fourier phase-demodulation.

PubMed

Servin, Manuel; Padilla, Moises; Garnica, Guillermo

2016-01-11

360 degrees (360°) digitalization of three dimensional (3D) solids using a projected light-strip is a well-established technique in academic and commercial profilometers. These profilometers project a light-strip over the digitizing solid while the solid is rotated a full revolution or 360-degrees. Then, a computer program typically extracts the centroid of this light-strip, and by triangulation one obtains the shape of the solid. Here instead of using intensity-based light-strip centroid estimation, we propose to use Fourier phase-demodulation for 360° solid digitalization. The advantage of Fourier demodulation over strip-centroid estimation is that the accuracy of phase-demodulation linearly-increases with the fringe density, while in strip-light the centroid-estimation errors are independent. Here we proposed first to construct a carrier-frequency fringe-pattern by closely adding the individual light-strip images recorded while the solid is being rotated. Next, this high-density fringe-pattern is phase-demodulated using the standard Fourier technique. To test the feasibility of this Fourier demodulation approach, we have digitized two solids with increasing topographic complexity: a Rubik's cube and a plastic model of a human-skull. According to our results, phase demodulation based on the Fourier technique is less noisy than triangulation based on centroid light-strip estimation. Moreover, Fourier demodulation also provides the amplitude of the analytic signal which is a valuable information for the visualization of surface details.

Performance improvement of coherent free-space optical communication with quadrature phase-shift keying modulation using digital phase estimation.

PubMed

Li, Xueliang; Geng, Tianwen; Ma, Shuang; Li, Yatian; Gao, Shijie; Wu, Zhiyong

2017-06-01

The performance of coherent free-space optical (CFSO) communication with phase modulation is limited by both phase fluctuations and intensity scintillations induced by atmospheric turbulence. To improve the system performance, one effective way is to use digital phase estimation. In this paper, a CFSO communication system with quadrature phase-shift keying modulation is studied. With consideration of the effects of log-normal amplitude fluctuations and Gauss phase fluctuations, a two-stage Mth power carrier phase estimation (CPE) scheme is proposed. The simulation results show that the phase noise can be suppressed greatly by this scheme, and the system symbol error rate performance with the two-stage Mth power CPE can be three orders lower than that of the single-stage Mth power CPE. Therefore, the two-stage CPE we proposed can contribute to the performance improvements of the CFSO communication system and has determinate guidance sense to its actual application.

Hierarchical CAD Tools for Radiation Hardened Mixed Signal Electronic Circuits

DTIC Science & Technology

2005-01-28

11 Figure 3: Schematic of Analog and Digital Components 12 Figure 4: Dose Rate Syntax 14 Figure 5: Single Event Effects (SEE) Syntax 15 Figure 6...Harmony-AMS simulation of a Digital Phase Locked Loop 19 Figure 10: SEE results from DPLL Simulation 20 Figure 11: Published results used for validation...analog and digital circuitry. Combining the analog and digital elements onto a single chip has several advantages, but also creates unique challenges

Deformation-induced speckle-pattern evolution and feasibility of correlational speckle tracking in optical coherence elastography.

PubMed

Zaitsev, Vladimir Y; Matveyev, Alexandr L; Matveev, Lev A; Gelikonov, Grigory V; Gelikonov, Valentin M; Vitkin, Alex

2015-07-01

Feasibility of speckle tracking in optical coherence tomography (OCT) based on digital image correlation (DIC) is discussed in the context of elastography problems. Specifics of applying DIC methods to OCT, compared to processing of photographic images in mechanical engineering applications, are emphasized and main complications are pointed out. Analytical arguments are augmented by accurate numerical simulations of OCT speckle patterns. In contrast to DIC processing for displacement and strain estimation in photographic images, the accuracy of correlational speckle tracking in deformed OCT images is strongly affected by the coherent nature of speckles, for which strain-induced complications of speckle “blinking” and “boiling” are typical. The tracking accuracy is further compromised by the usually more pronounced pixelated structure of OCT scans compared with digital photographic images in classical DIC applications. Processing of complex-valued OCT data (comprising both amplitude and phase) compared to intensity-only scans mitigates these deleterious effects to some degree. Criteria of the attainable speckle tracking accuracy and its dependence on the key OCT system parameters are established.

Digital Mirror Device Application in Reduction of Wave-front Phase Errors

PubMed Central

Zhang, Yaping; Liu, Yan; Wang, Shuxue

2009-01-01

In order to correct the image distortion created by the mixing/shear layer, creative and effectual correction methods are necessary. First, a method combining adaptive optics (AO) correction with a digital micro-mirror device (DMD) is presented. Second, performance of an AO system using the Phase Diverse Speckle (PDS) principle is characterized in detail. Through combining the DMD method with PDS, a significant reduction in wavefront phase error is achieved in simulations and experiments. This kind of complex correction principle can be used to recovery the degraded images caused by unforeseen error sources. PMID:22574016

Is phase measurement necessary for incoherent holographic 3D imaging?

NASA Astrophysics Data System (ADS)

Rosen, Joseph; Vijayakumar, A.; Rai, Mani Ratnam; Mukherjee, Saswata

2018-02-01

Incoherent digital holography can be used for several applications, among which are high resolution fluorescence microscopy and imaging through a scattering medium. Historically, an incoherent digital hologram has been usually recorded by self-interference systems in which both interfering beams are originated from the same observed object. The self-interference system enables to read the phase distribution of the wavefronts propagating from an object and consequently to decode the 3D location of the object points. In this presentation, we survey several cases in which 3D holographic imaging can be done without the phase information and without two-wave interference.

Concept design of an 80-dual polarization element cryogenic phased array camera for the Arecibo Radio Telescope

NASA Astrophysics Data System (ADS)

Cortes-Medellin, German; Parshley, Stephen; Campbell, Donald B.; Warnick, Karl F.; Jeffs, Brian D.; Ganesh, Rajagopalan

2016-08-01

This paper presents the current concept design for ALPACA (Advanced L-Band Phased Array Camera for Arecibo) an L-Band cryo-phased array instrument proposed for the 305 m radio telescope of Arecibo. It includes the cryogenically cooled front-end with 160 low noise amplifiers, a RF-over-fiber signal transport and a digital beam former with an instantaneous bandwidth of 312.5 MHz per channel. The camera will digitally form 40 simultaneous beams inside the available field of view of the Arecibo telescope optics, with an expected system temperature goal of 30 K.

The elimination of zero-order diffraction of 10.6 μm infrared digital holography

NASA Astrophysics Data System (ADS)

Liu, Ning; Yang, Chao

2017-05-01

A new method of eliminating the zero-order diffraction in infrared digital holography has been raised in this paper. Usually in the reconstruction of digital holography, the spatial frequency of the infrared thermal imager, such as microbolometer, cannot be compared to the common visible CCD or CMOS devices. The infrared imager suffers the problems of large pixel size and low spatial resolution, which cause the zero-order diffraction a severe influence of the reconstruction process of digital holograms. The zero-order diffraction has very large energy and occupies the central region in the spectrum domain. In this paper, we design a new filtering strategy to overcome this problem. This filtering strategy contains two kinds of filtering process which are the Gaussian low-frequency filter and the high-pass phase averaging filter. With the correct set of the calculating parameters, these filtering strategies can work effectively on the holograms and fully eliminate the zero-order diffraction, as well as the two crossover bars shown in the spectrum domain. Detailed explanation and discussion about the new method have been proposed in this paper, and the experiment results are also demonstrated to prove the performance of this method.

Quality of reconstruction of compressed off-axis digital holograms by frequency filtering and wavelets.

PubMed

Cheremkhin, Pavel A; Kurbatova, Ekaterina A

2018-01-01

Compression of digital holograms can significantly help with the storage of objects and data in 2D and 3D form, its transmission, and its reconstruction. Compression of standard images by methods based on wavelets allows high compression ratios (up to 20-50 times) with minimum losses of quality. In the case of digital holograms, application of wavelets directly does not allow high values of compression to be obtained. However, additional preprocessing and postprocessing can afford significant compression of holograms and the acceptable quality of reconstructed images. In this paper application of wavelet transforms for compression of off-axis digital holograms are considered. The combined technique based on zero- and twin-order elimination, wavelet compression of the amplitude and phase components of the obtained Fourier spectrum, and further additional compression of wavelet coefficients by thresholding and quantization is considered. Numerical experiments on reconstruction of images from the compressed holograms are performed. The comparative analysis of applicability of various wavelets and methods of additional compression of wavelet coefficients is performed. Optimum parameters of compression of holograms by the methods can be estimated. Sizes of holographic information were decreased up to 190 times.

Measurement of elastic and thermal properties of composite materials using digital speckle pattern interferometry

NASA Astrophysics Data System (ADS)

Kumar, Manoj; Khan, Gufran S.; Shakher, Chandra

2015-08-01

In the present work, application of digital speckle pattern interferometry (DSPI) was applied for the measurement of mechanical/elastic and thermal properties of fibre reinforced plastics (FRP). Digital speckle pattern interferometric technique was used to characterize the material constants (Poisson's ratio and Young's modulus) of the composite material. Poisson ratio based on plate bending and Young's modulus based on plate vibration of material are measured by using DSPI. In addition to this, the coefficient of thermal expansion of composite material is also measured. To study the thermal strain analysis, a single DSPI fringe pattern is used to extract the phase information by using Riesz transform and the monogenic signal. The phase extraction from a single DSPI fringe pattern by using Riesz transform does not require a phase-shifting system or spatial carrier. The elastic and thermal parameters obtained from DSPI are in close agreement with the theoretical predictions available in literature.

Assessing stability and performance of a digitally enabled supply chain: Retrospective of a pilot in Uttar Pradesh, India.

PubMed

Gilbert, Sarah Skye; Thakare, Neeraj; Ramanujapuram, Arun; Akkihal, Anup

2017-04-19

Immunization supply chains in low resource settings do not always reach children with necessary vaccines. Digital information systems can enable real time visibility of inventory and improve vaccine availability. In 2014, a digital, mobile/web-based information system was implemented in two districts of Uttar Pradesh, India. This retrospective investigates improvements and stabilization of supply chain performance following introduction of the digital information system. All data were collected via the digital information system between March 2014 and September 2015. Data included metadata and transaction logs providing information about users, facilities, and vaccines. Metrics evaluated include adoption (system access, timeliness and completeness), data quality (error rates), and performance (stock availability on immunization session days, replenishment response duration, rate of zero stock events). Stability was defined as the phase in which quality and performance metrics achieved equilibrium rates with minimal volatility. The analysis compared performance across different facilities and vaccines. Adoption appeared sufficiently high from the onset to commence stability measures of data quality and supply chain performance. Data quality stabilized from month 3 onwards, and supply chain performance stabilized from month 13 onwards. For data quality, error rates reduced by two thirds post stabilization. Although vaccine availability remained high throughout the pilot, the three lowest-performing facilities improved from 91.05% pre-stability to 98.70% post-stability (p<0.01; t-test). Average replenishment duration (as a corrective response to stock-out events) decreased 52.3% from 4.93days to 2.35days (p<0.01; t-test). Diphtheria-tetanus-pertussis vaccine was significantly less likely to be stocked out than any other material. The results suggest that given sufficient adoption, stability is sequentially achieved, beginning with data quality, and then performance. Identifying when a pilot stabilizes can enable more predictable, reliable cost estimates, and outcome forecasts in the scale-up phase. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Inventory and mapping of flood inundation using interactive digital image analysis techniques

USGS Publications Warehouse

Rohde, Wayne G.; Nelson, Charles A.; Taranik, J.V.

1979-01-01

LANDSAT digital data and color infra-red photographs were used in a multiphase sampling scheme to estimate the area of agricultural land affected by a flood. The LANDSAT data were classified with a maximum likelihood algorithm. Stratification of the LANDSAT data, prior to classification, greatly reduced misclassification errors. The classification results were used to prepare a map overlay showing the areal extent of flooding. These data also provided statistics required to estimate sample size in a two phase sampling scheme, and provided quick, accurate estimates of areas flooded for the first phase. The measurements made in the second phase, based on ground data and photo-interpretation, were used with two phase sampling statistics to estimate the area of agricultural land affected by flooding These results show that LANDSAT digital data can be used to prepare map overlays showing the extent of flooding on agricultural land and, with two phase sampling procedures, can provide acreage estimates with sampling errors of about 5 percent. This procedure provides a technique for rapidly assessing the areal extent of flood conditions on agricultural land and would provide a basis for designing a sampling framework to estimate the impact of flooding on crop production.

Controlling Energy Radiations of Electromagnetic Waves via Frequency Coding Metamaterials.

PubMed

Wu, Haotian; Liu, Shuo; Wan, Xiang; Zhang, Lei; Wang, Dan; Li, Lianlin; Cui, Tie Jun

2017-09-01

Metamaterials are artificial structures composed of subwavelength unit cells to control electromagnetic (EM) waves. The spatial coding representation of metamaterial has the ability to describe the material in a digital way. The spatial coding metamaterials are typically constructed by unit cells that have similar shapes with fixed functionality. Here, the concept of frequency coding metamaterial is proposed, which achieves different controls of EM energy radiations with a fixed spatial coding pattern when the frequency changes. In this case, not only different phase responses of the unit cells are considered, but also different phase sensitivities are also required. Due to different frequency sensitivities of unit cells, two units with the same phase response at the initial frequency may have different phase responses at higher frequency. To describe the frequency coding property of unit cell, digitalized frequency sensitivity is proposed, in which the units are encoded with digits "0" and "1" to represent the low and high phase sensitivities, respectively. By this merit, two degrees of freedom, spatial coding and frequency coding, are obtained to control the EM energy radiations by a new class of frequency-spatial coding metamaterials. The above concepts and physical phenomena are confirmed by numerical simulations and experiments.

Estimation of vibration frequency of loudspeaker diaphragm by parallel phase-shifting digital holography

NASA Astrophysics Data System (ADS)

Kakue, T.; Endo, Y.; Shimobaba, T.; Ito, T.

2014-11-01

We report frequency estimation of loudspeaker diaphragm vibrating at high speed by parallel phase-shifting digital holography which is a technique of single-shot phase-shifting interferometry. This technique records multiple phaseshifted holograms required for phase-shifting interferometry by using space-division multiplexing. We constructed a parallel phase-shifting digital holography system consisting of a high-speed polarization-imaging camera. This camera has a micro-polarizer array which selects four linear polarization axes for 2 × 2 pixels. We set a loudspeaker as an object, and recorded vibration of diaphragm of the loudspeaker by the constructed system. By the constructed system, we demonstrated observation of vibration displacement of loudspeaker diaphragm. In this paper, we aim to estimate vibration frequency of the loudspeaker diaphragm by applying the experimental results to frequency analysis. Holograms consisting of 128 × 128 pixels were recorded at a frame rate of 262,500 frames per second by the camera. A sinusoidal wave was input to the loudspeaker via a phone connector. We observed displacement of the loudspeaker diaphragm vibrating by the system. We also succeeded in estimating vibration frequency of the loudspeaker diaphragm by applying frequency analysis to the experimental results.

Backside imaging of a microcontroller with common-path digital holography

NASA Astrophysics Data System (ADS)

Finkeldey, Markus; Göring, Lena; Schellenberg, Falk; Gerhardt, Nils C.; Hofmann, Martin

2017-03-01

The investigation of integrated circuits (ICs), such as microcontrollers (MCUs) and system on a chip (SoCs) devices is a topic with growing interests. The need for fast and non-destructive imaging methods is given by the increasing importance of hardware Trojans, reverse engineering and further security related analysis of integrated cryptographic devices. In the field of side-channel attacks, for instance, the precise spot for laser fault attacks is important and could be determined by using modern high resolution microscopy methods. Digital holographic microscopy (DHM) is a promising technique to achieve high resolution phase images of surface structures. These phase images provide information about the change of the refractive index in the media and the topography. For enabling a high phase stability, we use the common-path geometry to create the interference pattern. The interference pattern, or hologram, is captured with a water cooled sCMOS camera. This provides a fast readout while maintaining a low level of noise. A challenge for these types of holograms is the interference of the reflected waves from the different interfaces inside the media. To distinguish between the phase signals from the buried layer and the surface reflection we use specific numeric filters. For demonstrating the performance of our setup we show results with devices under test (DUT), using a 1064 nm laser diode as light source. The DUTs are modern microcontrollers thinned to different levels of thickness of the Si-substrate. The effect of the numeric filter compared to unfiltered images is analyzed.

Open-loop digital frequency multiplier

NASA Technical Reports Server (NTRS)

Moore, R. C.

1977-01-01

Monostable multivibrator is implemented by using digital integrated circuits where multiplier constant is too large for conventional phase-locked-loop integrated circuit. A 400 Hz clock is generated by divide-by-N counter from 1 Hz timing reference.

Comparison of Autograft and Allograft with Surface Modification for Flexor Tendon Reconstruction: A Canine in Vivo Model.

PubMed

Wei, Zhuang; Reisdorf, Ramona L; Thoreson, Andrew R; Jay, Gregory D; Moran, Steven L; An, Kai-Nan; Amadio, Peter C; Zhao, Chunfeng

2018-04-04

Flexor tendon injury is common, and tendon reconstruction is indicated clinically if the primary repair fails or cannot be performed immediately after tendon injury. The purpose of the current study was to compare clinically standard extrasynovial autologous graft (EAG) tendon and intrasynovial allogeneic graft (IAG) that had both undergone biolubricant surface modification in a canine in vivo model. Twenty-four flexor digitorum profundus (FDP) tendons from the second and fifth digits of 12 dogs were used for this study. In the first phase, a model of failed FDP tendon repair was created. After 6 weeks, the ruptured FDP tendons with a scarred digit were reconstructed with the use of either EAG or IAG tendons treated with carbodiimide-derivatized hyaluronic acid and lubricin. At 12 weeks after tendon reconstruction, the digits were harvested for functional, biomechanical, and histologic evaluations. The tendon failure model was a clinically relevant and reproducible model for tendon reconstruction. The IAG group demonstrated improved digit function with decreased adhesion formation, lower digit work of flexion, and improved graft gliding ability compared with the EAG group. However, the IAG group had decreased healing at the distal tendon-bone junction. Our histologic findings verified the biomechanical evaluations and, further, showed that cellular repopulation of allograft at 12 weeks after reconstruction is still challenging. FDP tendon reconstruction using IAG with surface modification has some beneficial effects for reducing adhesions but demonstrated inferior healing at the distal tendon-bone junction compared with EAG. These mixed results indicate that vitalization and turnover acceleration are crucial to reducing failure of reconstruction with allograft. Flexor tendon reconstruction is a common surgical procedure. However, postoperative adhesion formation may lead to unsatisfactory clinical outcomes. In this study, we developed a potential flexor tendon allograft using chemical and tissue-engineering approaches. This technology could improve function following tendon reconstruction.

High-speed high-accuracy three-dimensional shape measurement using digital binary defocusing method versus sinusoidal method

NASA Astrophysics Data System (ADS)

Hyun, Jae-Sang; Li, Beiwen; Zhang, Song

2017-07-01

This paper presents our research findings on high-speed high-accuracy three-dimensional shape measurement using digital light processing (DLP) technologies. In particular, we compare two different sinusoidal fringe generation techniques using the DLP projection devices: direct projection of computer-generated 8-bit sinusoidal patterns (a.k.a., the sinusoidal method), and the creation of sinusoidal patterns by defocusing binary patterns (a.k.a., the binary defocusing method). This paper mainly examines their performance on high-accuracy measurement applications under precisely controlled settings. Two different projection systems were tested in this study: a commercially available inexpensive projector and the DLP development kit. Experimental results demonstrated that the binary defocusing method always outperforms the sinusoidal method if a sufficient number of phase-shifted fringe patterns can be used.

High-speed 3D imaging using digital binary defocusing method vs sinusoidal method

NASA Astrophysics Data System (ADS)

Zhang, Song; Hyun, Jae-Sang; Li, Beiwen

2017-02-01

This paper presents our research findings on high-speed 3D imaging using digital light processing (DLP) technologies. In particular, we compare two different sinusoidal fringe generation techniques using the DLP projection devices: direct projection of 8-bit computer generated sinusoidal patterns (a.k.a, the sinusoidal method), and the creation of sinusoidal patterns by defocusing binary patterns (a.k.a., the binary defocusing method). This paper mainly examines their performance on high-accuracy measurement applications under precisely controlled settings. Two different projection systems were tested in this study: the commercially available inexpensive projector, and the DLP development kit. Experimental results demonstrated that the binary defocusing method always outperforms the sinusoidal method if a sufficient number of phase-shifted fringe patterns can be used.

A Comparison of Strategies for Retinopathy of Prematurity Detection

PubMed Central

Prosser, Lisa A.; Wade, Kelly C.; Repka, Michael X.; Ying, Gui-shuang; Baumritter, Agnieshka; Quinn, Graham E.

2016-01-01

BACKGROUND AND OBJECTIVES: Delayed detection of type 1 retinopathy of prematurity (ROP) can lead to permanent visual impairment. Providing ROP examinations is challenging because of the limited ophthalmology workforce. This study compares digital imaging–based ROP detection strategies versus serial ROP examinations. METHODS: We conducted an individual-level microsimulation studyof a hypothetical cohort of 650 infants with gestational age from 23 to 30 weeks. Infants were evaluated by using strategies based on indirect ophthalmoscopy or digital imaging beginning at 32 weeks’ postmenstrual age (PMA) and continuing to discharge, transfer, or 40 weeks’ PMA. ROP status and the accuracy of digital imaging were based on the e-ROP (Telemedicine Approaches to Evaluating Acute-Phase ROP) study, which enrolled high-risk infants. RESULTS: Within the hypothetical NICU, the strategy of ROP examinations identified an average of 45.8 cases of type 1 ROP by discharge, transfer, or 40 weeks’ PMA, and another 1.9 cases were included in the group of infants recommended to have later follow-up. Digital imaging with an ROP examination at discharge identified all 47.7 cases of type 1 ROP. On average, the ROP examination–only strategy required 1745.7 ROP examinations, whereas digital imaging with a discharge examination required 1065.5 ROP examinations and 1786.2 digital imaging sessions. CONCLUSIONS: Although digital imaging decreased the number of ROP examinations per infant, there was an increase in the total number of interventions (ie, ROP examinations and imaging sessions). Providing an ROP examination at the time of NICU discharge can significantly reduce the number of infants who require follow-up. PMID:26672022

Demosaiced pixel super-resolution in digital holography for multiplexed computational color imaging on-a-chip (Conference Presentation)

NASA Astrophysics Data System (ADS)

Wu, Yichen; Zhang, Yibo; Luo, Wei; Ozcan, Aydogan

2017-03-01

Digital holographic on-chip microscopy achieves large space-bandwidth-products (e.g., >1 billion) by making use of pixel super-resolution techniques. To synthesize a digital holographic color image, one can take three sets of holograms representing the red (R), green (G) and blue (B) parts of the spectrum and digitally combine them to synthesize a color image. The data acquisition efficiency of this sequential illumination process can be improved by 3-fold using wavelength-multiplexed R, G and B illumination that simultaneously illuminates the sample, and using a Bayer color image sensor with known or calibrated transmission spectra to digitally demultiplex these three wavelength channels. This demultiplexing step is conventionally used with interpolation-based Bayer demosaicing methods. However, because the pixels of different color channels on a Bayer image sensor chip are not at the same physical location, conventional interpolation-based demosaicing process generates strong color artifacts, especially at rapidly oscillating hologram fringes, which become even more pronounced through digital wave propagation and phase retrieval processes. Here, we demonstrate that by merging the pixel super-resolution framework into the demultiplexing process, such color artifacts can be greatly suppressed. This novel technique, termed demosaiced pixel super-resolution (D-PSR) for digital holographic imaging, achieves very similar color imaging performance compared to conventional sequential R,G,B illumination, with 3-fold improvement in image acquisition time and data-efficiency. We successfully demonstrated the color imaging performance of this approach by imaging stained Pap smears. The D-PSR technique is broadly applicable to high-throughput, high-resolution digital holographic color microscopy techniques that can be used in resource-limited-settings and point-of-care offices.

Effect of various features on the life cycle cost of the timing/synchronization subsystem of the DCS digital communications network

NASA Technical Reports Server (NTRS)

Kimsey, D. B.

1978-01-01

The effect on the life cycle cost of the timing subsystem was examined, when these optional features were included in various combinations. The features included mutual control, directed control, double-ended reference links, independence of clock error measurement and correction, phase reference combining, self-organization, smoothing for link and nodal dropouts, unequal reference weightings, and a master in a mutual control network. An overall design of a microprocessor-based timing subsystem was formulated. The microprocessor (8080) implements the digital filter portion of a digital phase locked loop, as well as other control functions such as organization of the network through communication with processors at neighboring nodes.

Linear programming phase unwrapping for dual-wavelength digital holography.

PubMed

Wang, Zhaomin; Jiao, Jiannan; Qu, Weijuan; Yang, Fang; Li, Hongru; Tian, Ailing; Asundi, Anand

2017-01-20

A linear programming phase unwrapping method in dual-wavelength digital holography is proposed and verified experimentally. The proposed method uses the square of height difference as a convergence standard and theoretically gives the boundary condition in a searching process. A simulation was performed by unwrapping step structures at different levels of Gaussian noise. As a result, our method is capable of recovering the discontinuities accurately. It is robust and straightforward. In the experiment, a microelectromechanical systems sample and a cylindrical lens were measured separately. The testing results were in good agreement with true values. Moreover, the proposed method is applicable not only in digital holography but also in other dual-wavelength interferometric techniques.

Tanlock loop noise reduction using an optimised phase detector

NASA Astrophysics Data System (ADS)

Al-kharji Al-Ali, Omar; Anani, Nader; Al-Qutayri, Mahmoud; Al-Araji, Saleh

2013-06-01

This article proposes a time-delay digital tanlock loop (TDTL), which uses a new phase detector (PD) design that is optimised for noise reduction making it amenable for applications that require wide lock range without sacrificing the level of noise immunity. The proposed system uses an improved phase detector design which uses two phase detectors; one PD is used to optimise the noise immunity whilst the other is used to control the acquisition time of the TDTL system. Using the modified phase detector it is possible to reduce the second- and higher-order harmonics by at least 50% compared with the conventional TDTL system. The proposed system was simulated and tested using MATLAB/Simulink using frequency step inputs and inputs corrupted with varying levels of harmonic distortion. A hardware prototype of the system was implemented using a field programmable gate array (FPGA). The practical and simulation results indicate considerable improvement in the noise performance of the proposed system over the conventional TDTL architecture.

[Absorption spectrum of Quasi-continuous laser modulation demodulation method].

PubMed

Shao, Xin; Liu, Fu-Gui; Du, Zhen-Hui; Wang, Wei

2014-05-01

A software phase-locked amplifier demodulation method is proposed in order to demodulate the second harmonic (2f) signal of quasi-continuous laser wavelength modulation spectroscopy (WMS) properly, based on the analysis of its signal characteristics. By judging the effectiveness of the measurement data, filter, phase-sensitive detection, digital filtering and other processing, the method can achieve the sensitive detection of quasi-continuous signal The method was verified by using carbon dioxide detection experiments. The WMS-2f signal obtained by the software phase-locked amplifier and the high-performance phase-locked amplifier (SR844) were compared simultaneously. The results show that the Allan variance of WMS-2f signal demodulated by the software phase-locked amplifier is one order of magnitude smaller than that demodulated by SR844, corresponding two order of magnitude lower of detection limit. And it is able to solve the unlocked problem caused by the small duty cycle of quasi-continuous modulation signal, with a small signal waveform distortion.

Simultaneous estimation of multiple phases in digital holographic interferometry using state space analysis

NASA Astrophysics Data System (ADS)

Kulkarni, Rishikesh; Rastogi, Pramod

2018-05-01

A new approach is proposed for the multiple phase estimation from a multicomponent exponential phase signal recorded in multi-beam digital holographic interferometry. It is capable of providing multidimensional measurements in a simultaneous manner from a single recording of the exponential phase signal encoding multiple phases. Each phase within a small window around each pixel is appproximated with a first order polynomial function of spatial coordinates. The problem of accurate estimation of polynomial coefficients, and in turn the unwrapped phases, is formulated as a state space analysis wherein the coefficients and signal amplitudes are set as the elements of a state vector. The state estimation is performed using the extended Kalman filter. An amplitude discrimination criterion is utilized in order to unambiguously estimate the coefficients associated with the individual signal components. The performance of proposed method is stable over a wide range of the ratio of signal amplitudes. The pixelwise phase estimation approach of the proposed method allows it to handle the fringe patterns that may contain invalid regions.

PLZT block data composers operated in differential phase mode. [lanthanum-modified lead zirconate titanate ceramic device for digital holographic memory

NASA Technical Reports Server (NTRS)

Drake, M. D.; Klingler, D. E.

1973-01-01

The use of PLZT ceramics with the 7/65/35 composition in block data composer (BDC) input devices for holographic memory systems has previously been described for operation in the strain biased, scattering, and edge effect modes. A new and promising mode of BDC operation is the differential phase mode in which each element of a matrix array BDC acts as a phase modulator. The phase modulation results from a phase difference in the optical path length between the electrically poled and depoled states of the PLZT. It is shown that a PLZT BDC can be used as a matrix-type phase modulator to record and process digital data by the differential phase mode in a holographic recording/processing system with readout contrast ratios of between 10:1 and 15:1. The differential phase mode has the advantages that strain bias is not required and that the thickness and strain variations in the PLZT are cancelled out.

Real-Time Phase Correction Based on FPGA in the Beam Position and Phase Measurement System

NASA Astrophysics Data System (ADS)

Gao, Xingshun; Zhao, Lei; Liu, Jinxin; Jiang, Zouyi; Hu, Xiaofang; Liu, Shubin; An, Qi

2016-12-01

A fully digital beam position and phase measurement (BPPM) system was designed for the linear accelerator (LINAC) in Accelerator Driven Sub-critical System (ADS) in China. Phase information is obtained from the summed signals from four pick-ups of the Beam Position Monitor (BPM). Considering that the delay variations of different analog circuit channels would introduce phase measurement errors, we propose a new method to tune the digital waveforms of four channels before summation and achieve real-time error correction. The process is based on the vector rotation method and implemented within one single Field Programmable Gate Array (FPGA) device. Tests were conducted to evaluate this correction method and the results indicate that a phase correction precision better than ± 0.3° over the dynamic range from -60 dBm to 0 dBm is achieved.

Opposition effect of the Moon from LROC WAC data

NASA Astrophysics Data System (ADS)

Velikodsky, Yu. I.; Korokhin, V. V.; Shkuratov, Yu. G.; Kaydash, V. G.; Videen, Gorden

2016-09-01

LROC WAC images acquired in 5 bands of the visible spectral range were used to study the opposition effect for two mare and two highland regions near the lunar equator. Opposition phase curves were extracted from the images containing the opposition by separating the phase-curve effect from the albedo pattern by comparing WAC images at different phase angles (from 0° to 30°). Akimov's photometric function and the NASA Digital Terrain Model GLD100 were used in the processing. It was found that phase-curve slopes at small phase angles directly correlate with albedo, while at larger phase angles, they are anti-correlated. We suggest a parameter to characterize the coherent-backscattering component of the lunar opposition surge, which is defined as the maximum phase angle for which the opposition-surge slope increases with growing albedo. The width of the coherent-backscattering opposition effect varies from approximately 1.2° for highlands in red light to 3.9° for maria in blue light. The parameter depends on albedo, which is in agreement with the coherent-backscattering theory. The maximum amplitude of the coherent opposition effect is estimated to be near 8%. Maps of albedo and phase-curve slope at phase angles larger than those, at which the coherent-backscattering occurs, were built for the areas under study. Absolute calibration of WAC images was compared with Earth-based observations: the WAC-determined albedo is very close to the mean lunar albedo calculated using available Earth-based observations.

A semi-automated method of monitoring dam passage of American Eels Anguilla rostrata

USGS Publications Warehouse

Welsh, Stuart A.; Aldinger, Joni L.

2014-01-01

Fish passage facilities at dams have become an important focus of fishery management in riverine systems. Given the personnel and travel costs associated with physical monitoring programs, automated or semi-automated systems are an attractive alternative for monitoring fish passage facilities. We designed and tested a semi-automated system for eel ladder monitoring at Millville Dam on the lower Shenandoah River, West Virginia. A motion-activated eel ladder camera (ELC) photographed each yellow-phase American Eel Anguilla rostrata that passed through the ladder. Digital images (with date and time stamps) of American Eels allowed for total daily counts and measurements of eel TL using photogrammetric methods with digital imaging software. We compared physical counts of American Eels with camera-based counts; TLs obtained with a measuring board were compared with TLs derived from photogrammetric methods. Data from the ELC were consistent with data obtained by physical methods, thus supporting the semi-automated camera system as a viable option for monitoring American Eel passage. Time stamps on digital images allowed for the documentation of eel passage time—data that were not obtainable from physical monitoring efforts. The ELC has application to eel ladder facilities but can also be used to monitor dam passage of other taxa, such as crayfishes, lampreys, and water snakes.

Fast Offset Laser Phase-Locking System

NASA Technical Reports Server (NTRS)

Shaddock, Daniel; Ware, Brent

2008-01-01

Figure 1 shows a simplified block diagram of an improved optoelectronic system for locking the phase of one laser to that of another laser with an adjustable offset frequency specified by the user. In comparison with prior systems, this system exhibits higher performance (including higher stability) and is much easier to use. The system is based on a field-programmable gate array (FPGA) and operates almost entirely digitally; hence, it is easily adaptable to many different systems. The system achieves phase stability of less than a microcycle. It was developed to satisfy the phase-stability requirement for a planned spaceborne gravitational-wave-detecting heterodyne laser interferometer (LISA). The system has potential terrestrial utility in communications, lidar, and other applications. The present system includes a fast phasemeter that is a companion to the microcycle-accurate one described in High-Accuracy, High-Dynamic-Range Phase-Measurement System (NPO-41927), NASA Tech Briefs, Vol. 31, No. 6 (June 2007), page 22. In the present system (as in the previously reported one), beams from the two lasers (here denoted the master and slave lasers) interfere on a photodiode. The heterodyne photodiode output is digitized and fed to the fast phasemeter, which produces suitably conditioned, low-latency analog control signals which lock the phase of the slave laser to that of the master laser. These control signals are used to drive a thermal and a piezoelectric transducer that adjust the frequency and phase of the slave-laser output. The output of the photodiode is a heterodyne signal at the difference between the frequencies of the two lasers. (The difference is currently required to be less than 20 MHz due to the Nyquist limit of the current sampling rate. We foresee few problems in doubling this limit using current equipment.) Within the phasemeter, the photodiode-output signal is digitized to 15 bits at a sampling frequency of 40 MHz by use of the same analog-to-digital converter (ADC) as that of the previously reported phasemeter. The ADC output is passed to the FPGA, wherein the signal is demodulated using a digitally generated oscillator signal at the offset locking frequency specified by the user. The demodulated signal is low-pass filtered, decimated to a sample rate of 1 MHz, then filtered again. The decimated and filtered signal is converted to an analog output by a 1 MHz, 16-bit digital-to-analog converters. After a simple low-pass filter, these analog signals drive the thermal and piezoelectric transducers of the laser.

Dual-wavelength common-path digital holographic microscopy for quantitative phase imaging of biological cells

NASA Astrophysics Data System (ADS)

Di, Jianglei; Song, Yu; Xi, Teli; Zhang, Jiwei; Li, Ying; Ma, Chaojie; Wang, Kaiqiang; Zhao, Jianlin

2017-11-01

Biological cells are usually transparent with a small refractive index gradient. Digital holographic interferometry can be used in the measurement of biological cells. We propose a dual-wavelength common-path digital holographic microscopy for the quantitative phase imaging of biological cells. In the proposed configuration, a parallel glass plate is inserted in the light path to create the lateral shearing, and two lasers with different wavelengths are used as the light source to form the dual-wavelength composite digital hologram. The information of biological cells for different wavelengths is separated and extracted in the Fourier domain of the hologram, and then combined to a shorter wavelength in the measurement process. This method could improve the system's temporal stability and reduce speckle noises simultaneously. Mouse osteoblastic cells and peony pollens are measured to show the feasibility of this method.

Flight evaluation of modifications to a digital electronic engine control system in an F-15 airplane

NASA Technical Reports Server (NTRS)

Burcham, F. W., Jr.; Myers, L. P.; Zeller, J. R.

1983-01-01

The third phase of a flight evaluation of a digital electronic engine control system in an F-15 has recently been completed. It was found that digital electronic engine control software logic changes and augmentor hardware improvements resulted in significant improvements in engine operation. For intermediate to maximum power throttle transients, an increase in altitude capability of up to 8000 ft was found, and for idle to maximum transients, an increase of up to 4000 ft was found. A nozzle instability noted in earlier flight testing was investigated on a test engine at NASA Lewis Research Center, a digital electronic engine control software logic change was developed and evaluated, and no instability occurred in the Phase 3 flight evaluation. The backup control airstart modification was evaluated, and gave an improvement of airstart capability by reducing the minimum airspeed for successful airstarts by 50 to 75 knots.

Noise management to achieve superiority in quantum information systems

NASA Astrophysics Data System (ADS)

Nemoto, Kae; Devitt, Simon; Munro, William J.

2017-06-01

Quantum information systems are expected to exhibit superiority compared with their classical counterparts. This superiority arises from the quantum coherences present in these quantum systems, which are obviously absent in classical ones. To exploit such quantum coherences, it is essential to control the phase information in the quantum state. The phase is analogue in nature, rather than binary. This makes quantum information technology fundamentally different from our classical digital information technology. In this paper, we analyse error sources and illustrate how these errors must be managed for the system to achieve the required fidelity and a quantum superiority. This article is part of the themed issue 'Quantum technology for the 21st century'.

Noise management to achieve superiority in quantum information systems.

PubMed

Nemoto, Kae; Devitt, Simon; Munro, William J

2017-08-06

Quantum information systems are expected to exhibit superiority compared with their classical counterparts. This superiority arises from the quantum coherences present in these quantum systems, which are obviously absent in classical ones. To exploit such quantum coherences, it is essential to control the phase information in the quantum state. The phase is analogue in nature, rather than binary. This makes quantum information technology fundamentally different from our classical digital information technology. In this paper, we analyse error sources and illustrate how these errors must be managed for the system to achieve the required fidelity and a quantum superiority.This article is part of the themed issue 'Quantum technology for the 21st century'. © 2017 The Author(s).

Measurement of the traction force of biological cells by digital holography

PubMed Central

Yu, Xiao; Cross, Michael; Liu, Changgeng; Clark, David C.; Haynie, Donald T.; Kim, Myung K.

2011-01-01

The traction force produced by biological cells has been visualized as distortions in flexible substrata. We have utilized quantitative phase microscopy by digital holography (DH-QPM) to study the wrinkling of a silicone rubber film by motile fibroblasts. Surface deformation and the cellular traction force have been measured from phase profiles in a direct and straightforward manner. DH-QPM is shown to provide highly efficient and versatile means for quantitatively analyzing cellular motility. PMID:22254175

MANUFACTURING METHODS FOR PHASE SHIFTERS.

DTIC Science & Technology

MANUFACTURING), (*PHASE SHIFT CIRCUITS, FERRITES, GARNET , DIGITAL SYSTEMS, X BAND, C BAND, S BAND, RADAR EQUIPMENT, MAGNETIC MATERIALS, YTTRIUM COMPOUNDS, GADOLINIUM COMPOUNDS, ALUMINUM COMPOUNDS, IRON COMPOUNDS, OXIDES.

Quantizing and sampling considerations in digital phased-locked loops

NASA Technical Reports Server (NTRS)

Hurst, G. T.; Gupta, S. C.

1974-01-01

The quantizer problem is first considered. The conditions under which the uniform white sequence model for the quantizer error is valid are established independent of the sampling rate. An equivalent spectral density is defined for the quantizer error resulting in an effective SNR value. This effective SNR may be used to determine quantized performance from infinitely fine quantized results. Attention is given to sampling rate considerations. Sampling rate characteristics of the digital phase-locked loop (DPLL) structure are investigated for the infinitely fine quantized system. The predicted phase error variance equation is examined as a function of the sampling rate. Simulation results are presented and a method is described which enables the minimum required sampling rate to be determined from the predicted phase error variance equations.

Absolute distance measurement by dual-comb interferometry with multi-channel digital lock-in phase detection

NASA Astrophysics Data System (ADS)

Yang, Ruitao; Pollinger, Florian; Meiners-Hagen, Karl; Krystek, Michael; Tan, Jiubin; Bosse, Harald

2015-08-01

We present a dual-comb-based heterodyne multi-wavelength absolute interferometer capable of long distance measurements. The phase information of the various comb modes is extracted in parallel by a multi-channel digital lock-in phase detection scheme. Several synthetic wavelengths of the same order are constructed and the corresponding phases are averaged to deduce the absolute lengths with significantly reduced uncertainty. Comparison experiments with an incremental HeNe reference interferometer show a combined relative measurement uncertainty of 5.3 × 10-7 at a measurement distance of 20 m. Combining the advantage of synthetic wavelength interferometry and dual-comb interferometry, our compact and simple approach provides sufficient precision for many industrial applications.

Digital-data receiver synchronization

DOEpatents

Smith, Stephen F.; Turner, Gary W.

2005-08-02

Digital-data receiver synchronization is provided with composite phase-frequency detectors, mutually cross-connected comparison feedback or both to provide robust reception of digital data signals. A single master clock can be used to provide frequency signals. Advantages can include fast lock-up time in moderately to severely noisy conditions, greater tolerance to noise and jitter when locked, and improved tolerance to clock asymmetries.

Digital-data receiver synchronization method and apparatus

DOEpatents

Smith, Stephen F.; Turner, Gary W.

2005-12-06

Digital-data receiver synchronization is provided with composite phase-frequency detectors, mutually cross-connected comparison feedback or both to provide robust reception of digital data signals. A single master clock may be used to provide frequency signals. Advantages can include fast lock-up time in moderately to severely noisy conditions, greater tolerance to noise and jitter when locked, and improved tolerance to clock asymmetries.

Digital-data receiver synchronization method and apparatus

DOEpatents

Smith, Stephen F [Loudon, TN; Turner, Gary W [Clinton, TN

2009-09-08

Digital data receiver synchronization is provided with composite phase-frequency detectors, mutually cross-connected comparison feedback or both to provide robust reception of digital data signals. A single master clock can be used to provide frequency signals. Advantages can include fast lock-up time in moderately to severely noisy conditions, greater tolerance to noise and jitter when locked, and improved tolerance to clock asymmetries.

User-Centered Digital Library Project Phase 2: User Testing with Teachers and Students with Disabilities. Evaluation Report

ERIC Educational Resources Information Center

Moeller, Babette

2010-01-01

The goal of the User-Centered Digital Library Project, conducted by the National Center for Accessible Media (NCAM) at WGBH, was to adapt the Teachers' Domain online digital library to enable teachers and students with disabilities to more readily use the resources in science classrooms. NCAM added accessibility features such as captions and audio…

Cost analysis of a project to digitize classic articles in neurosurgery*

PubMed Central

Bauer, Kathleen

2002-01-01

In summer 2000, the Cushing/Whitney Medical Library at Yale University began a demonstration project to digitize classic articles in neurosurgery from the late 1800s and early 1900s. The objective of the first phase of the project was to measure the time and costs involved in digitization, and those results are reported here. In the second phase, metadata will be added to the digitized articles, and the project will be publicized. Thirteen articles were scanned using optical character recognition (OCR) software, and the resulting text files were carefully proofread. Time for photocopying, scanning, and proofreading were recorded. This project achieved an average cost per item (total pages plus images) of $4.12, a figure at the high end of average costs found in other studies. This project experienced high costs for two reasons. First, the articles contained many images, which required extra processing. Second, the older fonts and the poor condition of many of these articles complicated the OCR process. The average article cost $84.46 to digitize. Although costs were high, the selection of historically important articles maximized the benefit gained from the investment in digitization. PMID:11999182

Cost analysis of a project to digitize classic articles in neurosurgery.

PubMed

Bauer, Kathleen

2002-04-01

In summer 2000, the Cushing/Whitney Medical Library at Yale University began a demonstration project to digitize classic articles in neurosurgery from the late 1800s and early 1900s. The objective of the first phase of the project was to measure the time and costs involved in digitization, and those results are reported here. In the second phase, metadata will be added to the digitized articles, and the project will be publicized. Thirteen articles were scanned using optical character recognition (OCR) software, and the resulting text files were carefully proofread. Time for photocopying, scanning, and proofreading were recorded. This project achieved an average cost per item (total pages plus images) of $4.12, a figure at the high end of average costs found in other studies. This project experienced high costs for two reasons. First, the articles contained many images, which required extra processing. Second, the older fonts and the poor condition of many of these articles complicated the OCR process. The average article cost $84.46 to digitize. Although costs were high, the selection of historically important articles maximized the benefit gained from the investment in digitization.

Demonstration of digital phase-sensitive boosting to extend signal reach for long-haul WDM systems using optical phase-conjugated copy.

PubMed

Tian, Yue; Huang, Yue-Kai; Zhang, Shaoliang; Prucnal, Paul R; Wang, Ting

2013-02-25

We demonstrate a hybrid optical/digital phase-sensitive boosting (PSB) technique for long-haul wavelength division multiplexing (WDM) transmission systems. The approach uses four-wave mixing (FWM) to generate a phase-conjugated idler alongside the original signal. At the receiver, the signal and idler are jointly detected, and the phases of the idler symbols are conjugated and summed with the signal symbols to suppress noise and nonlinear phase distortion. The proposed hybrid PSB scheme is independent of modulation format and does not require an optical phase-locked loop to achieve phase matching required by conventional phase-sensitive amplifiers. Our simulation and experimental results of 112-Gb/s dual-polarization quadrature phase-shift-keying (DP-QPSK) transmission confirmed the principle of the PSB scheme, attaining a Q-factor improvement of 2.4 dB over conventional single-channel transmission after 4,800 km of dispersion-managed fiber (DMF) link at the expense of 50% reduction in spectral efficiency and extending the system reach by 60% to 7,680 km.

Preliminary study of first motion from nuclear explosions recorded on seismograms in the first zone

USGS Publications Warehouse

Healy, J.H.; Mangan, G.B.

1963-01-01

The U.S. Geological Survey has recorded more than 300 seismograms from more than 50 underground nuclear explosions. Most were recorded at distances of less than 1,000 km. These seismograms have been studied to obtain travel times and amplitudes which have been presented in reports on crustal structure and in a new series of nuclear shot reports. This report describes preliminary studies of first motion of seismic waves generated by underground nuclear explosions. Visual inspection of all seismograms was made in an attempt to identify the direction of first motion, and to estimate the probability of recording detectable first motion at various distances for various charge sizes and in different geologic environments. In this study, a characteristic pattern of the first phase became apparent on seismograms where first motion was clearly recorded. When an interpreter became familiar with this pattern, he was frequently able to identify the polarity of the first arrival even though the direction of first motion could not be seen clearly on the seismogram. In addition, it was sometimes possible to recognize this pattern for secondary arrivals of larger amplitude. These qualitative visual observations suggest that it might be possible to define a simple criterion that could be used in a digital computer to identify polarity, not only of the first phase, but of secondary phases as well. A short segment of recordings near the first motion on 56 seismograms was digitized on an optical digitizer. Spectral analyses of these digitized recordings were made to determine the range of frequencies present, and studies were made with various simple digital filters to explore the nature of polarity as a function of frequency. These studies have not yet led to conclusive results, partly because of inaccuracies resulting from optical digitization. The work is continuing, using an electronic digitizer that will allow study of a much larger sample of more accurately digitized data.

Digital Analysis and Sorting of Fluorescence Lifetime by Flow Cytometry

PubMed Central

Houston, Jessica P.; Naivar, Mark A.; Freyer, James P.

2010-01-01

Frequency-domain flow cytometry techniques are combined with modifications to the digital signal processing capabilities of the Open Reconfigurable Cytometric Acquisition System (ORCAS) to analyze fluorescence decay lifetimes and control sorting. Real-time fluorescence lifetime analysis is accomplished by rapidly digitizing correlated, radiofrequency modulated detector signals, implementing Fourier analysis programming with ORCAS’ digital signal processor (DSP) and converting the processed data into standard cytometric list mode data. To systematically test the capabilities of the ORCAS 50 MS/sec analog-to-digital converter (ADC) and our DSP programming, an error analysis was performed using simulated light scatter and fluorescence waveforms (0.5–25 ns simulated lifetime), pulse widths ranging from 2 to 15 µs, and modulation frequencies from 2.5 to 16.667 MHz. The standard deviations of digitally acquired lifetime values ranged from 0.112 to >2 ns, corresponding to errors in actual phase shifts from 0.0142° to 1.6°. The lowest coefficients of variation (<1%) were found for 10-MHz modulated waveforms having pulse widths of 6 µs and simulated lifetimes of 4 ns. Direct comparison of the digital analysis system to a previous analog phase-sensitive flow cytometer demonstrated similar precision and accuracy on measurements of a range of fluorescent microspheres, unstained cells and cells stained with three common fluorophores. Sorting based on fluorescence lifetime was accomplished by adding analog outputs to ORCAS and interfacing with a commercial cell sorter with a radiofrequency modulated solid-state laser. Two populations of fluorescent microspheres with overlapping fluorescence intensities but different lifetimes (2 and 7 ns) were separated to ~98% purity. Overall, the digital signal acquisition and processing methods we introduce present a simple yet robust approach to phase-sensitive measurements in flow cytometry. The ability to simply and inexpensively implement this system on a commercial flow sorter will both allow better dissemination of this technology and better exploit the traditionally underutilized parameter of fluorescence lifetime. PMID:20662090

Designing, Prototyping and Evaluating Digital Mindfulness Applications: A Case Study of Mindful Breathing for Stress Reduction.

PubMed

Zhu, Bin; Hedman, Anders; Feng, Shuo; Li, Haibo; Osika, Walter

2017-06-14

During the past decade, there has been a rapid increase of interactive apps designed for health and well-being. Yet, little research has been published on developing frameworks for design and evaluation of digital mindfulness facilitating technologies. Moreover, many existing digital mindfulness applications are purely software based. There is room for further exploration and assessment of designs that make more use of physical qualities of artifacts. The study aimed to develop and test a new physical digital mindfulness prototype designed for stress reduction. In this case study, we designed, developed, and evaluated HU, a physical digital mindfulness prototype designed for stress reduction. In the first phase, we used vapor and light to support mindful breathing and invited 25 participants through snowball sampling to test HU. In the second phase, we added sonification. We deployed a package of probes such as photos, diaries, and cards to collect data from users who explored HU in their homes. Thereafter, we evaluated our installation using both self-assessed stress levels and heart rate (HR) and heart rate variability (HRV) measures in a pilot study, in order to measure stress resilience effects. After the experiment, we performed a semistructured interview to reflect on HU and investigate the design of digital mindfulness apps for stress reduction. The results of the first phase showed that 22 of 25 participants (88%) claimed vapor and light could be effective ways of promoting mindful breathing. Vapor could potentially support mindful breathing better than light (especially for mindfulness beginners). In addition, a majority of the participants mentioned sound as an alternative medium. In the second phase, we found that participants thought that HU could work well for stress reduction. We compared the effect of silent HU (using light and vapor without sound) and sonified HU on 5 participants. Subjective stress levels were statistically improved with both silent and sonified HU. The mean value of HR using silent HU was significantly lower than resting baseline and sonified HU. The mean value of root mean square of differences (RMSSD) using silent HU was significantly higher than resting baseline. We found that the differences between our objective and subjective assessments were intriguing and prompted us to investigate them further. Our evaluation of HU indicated that HU could facilitate relaxed breathing and stress reduction. There was a difference in outcome between the physiological measures of stress and the subjective reports of stress, as well as a large intervariability among study participants. Our conclusion is that the use of stress reduction tools should be customized and that the design work of mindfulness technology for stress reduction is a complex process, which requires cooperation of designers, HCI (Human-Computer Interaction) experts and clinicians. ©Bin Zhu, Anders Hedman, Shuo Feng, Haibo Li, Walter Osika. Originally published in the Journal of Medical Internet Research (http://www.jmir.org), 14.06.2017.

Quantitative phase imaging of cell division in yeast cells and E.coli using digital holographic microscopy

NASA Astrophysics Data System (ADS)

Pandiyan, Vimal Prabhu; John, Renu

2015-12-01

Digital holographic microscope (DHM) is an emerging quantitative phase imaging technique with unique imaging scales and resolutions leading to multitude of applications. DHM is promising as a novel investigational and applied tool for cell imaging, studying the morphology and real time dynamics of cells and a number of related applications. The use of numerical propagation and computational digital optics offer unique flexibility to tune the depth of focus, and compensate for image aberrations. In this work, we report imaging the dynamics of cell division in E.coli and yeast cells using a DHM platform. We demonstrate 3-D and depth imaging as well as reconstruction of phase profiles of E.coli and yeast cells using the system. We record a digital hologram of E.coli and yeast cells and reconstruct the image using Fresnel propagation algorithm. We also use aberration compensation algorithms for correcting the aberrations that are introduced by the microscope objective in the object path using linear least square fitting techniques. This work demonstrates the strong potential of a DHM platform in 3-D live cell imaging, fast clinical quantifications and pathological applications.

Digital Intermediate Frequency Receiver Module For Use In Airborne Sar Applications

DOEpatents

Tise, Bertice L.; Dubbert, Dale F.

2005-03-08

A digital IF receiver (DRX) module directly compatible with advanced radar systems such as synthetic aperture radar (SAR) systems. The DRX can combine a 1 G-Sample/sec 8-bit ADC with high-speed digital signal processor, such as high gate-count FPGA technology or ASICs to realize a wideband IF receiver. DSP operations implemented in the DRX can include quadrature demodulation and multi-rate, variable-bandwidth IF filtering. Pulse-to-pulse (Doppler domain) filtering can also be implemented in the form of a presummer (accumulator) and an azimuth prefilter. An out of band noise source can be employed to provide a dither signal to the ADC, and later be removed by digital signal processing. Both the range and Doppler domain filtering operations can be implemented using a unique pane architecture which allows on-the-fly selection of the filter decimation factor, and hence, the filter bandwidth. The DRX module can include a standard VME-64 interface for control, status, and programming. An interface can provide phase history data to the real-time image formation processors. A third front-panel data port (FPDP) interface can send wide bandwidth, raw phase histories to a real-time phase history recorder for ground processing.

Quantitative phase-digital holographic microscopy: a new imaging modality to identify original cellular biomarkers of diseases

NASA Astrophysics Data System (ADS)

Marquet, P.; Rothenfusser, K.; Rappaz, B.; Depeursinge, C.; Jourdain, P.; Magistretti, P. J.

2016-03-01

Quantitative phase microscopy (QPM) has recently emerged as a powerful label-free technique in the field of living cell imaging allowing to non-invasively measure with a nanometric axial sensitivity cell structure and dynamics. Since the phase retardation of a light wave when transmitted through the observed cells, namely the quantitative phase signal (QPS), is sensitive to both cellular thickness and intracellular refractive index related to the cellular content, its accurate analysis allows to derive various cell parameters and monitor specific cell processes, which are very likely to identify new cell biomarkers. Specifically, quantitative phase-digital holographic microscopy (QP-DHM), thanks to its numerical flexibility facilitating parallelization and automation processes, represents an appealing imaging modality to both identify original cellular biomarkers of diseases as well to explore the underlying pathophysiological processes.

The design and implementation of a broadband digital low-level RF control system for the cyclotron accelerators at iThemba LABS

NASA Astrophysics Data System (ADS)

Duckitt, W. D.; Conradie, J. L.; van Niekerk, M. J.; Abraham, J. K.; Niesler, T. R.

2018-07-01

iThemba LABS has successfully designed a new broadband digital low-level RF control system for cyclotrons, that operates over the wide frequency range of 2-100 MHz and can achieve peak-peak amplitude and phase stabilities of 0.01% and 0.01°, respectively. The presented system performs direct digital synthesis (DDS) to directly convert the digital RF signals to analog RF and local-oscillator (LO) signals with 16-bit amplitude accuracy, programmable in steps of 1 μHz and 0.0001°. Down-conversion of the RF pick-up signals to an optimal intermediate frequency (IF) of 1 MHz and sampling of the IF channels by 16-bit, single sample-latency 10 MHz ADCs was implemented to allow digital high-speed low-latency in-phase/quadrature (I/Q) demodulation of the IF channels within the FPGA. This in turn allows efficient real-time digital closed-loop control of the amplitude and phase of the RF drive-signal to be achieved. The systems have been successfully integrated at iThemba LABS into the K = 8 and K = 10 injector cyclotrons (SPC1, and SPC2), the K = 200 separated sector cyclotron (SSC), the SSC flat-topping system, the pulse-selector system and the AX , J, and K-line RF bunchers. The systems have led to a substantial improvement in the beam quality of the SSC at iThemba LABS with a reduction in beam losses by more than 90%. The design, implementation and performance is discussed.

Computer-assisted techniques to evaluate fringe patterns

NASA Astrophysics Data System (ADS)

Sciammarella, Cesar A.; Bhat, Gopalakrishna K.

1992-01-01

Strain measurement using interferometry requires an efficient way to extract the desired information from interferometric fringes. Availability of digital image processing systems makes it possible to use digital techniques for the analysis of fringes. In the past, there have been several developments in the area of one dimensional and two dimensional fringe analysis techniques, including the carrier fringe method (spatial heterodyning) and the phase stepping (quasi-heterodyning) technique. This paper presents some new developments in the area of two dimensional fringe analysis, including a phase stepping technique supplemented by the carrier fringe method and a two dimensional Fourier transform method to obtain the strain directly from the discontinuous phase contour map.

Shaping Laguerre-Gaussian laser modes with binary gratings using a digital micromirror device.

PubMed

Lerner, Vitaly; Shwa, David; Drori, Yehonathan; Katz, Nadav

2012-12-01

Laguerre-Gaussian (LG) beams are used in many research fields, including microscopy, laser cavity modes, and optical tweezing. We developed a holographic method to generate pure LG modes (amplitude and phase) with a binary amplitude-only digital micromirror device (DMD) as an alternative to the commonly used phase-only spatial light modulator. The advantages of such a DMD include very high frame rates, low cost, and high damage thresholds. We have shown that the propagating shaped beams are self-similar and their phase fronts are of helical shape as demanded. We estimate the purity of the resultant beams to be above 94%.

Rotational scanning and multiple-spot focusing through a multimode fiber based on digital optical phase conjugation

NASA Astrophysics Data System (ADS)

Ma, Chaojie; Di, Jianglei; Li, Ying; Xiao, Fajun; Zhang, Jiwei; Liu, Kaihui; Bai, Xuedong; Zhao, Jianlin

2018-06-01

We demonstrate, for the first time, the rotational memory effect of a multimode fiber (MMF) based on digital optical phase conjugation (DOPC) to achieve multiple-spot focusing. An implementation interferometer is used to address the challenging alignments in DOPC. By rotating the acquired phase conjugate pattern, rotational scanning through a MMF could be achieved by recording a single off-axis hologram. The generation of two focal spots through a MMF is also demonstrated by combining the rotational memory effect with the superposition principle. The results may be useful for ultrafast scanning imaging and optical manipulation of multiple objects through a MMF.

Digital receiver study and implementation

NASA Technical Reports Server (NTRS)

Fogle, D. A.; Lee, G. M.; Massey, J. C.

1972-01-01

Computer software was developed which makes it possible to use any general purpose computer with A/D conversion capability as a PSK receiver for low data rate telemetry processing. Carrier tracking, bit synchronization, and matched filter detection are all performed digitally. To aid in the implementation of optimum computer processors, a study of general digital processing techniques was performed which emphasized various techniques for digitizing general analog systems. In particular, the phase-locked loop was extensively analyzed as a typical non-linear communication element. Bayesian estimation techniques for PSK demodulation were studied. A hardware implementation of the digital Costas loop was developed.

Automatic Mexican sign language and digits recognition using normalized central moments

NASA Astrophysics Data System (ADS)

Solís, Francisco; Martínez, David; Espinosa, Oscar; Toxqui, Carina

2016-09-01

This work presents a framework for automatic Mexican sign language and digits recognition based on computer vision system using normalized central moments and artificial neural networks. Images are captured by digital IP camera, four LED reflectors and a green background in order to reduce computational costs and prevent the use of special gloves. 42 normalized central moments are computed per frame and used in a Multi-Layer Perceptron to recognize each database. Four versions per sign and digit were used in training phase. 93% and 95% of recognition rates were achieved for Mexican sign language and digits respectively.

First-Order-hold interpolation digital-to-analog converter with application to aircraft simulation

NASA Technical Reports Server (NTRS)

Cleveland, W. B.

1976-01-01

Those who design piloted aircraft simulations must contend with the finite size and speed of the available digital computer and the requirement for simulation reality. With a fixed computational plant, the more complex the model, the more computing cycle time is required. While increasing the cycle time may not degrade the fidelity of the simulated aircraft dynamics, the larger steps in the pilot cue feedback variables (such as the visual scene cues), may be disconcerting to the pilot. The first-order-hold interpolation (FOHI) digital-to-analog converter (DAC) is presented as a device which offers smooth output, regardless of cycle time. The Laplace transforms of these three conversion types are developed and their frequency response characteristics and output smoothness are compared. The FOHI DAC exhibits a pure one-cycle delay. Whenever the FOHI DAC input comes from a second-order (or higher) system, a simple computer software technique can be used to compensate for the DAC phase lag. When so compensated, the FOHI DAC has (1) an output signal that is very smooth, (2) a flat frequency response in frequency ranges of interest, and (3) no phase error. When the input comes from a first-order system, software compensation may cause the FOHI DAC to perform as an FOHE DAC, which, although its output is not as smooth as that of the FOHI DAC, has a smoother output than that of the ZOH DAC.

Digitally synthesized high purity, high-voltage radio frequency drive electronics for mass spectrometry.

PubMed

Schaefer, R T; MacAskill, J A; Mojarradi, M; Chutjian, A; Darrach, M R; Madzunkov, S M; Shortt, B J

2008-09-01

Reported herein is development of a quadrupole mass spectrometer controller (MSC) with integrated radio frequency (rf) power supply and mass spectrometer drive electronics. Advances have been made in terms of the physical size and power consumption of the MSC, while simultaneously making improvements in frequency stability, total harmonic distortion, and spectral purity. The rf power supply portion of the MSC is based on a series-resonant LC tank, where the capacitive load is the mass spectrometer itself, and the inductor is a solenoid or toroid, with various core materials. The MSC drive electronics is based on a field programmable gate array (FPGA), with serial peripheral interface for analog-to-digital and digital-to-analog converter support, and RS232/RS422 communications interfaces. The MSC offers spectral quality comparable to, or exceeding, that of conventional rf power supplies used in commercially available mass spectrometers; and as well an inherent flexibility, via the FPGA implementation, for a variety of tasks that includes proportional-integral derivative closed-loop feedback and control of rf, rf amplitude, and mass spectrometer sensitivity. Also provided are dc offsets and resonant dipole excitation for mass selective accumulation in applications involving quadrupole ion traps; rf phase locking and phase shifting for external loading of a quadrupole ion trap; and multichannel scaling of acquired mass spectra. The functionality of the MSC is task specific, and is easily modified by simply loading FPGA registers or reprogramming FPGA firmware.

A simulation analysis of phase processing circuitry in the Ohio University Omega receiver prototype

NASA Technical Reports Server (NTRS)

Palkovic, R. A.

1975-01-01

A FORTRAN IV simulation study of the all-digital phase-processing circuitry is described. A digital phase-lock loop (DPLL) forms the heart of the Omega navigation receiver prototype, and through the DPLL, the phase of the 10.2 KHz Omega signal was estimated when the true signal phase is contaminated with noise. The DPLL uses a frequency synthesizer as the reference oscillator. The synthesizer is composed of synchronous rate multipliers (SRM's) driven by a temperature-compensated crystal oscillator, and the use of the SRM's in this application introduces phase jitter which degrades system performance. Simulation of the frequency synthesizer discussed was to analyze the circuits on a bit-by-bit level in order to evaluate the overall design, to see easily the effects of proposed design changes prior to actual breadboarding, to determine the optimum integration time for the DPLL in an environment typical of general aviation conditions, and to quantify the phase error introduced by the SRM synthesizer and examine its effect on the system.

Digital communication constraints in prior space missions

NASA Technical Reports Server (NTRS)

Yassine, Nathan K.

2004-01-01

Digital communication is crucial for space endeavors. Jt transmits scientific and command data between earth stations and the spacecraft crew. It facilitates communications between astronauts, and provides live coverage during all phases of the mission. Digital communications provide ground stations and spacecraft crew precise data on the spacecraft position throughout the entire mission. Lessons learned from prior space missions are valuable for our new lunar and Mars missions set by our president s speech. These data will save our agency time and money, and set course our current developing technologies. Limitations on digital communications equipment pertaining mass, volume, data rate, frequency, antenna type and size, modulation, format, and power in the passed space missions are of particular interest. This activity is in support of ongoing communication architectural studies pertaining to robotic and human lunar exploration. The design capabilities and functionalities will depend on the space and power allocated for digital communication equipment. My contribution will be gathering these data, write a report, and present it to Communications Technology Division Staff. Antenna design is very carefully studied for each mission scenario. Currently, Phased array antennas are being developed for the lunar mission. Phased array antennas use little power, and electronically steer a beam instead of DC motors. There are 615 patches in the phased array antenna. These patches have to be modified to have high yield. 50 patches were created for testing. My part is to assist in the characterization of these patch antennas, and determine whether or not certain modifications to quartz micro-strip patch radiators result in a significant yield to warrant proceeding with repairs to the prototype 19 GHz ferroelectric reflect-array antenna. This work requires learning how to calibrate an automatic network, and mounting and testing antennas in coaxial fixtures. The purpose of this activity is to assist in the set-up of phase noise instrumentation, assist in the process of automated wire bonding, assist in the design and optimization of tunable microwave components, especially phase shifters, based on thin ferroelectric films, and learn how to use commercial electromagnetic simulation software.

Timing performance of phase-locked loops in optical pulse position modulation communication systems

NASA Astrophysics Data System (ADS)

Lafaw, D. A.

In an optical digital communication system, an accurate clock signal must be available at the receiver to provide proper synchronization with the transmitted signal. Phase synchronization is especially critical in M-ary pulse position modulation (PPM) systems where the optimum decision scheme is an energy detector which compares the energy in each of M time slots to decide which of M possible words was sent. A timing error causes energy spillover into adjacent time slots (a form of intersymbol interference) so that only a portion of the signal energy may be attributed to the correct time slot. This effect decreases the effective signal, increases the effective noise, and increases the probability of error. This report simulates a timing subsystem for a satellite-to-satellite optical PPM communication link. The receiver employs direct photodetection, preprocessing of the optical signal, and a phase-locked loop for timing synchronization. The photodetector output is modeled as a filtered, doubly stochastic Poisson shot noise process. The variance of the relative phase error is examined under varying signal strength conditions as an indication of loop performance, and simulation results are compared to theoretical relations.

Digital phased array beamforming using single-bit delta-sigma conversion with non-uniform oversampling.

PubMed

Kozak, M; Karaman, M

2001-07-01

Digital beamforming based on oversampled delta-sigma (delta sigma) analog-to-digital (A/D) conversion can reduce the overall cost, size, and power consumption of phased array front-end processing. The signal resampling involved in dynamic delta sigma beamforming, however, disrupts synchronization between the modulators and demodulator, causing significant degradation in the signal-to-noise ratio. As a solution to this, we have explored a new digital beamforming approach based on non-uniform oversampling delta sigma A/D conversion. Using this approach, the echo signals received by the transducer array are sampled at time instants determined by the beamforming timing and then digitized by single-bit delta sigma A/D conversion prior to the coherent beam summation. The timing information involves a non-uniform sampling scheme employing different clocks at each array channel. The delta sigma coded beamsums obtained by adding the delayed 1-bit coded RF echo signals are then processed through a decimation filter to produce final beamforming outputs. The performance and validity of the proposed beamforming approach are assessed by means of emulations using experimental raw RF data.

Latency study of the High Performance Time to Digital Converter for the ATLAS Muon Spectrometer trigger upgrade

NASA Astrophysics Data System (ADS)

Meng, X. T.; Levin, D. S.; Chapman, J. W.; Li, D. C.; Yao, Z. E.; Zhou, B.

2017-02-01

The High Performance Time to Digital Converter (HPTDC), a multi-channel ASIC designed by the CERN Microelectronics group, has been proposed for the digitization of the thin-Resistive Plate Chambers (tRPC) in the ATLAS Muon Spectrometer Phase-1 upgrade project. These chambers, to be staged for higher luminosity LHC operation, will increase trigger acceptance and reduce or eliminate the fake muon trigger rates in the barrel-endcap transition region, corresponding to pseudo-rapidity range 1<|η|<1.3. Low level trigger candidates must be flagged within a maximum latency of 1075 ns, thus imposing stringent signal processing time performance requirements on the readout system in general, and on the digitization electronics in particular. This paper investigates the HPTDC signal latency performance based on a specially designed evaluation board coupled with an external FPGA evaluation board, when operated in triggerless mode, and under hit rate conditions expected in Phase-I. This hardware based study confirms previous simulations and demonstrates that the HPTDC in triggerless operation satisfies the digitization timing requirements in both leading edge and pair modes.

Locality of Area Coverage on Digital Acoustic Communication in Air using Differential Phase Shift Keying

NASA Astrophysics Data System (ADS)

Mizutani, Keiichi; Ebihara, Tadashi; Wakatsuki, Naoto; Mizutani, Koichi

2009-07-01

We experimentally evaluate the locality of digital acoustic communication in air. Digital acoustic communication in air is suitable for a small cell system, because acoustic waves have a short propagation distance in air. In this study, optimal cell size is experimentally evaluated. Each base station (BS) transmits different commands. In our experiment, differential phase shift keying (DPSK), especially binary DPSK (DBPSK), is adopted as a modulation and demodulation scheme. The evaluated system consists of a personal computer (PC), a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), a loud speaker (SP), a microphone (MIC), and transceiver software. All experiments are performed in an anechoic room. The cell size of the transmitter can be limited under low signal-to-noise ratio (SNR) condition. If another transmitter works, cell size is limited by the effect of the interference from that transmitter. The cell size-to-distance ratio of transmitter A to transmitter B is 37.5%, if cell edge bit-error-rate (BER) is taken as 10-3.

Improvement of the energy resolution via an optimized digital signal processing in GERDA Phase I

NASA Astrophysics Data System (ADS)

Agostini, M.; Allardt, M.; Bakalyarov, A. M.; Balata, M.; Barabanov, I.; Barros, N.; Baudis, L.; Bauer, C.; Becerici-Schmidt, N.; Bellotti, E.; Belogurov, S.; Belyaev, S. T.; Benato, G.; Bettini, A.; Bezrukov, L.; Bode, T.; Borowicz, D.; Brudanin, V.; Brugnera, R.; Budjáš, D.; Caldwell, A.; Cattadori, C.; Chernogorov, A.; D'Andrea, V.; Demidova, E. V.; Vacri, A. di; Domula, A.; Doroshkevich, E.; Egorov, V.; Falkenstein, R.; Fedorova, O.; Freund, K.; Frodyma, N.; Gangapshev, A.; Garfagnini, A.; Grabmayr, P.; Gurentsov, V.; Gusev, K.; Hegai, A.; Heisel, M.; Hemmer, S.; Heusser, G.; Hofmann, W.; Hult, M.; Inzhechik, L. V.; Janicskó Csáthy, J.; Jochum, J.; Junker, M.; Kazalov, V.; Kihm, T.; Kirpichnikov, I. V.; Kirsch, A.; Klimenko, A.; Knöpfle, K. T.; Kochetov, O.; Kornoukhov, V. N.; Kuzminov, V. V.; Laubenstein, ********************M.; Lazzaro, A.; Lebedev, V. I.; Lehnert, B.; Liao, H. Y.; Lindner, M.; Lippi, I.; Lubashevskiy, A.; Lubsandorzhiev, B.; Lutter, G.; Macolino, C.; Majorovits, B.; Maneschg, W.; Medinaceli, E.; Misiaszek, M.; Moseev, P.; Nemchenok, I.; Palioselitis, D.; Panas, K.; Pandola, L.; Pelczar, K.; Pullia, A.; Riboldi, S.; Rumyantseva, N.; Sada, C.; Salathe, M.; Schmitt, C.; Schneider, B.; Schönert, S.; Schreiner, J.; Schütz, A.-K.; Schulz, O.; Schwingenheuer, B.; Selivanenko, O.; Shirchenko, M.; Simgen, H.; Smolnikov, A.; Stanco, L.; Stepaniuk, M.; Ur, C. A.; Vanhoefer, L.; Vasenko, A. A.; Veresnikova, A.; von Sturm, K.; Wagner, V.; Walter, M.; Wegmann, A.; Wester, T.; Wilsenach, H.; Wojcik, M.; Yanovich, E.; Zavarise, P.; Zhitnikov, I.; Zhukov, S. V.; Zinatulina, D.; Zuber, K.; Zuzel, G.

2015-06-01

An optimized digital shaping filter has been developed for the Gerda experiment which searches for neutrinoless double beta decay in Ge. The Gerda Phase I energy calibration data have been reprocessed and an average improvement of 0.3 keV in energy resolution (FWHM) corresponding to 10 % at the value for decay in Ge is obtained. This is possible thanks to the enhanced low-frequency noise rejection of this Zero Area Cusp (ZAC) signal shaping filter.

Near optimum digital phase locked loops.

NASA Technical Reports Server (NTRS)

Polk, D. R.; Gupta, S. C.

1972-01-01

Near optimum digital phase locked loops are derived utilizing nonlinear estimation theory. Nonlinear approximations are employed to yield realizable loop structures. Baseband equivalent loop gains are derived which under high signal to noise ratio conditions may be calculated off-line. Additional simplifications are made which permit the application of the Kalman filter algorithms to determine the optimum loop filter. Performance is evaluated by a theoretical analysis and by simulation. Theoretical and simulated results are discussed and a comparison to analog results is made.

Two AFC Loops For Low CNR And High Dynamics

NASA Technical Reports Server (NTRS)

Hinedi, Sami M.; Aguirre, Sergio

1992-01-01

Two alternative digital automatic-frequency-control (AFC) loops proposed to acquire (or reacquire) and track frequency of received carrier radio signal. Intended for use where carrier-to-noise ratios (CNR's) low and carrier frequency characterized by high Doppler shift and Doppler rate because of high relative speed and acceleration, respectively, between transmitter and receiver. Either AFC loops used in place of phase-locked loop. New loop concepts integrate ideas from classical spectrum-estimation, digital-phase-locked-loop, and Kalman-Filter theories.

Ultra-High Speed Analog-to-Digital Converters in 14nm FinFET Process and Usage in Digital and Hybrid Phased Array Systems

DTIC Science & Technology

2017-03-01

enable extremely high dynamic range receivers to be realized in very compact dimensions. This paper provides information on the performance...this is the “Butler Matrix” topology in which N beam angular positions into N matrix ports. With this topology , by selecting a particular...waveguide port to connect a receiver or transmitter chain to a particular beam direction would be enabled. RF phase shifters and amplitude weighting

Optical phase analysis in drilled cortical porcine bones using digital holographic interferometry

NASA Astrophysics Data System (ADS)

Tavera R., César G.; De la Torre I., Manuel H.; Flores M., J. Mauricio; Luna H., Juan M.; Briones R., Manuel de J.; Mendoza S., Fernando

2016-03-01

A study in porcine femoral bones with and without the presence of cortical drilling is presented. An out of plane digital holographic interferometer is used to retrieve the optical phase during the controlled compression tests. These tests try to simulate physiological deformations in postmortem healthy bones and compare their mechanical response with those having a cortical hole. The cortical drilling technique is widely used in medical procedures to fix plaques and metallic frames to a bone recovering from a fracture. Several materials and drilling techniques are used for this purpose. In this work we analyze the superficial variations of the bone when different drilling diameters are used. By means of the optical phase it is possible to recover the superficial deformation of the tissue during a controlled deformation with high resolution. This information could give a better understand about the micro structural variations of the bone instead of a bulk response. As proof of principle, several tests were performed to register the modes and ranges of the displacements for compressive loads. From these tests notorious differences are observed between both groups of bones, having less structural stiffness the drilled ones as expected. However, the bone's characteristic to absorb and adjust itself due the load is also highly affected according to the number of holes. Results from different kind of samples (undrilled and drilled) are presented and discussed in this work.

Lensless digital holography with diffuse illumination through a pseudo-random phase mask.

PubMed

Bernet, Stefan; Harm, Walter; Jesacher, Alexander; Ritsch-Marte, Monika

2011-12-05

Microscopic imaging with a setup consisting of a pseudo-random phase mask, and an open CMOS camera, without an imaging objective, is demonstrated. The pseudo random phase mask acts as a diffuser for an incoming laser beam, scattering a speckle pattern to a CMOS chip, which is recorded once as a reference. A sample which is afterwards inserted somewhere in the optical beam path changes the speckle pattern. A single (non-iterative) image processing step, comparing the modified speckle pattern with the previously recorded one, generates a sharp image of the sample. After a first calibration the method works in real-time and allows quantitative imaging of complex (amplitude and phase) samples in an extended three-dimensional volume. Since no lenses are used, the method is free from lens abberations. Compared to standard inline holography the diffuse sample illumination improves the axial sectioning capability by increasing the effective numerical aperture in the illumination path, and it suppresses the undesired so-called twin images. For demonstration, a high resolution spatial light modulator (SLM) is programmed to act as the pseudo-random phase mask. We show experimental results, imaging microscopic biological samples, e.g. insects, within an extended volume at a distance of 15 cm with a transverse and longitudinal resolution of about 60 μm and 400 μm, respectively.

Phase-Shift Interferometry with a Digital Photocamera

ERIC Educational Resources Information Center

Vannoni, Maurizio; Trivi, Marcelo; Molesini, Giuseppe

2007-01-01

A phase-shift interferometry experiment is proposed, working on a Twyman-Green optical configuration with additional polarization components. A guideline is provided to modern phase-shift interferometry, using concepts and laboratory equipment at the level of undergraduate optics courses. (Contains 5 figures.)

Digital second-order phase-locked loop

NASA Technical Reports Server (NTRS)

Holes, J. K.; Carl, C.; Tegnelia, C. R. (Inventor)

1973-01-01

A digital second-order phase-locked loop is disclosed in which a counter driven by a stable clock pulse source is used to generate a reference waveform of the same frequency as an incoming waveform, and to sample the incoming waveform at zero-crossover points. The samples are converted to digital form and accumulated over M cycles, reversing the sign of every second sample. After every M cycles, the accumulated value of samples is hard limited to a value SGN = + or - 1 and multiplied by a value delta sub 1 equal to a number of n sub 1 of fractions of a cycle. An error signal is used to advance or retard the counter according to the sign of the sum by an amount equal to the sum.

Effects of low sampling rate in the digital data-transition tracking loop

NASA Technical Reports Server (NTRS)

Mileant, A.; Million, S.; Hinedi, S.

1994-01-01

This article describes the performance of the all-digital data-transition tracking loop (DTTL) with coherent and noncoherent sampling using nonlinear theory. The effects of few samples per symbol and of noncommensurate sampling and symbol rates are addressed and analyzed. Their impact on the probability density and variance of the phase error are quantified through computer simulations. It is shown that the performance of the all-digital DTTL approaches its analog counterpart when the sampling and symbol rates are noncommensurate (i.e., the number of samples per symbol is an irrational number). The loop signal-to-noise ratio (SNR) (inverse of phase error variance) degrades when the number of samples per symbol is an odd integer but degrades even further for even integers.

Adaptive frequency-domain equalization in digital coherent optical receivers.

PubMed

Faruk, Md Saifuddin; Kikuchi, Kazuro

2011-06-20

We propose a novel frequency-domain adaptive equalizer in digital coherent optical receivers, which can reduce computational complexity of the conventional time-domain adaptive equalizer based on finite-impulse-response (FIR) filters. The proposed equalizer can operate on the input sequence sampled by free-running analog-to-digital converters (ADCs) at the rate of two samples per symbol; therefore, the arbitrary initial sampling phase of ADCs can be adjusted so that the best symbol-spaced sequence is produced. The equalizer can also be configured in the butterfly structure, which enables demultiplexing of polarization tributaries apart from equalization of linear transmission impairments. The performance of the proposed equalization scheme is verified by 40-Gbits/s dual-polarization quadrature phase-shift keying (QPSK) transmission experiments.

Maritime Cyber Security University Research: Phase 1

DTIC Science & Technology

2016-05-01

the global economy . The vulnerabilities associated with reliance on digital systems in the maritime environment must be continuously examined. System...Report: Modern maritime systems are highly complex digital systems to ensure the safety and efficient operation of the shipping traffic so vital to...entrances to our " digital ports" and work to develop practical cyber security solutions to protect the nation’s maritime infrastructure. 17. Key

Library Digitisation Project Management.

ERIC Educational Resources Information Center

Middleton, Michael

Supervision of library digitization is the focus of this paper. First outlined are the definition, formalization, implementation, and completion phases of project management. Descriptions of management decisions involved in digitization projects follow on matters such as: collection analysis, resourcing, project personnel, production, access and…

Controlling Energy Radiations of Electromagnetic Waves via Frequency Coding Metamaterials

PubMed Central

Wu, Haotian; Liu, Shuo; Wan, Xiang; Zhang, Lei; Wang, Dan; Li, Lianlin

2017-01-01

Metamaterials are artificial structures composed of subwavelength unit cells to control electromagnetic (EM) waves. The spatial coding representation of metamaterial has the ability to describe the material in a digital way. The spatial coding metamaterials are typically constructed by unit cells that have similar shapes with fixed functionality. Here, the concept of frequency coding metamaterial is proposed, which achieves different controls of EM energy radiations with a fixed spatial coding pattern when the frequency changes. In this case, not only different phase responses of the unit cells are considered, but also different phase sensitivities are also required. Due to different frequency sensitivities of unit cells, two units with the same phase response at the initial frequency may have different phase responses at higher frequency. To describe the frequency coding property of unit cell, digitalized frequency sensitivity is proposed, in which the units are encoded with digits “0” and “1” to represent the low and high phase sensitivities, respectively. By this merit, two degrees of freedom, spatial coding and frequency coding, are obtained to control the EM energy radiations by a new class of frequency‐spatial coding metamaterials. The above concepts and physical phenomena are confirmed by numerical simulations and experiments. PMID:28932671

Fiber Optic Geophysics Sensor Array

NASA Astrophysics Data System (ADS)

Grochowski, Lucjan

1989-01-01

The distributed optical sensor arrays are analysed in view of specific needs of 3-D seismic explorations methods. There are compared advantages and disadventages of arrays supported by the sensors which are modulated in intensity and phase. In these systems all-fiber optic structures and their compabilities with digital geophysic formats are discussed. It was shown that the arrays based on TDM systems with the intensity modulated sensors are economically and technically the best matched for geophysic systems supported by a large number of the sensors.

Ghost imaging for three-dimensional optical security

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Wen, E-mail: elechenw@nus.edu.sg; Chen, Xudong

2013-11-25

Ghost imaging has become increasingly popular in quantum and optical application fields. Here, we report three-dimensional (3D) optical security using ghost imaging. The series of random phase-only masks are sparsified, which are further converted into particle-like distributions placed in 3D space. We show that either an optical or digital approach can be employed for the encoding. The results illustrate that a larger key space can be generated due to the application of 3D space compared with previous works.

Smart Phase Tuning in Microwave Photonic Integrated Circuits Toward Automated Frequency Multiplication by Design

NASA Astrophysics Data System (ADS)

Nabavi, N.

2018-07-01

The author investigates the monitoring methods for fine adjustment of the previously proposed on-chip architecture for frequency multiplication and translation of harmonics by design. Digital signal processing (DSP) algorithms are utilized to create an optimized microwave photonic integrated circuit functionality toward automated frequency multiplication. The implemented DSP algorithms are formed on discrete Fourier transform and optimization-based algorithms (Greedy and gradient-based algorithms), which are analytically derived and numerically compared based on the accuracy and speed of convergence criteria.

Multi-GHz Synchronous Waveform Acquisition With Real-Time Pattern-Matching Trigger Generation

NASA Astrophysics Data System (ADS)

Kleinfelder, Stuart A.; Chiang, Shiuh-hua Wood; Huang, Wei

2013-10-01

A transient waveform capture and digitization circuit with continuous synchronous 2-GHz sampling capability and real-time programmable windowed trigger generation has been fabricated and tested. Designed in 0.25 μm CMOS, the digitizer contains a circular array of 128 sample and hold circuits for continuous sample acquisition, and attains 2-GHz sample speeds with over 800-MHz analog bandwidth. Sample clock generation is synchronous, combining a phase-locked loop for high-speed clock generation and a high-speed fully-differential shift register for distributing clocks to all 128 sample circuits. Using two comparators per sample, the sampled voltage levels are compared against two reference levels, a high threshold and a low threshold, that are set via per-comparator digital to analog converters (DACs). The 256 per-comparator 5-bit DACs compensate for comparator offsets and allow for fine reference level adjustment. The comparator results are matched in 8-sample-wide windows against up to 72 programmable patterns in real time using an on-chip programmable logic array. Each 8-sample trigger window is equivalent to 4 ns of acquisition, overlapped sample by sample in a circular fashion through the entire 128-sample array. The 72 pattern-matching trigger criteria can be programmed to be any combination of High-above the high threshold, Low-below the low threshold, Middle-between the two thresholds, or “Don't Care”-any state is accepted. A trigger pattern of “HLHLHLHL,” for example, watches for a waveform that is oscillating at about 1 GHz given the 2-GHz sample rate. A trigger is flagged in under 20 ns if there is a match, after which sampling is stopped, and on-chip digitization can proceed via 128 parallel 10-bit converters, or off-chip conversion can proceed via an analog readout. The chip exceeds 11 bits of dynamic range, nets over 800-MHz -3-dB bandwidth in a realistic system, and jitter in the PLL-based sampling clock has been measured to be about 1 part per million, RMS.

Digital multi-channel high resolution phase locked loop for surveillance radar systems

NASA Astrophysics Data System (ADS)

Rizk, Mohamed; Shaaban, Shawky; Abou-El-Nadar, Usama M.; Hafez, Alaa El-Din Sayed

This paper present a multi-channel, high resolution, fast lock phase locked loop (PLL) for surveillance radar applications. Phase detector based PLLs are simple to design, suffer no systematic phase error, and can run at the highest speed. Reducing loop gain can proportionally improve jitter performance, but also reduces locking time and pull-in range. The proposed system is based on digital process and control the error signal to the voltage controlled oscillator (VCO) adaptively to control its gain in order to achieve fast lock times while improving in lock jitter performance. Under certain circumstances the design also improves the frequency agility capability of the radar system. The results show a fast lock, high resolution PLL with transient time less than 10 µ sec which is suitable to radar applications.

Digital-only PLL with adaptive search step

NASA Astrophysics Data System (ADS)

Lin, Ming-Lang; Huang, Shu-Chuan; Liu, Jie-Cherng

2014-06-01

In this paper, an all-digital phase-locked loop (PLL) with adaptively controlled up/down counter serves as the loop filter is presented, and it is implemented on a field-programmable gate array. The detailed circuit of the adaptive up/down counter implementing the adaptive search algorithm is also given, in which the search step for frequency acquisition is adaptively scaled down in half until it is reduced to zero. The phase jitter of the proposed PLL can be lowered, yet keeping with fast lock-in time. Thus, the dilemma between the low phase jitter and fast lock-in time of the traditional PLL can be resolved. Simulation results and circuit implementation show that the locked count, phase jitter and lock-in time of the proposed PLL are consistent with the theoretical predictions.

Electrical crosstalk-coupling measurement and analysis for digital closed loop fibre optic gyro

NASA Astrophysics Data System (ADS)

Jin, Jing; Tian, Hai-Ting; Pan, Xiong; Song, Ning-Fang

2010-03-01

The phase modulation and the closed-loop controller can generate electrical crosstalk-coupling in digital closed-loop fibre optic gyro. Four electrical cross-coupling paths are verified by the open-loop testing approach. It is found the variation of ramp amplitude will lead to the alternation of gyro bias. The amplitude and the phase parameters of the electrical crosstalk signal are measured by lock-in amplifier, and the variation of gyro bias is confirmed to be caused by the alternation of phase according to the amplitude of the ramp. A digital closed-loop fibre optic gyro electrical crosstalk-coupling model is built by approximating the electrical cross-coupling paths as a proportion and integration segment. The results of simulation and experiment show that the modulation signal electrical crosstalk-coupling can cause the dead zone of the gyro when a small angular velocity is inputted, and it could also lead to a periodic vibration of the bias error of the gyro when a large angular velocity is inputted.

Noise reduction and control in mode-locked semiconductor diode lasers for use in next-generation all-optical analog-to-digital converters

NASA Astrophysics Data System (ADS)

DePriest, Christopher M.; Abeles, Joseph H.; Braun, Alan; Delfyett, Peter J., Jr.

2000-07-01

External-cavity, actively-modelocked semiconductor diode lasers (SDLs) have proven to be attractive candidates for forming the backbone of next-generation analog-to-digital converters (ADCs), which are currently being developed to sample signals at repetition rates exceeding several GHz with up to 12 bits of digital resolution. Modelocked SDLs are capable of producing waveform-sampling pulse trains with very low temporal jitter (phase noise) and very small fluctuations in pulse height (amplitude noise)--two basic conditions that must be met in order for high-speed ADCs to achieve projected design goals. Single-wavelength modelocked operation (at nominal repetition frequencies of 400 MHz) has produced pulse trains with very low amplitude noise (approximately 0.08%), and the implementation of a phase- locked-loop has been effective in reducing the system's low- frequency phase noise (RMS timing jitter for offset frequencies between 10 Hz and 10 kHz has been reduced from 240 fs to 27 fs).

A clocking discipline for two-phase digital integrated circuits

NASA Astrophysics Data System (ADS)

Noice, D. C.

1983-09-01

Sooner or later a designer of digital circuits must face the problem of timing verification so he can avoid errors caused by clock skew, critical races, and hazards. Unlike previous verification methods, such as timing simulation and timing analysis, the approach presented here guarantees correct operation despite uncertainty about delays in the circuit. The result is a clocking discipline that deals with timing abstractions only. It is not based on delay calculations; it is only concerned with the correct, synchronous operation at some clock rate. Accordingly, it may be used earlier in the design cycle, which is particularly important to integrated circuit designs. The clocking discipline consists of a notation of clocking types, and composition rules for using the types. Together, the notation and rules define a formal theory of two phase clocking. The notation defines the names and exact characteristics for different signals that are used in a two phase digital system. The notation makes it possible to develop rules for propagating the clocking types through particular circuits.

Digital Geology from field to 3D modelling and Google Earth virtual environment: methods and goals from the Furlo Gorge (Northern Apennines - Italy)

NASA Astrophysics Data System (ADS)

De Donatis, Mauro; Susini, Sara

2014-05-01

A new map of the Furlo Gorge was surveyed and elaborated in a digital way. In every step of work we used digital tools as mobile GIS and 3D modelling software. Phase 1st Starting in the lab, planning the field project development, base cartography, forms and data base were designed in the way we thought was the best for collecting and store data in order of producing a digital n­-dimensional map. Bedding attitudes, outcrops sketches and description, stratigraphic logs, structural features and other informations were collected and organised in a structured database using rugged tablet PC, GPS receiver, digital cameras and later also an Android smartphone with some survey apps in-­house developed. A new mobile GIS (BeeGIS) was developed starting from an open source GIS (uDig): a number of tools like GPS connection, pen drawing annotations, geonotes, fieldbook, photo synchronization and geotagging were originally designed. Phase 2nd After some month of digital field work, all the informations were elaborated for drawing a geologic map in GIS environment. For that we use both commercial (ArcGIS) and open source (gvSig, QGIS, uDig) without big technical problems. Phase 3rd When we get to the step of building a 3D model (using 3DMove), passing trough the assisted drawing of cross-­sections (2DMove), we discovered a number of problems in the interpretation of geological structures (thrusts, normal faults) and more in the interpretation of stratigraphic thickness and boundaries and their relationships with topography. Phase 4th Before an "on­-armchair" redrawing of map, we decide to go back to the field and check directly what was wrong. Two main vantages came from this: (1) the mistakes we found could be reinterpreted and corrected directly in the field having all digital tools we need; (2) previous interpretations could be stored in GIS layers keeping memory of the previous work (also mistakes). Phase 5th A 3D model built with 3D Move is already almost self­-consistent in showing the structural features of the study area. The work was not so straightforward, but the result is more then satisfying, even if some limitations were not solved (i.e. visualisation of bedding attitudes). Geological maps are fundamental for knowledge transfer among experts but, if combined with the innovative digital methods from survey to 3D model, this knowledges could reach a much larger number of people, allowing a cultural growth and the establishment of a larger awareness of the Earth and Environment.

Independent component analysis applied to long bunch beams in the Los Alamos Proton Storage Ring

NASA Astrophysics Data System (ADS)

Kolski, Jeffrey S.; Macek, Robert J.; McCrady, Rodney C.; Pang, Xiaoying

2012-11-01

Independent component analysis (ICA) is a powerful blind source separation (BSS) method. Compared to the typical BSS method, principal component analysis, ICA is more robust to noise, coupling, and nonlinearity. The conventional ICA application to turn-by-turn position data from multiple beam position monitors (BPMs) yields information about cross-BPM correlations. With this scheme, multi-BPM ICA has been used to measure the transverse betatron phase and amplitude functions, dispersion function, linear coupling, sextupole strength, and nonlinear beam dynamics. We apply ICA in a new way to slices along the bunch revealing correlations of particle motion within the beam bunch. We digitize beam signals of the long bunch at the Los Alamos Proton Storage Ring with a single device (BPM or fast current monitor) for an entire injection-extraction cycle. ICA of the digitized beam signals results in source signals, which we identify to describe varying betatron motion along the bunch, locations of transverse resonances along the bunch, measurement noise, characteristic frequencies of the digitizing oscilloscopes, and longitudinal beam structure.

Phase retrieval in digital speckle pattern interferometry by use of a smoothed space-frequency distribution.

PubMed

Federico, Alejandro; Kaufmann, Guillermo H

2003-12-10

We evaluate the use of a smoothed space-frequency distribution (SSFD) to retrieve optical phase maps in digital speckle pattern interferometry (DSPI). The performance of this method is tested by use of computer-simulated DSPI fringes. Phase gradients are found along a pixel path from a single DSPI image, and the phase map is finally determined by integration. This technique does not need the application of a phase unwrapping algorithm or the introduction of carrier fringes in the interferometer. It is shown that a Wigner-Ville distribution with a smoothing Gaussian kernel gives more-accurate results than methods based on the continuous wavelet transform. We also discuss the influence of filtering on smoothing of the DSPI fringes and some additional limitations that emerge when this technique is applied. The performance of the SSFD method for processing experimental data is then illustrated.

Three-dimensional surface contouring of macroscopic objects by means of phase-difference images.

PubMed

Velásquez Prieto, Daniel; Garcia-Sucerquia, Jorge

2006-09-01

We report a technique to determine the 3D contour of objects with dimensions of at least 4 orders of magnitude larger than the illumination optical wavelength. Our proposal is based on the numerical reconstruction of the optical wave field of digitally recorded holograms. The required modulo 2pi phase map in any contouring process is obtained by means of the direct subtraction of two phase-contrast images under different illumination angles to create a phase-difference image of a still object. Obtaining the phase-difference images is only possible by using the capability of numerical reconstruction of the complex optical field provided by digital holography. This unique characteristic leads us to a robust, reliable, and fast procedure that requires only two images. A theoretical analysis of the contouring system is shown, with verification by means of numerical and experimental results.

The modulation and demodulation module of a high resolution MOEMS accelerometer

NASA Astrophysics Data System (ADS)

Jiao, Xufen; Bai, Jian; Lu, Qianbo; Lou, Shuqi

2016-02-01

A MOEMS accelerometer with high precision based on grating interferometer is demonstrated in this paper. In order to increase the signal-to-noise ratio (SNR) and accuracy, a specific modulator and an orthogonal phase-lock demodulator are proposed. Phase modulation is introduced to this accelerometer by applying a sinusoidal signal to a piezoelectric translator (PZT) amounted to the accelerometer. Phase demodulation module consists of a circuit design and a digital design. In the circuit design, the modulated light intensity signal is converted to a voltage signal and processed. In the digital part, the demodulator is mainly composed of a Band Pass Filter, two Phase-Sensitive Detectors, a phase shifter, and two Low Pass Filters based on virtual instrument. Simulation results indicate that this approach can decrease the noise greatly, and the SNR of this demodulator is 50dB and the relative error is less than 4%.

Multi-Contrast Imaging and Digital Refocusing on a Mobile Microscope with a Domed LED Array.

PubMed

Phillips, Zachary F; D'Ambrosio, Michael V; Tian, Lei; Rulison, Jared J; Patel, Hurshal S; Sadras, Nitin; Gande, Aditya V; Switz, Neil A; Fletcher, Daniel A; Waller, Laura

2015-01-01

We demonstrate the design and application of an add-on device for improving the diagnostic and research capabilities of CellScope--a low-cost, smartphone-based point-of-care microscope. We replace the single LED illumination of the original CellScope with a programmable domed LED array. By leveraging recent advances in computational illumination, this new device enables simultaneous multi-contrast imaging with brightfield, darkfield, and phase imaging modes. Further, we scan through illumination angles to capture lightfield datasets, which can be used to recover 3D intensity and phase images without any hardware changes. This digital refocusing procedure can be used for either 3D imaging or software-only focus correction, reducing the need for precise mechanical focusing during field experiments. All acquisition and processing is performed on the mobile phone and controlled through a smartphone application, making the computational microscope compact and portable. Using multiple samples and different objective magnifications, we demonstrate that the performance of our device is comparable to that of a commercial microscope. This unique device platform extends the field imaging capabilities of CellScope, opening up new clinical and research possibilities.

Multi-Contrast Imaging and Digital Refocusing on a Mobile Microscope with a Domed LED Array

PubMed Central

Phillips, Zachary F.; D'Ambrosio, Michael V.; Tian, Lei; Rulison, Jared J.; Patel, Hurshal S.; Sadras, Nitin; Gande, Aditya V.; Switz, Neil A.; Fletcher, Daniel A.; Waller, Laura

2015-01-01

We demonstrate the design and application of an add-on device for improving the diagnostic and research capabilities of CellScope—a low-cost, smartphone-based point-of-care microscope. We replace the single LED illumination of the original CellScope with a programmable domed LED array. By leveraging recent advances in computational illumination, this new device enables simultaneous multi-contrast imaging with brightfield, darkfield, and phase imaging modes. Further, we scan through illumination angles to capture lightfield datasets, which can be used to recover 3D intensity and phase images without any hardware changes. This digital refocusing procedure can be used for either 3D imaging or software-only focus correction, reducing the need for precise mechanical focusing during field experiments. All acquisition and processing is performed on the mobile phone and controlled through a smartphone application, making the computational microscope compact and portable. Using multiple samples and different objective magnifications, we demonstrate that the performance of our device is comparable to that of a commercial microscope. This unique device platform extends the field imaging capabilities of CellScope, opening up new clinical and research possibilities. PMID:25969980

Detector Apparatus and Method

NASA Technical Reports Server (NTRS)

Arndt, G. Dickey (Inventor); Ngo, Phong H. (Inventor); Carl, James R. (Inventor); Byerly, Kent A. (Inventor); Dusl, John (Inventor)

2003-01-01

Transceiver and methods are included that are especially suitable for detecting metallic materials, such as metallic mines, within an environment. The transceiver includes a digital waveform generator used to transmit a signal into the environment and a receiver that produces a digital received signal. A tracking module preferably compares an in-phase and quadrature transmitted signal with an in-phase and quadrature received signal to produce a spectral transfer function of the magnetic transceiver over a selected range of frequencies. The transceiver initially preferably creates a reference transfer function which is then stored in a memory. Subsequently measured transfer functions will vary depending on the presence of metal in the environment which was not in the environment when the reference transfer function was determined. The system may be utilized in the presence of other antennas, metal, and electronics which may comprise a plastic mine detector for detecting plastic mines. Despite the additional antennas and other metallic materials that may be in the environment due to the plastic mine detector, the magnetic transceiver remains highly sensitive to metallic material which may be located in various portions of the environment and which may be detected by sweeping the detector over ground that may contain metals or mines.

Holographic fluorescence microscopy with incoherent digital holographic adaptive optics.

PubMed

Jang, Changwon; Kim, Jonghyun; Clark, David C; Lee, Seungjae; Lee, Byoungho; Kim, Myung K

2015-01-01

Introduction of adaptive optics technology into astronomy and ophthalmology has made great contributions in these fields, allowing one to recover images blurred by atmospheric turbulence or aberrations of the eye. Similar adaptive optics improvement in microscopic imaging is also of interest to researchers using various techniques. Current technology of adaptive optics typically contains three key elements: a wavefront sensor, wavefront corrector, and controller. These hardware elements tend to be bulky, expensive, and limited in resolution, involving, for example, lenslet arrays for sensing or multiactuator deformable mirrors for correcting. We have previously introduced an alternate approach based on unique capabilities of digital holography, namely direct access to the phase profile of an optical field and the ability to numerically manipulate the phase profile. We have also demonstrated that direct access and compensation of the phase profile are possible not only with conventional coherent digital holography, but also with a new type of digital holography using incoherent light: selfinterference incoherent digital holography (SIDH). The SIDH generates a complex—i.e., amplitude plus phase—hologram from one or several interferograms acquired with incoherent light, such as LEDs, lamps, sunlight, or fluorescence. The complex point spread function can be measured using guide star illumination and it allows deterministic deconvolution of the full-field image. We present experimental demonstration of aberration compensation in holographic fluorescence microscopy using SIDH. Adaptive optics by SIDH provides new tools for improved cellular fluorescence microscopy through intact tissue layers or other types of aberrant media.

CMOS Bit-Stream Band-Pass Beamforming

DTIC Science & Technology

2016-03-31

unlimited. with direct IF sampling, most of the signal processing, including digital down-conversion ( DDC ), is carried out in the digital domain, and I/Q...level digitized signals are directly processed without decimation filtering for I/Q DDC and phase shifting. This novel BSP approach replaces bulky...positive feedback. The resonator center frequency of fs/4 (260MHz) simplifies the design of DDC . 4b tunable capacitors adjust the center frequency

Single-Event Upset Characterization of Common First- and Second-Order All-Digital Phase-Locked Loops

NASA Astrophysics Data System (ADS)

Chen, Y. P.; Massengill, L. W.; Kauppila, J. S.; Bhuva, B. L.; Holman, W. T.; Loveless, T. D.

2017-08-01

The single-event upset (SEU) vulnerability of common first- and second-order all-digital-phase-locked loops (ADPLLs) is investigated through field-programmable gate array-based fault injection experiments. SEUs in the highest order pole of the loop filter and fraction-based phase detectors (PDs) may result in the worst case error response, i.e., limit cycle errors, often requiring system restart. SEUs in integer-based linear PDs may result in loss-of-lock errors, while SEUs in bang-bang PDs only result in temporary-frequency errors. ADPLLs with the same frequency tuning range but fewer bits in the control word exhibit better overall SEU performance.

The laboratory demonstration and signal processing of the inverse synthetic aperture imaging ladar

NASA Astrophysics Data System (ADS)

Gao, Si; Zhang, ZengHui; Xu, XianWen; Yu, WenXian

2017-10-01

This paper presents a coherent inverse synthetic-aperture imaging ladar(ISAL)system to obtain high resolution images. A balanced coherent optics system in laboratory is built with binary phase coded modulation transmit waveform which is different from conventional chirp. A whole digital signal processing solution is proposed including both quality phase gradient autofocus(QPGA) algorithm and cubic phase function(CPF) algorithm. Some high-resolution well-focused ISAL images of retro-reflecting targets are shown to validate the concepts. It is shown that high resolution images can be achieved and the influences from vibrations of platform involving targets and radar can be automatically compensated by the distinctive laboratory system and digital signal process.

DIGIMEN, optical mass memory investigations, volume 2

NASA Technical Reports Server (NTRS)

1977-01-01

The DIGIMEM phase of the Optical Mass Memory Investigation Program addressed problems related to the analysis, design, and implementation of a direct digital optical recorder/reproducer. Effort was placed on developing an operational archival mass storage system to support one or more key NASA missions. The primary activity of the DIGIMEM program phase was the design, fabrication, and test and evaluation of a breadboard digital optical recorder/reproducer. Starting with technology and subsystem perfected during the HOLOMEM program phase, a fully operational optical spot recording breadboard that met or exceeded all program goals was evaluated. A thorough evaluation of several high resolution electrophotographic recording films was performed and a preliminary data base management/end user requirements survey was completed.

Influence of sample preparation and reliability of automated numerical refocusing in stain-free analysis of dissected tissues with quantitative phase digital holographic microscopy

NASA Astrophysics Data System (ADS)

Kemper, Björn; Lenz, Philipp; Bettenworth, Dominik; Krausewitz, Philipp; Domagk, Dirk; Ketelhut, Steffi

2015-05-01

Digital holographic microscopy (DHM) has been demonstrated to be a versatile tool for high resolution non-destructive quantitative phase imaging of surfaces and multi-modal minimally-invasive monitoring of living cell cultures in-vitro. DHM provides quantitative monitoring of physiological processes through functional imaging and structural analysis which, for example, gives new insight into signalling of cellular water permeability and cell morphology changes due to toxins and infections. Also the analysis of dissected tissues quantitative DHM phase contrast prospects application fields by stain-free imaging and the quantification of tissue density changes. We show that DHM allows imaging of different tissue layers with high contrast in unstained tissue sections. As the investigation of fixed samples represents a very important application field in pathology, we also analyzed the influence of the sample preparation. The retrieved data demonstrate that the quality of quantitative DHM phase images of dissected tissues depends strongly on the fixing method and common staining agents. As in DHM the reconstruction is performed numerically, multi-focus imaging is achieved from a single digital hologram. Thus, we evaluated the automated refocussing feature of DHM for application on different types of dissected tissues and revealed that on moderately stained samples highly reproducible holographic autofocussing can be achieved. Finally, it is demonstrated that alterations of the spatial refractive index distribution in murine and human tissue samples represent a reliable absolute parameter that is related of different degrees of inflammation in experimental colitis and Crohn's disease. This paves the way towards the usage of DHM in digital pathology for automated histological examinations and further studies to elucidate the translational potential of quantitative phase microscopy for the clinical management of patients, e.g., with inflammatory bowel disease.

A simple and versatile phase detector for heterodyne interferometers

NASA Astrophysics Data System (ADS)

Mlynek, A.; Faugel, H.; Eixenberger, H.; Pautasso, G.; Sellmair, G.

2017-02-01

The measurement of the relative phase of two sinusoidal electrical signals is a frequently encountered task in heterodyne interferometry, but also occurs in many other applications. Especially in interferometry, multi-radian detectors are often required, which track the temporal evolution of the phase difference and are able to register phase changes that exceed 2π. While a large variety of solutions to this problem is already known, we present an alternative approach, which pre-processes the signals with simple analog circuitry and digitizes two resulting voltages with an analog-to-digital converter (ADC), whose sampling frequency can be far below the frequency of the sinusoidal signals. Phase reconstruction is finally carried out by software. The main advantage of this approach is its simplicity, using only few low-cost hardware components and a standard 2-channel ADC with low performance requirements. We present an application on the two-color interferometer of the ASDEX Upgrade tokamak, where the relative phase of 40 MHz sinusoids is measured.

Determination of torque speed current characteristics of a brushless DC motor by utilizing back-EMF of non-energized phase

NASA Astrophysics Data System (ADS)

Jang, G. H.; Yeom, J. H.; Kim, M. G.

2007-03-01

This paper presents a method to determine the torque constant and the torque-speed-current characteristics of a brushless DC (BLDC) motor by utilizing back-EMF variation of nonenergized phase. It also develops a BLDC motor controller with a digital signal processor (DSP) to monitor its current, voltage and speed in real time. Torque-speed-current characteristics of a BLDC motor are determined by using the proposed method and the developed controller. They are compared with the torque-speed-current characteristics measured by dynamometer experimentally. This research shows that the proposed method is an effective method to determine the torque constant and the torque-speed-current characteristics of the BLDC motor without using dynamometer.

Detection of interference phase by digital computation of quadrature signals in homodyne laser interferometry.

PubMed

Rerucha, Simon; Buchta, Zdenek; Sarbort, Martin; Lazar, Josef; Cip, Ondrej

2012-10-19

We have proposed an approach to the interference phase extraction in the homodyne laser interferometry. The method employs a series of computational steps to reconstruct the signals for quadrature detection from an interference signal from a non-polarising interferometer sampled by a simple photodetector. The complexity trade-off is the use of laser beam with frequency modulation capability. It is analytically derived and its validity and performance is experimentally verified. The method has proven to be a feasible alternative for the traditional homodyne detection since it performs with comparable accuracy, especially where the optical setup complexity is principal issue and the modulation of laser beam is not a heavy burden (e.g., in multi-axis sensor or laser diode based systems).

Digitally grown AlInAsSb for high gain separate absorption, grading, charge, and multiplication avalanche photodiodes

NASA Astrophysics Data System (ADS)

Lyu, Yuexi; Han, Xi; Sun, Yaoyao; Jiang, Zhi; Guo, Chunyan; Xiang, Wei; Dong, Yinan; Cui, Jie; Yao, Yuan; Jiang, Dongwei; Wang, Guowei; Xu, Yingqiang; Niu, Zhichuan

2018-01-01

We report on the growth of high quality GaSb-based AlInAsSb quaternary alloy by molecular beam epitaxy (MBE) to fabricate avalanche photodiodes (APDs). By means of high resolution X-ray diffraction (HRXRD) and scanning transmission electron microscope (STEM), phase separation phenomenon of AlInAsSb random alloy with naturally occurring vertical superlattice configuration was demonstrated. To overcome the tendency for phase segregation while maintaining a highly crystalline film, a digital alloy technique with migration-enhanced epitaxy growth method was employed, using a shutter sequence of AlSb, AlAs, AlSb, Sb, In, InAs, In, Sb. AlInAsSb digital alloy has proved to be reproducible and consistent with single phase, showing sharp satellite peaks on HRXRD rocking curve and smooth surface morphology under atomic force microscopy (AFM). Using optimized digital alloy, AlInAsSb separate absorption, grading, charge, and multiplication (SAGCM) APD was grown and fabricated. At room temperature, the device showed high performance with low dark current density of ∼14.1 mA/cm2 at 95% breakdown and maximum stable gain before breakdown as high as ∼200, showing the potential for further applications in optoelectronic devices.

Vibration measurement by temporal Fourier analyses of a digital hologram sequence.

PubMed

Fu, Yu; Pedrini, Giancarlo; Osten, Wolfgang

2007-08-10

A method for whole-field noncontact measurement of displacement, velocity, and acceleration of a vibrating object based on image-plane digital holography is presented. A series of digital holograms of a vibrating object are captured by use of a high-speed CCD camera. The result of the reconstruction is a three-dimensional complex-valued matrix with noise. We apply Fourier analysis and windowed Fourier analysis in both the spatial and the temporal domains to extract the displacement, the velocity, and the acceleration. The instantaneous displacement is obtained by temporal unwrapping of the filtered phase map, whereas the velocity and acceleration are evaluated by Fourier analysis and by windowed Fourier analysis along the time axis. The combination of digital holography and temporal Fourier analyses allows for evaluation of the vibration, without a phase ambiguity problem, and smooth spatial distribution of instantaneous displacement, velocity, and acceleration of each instant are obtained. The comparison of Fourier analysis and windowed Fourier analysis in velocity and acceleration measurements is also presented.