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1

Generating nonlinear FM chirp waveforms for radar.  

SciTech Connect

Nonlinear FM waveforms offer a radar matched filter output with inherently low range sidelobes. This yields a 1-2 dB advantage in Signal-to-Noise Ratio over the output of a Linear FM waveform with equivalent sidelobe filtering. This report presents design and implementation techniques for Nonlinear FM waveforms.

Doerry, Armin Walter

2006-09-01

2

SAR processing with non-linear FM chirp waveforms.  

SciTech Connect

Nonlinear FM (NLFM) waveforms offer a radar matched filter output with inherently low range sidelobes. This yields a 1-2 dB advantage in Signal-to-Noise Ratio over the output of a Linear FM (LFM) waveform with equivalent sidelobe filtering. This report presents details of processing NLFM waveforms in both range and Doppler dimensions, with special emphasis on compensating intra-pulse Doppler, often cited as a weakness of NLFM waveforms.

Doerry, Armin Walter

2006-12-01

3

Linear fm chirp laser  

SciTech Connect

The method is described of operating a laser radar system comprising the steps of: actuating a transmitter laser to emit laser light at approximately a preselected center frequency; frequency modulating the light of the transmitter laser in linear chirps by passing it through an electro-optical crystal disposed within the cavity of the transmitter and driving the crystal with linear chirp drive signal from a precision linear driver; and actuating a local oscillator laser to emit laser light at a predetermined frequency offset from the center frequency by a frequency substantially greater than the maximum frequency shift of the transmitter laser.

Duvall, R.L.; Halmos, M.J.; Henderson, D.M.

1987-05-19

4

Linear FM chirp laser  

SciTech Connect

The method is described of operating a laser radar system comprising: actuating a transmitter laser and a local oscillator laser to emit laser light at approximately a preselected common base frequency; frequency modulating the light of the transmitter laser in linear chirps by passing it through an electro-optical crystal disposed within the cavity of the transmitter and driving crystal with a linear chirp drive signal from a precision linear driver; sensing a portion of the laser light from the transmitter laser and the local oscillator laser to determine the base frequency thereof and adjusting the piezoelectric translators of the two lasers as a function of the sensed portion to maintain the lasers emitting at exactly the preselected base frequency; and using the balance of the light from the transmitter laser as the transmitted laser beam.

Duvall, R.L. III; Halmos, M.J.; Henderson, D.M.

1987-05-05

5

Continuously tunable chirped microwave waveform generation using an optically pumped linear chirped fiber Bragg grating  

Microsoft Academic Search

A novel approach to generat ing a chirped microwave waveform with continuously tunable chirp rate using an optically pumped linearly chirped fiber Bragg grating (LCFBG) based on a temporal interferometer is proposed and demonstrated. A theoretical analys is is performed which is verified by an experiment. A linearly chirped microwave waveform with a tunable chirp rate from 79 to 64

Ming Li; Weilin Liu; Jianping Yao

2011-01-01

6

Pulse compression of an FM chirped CO sub 2 Laser  

SciTech Connect

A CO{sub 2} laser has been FM chirp modulated by a CdTe intracavity modulator. A frequency deviation-of-100 MHz in 2 {mu}s was attained in this fashion. Following heterodyne detection the chirped pulse was compressed to 15 ns using a surface acoustic wave compression filter. This corresponded to a compression factor of 130. The suppression of unwanted sidelobes with a weighting filter was demonstrated. We have explored the use of this technique for laser radar systems and described an electrooptically FM modulated CO{sub 2} waveguide laser with postdetection pulse compression by a surface acoustic wave compressive filter. To our knowledge this is the first report of the successful operation of this important system.

Halmos, M.J.; Henderson, D.M.; Duvall, R.,III (Hughes Aircraft Company, Laser Sensors Laboratories, Tactical Engineering Division, Electro-Optical Data Systems Group, P.O. Box 902, El Segundo, California 90245 (US))

1989-09-01

7

Optical linear sideband chirp compression for microwave arbitrary waveform generation  

Microsoft Academic Search

A novel approach for the practical implementation of photonic arbitrary waveform generation of microwave signals is explored. Here we describe and demonstrate linear sideband chirp compression over 1 GHz bandwidth with a compression factor of >4000.

Randy R. Reibel; Tiejun Chang; Mingzhen Tian; W. Randall Babbitt

2004-01-01

8

Photonic generation of microwave waveforms with wide chirp tuning range  

NASA Astrophysics Data System (ADS)

We show analytically as well as demonstrate experimentally an approach to generate microwave waveforms with wide chirp tuning range. The approach is based on the interference of two temporally-stretched pulses which are time-delayed with respect to each other and having different frequency chirp. This approach is realized by an unbalanced Mach Zehnder Interferometer (MZI) incorporating a linearly-chirped fiber-Bragg-grating (LCFBG) whose group-delay-dispersion (GDD) can be tuned across a wide range. In general, tuning the GDD of the LCFBG changes the chirp rate of the generated microwave waveform and tuning the relative time-delay between the interferometer arms changes the center frequency of the generated microwave waveform. Balanced photodetection is also implemented to obtain DC-free microwave waveforms. Based on this approach, we demonstrate the generation of microwave waveforms with different center frequencies and with the chirp rates ranging from˜-126.7 GHz/ns to ˜+120.8 GHz/ns, including the zero-chirp case.

Wong, Jia Haur; Liu, Huan Huan; Lam, Huy Quoc; Aditya, Sheel; Zhou, Junqiang; Lim, Peng Huei; Lee, Kenneth Eng Kian; Wu, Kan; Chow, Kin Kee; Shum, Perry Ping

2013-09-01

9

Tilted Fiber Bragg Grating for Chirped Microwave Waveform Generation  

Microsoft Academic Search

At iltedfiber Bragg grating (TFBG) as an optical spectral shaper to generate a chirped microwave waveform in a spectral-shaping and wavelength-to-time (SS-WTT) mapping system is proposed and demonstrated. The key component in the system is the TFBG, which has multiple resonant peaks with linearly increasing spacing in its transmission spectrum. By incor- porating aT FBG into an SS-WTT system, ac

Ming Li; Li-Yang Shao; Jacques Albert; Jianping Yao

2011-01-01

10

High Resolution Pulse Compression Imaging Using Super Resolution FM-Chirp Correlation Method (SCM)  

NASA Astrophysics Data System (ADS)

This study addresses the issue of the super-resolution pulse compression technique (PCT) for ultrasound imaging. Time resolution of multiple ultrasonic echoes using the FM-Chirp PCT is limited by the bandwidth of the sweep-frequency. That is, the resolution depends on the sharpness of auto-correlation function. We propose the Super resolution FM-Chirp correlation Method (SCM) and evaluate its performance. This method is based on the multiple signal classification (MUSIC) algorithm. Our simulations were made for the model assuming multiple signals reflected from some scatterers. We confirmed that SCM detects time delay of complicated reflected signals successfully with high resolution.

Fujiwara, M.; Okubo, K.; Tagawa, N.

11

Generating nonlinear FM chirp radar signals by multiple integrations  

DOEpatents

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.

Doerry, Armin W. (Albuquerque, NM) [Albuquerque, NM

2011-02-01

12

Photonic Generation of Continuously Tunable Chirped Microwave Waveforms Based on a Temporal Interferometer Incorporating an Optically Pumped Linearly Chirped Fiber Bragg Grating  

Microsoft Academic Search

A novel approach to generating a chirped microwave waveform with continuously tunable chirp rate based on a temporal interferometer incorporating an optically pumped linearly chirped fiber Bragg grating (LCFBG) is proposed and demonstrated. The temporal interferometer is realized using a Mach–Zehnder interferometer (MZI) that incorporates an LCFBG and a dispersion compensating fiber to generate a temporal interference pattern with an

Ming Li; Jianping Yao

2011-01-01

13

An Unbalanced Temporal Pulse-Shaping System for Chirped Microwave Waveform Generation  

Microsoft Academic Search

An unbalanced temporal pulse-shaping (TPS) system for chirped microwave waveform generation is proposed and demonstrated. The proposed system consists of an ultrashort pulsed source, a Mach-Zehnder modulator and two dispersive elements. The dispersions of the two dispersive elements are opposite in sign, but not identical in magnitude. The entire system is equivalent to a conventional balanced TPS system with two

Ming Li; Chao Wang; Wangzhe Li; Jianping Yao

2010-01-01

14

Analysis of a digital chirp synthesizer  

SciTech Connect

Definite advantages are gained by using a chirp (linear-FM) waveform for radar pulse compression. Digital generation of this waveform provides programmability, predictability, and repeatability. Of the digital implementations considered, the digital chirp synthesizer is shown to have the most flexibility and is more readily miniaturized than the arbitrary waveform generator design. Elements and features of the digital chirp synthesizer are examined and design considerations are presented. A TTL breadboard circuit that was built demonstrates the soundness of the fundamental design of the digital chirp synthesizer concept. 10 refs., 18 figs., 10 tabs.

Allen, C.T.

1988-08-01

15

Complex, aperiodic random signal modulation on pulse-LFM chirp radar waveform  

NASA Astrophysics Data System (ADS)

In an effort to enhance the security of radar, the plausibility of using a complex, aperiodic random signal to modulate a pulse linear frequency modulation (LFM) or "chirp" radar waveform across both its fast-time and slow-time samples is investigated. A non-conventional threat is considered when illustrating the effectiveness of the proposed waveform as an electronic counter-countermeasure (ECCM). Results are derived using stretch processing and are assessed using the receiver cross-correlation function with a consideration for the unmodulated case as a basis for comparison. A tailored radar ambiguity function is also included in the analysis, and is used to demonstrate how the proposed waveform possesses an ideal characteristic suitable for combating today's electronic warfare (EW) threats while preserving its inherent functionality to detect targets.

Govoni, Mark A.; Li, Hongbin

2010-04-01

16

Ultrafast chirped optical waveform recorder using referenced heterodyning and a time microscope  

DOEpatents

A new technique for capturing both the amplitude and phase of an optical waveform is presented. This technique can capture signals with many THz of bandwidths in a single shot (e.g., temporal resolution of about 44 fs), or be operated repetitively at a high rate. That is, each temporal window (or frame) is captured single shot, in real time, but the process may be run repeatedly or single-shot. This invention expands upon previous work in temporal imaging by adding heterodyning, which can be self-referenced for improved precision and stability, to convert frequency chirp (the second derivative of phase with respect to time) into a time varying intensity modulation. By also including a variety of possible demultiplexing techniques, this process is scalable to recoding continuous signals.

Bennett, Corey Vincent (Livermore, CA)

2011-11-22

17

An arbitrary waveform generator based chirped pulse Fourier transform spectrometer operating from 260 to 295 GHz  

NASA Astrophysics Data System (ADS)

The performance of a chirped-pulse Fourier transform millimeter-wave spectrometer operating from 260 to 295 GHz is described. The spectrometer uses a high-speed arbitrary waveform generator (AWG) to create both a chirped excitation pulse and the single-frequency local oscillator (LO) used for the final down conversion detection stage. The mm-wave excitation source is an active multiplier chain (factor of 24 frequency multiplication) with power output of greater than 10 mW across the 260-295 GHz frequency range. The LO, produced by a separate active multiplier chain (factor of 12 frequency multiplication), drives a subharmonic mixer which downconverts the molecular emission to the microwave region for digitization on a 100 GS/s digital oscilloscope. All frequency sources in the experiment are locked to a 10 MHz Rb-disciplined oscillator providing direct frequency calibration for molecular transitions in the Fourier transform frequency-domain spectrum. Benchmark measurements are presented on ethyl cyanide and 1-butyne and are used to illustrate advantages and tradeoffs compared with direct absorption millimeter-wave spectroscopy.

Steber, Amanda L.; Harris, Brent J.; Neill, Justin L.; Pate, Brooks H.

2012-10-01

18

Continuously Tunable Chirped Microwave Waveform Generation Using a Tilted Fiber Bragg Grating Written in an Erbium\\/Ytterbium Codoped Fiber  

Microsoft Academic Search

An optical approach to generating continuously tunable chirped microwave waveforms using a tilted fiber Bragg grating (TFBG) written in an erbium\\/ytterbium (Er\\/Yb) codoped fiber is proposed. By pumping the TFBG, the magnitude and group delay responses of the cladding mode resonances are changed, which can be used to implement a photonic microwave delay-line filter with increasing or decreasing tap spacing.

Hiva Shahoei; Jianping Yao

2012-01-01

19

Dependence on chirp rate and spectral resolution of the terahertz field pulse waveform measured by electro-optic detection using a chirped optical pulse and a spectrometer and its effect on terahertz spectroscopy  

NASA Astrophysics Data System (ADS)

Single-shot measurement of a terahertz field pulse waveform by electro-optic sampling using a chirped optical pulse and a spectrometer was demonstrated by and Jiang and Zhang [Appl. Phys. Lett. 72, 1945 (1998)]. We have performed an experimental and theoretical investigation into the dependence of the waveform thus measured on the chirp rate and spectral resolution. It was found that the waveform exhibits multicyclic behavior at a chirp rate of -0.24 THz2, which corresponds to a chirped-pulse width of over 10 ps, for the monocyclic original terahertz field, while it approaches the monocyclic behavior with decreasing pulse width. Further, broadening of the spectral resolution of the spectrometer gives rise to a monocyclic waveform in the chirp rate range where the waveform is expected to be multicyclic. In addition, we have derived an analytical expression for the terahertz field pulse waveform thus measured without using the method of stationary phase. The theoretical results were found to be consistent with measured ones. Finally, we examined the spectral bandwidth and resolution of terahertz spectroscopy using this method.

Murakami, H.; Shimizu, K.; Katsurada, M.; Nashima, S.

2008-11-01

20

Error analysis of the chirp-z transform when implemented using waveform synthesizers and FFTs.  

National Technical Information Service (NTIS)

This report analyzes the effects of finite-precision arithmetic on discrete Fourier transforms (DFTs) calculated using the chirp-z transform algorithm. An introduction to the chirp-z transform is given together with a description of how the chirp-z transf...

T. P. Bielek

1990-01-01

21

Waveform error analysis for bistatic synthetic aperture radar systems  

Microsoft Academic Search

The signal phase histories at the transmitter, receiver, and radar signal processor in bistatic SAR systems are described. The fundamental problem of mismatches in the waveform generators for the illuminating and receiving radar systems is analyzed. The effects of errors in carrier frequency and chirp slope are analyzed for bistatic radar systems which use linear FM waveforms. It is shown

J. W. Adams; T. M. Schifani

1987-01-01

22

Effect of chirping-induced waveform distortion on the performance of direct detection receivers using traveling-wave semiconductor optical preamplifiers  

Microsoft Academic Search

The influence of chirping-induced waveform distortion on the performance of multigigabit-per-second traveling-wave semiconductor optical amplifier (TWSOA)\\/p-i-n direct detection receivers is evaluated. The results are based on a novel method of evaluating the probability of error in the presence of the signal-spontaneous and spontaneous-spontaneous beat noise components. Laser chirping causes the dependence of the receiver sensitivity on the fiber dispersion coefficient×length

John C. Cartledge; Aly F. Elrefaie

1991-01-01

23

Maximum-likelihood estimation of range, velocity, and acceleration using a linear FM train radar waveform  

Microsoft Academic Search

An efficient implementation of the maximum likelihood estimator (MLE) is presented for the estimation of target range, radial velocity and acceleration when the radar waveform consists of a wideband linear frequency modulated (LFM) pulse train. Analytic properties of the associated wideband ambiguity function are derived; in particular the ambiguity function, with acceleration set to zero, is derived in closed form.

Theagenis J. Abatzoglou; Gregory O. Gheen

1997-01-01

24

Analytic signal demodulation of phase-modulated frequency-chirped signals.  

PubMed

Both interferometers and frequency-modulated (FM) radios create sinusoidal signals with phase information that must be recovered. Often these two applications use narrow band signals but some applications create signals with a large bandwidth. For example, accelerated mirrors in an interferometer naturally create a chirped frequency that linearly increases with time. Chirped carriers are also used for spread-spectrum, FM transmission to reduce interference or avoid detection. In both applications, it is important to recover the underlying phase modulations that are superimposed on the chirped carrier. A common way to treat a chirped waveform is to fit zero crossings of the signal. For lower signal-to-noise applications, however, it is helpful to have a technique that utilizes data over the entire waveform (not just at zero crossings). We present a technique called analytic signal demodulation (ASD), which employs a complex heterodyne of the analytic signal to fully demodulate the chirped waveform. ASD has a much higher sensitivity for recovering phase information than is possible using a chirp demodulation on the raw data. This paper introduces a phase residual function, R(?), that forms an analytic signal and provides a complex demodulation from the received signal in one step. The function defines a phase residual at each point on the chirped waveform, not just at the zero crossings. ASD allows sensitive detection of phase-modulated signals with a very small modulation index (much less than 0.01) that would otherwise be swamped by noise if the raw signal were complex demodulated. The mathematics used to analyze a phase-modulated chirped signal is quite general and can easily be extended for frequency profiles more complicated than a simple chirp. PMID:23518726

Niebauer, T M

2013-03-20

25

SAR Impulse Response with Residual Chirps.  

National Technical Information Service (NTIS)

A residual chirp waveform is a quadratic phase error that broadens the Impulse Response (IPR) and diminishes its peak value in a predictable manner. This report qualitatively and quantitatively analyzes the effects of a residual chirp on the IPR. .

A. W. Doerry

2009-01-01

26

Chirped microwave pulse generation using a tilted fiber Bragg grating  

Microsoft Academic Search

A technique to generate a chirped microwave waveform based on spectral-shaping and wavelength-to-time-mapping using a tilted fiber Bragg grating (TFBG) is proposed. A 24.21-GHz chirped microwave pulse with a chirp-rate of 0.0070 GHz\\/ps is generated.

Ming Li; Liyang Shao; Jacques Albert; Jianping Yao

2010-01-01

27

A Programmable Radar Pulse Compression Filter Utilizing Chirp Transform Correlation  

Microsoft Academic Search

A programmable matched Elter for pulse compression of large TB product chirp radar waveforms is described. This Elter is based on SAW chirp transform correlation, CTC. Pulse compression is achieved through cross- correlation of the radar return with a reference waveform. Correlation processing is superior to conventional SAW matched filtering in three ways. First, a single processor is capable of

H. M. Gerard; O. W. Otto

1976-01-01

28

Transmission performance of chirp-controlled signal by using semiconductor optical amplifier  

Microsoft Academic Search

We examine the fiber transmission performance of the optical signal whose chirp is controlled by utilizing phase modulation in semiconductor optical amplifier (SOA) with both simulations and experiments. This chirp control technique converts a positive chirp created by electroabsorption (EA) modulator into negative chirp, which reduces the waveform degradation due to the chromatic dispersion in transmission over standard single-mode fiber

Toshio Watanabe; Norio Sakaida; Hiroshi Yasaka; Fumiyoshi Kano; Masafumi Koga

2000-01-01

29

SAR impulse response with residual chirps.  

SciTech Connect

A Linear Frequency-Modulated (LFM) chirp is a function with unit amplitude and quadratic phase characteristic. In a focused Synthetic Aperture Radar (SAR) image, a residual chirp is undesired for targets of interest, as it coarsens the manifested resolution. However, for undesired spurious signals, a residual chirp is often advantageous because it spreads the energy and thereby diminishes its peak value. In either case, a good understanding of the effects of a residual LFM chirp on a SAR Impulse Response (IPR) is required to facilitate system analysis and design. This report presents an analysis of the effects of a residual chirp on the IPR. As reference, there is a rich body of publications on various aspects of LFM chirps. A quick search reveals a plethora of articles, going back to the early 1950s. We mention here purely as trivia one of the earlier analysis papers on this waveform by Klauder, et al.

Doerry, Armin Walter

2009-06-01

30

Coherent lidar imaging of dust clouds: waveform comparison with the poly-phase (P4) modulation waveform  

NASA Astrophysics Data System (ADS)

A dust or aerosol cloud represents a convenient target to examine the capabilities of range-resolved Doppler and intensity (RRDI) or inverse synthetic aperture ladar (ISAR) imaging coherent laser radar, known as coherent "lidar" for optically thin targets. The poly-phase P4 ladar waveform and its RRDI images are described and compared with previous pulse-burst, linear-FM chirp pulse-compression, pseudo-random phase modulation waveforms, and several other waveforms which have not been utilized to date. A "dust cloud" has very many independently moving point scatterers with velocities that are approximately Gaussian randomly distributed in x,y,z with standard deviations of about 10% of the mean wind + aerosol velocity. This is contrary to a hard-target where the point scatterers are rigidly attached and moving together. The dust cloud produced speckle effects for the various ladar waveforms are compared. In addition, a reference set of four corner-cube retro-reflectors within the dust cloud further illustrates the differences in the various waveform capabilities and resolution.

Youmans, Douglas G.

2008-05-01

31

Analysis and Emulation of FM Radio Signals for Passive Radar  

Microsoft Academic Search

Due to its high power levels provided, and its wide coverage, FM radio could be a good opportunity transmitter for passive coherent location (PCL) radar systems. In this paper we study the effectiveness of FM signals as radar waveforms by means of simulated and real data analysis. To this purpose, an emulation of FM radio transmitter is presented, whose outputs

A. Lauri; F. Colone; R. Cardinali; C. Bongioanni; P. Lombardo

2007-01-01

32

A chirp scaling approach for processing squint mode SAR data  

Microsoft Academic Search

Image formation from squint mode synthetic aperture radar (SAR) is limited by image degradations caused by neglecting the range-variant filtering required by secondary range compression (SRC). Introduced here is a nonlinear FM chirp scaling, an extension of the chirp scaling algorithm, as an efficient and accurate approach to range variant SRC. Two methods of implementing the approach are described. The

G. W. Davidson; I. G. Cumming; M. R. Ito

1996-01-01

33

A stepped chirp technique for range resolution enhancement  

Microsoft Academic Search

A novel stepped frequency chirp waveform concept for increasing the range resolution of an existing pulse compression radar is presented. The stepped frequency chirp technique is ideally suited to obtaining high range resolution in a radar system that has a limited instantaneous bandwidth, but a large tunable bandwidth. To achieve high range resolution using these given bandwidths, two or more

F. McGroary; K. Lindell

1991-01-01

34

Intrinsic chirp of single-cycle pulses  

SciTech Connect

The Fourier transform-limited electromagnetic pulse has been regarded to be free of chirps for a long time. This is no longer true if the pulse duration goes down to or less than one optical cycle. We report the experimental observation of intrinsic chirps in such pulses with the sub-single-cycle terahertz (THz) waveforms obtained with a standard THz time-domain spectroscopy system. The results confirm the break down of the carrier-envelope (CE) expression for single-cycle optical pulses, and may influence the experimental measurements and theoretical modeling with single-cycle pulses.

Lin Qiang; Zheng Jian [Institute of Optics, Department of Physics, Zhejiang University, Hangzhou 310027 (China); Dai Jianming; Ho, I-Chen; Zhang, X.-C. [Center for Terahertz Research, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

2010-04-15

35

Effect of Fresnel ripples on sidelobe suppression in low time-bandwidth production linear FM pulse compression  

NASA Astrophysics Data System (ADS)

The paper discusses the effects of Fresnel ripples on the suppression of peak time sidelobes in low time-bandwidth (TB) product linear-FM pulse compression systems employing internally Hamming weighted compression filters. Two methods for the reduction of these effects are investigated. The first, amplitude tapering of the rectangular FM pulse, yields significantly diminished sidelobes for TB products less than about 100 and is of particular interest for spectrum analysis. The second, applicable to short risetime high-power radar transmitters, is cubic phase predistortion of the rectangular transmitted pulse. This procedure is found to be very effective for TB products less than about 50 (e.g. about 10 dB improvement for TB equals 10 compared with usual chirp). Both techniques force the fall-off of far sidelobes. Computed results on the achievable sidelobe suppression are presented as a function of the TB product and compared with conventional Hamming weighting. Finally, it is shown that the superior Doppler performance of linear FM is not affected by the discussed waveform modifications.

Kowatsch, M.; Stocker, H. R.

1982-02-01

36

Waveform for Short-Dwell-Time Meteorological Doppler Radars.  

National Technical Information Service (NTIS)

A modulation waveform for meteorological Doppler radars that obtain estimates of radar reflectivity, mean velocity, and Doppler width with very short dwell time is described. The transmitted signal is a sequence of three identical chirp pulses; signal par...

R. G. Strauch

1987-01-01

37

Photonic generation of microwave arbitrary waveforms  

Microsoft Academic Search

In this paper, techniques to generate microwave arbitrary waveforms based on all-fiber solutions are reviewed, with an emphasis on the system architectures based on direct space-to-time pulse shaping, spectral-shaping and wavelength-to-time mapping, temporal pulse shaping, and photonic microwave delay-line filtering. The generation of phase-coded and frequency-chirped microwave waveforms is discussed. The challenges in the implementation of the systems for practical

Jianping Yao

2011-01-01

38

Waveform Libraries  

Microsoft Academic Search

Our goal was to provide an overview of a circle of emerging ideas in the area of waveform scheduling for active radar. Principled scheduling of waveforms in radar and other active sensing modalities is motivated by the nonexistence of any single waveform that is ideal for all situations encountered in typical operational scenarios. This raises the possibility of achieving operationally

D. Cochran; S. Suvorova; S. Howard; B. Moran

2009-01-01

39

Reconfigurability and tunability of a chirped microwave photonic pulse generator  

Microsoft Academic Search

We propose and demonstrate a microwave chirped pulse generator which is based on the effects of the dispersion slope over the propagation of an optical broadband signal. A complete reconfigurability of the generated signal waveform is easily achieved by a suitable adjustment of the optical source power distribution profile. Moreover, large frequency tuning range and TBWP control of the pulse

M. Bolea; J. Mora; B. Ortega; J. Capmany

2010-01-01

40

UTILIZING A CHIRP SONAR TO ACCURATELY CHARACTERIZE NEWLY DEPOSITED MATERIAL AT THE CALCASIEU OCEAN DREDGED MATERIAL DISPOSAL SITE, LOUISIANA  

EPA Science Inventory

The distribution of dredged sediments is measured at the Calcasieu Ocean Dredged Material Disposal Site (ODMDS) using a chirp sonar immediately after disposal and two months later. ubbottom reflection data, generated by a chirp sonar transmitting a 4 to 20 kHz FM sweep, is proces...

41

Complex heterodyne for undersampled chirped sinusoidal signals  

NASA Astrophysics Data System (ADS)

We describe a method for analyzing frequency-chirped sinusoidal signals using a complex heterodyne, sometimes also known as complex demodulation on the digitized waveform. This method allows one to use prior knowledge of the signal to reduce the effective bandwidth of the signal. The method can be used to extract a frequency-chirped signal even when it is sampled well below the Nyquist criterion. Accordingly, the method facilitates the use of less-expensive data acquisition and signal processing hardware than has traditionally been used for these applications. This technique is particularly useful for high-precision (parts in 109) interferometer applications in which there exists a differential acceleration between the two arms (commonly found in absolute gravity meters or gradiometers).

Niebauer, T. M.; Schiel, A.; van Westrum, D.

2006-11-01

42

Complex heterodyne for undersampled chirped sinusoidal signals.  

PubMed

We describe a method for analyzing frequency-chirped sinusoidal signals using a complex heterodyne, sometimes also known as complex demodulation on the digitized waveform. This method allows one to use prior knowledge of the signal to reduce the effective bandwidth of the signal. The method can be used to extract a frequency-chirped signal even when it is sampled well below the Nyquist criterion. Accordingly, the method facilitates the use of less-expensive data acquisition and signal processing hardware than has traditionally been used for these applications. This technique is particularly useful for high-precision (parts in 10(9)) interferometer applications in which there exists a differential acceleration between the two arms (commonly found in absolute gravity meters or gradiometers). PMID:17068577

Niebauer, T M; Schiel, A; van Westrum, D

2006-11-10

43

Phase-locking and coherent power combining of broadband linearly chirped optical waves.  

PubMed

We propose, analyze and demonstrate the optoelectronic phase-locking of optical waves whose frequencies are chirped continuously and rapidly with time. The optical waves are derived from a common optoelectronic swept-frequency laser based on a semiconductor laser in a negative feedback loop, with a precisely linear frequency chirp of 400 GHz in 2 ms. In contrast to monochromatic waves, a differential delay between two linearly chirped optical waves results in a mutual frequency difference, and an acoustooptic frequency shifter is therefore used to phase-lock the two waves. We demonstrate and characterize homodyne and heterodyne optical phase-locked loops with rapidly chirped waves, and show the ability to precisely control the phase of the chirped optical waveform using a digital electronic oscillator. A loop bandwidth of ~ 60 kHz, and a residual phase error variance of < 0.01 rad(2) between the chirped waves is obtained. Further, we demonstrate the simultaneous phase-locking of two optical paths to a common master waveform, and the ability to electronically control the resultant two-element optical phased array. The results of this work enable coherent power combining of high-power fiber amplifiers-where a rapidly chirping seed laser reduces stimulated Brillouin scattering-and electronic beam steering of chirped optical waves. PMID:23187338

Satyan, Naresh; Vasilyev, Arseny; Rakuljic, George; White, Jeffrey O; Yariv, Amnon

2012-11-01

44

Waveform Analysis.  

National Technical Information Service (NTIS)

The report consists of one chapter and three appendices. The purpose of this study was to determine whether the techniques of waveform analysis described in Appendix I are effective in detecting and segmenting for classification events of interest to USL....

H. L. Resnikoff W. E. Houchin J. L. Dolby H. Chernoff

1969-01-01

45

Coded multiple chirp spread spectrum system and overlay service  

NASA Technical Reports Server (NTRS)

An asynchronous spread-spectrum system called coded multiple chirp is proposed, and the possible spread-spectrum overlay over an analog FM-TV signal is investigated by computer simulation. Multiple single-sloped up and down chirps are encoded by a pseudonoise code and decoded by dechirpers (pulse-compression filters) followed by a digital code correlator. The performance of the proposed system, expressed in terms of in probability of bit error and code miss probability, is similar to that of FSK (frequency shift keying) using codewords if sufficient compression gain is used. When chirp is used to overlay an FM-TV channel, two chirp signals with data rate up to 25 kb/s could be overlaid in a 36-MHz satellite transponder without significant mutual interference. Performance estimates for a VSAT (very small aperture terminal) earth station operating at C-band show that a 2.4-m antenna and 300-mW transmitter could send a 2.4-kb/s signal to a large central earth station over an occupied channel.

Kim, Junghwan; Pratt, Timothy; Ha, Tri T.

1988-01-01

46

a KA-BAND Chirped-Pulse Fourier Transform Microwave Spectrometer  

Microsoft Academic Search

The design and performance of a new chirped-pulse Fourier transform microwave (CP-FTMW) spectrometer operating from 25-40 GHz will be discussed. A 10.5-3 GHz linear frequency sweep, generated by a 24 GS\\/s arbitrary waveform generator, is upconverted by a 23.00 GHz phase-locked oscillator, then fed into an active doubler to create a 25-40 GHz chirped pulse. After amplification with a 60-80

Daniel P. Zaleski; Justin L. Neill; Matthew T. Muckle; Brooks H. Pate; P. Brandon Carroll; Susanna L. Widicus Weaver

2010-01-01

47

The IT Vision in FM.  

ERIC Educational Resources Information Center

Provides a forward-looking vision, including goals, objectives, and principles, of information technology (IT) use within facilities management (FM). This vision includes the evolution of the FM/IT organization from an operational role to a strategic role--from an FM divisional role to an enterprise role. (EV)

NeSmith, Jerry

2002-01-01

48

Carrier Modulation Via Waveform Probability Density Function  

NASA Technical Reports Server (NTRS)

Beyond the classic modes of carrier modulation by varying amplitude (AM), phase (PM), or frequency (FM), we extend the modulation domain of an analog carrier signal to include a class of general modulations which are distinguished by their probability density function histogram. Separate waveform states are easily created by varying the pdf of the transmitted waveform. Individual waveform states are assignable as proxies for digital one's or zero's. At the receiver, these states are easily detected by accumulating sampled waveform statistics and performing periodic pattern matching, correlation, or statistical filtering. No fundamental physical laws are broken in the detection process. We show how a typical modulation scheme would work in the digital domain and suggest how to build an analog version. We propose that clever variations of the modulating waveform (and thus the histogram) can provide simple steganographic encoding.

Williams, Glenn L.

2006-01-01

49

Carrier Modulation Via Waveform Probability Density Function  

NASA Technical Reports Server (NTRS)

Beyond the classic modes of carrier modulation by varying amplitude (AM), phase (PM), or frequency (FM), we extend the modulation domain of an analog carrier signal to include a class of general modulations which are distinguished by their probability density function histogram. Separate waveform states are easily created by varying the pdf of the transmitted waveform. Individual waveform states are assignable as proxies for digital ONEs or ZEROs. At the receiver, these states are easily detected by accumulating sampled waveform statistics and performing periodic pattern matching, correlation, or statistical filtering. No fundamental natural laws are broken in the detection process. We show how a typical modulation scheme would work in the digital domain and suggest how to build an analog version. We propose that clever variations of the modulating waveform (and thus the histogram) can provide simple steganographic encoding.

Williams, Glenn L.

2004-01-01

50

Chirped Attosecond Photoelectron Spectroscopy  

SciTech Connect

We study analytically the photoionization of a coherent superposition of electronic states and show that chirped pulses can measure attosecond time scale electron dynamics just as effectively as transform-limited attosecond pulses of the same bandwidth. The chirped pulse with a frequency-dependent phase creates the interfering photoelectron amplitudes that measure the electron dynamics. We show that at a given pump-probe time delay the differential asymmetry oscillates as a function of photoelectron energy. Our results suggest that the important parameter for attosecond science is not the pulse duration, but the bandwidth of phased radiation.

Yudin, G.L. [Laboratoire de Chimie Theorique, Universite de Sherbrooke, Sherbrooke, Quebec J1K 2R1 (Canada); National Research Council of Canada, Ottawa, Ontario K1A 0R6 (Canada); Bandrauk, A.D. [Laboratoire de Chimie Theorique, Universite de Sherbrooke, Sherbrooke, Quebec J1K 2R1 (Canada); Corkum, P.B. [National Research Council of Canada, Ottawa, Ontario K1A 0R6 (Canada)

2006-02-17

51

Hybrid Chirped Pulse Amplification  

SciTech Connect

We present a novel chirped pulse amplification method which combines optical parametric amplification and laser amplification. We have demonstrated this hybrid CPA concept with a combination of beta-barium borate and Ti:sapphire. High-efficiency, multi-terawatt compatible amplification is achieved without gain narrowing and without electro-optic modulators using a simple commercial pump laser.

Jovanovic, I; Barty, C P J

2002-05-07

52

Nonlinearly strain-chirped fiber Bragg grating with an adjustable dispersion slope  

Microsoft Academic Search

In this letter, we demonstrate an adjustable dispersion slope compensator for waveform distortion compensation based on a nonlinearly strain-chirped fiber Bragg grating. The dispersion slope of the device can be tuned up to -18.9 ps\\/nm2 with a bandwidth >2.4 nm. After transmission through a 120-km-long dispersion-shifted fiber, the resulting waveform distortion for a 2.65-ps pulse is successfully compensated by using

Chee S. Goh; Sze Y. Set; Kenji Taira; Sunil K. Khijwania; Kazuro Kikuchi

2002-01-01

53

Frequency chirping in external modulators  

Microsoft Academic Search

A general formula is given that expresses frequency chirping in some types of external intensity modulators, such as the loss modulator, directional-coupler-type modulator, Mach-Zehnder interferometry-type modulator, and total-internal-reflection-type modulator. The chirping phenomenon treated is caused by the phase modulation due to an accompanied refractive index change. It is uniquely expressed in terms of an ?-parameter that contributes to frequency chirping

Fumio Koyama; KENICHI IGA

1988-01-01

54

Nuclear fission of Fm isotopes  

SciTech Connect

Multi-modal fission has been systematically investigated for the series of isotopes of Fm and Cf. The multi-dimensional Langevin-type stochastic differential equation is used for the dynamical calculation. The primary fission mode changes from mass-asymmetric fission to mass-symmetric fission with the increase of neutron numbers for both Fm and Cf cases.

Asano, T. [VBL, Hokkaido University, Sapporo (Japan); Wada, T. [Department of Pure and Applied Physics, Kansai University, Suita (Japan); Ohta, M. [Hirao School of Management, Konan University, Nishinomoya (Japan); Chiba, S. [Advanced Science Research Center, JAEA Tokai, Naka (Japan)

2010-06-01

55

The detection of chirped radar signals by means of electron spin echoes  

Microsoft Academic Search

The application of the electron spin echo phenomenon to the detection of chirped microwave pulses is considered. The attainable time resolution is determined by the width of the paramagnetic resonance line, and the length of the received waveform is limited by the phase memory time of the spin packets in the active material. Pulse compressions of 1000:1 appear to be

W. B. Mims

1963-01-01

56

Chirp signal matching and signal power optimization in pulse-echo mode ultrasonic nondestructive testing  

Microsoft Academic Search

Chirp pulse compression is a signal correlation technique that uses frequency modulated pulses as transmitted signals. Usually, signals with linear frequency modulation are applied. They can be generated rather easily, but their spectra are not totally matched to the transfer function of ultrasonic systems. In pulse-echo mode operation, with signal duration and consequently the time-bandwidth product being critical parameters, waveforms

Martin Pollakowski; Helmut Ermert

1994-01-01

57

Frequency chirp stabilization in semiconductor distributed feedback lasers with external control  

NASA Astrophysics Data System (ADS)

It is well known that current modulation in diode lasers generates amplitude (AM) and optical frequency (FM) modulations. The frequency chirp under direct current modulation originates from variations in the carrier density and from the finite difference in carrier density between the laser on and off states. Modulation of the carrier density modulates the gain and the optical index causing the resonant mode to shift. This frequency chirp broadens the spectrum, which is a serious limitation for high-speed applications and optical fiber communications. At low frequencies, thermal effects also alter the frequency chirp. The aim of this paper is to show that the laser's frequency chirp can be modified using an external control technique. The chirp response is evaluated via the determination of the chirp-to-power ratio (CPR) through a Mach-Zehnder interferometer. Experiments demonstrate that when an external optical feedback is properly adjusted, the CPR can be severely decreased over a wide range of modulation frequencies as compared to the free-running case. These preliminary results obtained on quantum well distributed feedback lasers (QW DFB) with low normalized coupling coefficient (?L) demonstrate how to stabilize the CPR through the DFB facet phase effects or parameters such as the linewidth enhancement factor. In order to confirm this frequency chirp engineering, selfconsistent calculations based on the transfer matrix method are also presented.

Grillot, F.; Provost, J. G.; Kechaou, K.; Thedrez, B.; Erasme, D.

2012-02-01

58

Dynamic chirped microwave photonic filter  

Microsoft Academic Search

A chirped single bandpass microwave photonic filter based on a broadband optical source, a Mach-Zehnder interferometer and a dispersive element is proposed. Special and unique features are shown such as the capacity of modifying the chirp in the passband using the dispersive element together in combination with the possibility of tunability and reconfigurability. The later features are achieved by means

M. Bolea; J. Mora; B. Ortega; J. Capmany; L. Chen

2009-01-01

59

Improved Chirp Filters/Signals.  

National Technical Information Service (NTIS)

A discrete chirp generator produces discrete chirp signals which correspond to either of two exponential functions, namely the functions exp (j pi (m sq + alpha)/N) or exp (j pi (m(m+beta)+alpha)/N), where m equal 0, 1, 2, ..., M. Typically, M and N might...

J. N. Alsup

1980-01-01

60

Bayesian Spectrum And Chirp Analysis  

Microsoft Academic Search

: We seek optimal methods of estimating power spectrum and chirp (frequency change)rate for the case that one has incomplete noisy data on values y(t) of a time series. The Schusterperiodogram turns out to be a "sufficient statistic" for the spectrum, a generalization playing thesame role for chirped signals. However, the optimal processing is not a linear filtering operation likethe

E. T. Jaynes; Wayman Crow

1987-01-01

61

Transionospheric chirp event classifier  

SciTech Connect

In this paper we will discuss a project designed to provide computer recognition of the transionospheric chirps/pulses measured by the Blackbeard (BB) satellite, and expected to be measured by the upcoming FORTE satellite. The Blackbeard data has been perused by human means -- this has been satisfactory for the relatively small amount of data taken by Blackbeard. But with the advent of the FORTE system, which by some accounts might ``see`` thousands of events per day, it is important to provide a software/hardware method of accurately analyzing the data. In fact, we are providing an onboard DSP system for FORTE, which will test the usefulness of our Event Classifier techniques in situ. At present we are constrained to work with data from the Blackbeard satellite, and will discuss the progress made to date.

Argo, P.E.; Fitzgerald, T.J.; Freeman, M.J.

1995-09-01

62

Waveform design for detection of weapons based on signature exploitation  

NASA Astrophysics Data System (ADS)

We present waveform design based on signature exploitation techniques for improved detection of weapons in urban sensing applications. A single-antenna monostatic radar system is considered. Under the assumption of exact knowledge of the target orientation and, hence, known impulse response, matched illumination approach is used for optimal target detection. For the case of unknown target orientation, we analyze the target signatures as random processes and perform signal-to-noise-ratio based waveform optimization. Numerical electromagnetic modeling is used to provide the impulse responses of an AK-47 assault rifle for various target aspect angles relative to the radar. Simulation results depict an improvement in the signal-to-noise-ratio at the output of the matched filter receiver for both matched illumination and stochastic waveforms as compared to a chirp waveform of the same duration and energy.

Ahmad, Fauzia; Amin, Moeness G.; Dogaru, Traian

2010-04-01

63

Description and performance results for a multi-h CPM telemetry waveform  

Microsoft Academic Search

Multi-h continuous phase modulation (CPM) offers significant improvements over both legacy telemetry waveforms (PCM\\/FM) and the newly-introduced waveform (Feher (International Telemetering Conference, Las Vegas,p.27-30, 1997) patented FQPSK) in terms of spectral containment and detection efficiency, while retaining a constant envelope characteristic. This paper describes the theoretical and measured performance of the multi-h CPM waveform as well as the implementation of

Mark Geoghegan

2000-01-01

64

Chirped four-wave mixing  

NASA Astrophysics Data System (ADS)

We will demonstrate that four-wave mixing with linearly chirped (phase-modulated) pulses is a unique tool for obtaining information on the dynamics and level structure of a system. Especially, it will be shown that the transient-grating-scattering type of experiment with chirped pulses provides an immediate answer to the question of whether the dynamics of a system occurs on a fast and/or slow time scale. In addition, we present compelling evidence that chirped four-wave mixing in a molecular system is a viable method for measuring excited-state vibrational frequencies. Double-sided Feynman diagrams are used for a third-order perturbative calculation of two-level four-wave-mixing effects and chirped coherent Raman scattering. The diagrams provide a visual representation of the quantum-mechanical pathways that the system can take as a result of the different field interactions. The number of quantum-mechanical pathways that contribute to the signal is shown to depend on the chirp rate compared to the time scale(s) of the system dynamics. A stochastic model is used to describe the optical dynamics of the system. The resulting expressions for the third-order nonlinear polarization are so complex that numerical calculations are necessary to simulate the time dependence of the optical response. It will also be shown that our theoretical results in the appropriate limits converge to those obtained for impulsive or continuous-wave excitation.

Duppen, Koos; de Haan, Foppe; Nibbering, Erik T. J.; Wiersma, Douwe A.

1993-06-01

65

Generation of Arbitrary UWB Waveforms by Spectral Pulse Shaping and Thermally-Controlled Apodized FBGs  

Microsoft Academic Search

We propose and experimentally demonstrate an arbitrary UWB pulse generator. The proposed technique is based on spectral pulse shaping and frequency-to-time conversion. The reconfigurability of this technique comes from changing the apodizaton of a chirped fiber Bragg grating (FBG) using a series of heating elements (HE). By setting the appropriate temperature set to the HEs, any predesigned UWB waveforms can

Mohammad Abtahi; Mansour Dastmalchi; Sophie Larochelle; Leslie A. Rusch

2009-01-01

66

Chirp Scaling Algorithms for SAR Processing  

NASA Technical Reports Server (NTRS)

The chirp scaling SAR processing algorithm is both accurate and efficient. Successful implementation requires proper selection of the interval of output samples, which is a function of the chirp interval, signal sampling rate, and signal bandwidth. Analysis indicates that for both airborne and spaceborne SAR applications in the slant range domain a linear chirp scaling is sufficient. To perform nonlinear interpolation process such as to output ground range SAR images, one can use a nonlinear chirp scaling interpolator presented in this paper.

Jin, M.; Cheng, T.; Chen, M.

1993-01-01

67

Amplitude modulated chirp excitation to reduce grating lobes and maintain ultrasound intensity at the focus of an array.  

PubMed

During application of high intensity focused ultrasound (HIFU) with therapy arrays, the existence of grating lobes can cause heating at unintended tissue regions. Therefore, the reduction of grating lobes in therapeutic arrays is an important goal. One way to reduce the grating lobes in therapy arrays is to excite the arrays with broadband signals (defined here as >10% fractional bandwidth). To achieve a reduction in grating lobe levels in an ultrasonic array, coded waveforms can be utilized that reduce the grating lobe levels while maintaining the spatial peak temporal average intensity. In this study, a 5-MHz, 9-element, 1.25 mm inter-elemental spacing linear array was excited by a sinusoidal waveform, a conventional linear chirp, and a modified linear chirp. Both chirps spanned the -3-dB bandwidth of the transducer. The conventional chirp was a broadband signal with a linear sweep of frequencies between 2.5 and 7.5 MHz, with all frequency components excited with equal amplitude. The modified chirp signal also swept the frequencies between 2.5 and 7.5 MHz, but the amplitude was weighted such that the edges (low and high frequencies of the band) were excited with more energy than the center of the band. In simulations, the field patterns for the sinusoidal, conventional chirp and modified chirp excitations were produced from the array using Field II and compared. For experiments, the beam pattern from a 5-MHz single-element transducer was mapped using a hydrophone for the sinusoidal, conventional chirp and modified chirp excitation. Each field from the transducer was repeated and summed to produce a field from an array of 9 elements. The difference in the time averaged intensity (in dB) in the main lobe and grating lobes were estimated for each excitation and compared. The results demonstrated that the chirp signals resulted in decreases in grating lobe levels compared to the main lobe, i.e. 10 dB down for focusing and 6 dB down for focusing and steering. A further 1 dB decrease in grating lobe levels was observed for the modified chirp excitation compared to the conventional chirp excitation, which corresponds to ~21% reduction in energy deposition at the grating lobe location. PMID:23648212

Karunakaran, Chandra P; Oelze, Michael L

2013-09-01

68

Transionospheric Propagation of FM Signals  

Microsoft Academic Search

Communication links to earth satellites are not usually affected adversely by propagating through the ionosphere. However, the nonlinear variation of the refractive index with frequency causes a dispersion which can result in significant signal distortion under certain circumstances. Such a case occurs, for example, when a wide-band frequency-modulated (FM) signal propagating at the lower carrier frequencies traverses a low-elevation path

EDWARD BEDROSIAN

1970-01-01

69

Frequency-chirped subwavelength nanoantennas.  

PubMed

Herein we propose, theoretically investigate, and numerically demonstrate the first use to our knowledge of frequency chirping to achieve broadband, efficient subwavelength vertical emission from a dielectric waveguide. We demonstrate this unique and effective approach in the telecom C band in a nanophotonic frequency-chirped dipole antenna. The structure utilizes a plasmonic antenna placed above an Si3N4 waveguide and a ground plane to enhance emission efficiency. Three-dimensional finite-difference time-domain simulations reveal up to 55% vertical emission efficiency, and a bandwidth of 500 nm is possible in a structure less than half a wavelength long. The design methodology and theoretical underpinnings of frequency-chirped nanophotonic antennas coupled to dielectric waveguides are presented. PMID:23202110

Yaacobi, Ami; Watts, Michael R

2012-12-01

70

The effect of amplitude modulation on subharmonic imaging with chirp excitation.  

PubMed

Subharmonic generation from ultrasound contrast agents depends on the spectral and temporal properties of the excitation signal. The subharmonic response can be improved by using wideband and long-duration signals. However, for sinusoidal tone-burst excitation, the effective bandwidth of the signal is inversely proportional to the signal duration. Linear frequency-modulated (LFM) and nonlinear frequency-modulated (NLFM) chirp excitations allow independent control over the signal bandwidth and duration; therefore, in this study LFM and NLFM signals were used for the insonation of microbubble populations. The amplitude modulation of the excitation waveform was achieved by applying different window functions. A customized window was designed for the NLFM chirp excitation by focusing on reducing the spectral leakage at the subharmonic frequency and increasing the subharmonic generation from microbubbles. Subharmonic scattering from a microbubble population was measured for various excitation signals and window functions. At a peak negative pressure of 600 kPa, the generated subharmonic energy by ultrasound contrast agents was 15.4 dB more for NLFM chirp excitation with 40% fractional bandwidth when compared with tone-burst excitation. For this reason, the NLFM chirp with a customized window was used as an excitation signal to perform subharmonic imaging in an ultrasound flow phantom. Results showed that the NLFM waveform with a customized window improved the subharmonic contrast by 4.35 ± 0.42 dB on average over a Hann-windowed LFM excitation. PMID:24297019

Harput, Sevan; Arif, Muhammad; McLaughlan, James; Cowell, David M J; Freear, Steven

2013-12-01

71

The rotational spectrum of epifluorohydrin measured by chirped-pulse Fourier transform microwave spectroscopy  

Microsoft Academic Search

The rotational spectrum of epifluorohydrin measured by chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy is presented. A new CP-FTMW spectrometer capable of measuring the entire 7.5–18.5GHz spectrum with a single polarizing pulse is described briefly. The CP-FTMW spectrometer takes advantage of recent advances in digital electronics by utilizing a 4.2GS\\/s arbitrary waveform generator as a frequency source and a 12GHz digital

Gordon G. Brown; Brian C. Dian; Kevin O. Douglass; Scott M. Geyer; Brooks H. Pate

2006-01-01

72

Optical parametric chirped-pulse amplifier and spatiotemporal shaping for a petawatt laser  

Microsoft Academic Search

We present a degenerate noncollinear optical parametric chirped-pulse amplifier pumped by a high-energy, diode-pumped Nd:Glass regenerative amplifier delivering monomode pulses at 527 nm. The spatial mode shaping of the pump pulses is achieved with a diffractive laser cavity element, and temporal pulse shaping makes use of an electro-optic modulator and an arbitrary electrical waveform generator. Amplification at gain saturation achieves

Emmanuel Hugonnot; Jacques Luce; Hervé Coïc

2006-01-01

73

Decay study of 246Fm at SHIP  

NASA Astrophysics Data System (ADS)

The decay chain of 246Fm has been investigated employing the SHIP separator at GSI Darmstadt. The 246Fm nuclei were produced via the 40Ar(208Pb, 2n)246Fm fusion-evaporation reaction. Improved values of the half-life, T 1/2 = 1.54(4) s, and of the spontaneous fission branching ratio, b SF = 0.068(6) , of 246Fm were obtained. The ?+_{} /electron capture branching ratio, b EC = 0.39(3) , of 242Cf was deduced. Possible structures of high- K states in 246Fm are discussed within the framework of a model calculation based on the Woods-Saxon potential.

Venhart, M.; Heßberger, F. P.; Ackermann, D.; Antalic, S.; Gray-Jones, C.; Greenlees, P. T.; Heinz, S.; Herzberg, R.-D.; Hofmann, S.; Ketelhut, S.; Kindler, B.; Kojouharov, I.; Leino, M.; Lommel, B.; Mann, R.; Papadakis, P.; Rostron, D.; Rudolph, D.; Šáro, Š.; Sulignano, B.

2011-02-01

74

The interlaced chirp Z transform  

Microsoft Academic Search

In this paper we introduce the interlaced chirp Z transform (Interlaced CZT). It is based on the computation of several carefully staggered CZT that are progressively interlaced to result in a spectrum that has denser frequency samples where needed. This simple modification of the CZT is shown to result in significant computational savings over the regular CZT, as well as

Indranil Sarkar; Adly T. Fam

2006-01-01

75

Tone signal generator for producing multioperator tone signals using an operator circuit including a waveform generator, a selector and an enveloper  

DOEpatents

A frequency modulation (FM) tone signal generator for generating a FM tone signal is disclosed. The tone signal generator includes a waveform generator having a plurality of wave tables, a selector and an enveloper. The waveform generator furnishes a waveform signal in response to a phase angle address signal. Each wave table stores a different waveform. The selector selects one of the wave tables in response to a plurality of selection signals such that the selected wave table largely provides the waveform signal upon being addressed largely by the phase angle address signal. Selection of the selected wave table varies with each selection signal. The enveloper impresses an envelope signal on the waveform signal. The envelope signal is used as a carrier or modulator for generating the FM tone signal.

Dong, Qiujie (Austin, TX); Jenkins, Michael V. (Austin, TX); Bernadas, Salvador R. (Austin, TX)

1997-01-01

76

Tone signal generator for producing multioperator tone signals using an operator circuit including a waveform generator, a selector and an enveloper  

DOEpatents

A frequency modulation (FM) tone signal generator for generating a FM tone signal is disclosed. The tone signal generator includes a waveform generator having a plurality of wave tables, a selector and an enveloper. The waveform generator furnishes a waveform signal in response to a phase angle address signal. Each wave table stores a different waveform. The selector selects one of the wave tables in response to a plurality of selection signals such that the selected wave table largely provides the waveform signal upon being addressed largely by the phase angle address signal. Selection of the selected wave table varies with each selection signal. The enveloper impresses an envelope signal on the waveform signal. The envelope signal is used as a carrier or modulator for generating the FM tone signal. 17 figs.

Dong, Q.; Jenkins, M.V.; Bernadas, S.R.

1997-09-09

77

An X-band Transmission Line Based CMOS VCO with FM Modulation  

Microsoft Academic Search

An X-band voltage-controlled oscillator (VCO with frequency modulation (FM) capability is realized in a 0.18mum 1P6M CMOS technology. The characteristics of the VCO modulated by a 100KHz triangular waveform are presented and investigated. The passive components of the VCO are implemented by two-dimensional (2-D) complementary-conducting strip transmission lines (CCS TLs), varactors and metal-oxide-metal (MOM) capacitors for substrate coupling consideration. The

Sen Wang; Hsien-Shun Wu; C.-K. C. Tzuang

2007-01-01

78

Influence of long-term social interaction on chirping behavior, steroid levels and neurogenesis in weakly electric fish.  

PubMed

Social interactions dramatically affect the brain and behavior of animals. Studies in birds and mammals indicate that socially induced changes in adult neurogenesis participate in the regulation of social behavior, but little is known about this relationship in fish. Here, we review studies in electric fish (Apteronotus leptorhychus) that link social stimulation, changes in electrocommunication behavior and adult neurogenesis in brain regions associated with electrocommunication. Compared with isolated fish, fish living in pairs have greater production of chirps, an electrocommunication signal, during dyadic interactions and in response to standardized artificial social stimuli. Social interaction also promotes neurogenesis in the periventricular zone, which contributes born cells to the prepacemaker nucleus, the brain region that regulates chirping. Both long-term chirp rate and periventricular cell addition depend on the signal dynamics (amplitude and waveform variation), modulations (chirps) and novelty of the stimuli from the partner fish. Socially elevated cortisol levels and cortisol binding to glucocorticoid receptors mediate, at least in part, the effect of social interaction on chirping behavior and brain cell addition. In a closely related electric fish (Brachyhypopomus gauderio), social interaction enhances cell proliferation specifically in brain regions for electrocommunication and only during the breeding season, when social signaling is most elaborate. Together, these studies demonstrate a consistent correlation between brain cell addition and environmentally regulated chirping behavior across many social and steroidal treatments and suggest a causal relationship. PMID:23761468

Dunlap, Kent D; Chung, Michael; Castellano, James F

2013-07-01

79

On waveform multigrid method  

NASA Technical Reports Server (NTRS)

Waveform multigrid method is an efficient method for solving certain classes of time dependent PDEs. This paper studies the relationship between this method and the analogous multigrid method for steady-state problems. Using a Fourier-Laplace analysis, practical convergence rate estimates of the waveform multigrid iterations are obtained. Experimental results show that the analysis yields accurate performance prediction.

Taasan, Shlomo; Zhang, Hong

1993-01-01

80

Automatic Radar Waveform Recognition  

Microsoft Academic Search

In this paper, a system for automatically recognizing radar waveforms is introduced. This type of techniques are needed in various spectrum management, surveillance and cognitive radio or radar applications. The intercepted radar signal is classified to eight classes based on the pulse compression waveform: linear frequency modulation (LFM), discrete frequency codes (Costas codes), binary phase, and Frank, P1, P2, P3,

Jarmo Lundn; Visa Koivunen

2007-01-01

81

Study for imaging of inside bone using FM-chirp pulse compression system  

Microsoft Academic Search

We measured the attenuation of ultrasound in animal bone in vitro, and determined successfully the correct dynamic range for the detection of echo signals from inside the bone. It was possible to display a B-mode image of a 6-mm thick porcine rib bone using a high frequency (5 MHz) transducer. However, it was difficult to obtain the image of a

T Irie; E Ohdaira; K Itoh

2004-01-01

82

An MSK Radar Waveform  

NASA Technical Reports Server (NTRS)

The minimum-shift-keying (MSK) radar waveform is formed by periodically extending a waveform that separately modulates the in-phase and quadrature- phase components of the carrier with offset pulse-shaped pseudo noise (PN) sequences. To generate this waveform, a pair of periodic PN sequences is each passed through a pulse-shaping filter with a half sinusoid impulse response. These shaped PN waveforms are then offset by half a chip time and are separately modulated on the in-phase and quadrature phase components of an RF carrier. This new radar waveform allows an increase in radar resolution without the need for additional spectrum. In addition, it provides self-interference suppression and configurable peak sidelobes. Compared strictly on the basis of the expressions for delay resolution, main-lobe bandwidth, effective Doppler bandwidth, and peak ambiguity sidelobe, it appears that bi-phase coded (BPC) outperforms the new MSK waveform. However, a radar waveform must meet certain constraints imposed by the transmission and reception of the modulation, as well as criteria dictated by the observation. In particular, the phase discontinuity of the BPC waveform presents a significant impediment to the achievement of finer resolutions in radar measurements a limitation that is overcome by using the continuous phase MSK waveform. The phase continuity, and the lower fractional out-of-band power of MSK, increases the allowable bandwidth compared with BPC, resulting in a factor of two increase in the range resolution of the radar. The MSK waveform also has been demonstrated to have an ambiguity sidelobe structure very similar to BPC, where the sidelobe levels can be decreased by increasing the length of the m-sequence used in its generation. This ability to set the peak sidelobe level is advantageous as it allows the system to be configured to a variety of targets, including those with a larger dynamic range. Other conventionally used waveforms that possess an even greater spectral efficiency than the MSK waveform, such as linear frequency modulation (LFM) and Costas frequency hopping, have a fixed peak sidelobe level that is therefore not configurable, and can be exceeded by high contrast targets. Furthermore, in the case of a multistatic experiment observing a target in motion, self-interference from the transmitter to the receiver is mitigated by the MSK waveform. Waveforms that have delay Doppler coupling, such as LFM, provide no such protection.

Quirk, Kevin J.; Srinivasan, Meera

2012-01-01

83

Nonlinearly chirped microwave pulse generation using a spatially discrete chirped fiber Bragg grating  

Microsoft Academic Search

In this paper, we propose an optical approach to generating nonlinearly chirped microwave pulses based on space-to-frequency-to-time mapping using a spatially discrete chirped fiber Bragg grating (SD-CFBG). The SD-CFBG functions to perform simultaneous spectral slicing, frequency-to-time mapping and temporal shifting. The generation of a nonlinearly chirped microwave pulse with a chirp rate varying from 93.6 to 11.2 GHz\\/ns is experimentally

Chao Wang; Jianping Yao

2009-01-01

84

Best chirplet chain: Near-optimal detection of gravitational wave chirps  

NASA Astrophysics Data System (ADS)

The list of putative sources of gravitational waves possibly detected by the ongoing worldwide network of large scale interferometers has been continuously growing in the last years. For some of them, the detection is made difficult by the lack of a complete information about the expected signal. We concentrate on the case where the expected gravitational wave (GW) is a quasiperiodic frequency modulated signal i.e., a chirp. In this article, we address the question of detecting an a priori unknown GW chirp. We introduce a general chirp model and claim that it includes all physically realistic GW chirps. We produce a finite grid of template waveforms which samples the resulting set of possible chirps. If we follow the classical approach (used for the detection of inspiralling binary chirps, for instance), we would build a bank of quadrature matched filters comparing the data to each of the templates of this grid. The detection would then be achieved by thresholding the output, the maximum giving the individual which best fits the data. In the present case, this exhaustive search is not tractable because of the very large number of templates in the grid. We show that the exhaustive search can be reformulated (using approximations) as a pattern search in the time-frequency plane. This motivates an approximate but feasible alternative solution which is clearly linked to the optimal one. The time-frequency representation and pattern search algorithm are fully determined by the reformulation. This contrasts with the other time-frequency based methods presented in the literature for the same problem, where these choices are justified by “ad hoc” arguments. In particular, the time-frequency representation has to be unitary. Finally, we assess the performance, robustness and computational cost of the proposed method with several benchmarks using simulated data.

Chassande-Mottin, Éric; Pai, Archana

2006-02-01

85

Best chirplet chain: Near-optimal detection of gravitational wave chirps  

SciTech Connect

The list of putative sources of gravitational waves possibly detected by the ongoing worldwide network of large scale interferometers has been continuously growing in the last years. For some of them, the detection is made difficult by the lack of a complete information about the expected signal. We concentrate on the case where the expected gravitational wave (GW) is a quasiperiodic frequency modulated signal i.e., a chirp. In this article, we address the question of detecting an a priori unknown GW chirp. We introduce a general chirp model and claim that it includes all physically realistic GW chirps. We produce a finite grid of template waveforms which samples the resulting set of possible chirps. If we follow the classical approach (used for the detection of inspiralling binary chirps, for instance), we would build a bank of quadrature matched filters comparing the data to each of the templates of this grid. The detection would then be achieved by thresholding the output, the maximum giving the individual which best fits the data. In the present case, this exhaustive search is not tractable because of the very large number of templates in the grid. We show that the exhaustive search can be reformulated (using approximations) as a pattern search in the time-frequency plane. This motivates an approximate but feasible alternative solution which is clearly linked to the optimal one. The time-frequency representation and pattern search algorithm are fully determined by the reformulation. This contrasts with the other time-frequency based methods presented in the literature for the same problem, where these choices are justified by 'ad hoc' arguments. In particular, the time-frequency representation has to be unitary. Finally, we assess the performance, robustness and computational cost of the proposed method with several benchmarks using simulated data.

Chassande-Mottin, Eric [CNRS, Observatoire de la Cote d'Azur, ARTEMIS, BP 4229 06304 Nice Cedex 4 (France); Pai, Archana [INFN, Sezione Roma 1-P.le Aldo Moro, 2 00185 Rome (Italy)

2006-02-15

86

Biomedical Waveform Vaidation.  

National Technical Information Service (NTIS)

Contents: Introduction; Validation, and the Analysis of the ECG; Sequence Comparison; Sequence Alignment; Classification and Validation; Conclusions and Recommendations; Waveforms and Parameters in Anesthesia; Notations and Conventions of the AAMI; Overvi...

E. Vullings

1999-01-01

87

Highly Chirped Reconfigurable Microwave Photonic Filter  

Microsoft Academic Search

A photonic structure is proposed to implement a chirped single-bandpass filter based on a broadband optical source, an inteferometric structure, and a nonlinear dispersive element. The ability of controlling a quasi-linear chirp in the pass- band by using the dispersive element in addition to the possibility of tuning and reconfiguring the passband by means of a proper configuration of the

Mario Bolea; José Mora; Lawrence R. Chen; José Capmany

2011-01-01

88

Chirped-microwave assisted magnetization reversal  

Microsoft Academic Search

This paper reports simulation results on microwave-assisted magnetization reversal in magnetic thin films with perpendicular anisotropy. In comparison with frequency-fixed microwaves, frequency-chirped microwaves have higher efficiency in pumping magnetization precession and, therefore, can lead to more significant reduction in switching fields. Through the use of chirped microwaves, switching with low fields is also possible for large damping films.

Zihui Wang; Mingzhong Wu

2009-01-01

89

Detection and frequency tracking of chirping signals.  

National Technical Information Service (NTIS)

This paper discusses several methods to detect the presence of and track the frequency of a chirping signal in broadband noise. The dynamic behavior of each of the methods is described and tracking error bounds are investigated in terms of the chirp rate....

G. R. Elliott S. D. Stearns

1990-01-01

90

Detection and frequency tracking of chirping signals  

SciTech Connect

This paper discusses several methods to detect the presence of and track the frequency of a chirping signal in broadband noise. The dynamic behavior of each of the methods is described and tracking error bounds are investigated in terms of the chirp rate. Frequency tracking and behavior in the presence of varying levels of noise are illustrated in examples. 11 refs., 29 figs.

Elliott, G.R.; Stearns, S.D.

1990-08-01

91

Population inversion by chirped pulses  

SciTech Connect

In this paper, we analyze the condition for complete population inversion by a chirped pulse over a finite duration. The nonadiabatic transition probability is mapped in the two-dimensional parameter space of coupling strength and detuning amplitude. Asymptotic forms of the probability are derived by the interference of nonadiabatic transitions for sinusoidal and triangular pulses. The qualitative difference between the maps for the two types of pulses is accounted for. The map is used for the design of stable inversion pulses under specific accuracy thresholds.

Lu Tianshi [Department of Mathematics and Statistics, Wichita State University, Wichita, Kansas 67260-0033 (United States)

2011-09-15

92

Raman forward scattering of chirped laser pulses  

SciTech Connect

Raman scattering of a high-intensity, short duration, frequency-chirped laser pulse propagating in an underdense plasma is examined. The growth of the direct forward scattered light is calculated for a laser pulse with a linear frequency chirp in various spatio-temporal regimes. This includes a previously undescribed regime of strongly-coupled four-wave nonresonant interaction, which is important for relativistic laser intensities. In all regimes of forward scattering, it is shown that the growth rate increases (decreases) for positive (negative) frequency chirp. The effect of chirp on the growth rate is relatively minor, i.e., a few percent chirp yields few percent changes in the growth rates. Numerical solutions based on fully nonlinear cold Maxwell-fluid model are presented which confirm analytical predictions. Relation of these results to recent experiments is discussed.

Schroeder, C.B.; Esarey, E.; Shadwick, B.A.; Leemans, W.P.

2002-12-05

93

Low frequency AC waveform generator  

DOEpatents

Low frequency sine, cosine, triangle and square waves are synthesized in circuitry which allows variation in the waveform amplitude and frequency while exhibiting good stability and without requiring significant stabilization time. A triangle waveform is formed by a ramped integration process controlled by a saturation amplifier circuit which produces the necessary hysteresis for the triangle waveform. The output of the saturation circuit is tapped to produce the square waveform. The sine waveform is synthesized by taking the absolute value of the triangular waveform, raising this absolute value to a predetermined power, multiplying the raised absolute value of the triangle wave with the triangle wave itself and properly scaling the resultant waveform and subtracting it from the triangular waveform itself. The cosine is synthesized by squaring the triangular waveform, raising the triangular waveform to a predetermined power and adding the squared waveform raised to the predetermined power with a DC reference and subtracting the squared waveform therefrom, with all waveforms properly scaled. The resultant waveform is then multiplied with a square wave in order to correct the polarity and produce the resultant cosine waveform.

Bilharz, Oscar W. (Scotia, NY) [Scotia, NY

1986-01-01

94

Project Echo: FM Demodulators with Negative Feedback  

NASA Technical Reports Server (NTRS)

The primary experimental objective of Project Echo was the transmission of radio communications between points on the earth by reflection from the balloon satellite. Owing to the large path losses from transmitter to receiver via the satellite, a wide-band frequency modulation technique was used in which bandwidth was traded for signal-to-noise ratio. This paper describes the FM receiving demodulators employed. Negative feedback applied to the local oscillator reduces the FM modulation index in the receiver IF amplifiers, resulting in threshold performance superior to that of conventional FM receivers.

Ruthroff, Clyde L.

1961-01-01

95

Heterodyne architecture for tunable laser chirped dispersion spectroscopy using optical processing.  

PubMed

Dispersion-based spectroscopic techniques present many desirable features when compared with classical absorption spectroscopy implementations, such as the normalization-free operation and the extended dynamic range. In this Letter, we present a new sensor design based on direct optical processing for heterodyne conversion in tunable laser chirped dispersion spectroscopy that allows sensor implementations using low-speed photodetectors and low-cost FM demodulators. The performance of the new setup has been validated using as a target the ro-vibrational transition of methane at approximately 1650.96 nm. PMID:24784058

Martín-Mateos, Pedro; Jerez, Borja; Acedo, Pablo

2014-05-01

96

Waveform Data Quality  

NASA Astrophysics Data System (ADS)

The Comprehensive Nuclear Test Ban Treaty Organization (CTBTO) is tasked with monitoring compliance with the CTBT. In order to fulfill this mission, the CTBTO is building the International Monitoring System (IMS), which includes seismic, hydroacoustic, and infrasound stations which must meet stringent data availability, timeliness, and quality requirements. Each station sends waveform data to the International Data Centre (IDC) in Vienna, where the data are processed and reviewed. In order to ensure high quality data and products, the quality of the waveform data from the IMS network must be measured and reported. Corrective actions are taken when quality deteriorates, so timely reporting is important. The first step in assessing waveform data quality is to separate useless data from data which may contain useful information. Useless data are defined as periods when no data are reported (data gaps), periods when several adjacent data samples contain the same value (constant data), and periods when there is no sensor input. Useless data cannot be used for analysis, and consequently are excluded from data availability calculations. The quality of waveform data can be assessed in many ways, including the following. The data stream from the station contains a status field which reports information on the waveform data, the equipment, and timing. The distribution of power spectral density can be assessed to determine when waveform data become abnormal. When a detection is declared at an array, the similarity of waveforms at each element of the array can be assessed to determine anomalous array elements. Ongoing activities in these areas will be presented.

John, Coyne; Kitov, Ivan; Johansson, Peder; Given, Jeffrey; Brown, David; Brachet, Nicolas; Mialle, Pierrick

2010-05-01

97

Auditory brainstem responses to a chirp stimulus designed from derived-band latencies in normal-hearing subjects  

PubMed Central

In an attempt to compensate for the temporal dispersion in the human cochlea, a chirp has previously been designed from estimates of the cochlear delay based on derived-band auditory brain-stem response (ABR) latencies [Elberling et al. (2007). “Auditory steady-state responses to chirp stimuli based on cochlear traveling wave delay,” J. Acoust. Soc. Am. 122, 2772–2785]. To evaluate intersubject variability and level effects of such delay estimates, a large dataset is analyzed from 81 normal-hearing adults (fixed click level) and from a subset thereof (different click levels). At a fixed click level, the latency difference between 5700 and 710 Hz ranges from about 2.0 to 5.0 ms, but over a range of 60 dB, the mean relative delay is almost constant. Modeling experiments demonstrate that the derived-band latencies depend on the cochlear filter buildup time and on the unit response waveform. Because these quantities are partly unknown, the relationship between the derived-band latencies and the basilar membrane group delay cannot be specified. A chirp based on the above delay estimates is used to record ABRs in ten normal-hearing adults (20 ears). For levels below 60 dB nHL, the gain in amplitude of chirp-ABRs to click-ABRs approaches 2, and the effectiveness of chirp-ABRs compares favorably to Stacked-ABRs obtained under similar conditions.

Elberling, Claus; Don, Manuel

2008-01-01

98

Full Waveform Inversion Using Waveform Sensitivity Kernels  

NASA Astrophysics Data System (ADS)

We present a full waveform inversion concept for applications ranging from seismological to enineering contexts, in which the steps of forward simulation, computation of sensitivity kernels, and the actual inversion are kept separate of each other. We derive waveform sensitivity kernels from Born scattering theory, which for unit material perturbations are identical to the Born integrand for the considered path between source and receiver. The evaluation of such a kernel requires the calculation of Green functions and their strains for single forces at the receiver position, as well as displacement fields and strains originating at the seismic source. We compute these quantities in the frequency domain using the 3D spectral element code SPECFEM3D (Tromp, Komatitsch and Liu, 2008) and the 1D semi-analytical code GEMINI (Friederich and Dalkolmo, 1995) in both, Cartesian and spherical framework. We developed and implemented the modularized software package ASKI (Analysis of Sensitivity and Kernel Inversion) to compute waveform sensitivity kernels from wavefields generated by any of the above methods (support for more methods is planned), where some examples will be shown. As the kernels can be computed independently from any data values, this approach allows to do a sensitivity and resolution analysis first without inverting any data. In the context of active seismic experiments, this property may be used to investigate optimal acquisition geometry and expectable resolution before actually collecting any data, assuming the background model is known sufficiently well. The actual inversion step then, can be repeated at relatively low costs with different (sub)sets of data, adding different smoothing conditions. Using the sensitivity kernels, we expect the waveform inversion to have better convergence properties compared with strategies that use gradients of a misfit function. Also the propagation of the forward wavefield and the backward propagation from the receiver into the medium (here realized by Green functions) can be done independently of each other. In comparison with the adjoint method, this can reduce the necessary number of wave propagation simulations, depending on the number of involved sources and receivers. One challenge, however, is that in order to calculate the kernels in the volume of interest, wavefields and strains have to be stored throughout that volume, which typically demands a large amount of storage capacity.

Schumacher, Florian; Friederich, Wolfgang

2013-04-01

99

Simultaneous Optical Spectral Shaping and Wavelength-to-Time Mapping for Photonic Microwave Arbitrary Waveform Generation  

Microsoft Academic Search

Photonic microwave arbitrary waveform generation (AWG) based on simultaneous optical spectral shaping and wavelength-to-time mapping in a single specially designed linearly chirped fiber Bragg grating (LCFBG) is proposed. In the proposed approach, the spectrum of a transform-limited ultrashort optical pulse is spectrally shaped, and at the same time is wavelength-to-time mapped by the LCFBG to generate a microwave pulse with

Chao Wang; Jianping Yao

2009-01-01

100

Spectral Efficiency of FM and ACSB Radios.  

National Technical Information Service (NTIS)

In this second of nine reports concerning spectrum efficient technologies, the spectral efficiency of amplitude compandored single sideband (ACSB) radios is compared with that of conventional frequency modulation (FM) radios utilizing five kilohertz frequ...

M. Herro

1980-01-01

101

Chirped femtosecond pulse scattering by spherical particles  

NASA Astrophysics Data System (ADS)

Generalized Lorentz-Mie formulas are used to study the scattering characteristics when a chirped femtosecond pulse illuminates a spherical particle. For a linear chirped Gaussian pulse with the envelope function g( tau ) = exp[- pi (1 + ib) tau 2], dimensionless parameter b is defined as a chirp. The calculation illustrated that even for pulses with a constant carrier wavelength ( lambda 0 = 0.5 mu m) and pulse-filling coefficient (l0 = 1.98), the efficiencies for extinction and scattering differ very much between the carrier wave and the different chirped pulses. The slowly varying background of the extinction and the scattering curves is damped by the chirp. When the pulse is deeply chirped, the maxima and minima of the background curves reduce to the point where they disappear, and the efficiency curves illustrate a steplike dependence on the sphere size. Another feature is that the only on the amount of chirp (|b|), regardless of upchirp (b greater than 0) or downchirp (b less than 0).

Kim, Dal-Woo; Xiao, Gang-Yao; Lee, Tong-Nyong

1996-05-01

102

47 CFR 73.297 - FM stereophonic sound broadcasting.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false FM stereophonic sound broadcasting. 73.297 Section 73...Stations § 73.297 FM stereophonic sound broadcasting. (a) An FM broadcast...stereophonic (biphonic, quadraphonic, etc.) sound programs upon installation of...

2013-10-01

103

47 CFR 73.597 - FM stereophonic sound broadcasting.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 2009-10-01 false FM stereophonic sound broadcasting. 73...COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.597 FM...

2009-10-01

104

47 CFR 73.597 - FM stereophonic sound broadcasting.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false FM stereophonic sound broadcasting. 73...COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.597 FM...

2010-10-01

105

High-Energy Sub-Cycle Waveform Synthesis and Characterization  

NASA Astrophysics Data System (ADS)

The control of atomic scale electronic motion by ultrafast optical electric field waveforms strong enough to mitigate the atomic Coulomb potential has broken tremendous new ground with the advent of phase controlled high-energy few-cycle pulse sources. Currently, such sources are based on Ti:sapphire amplifiers and hollow-core fiber post-compression or optical parametric chirped pulse amplification, together with optical gating techniques. Significant control of the waveform on sub-cycle time scales, however, requires a fully phase-controlled multiple-octave-spanning spectrum. Here, we present a first fully phase-controlled multi-octave-spanning source that supports gigawatt-peak-power isolated single-cycle waveforms based on pulse synthesis of two carrier-envelope phase (CEP) stable OPCPA systems. It is especially a challenge to fully characterize such ultrawide band waveforms. We apply two-dimensional spectral shearing interferometry (2DSI), which can measure the group delay between all spectral components of the synthesized pulse.

Kärtner, Franz

2011-03-01

106

Over-modulated AM-FM decomposition  

NASA Astrophysics Data System (ADS)

Most previous amplitude- and frequency-modulation (AM and FM) decomposition methods assume that the AM component is non-negative. However this assumption is not always valid. Over-modulation, where the AM component has both positive and negative values, may be present in not only synthetic signals, but also in natural signals like speech and music. Assuming all non-negative values for AM in an over-modulated signal will introduce significant phase discontinuities in the FM estimate. Because of this, previous methods yield significant errors for instantaneous frequency (IF) estimation at AM zero-crossings. We propose a two-step algorithm that utilizes coherent demodulation to estimate AM and FM correctly for over-modulated signals. For synthetic signals, the algorithm produces very accurate AM and FM estimates; for band-passed speech signals, the algorithm corrects the discontinuities in the FM estimate and produces more physically reasonable results. The evaluation of source sensitivity for the algorithm shows that the estimation errors generally increase with AM and FM frequencies, but are insensitive to carrier frequency. The robustness in noise is relatively low in the over-modulation case due to very low local SNR at AM zero-crossings. Limitations of the algorithm and future work are also discussed.

Li, Qin; Atlas, Les E.

2004-10-01

107

Transionospheric signal detection with chirped wavelets  

SciTech Connect

Chirped wavelets are utilized to detect dispersed signals in the joint time scale domain. Specifically, pulses that become dispersed by transmission through the ionosphere and are received by satellites as nonlinear chirps are investigated. Since the dispersion greatly lowers the signal to noise ratios, it is difficult to isolate the signals in the time domain. Satellite data are examined with discrete wavelet expansions. Detection is accomplished via a template matching threshold scheme. Quantitative experimental results demonstrate that the chirped wavelet detection scheme is successful in detecting the transionospheric pulses at very low signal to noise ratios.

Doser, A.B.; Dunham, M.E.

1997-11-01

108

CHIRP  

Cancer.gov

Skip to Main Content Headlines Pediatric Oncology Branch Home > Pediatric Psycho-Oncology Professionals > Training Headline Title Pediatric Psycho-Oncology Professionals Pediatric Psychology Postdoctoral Fellowship University of Louisville School of

109

Phase-shifted distributed feedback laser with linearly chirped grating fabricated by reconstruction equivalent chirp technique  

NASA Astrophysics Data System (ADS)

The phase-shifted distributed feedback (DFB) semiconductor laser with linearly chirped grating based on reconstruction equivalent chirp (REC) technique is theoretically analyzed and experimentally demonstrated for the first time. The asymmetric property of the lasing spectrum is analyzed according to the normalized threshold gain, and the different spectra from each facet of the laser are compared. Due to the low cost and fabrication flexibility, REC technique provides a promising way for the future practical applications of DFB lasers with chirped gratings.

Li, Lianyan; Lu, Linlin; Li, Simin; Guo, Renjia; Shi, Yuechun; Chen, Xiangfei

2014-09-01

110

Chirp-compensated 40GHz mode-locked lasers integrated with electroabsorption modulators and chirped gratings  

Microsoft Academic Search

40-GHz short-pulse generation of monolithic mode-locked lasers integrated with electroabsorption modulators and chirped gratings is reported. Theoretical analysis of active mode-locking based on a Gaussian model is described. Chirped gratings are shown to compensate the optical-frequency chirp and extend the repetition frequency range. Nearly transform-limited pulses of less than 4 ps are experimentally generated over a wide range of repetition

Kenji Sato; Akira Hirano; Hiroyuki Ishii

1999-01-01

111

Chaotic chirped-pulse oscillators.  

PubMed

We present results of experimental investigation of the chaotic and quasi-periodic regime in the chirped-pulsed (dissipative soliton) Cr:ZnS and Cr:ZnSe mid-IR oscillators with significant third-order dispersion. The instability develops when the spectrum edge approaches resonance with a linear wave either due to power increase or by dispersion adjustment. In practice, this occurs when the spectrum edge reaches zero dispersion wavelength. The analysis suggests a three-oscillator chaos model, which is confirmed by numerical simulations. The regime is long-term stable and can be easily overlooked in similar systems. We show that chaotic regime is accompanied by a characteristic spectral shape and can be reliably recognized by using wavelength-skewed filters and by second-harmonic or two-photon absorption detectors. PMID:24514508

Sorokin, Evgeni; Tolstik, Nikolai; Kalashnikov, Vladimir L; Sorokina, Irina T

2013-12-01

112

Low frequency ac waveform generator  

DOEpatents

Low frequency sine, cosine, triangle and square waves are synthesized in circuitry which allows variation in the waveform amplitude and frequency while exhibiting good stability and without requiring significant stablization time. A triangle waveform is formed by a ramped integration process controlled by a saturation amplifier circuit which produces the necessary hysteresis for the triangle waveform. The output of the saturation circuit is tapped to produce the square waveform. The sine waveform is synthesized by taking the absolute value of the triangular waveform, raising this absolute value to a predetermined power, multiplying the raised absolute value of the triangle wave with the triangle wave itself and properly scaling the resultant waveform and subtracting it from the triangular waveform to a predetermined power and adding the squared waveform raised to the predetermined power with a DC reference and subtracting the squared waveform therefrom, with all waveforms properly scaled. The resultant waveform is then multiplied with a square wave in order to correct the polarity and produce the resultant cosine waveform.

Bilharz, O.W.

1983-11-22

113

Chirped Pulse Amplification: Present and Future.  

National Technical Information Service (NTIS)

Short pulses with ultrahigh peak powers have been generated in Nd: glass and Alexandrite using the Chirped Pulse Amplification (CPA) technique. This technique has been successful in producing picosecond terawatt pulses with a table-top laser system. In th...

P. Maine D. Strickland M. Pessot J. Squier P. Bado

1988-01-01

114

Terahertz surface plasmon on chirped groove grating  

Microsoft Academic Search

The excitation of terahertz surface plasmon on metallized chirped groove gratings is studied in time- and frequency-domain. These gratings have a potential to launch and decouple broadband terahertz surface plasmon necessary for integrated optical circuits.

M. Martl; J. Darmo; K. Unterrainer; E. Gornik

2008-01-01

115

Structural Analysis of Biological Waveforms.  

National Technical Information Service (NTIS)

A characteristic of many biomedical waveforms in such applications is that many of the features by which classes of waveforms, e.g., abnormal vs. normal EKG's, are distinguished, are generally expressed by fuzzy descriptions of structural details; in EKG ...

D. C. Collins W. S. Meisel

1971-01-01

116

Full Waveform Teleseismic Tomography  

Microsoft Academic Search

We adapt a 2D spectral domain finite difference waveform tomography algorithm previously used in active source seismological imaging to the case of a plane wave propagating through a 2.5D viscoelastic medium in order to recover P and S wavespeed variations from body waves recorded at teleseismic distances. A transferable efficacy that permits recovery of arbitrarily heterogenousmodels on moderately sized computers

S. W. Roecker; B. Baker; J. McLaughlin

2009-01-01

117

Residual chirp in integrated-optic modulators  

Microsoft Academic Search

The authors have analyzed and measured the dispersion effects of residual chirp arising from asymmetry in field overlap in Mach-Zehnder structures. A clear influence of chirp was seen at 7 Gb\\/s and a propagation length of 75-km nondispersion shifted fiber at ?=1.55 ?m. It is shown that a MZ-modulator with field overlap in one arm only and operated in the

Anders Djupsjobacka

1992-01-01

118

Optical waveform generation using a directly modulated laser  

NASA Astrophysics Data System (ADS)

The capability of a directly modulated laser (DML) can be dramatically enhanced through precise control of the drive current waveform based on digital signal processing (DSP) and a digital-to-analog convertor (DAC). In this paper, a novel method to pre-compensate fiber dispersion for metro and regional networks is described for a bit rate of 10.709 Gb/s using a DML. A look-up table (LUT) for the drive current is optimized for dispersion mitigation. The entries of the LUT are determined based on the effects of the DML adiabatic and transient chirp on pulse propagation, the nonlinear mapping between the input current and the output optical power, and the bandwidth of the DML package. A DAC operating at 2 samples per bit (21.418 GSa/s with 6 bit resolution) converts the digital samples at the output of the LUT to an analog current waveform driving the DML. Experimental results for a bit rate of 10.709 Gb/s and on-off keying demonstrate a transmission reach of 252 km using a DML intended for 2.5 Gb/s operation and 608 km using a chirp managed laser intended for 10 Gb/s operation. Using this approach (DSP + DAC), the generation of 10.709 Gb/s differential phase shift keying (DPSK) and 56 Gb/s 16-ary quadrature amplitude modulation, sub-carrier multiplexed (QAM SCM) optical signals using the direct modulation of a passive feedback laser is also presented. 6-bit DACs operating at sampling rates of 21.418 GSa/s and 28 GSa/s, respectively, was used to generate the requisite analog current waveform.

Cartledge, John C.; Karar, Abdullah S.; Roberts, Kim

2013-10-01

119

Interplay of the chirps and chirped pulse compression in a high-gain seeded free-electron laser  

SciTech Connect

In a seeded high-gain free-electron laser (FEL), where a coherent laser pulse interacts with an ultrarelativistic electron beam, the seed laser pulse can be frequency chirped, and the electron beam can be energy chirped. Besides these two chirps, the FEL interaction introduces an intrinsic frequency chirp in the FEL even if the above-mentioned two chirps are absent. We examine the interplay of these three chirps. The problem is formulated as an initial value problem and solved via a Green function approach. Besides the chirp evolution, we also give analytical expressions for the pulse duration and bandwidth of the FEL, which remains fully longitudinally coherent in the high-gain exponential growth regime. Because the chirps are normally introduced for a final compression of the FEL pulse, some conceptual issues are discussed. We show that to get a short pulse duration, an energy chirp in the electron beam is important.

Wu Juhao; Murphy, James B.; Emma, Paul J.; Wang Xijie; Watanabe, Takahiro; Zhong Xinming [Stanford Linear Accelerator Center, Stanford University, Stanford, California 94309 (United States); National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973-5000 (United States); Stanford Linear Accelerator Center, Stanford University, Stanford, California 94309 (United States); National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973-5000 (United States); Institute of Low Energy Nuclear Physics, Beijing Normal University, Beijing 100875 (China)

2007-03-15

120

Interplay of the Chirps and Chirped Pulse Compression in a High-gain Seeded Free-electron Laser  

SciTech Connect

In a seeded high-gain Free-electron Laser (FEL), where a coherent laser pulse interacts with an ultra-relativistic electron beam, the seed laser pulse can be frequency chirped, and the electron beam can be energy chirped. Besides these two chirps, the FEL interaction introduces an intrinsic frequency chirp in the FEL even if the above mentioned two chirps are absent. In this paper we examine the interplay of these three chirps. The problem is formulated as an initial value problem, and solved via a Green function approach. Besides the chirp evolution, we also give analytical expressions for the pulse duration and bandwidth of the FEL, which remains fully longitudinally coherent in the high gain exponential growth regime. Because the chirps are normally introduced for a final compression of the FEL pulse, some conceptual issues are discussed. We show that in order to get a short pulse duration, an energy chirp in the electron beam is necessary.

Wu, Juhao; /SLAC; Murphy, J.B.; /LBNL, ALS; Emma, P.J.; /SLAC; Wang, X.J.; Watanabe, T.; /LBNL, ALS; Zhong, Xinming; /Beijing Normal U.

2007-01-03

121

Interaction of free charged particles with a chirped electromagnetic pulse.  

PubMed

We study the effect of chirp on electromagnetic (EM) pulse interaction with a charged particle. Both the one-dimensional (1D) and 3D cases are considered. It is found that, in contrast to the case of a nonchirped pulse, the charged particle energy can be changed after the interaction with a 1D EM chirped pulse. Different types of chirp and pulse envelopes are considered. In the case of small chirp, an analytical expression is found for arbitrary temporal profiles of the chirp and the pulse envelope. In the 3D case, the interaction with a chirped pulse results in a polarization-dependent scattering of charged particles. PMID:15697564

Khachatryan, A G; van Goor, F A; Boller, K-J

2004-12-01

122

Interaction of free charged particles with a chirped electromagnetic pulse  

SciTech Connect

We study the effect of chirp on electromagnetic (EM) pulse interaction with a charged particle. Both the one-dimensional (1D) and 3D cases are considered. It is found that, in contrast to the case of a nonchirped pulse, the charged particle energy can be changed after the interaction with a 1D EM chirped pulse. Different types of chirp and pulse envelopes are considered. In the case of small chirp, an analytical expression is found for arbitrary temporal profiles of the chirp and the pulse envelope. In the 3D case, the interaction with a chirped pulse results in a polarization-dependent scattering of charged particles.

Khachatryan, A.G.; Goor, F.A. van; Boller, K.-J. [Department of Applied Science, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands)

2004-12-01

123

GSSR Waveforms for Lunar Observations  

NASA Astrophysics Data System (ADS)

To increase the resolution of the Goldstone Solar System Radar (GSSR) for lunar observations, a new ranging waveform must be developed. Several candidate waveforms are identified and analytically characterized, including the existing GSSR biphase-coded (BPC) waveform; two commonly used waveforms, linear frequency modulation (LFM) and Costas frequency-hopped (Costas-FH); and a novel minimum-shift keying (MSK) type waveform developed during the course of this study. A set of requirements taking into consideration the spectrum allocation of the GSSR, the limitations of the transmit power amplifier, and the science objectives for a lunar observation were developed and used as selection criteria for the candidate waveforms. Windowed LFM, windowed Costas-FH, and MSK were identified as suitable for development consideration as a new GSSR ranging waveform for lunar observations.

Quirk, K. J.; Srinivasan, M.

2013-02-01

124

Reflection seismic waveform tomography  

Microsoft Academic Search

In seismic waveform tomography, if using reflection data with limited source-receiver offsets, it is difficult to reconstruct the deep part of the subsurface velocity model. We present two approaches to tackle this problem: layer stripping and weighted updating. In a layer-stripping procedure, we replace the top portion of seismic data with synthetics generated from the previous-layer inversion and make the

Yanghua Wang; Ying Rao

2009-01-01

125

Biosonar Performance and Processing in FM Bats.  

National Technical Information Service (NTIS)

Identification of the excitatory FM-sweep frequency for a representative IC neuron by reverse correlation (REVCOR) analysis, a method that searches over the time-interval prior to each spike to find any common element in all the stimuli that precedes resp...

J. A. Simmons

1999-01-01

126

FY05 FM Dial Summary Report  

SciTech Connect

Pacific Northwest National Laboratory's Infrared Sensors team is focused on developing methods for standoff detection of nuclear proliferation. In FY05, PNNL continued the development of the FM DIAL (frequency-modulated differential absorption LIDAR) experiment. Additional improvements to the FM DIAL trailer provided greater stability during field campaigns which made it easier to explore new locations for field campaigns. In addition to the Hanford Townsite, successful experiments were conducted at the Marine Science Laboratory in Sequim, WA and the Nevada Test Site located outside Las Vegas, NV. The range of chemicals that can be detected by FM DIAL has also increased. Prior to FY05, distributed feedback quantum cascade lasers (DFB-QCL) were used in the FM DIAL experiments. With these lasers, only simple chemicals with narrow (1-2 cm-1) absorption spectra, such as CO2 and N2O, could be detected. Fabry-Perot (FP) QC lasers have much broader spectra (20-40 cm-1) which allows for the detection of larger chemicals and a wider array of chemicals that can be detected. A FP-QCL has been characterized and used during initial studies detecting DMMP (dimethyl methylphosphonate).

Harper, Warren W.; Strasburg, Jana D.; Golovich, Elizabeth C.; Thompson, Jason S.; Stewart, Timothy L.; Batdorf, Michael T.

2005-12-01

127

Non-Commercial FM: Profiles of Service.  

ERIC Educational Resources Information Center

This paper examines the growth of noncommercial FM radio and the service it provides to various regions of the United States and to large metropolitan areas. It concludes that the service provided does not reflect the policies for noncommercial broadcasting set forth by Congress and the Federal Communications Commission and that it does not…

Clift, Charles; Lee, Varnell

128

Multiscale full waveform inversion  

NASA Astrophysics Data System (ADS)

We develop and apply a full waveform inversion method that incorporates seismic data on a wide range of spatio-temporal scales, thereby constraining the details of both crustal and upper-mantle structure. This is intended to further our understanding of crust-mantle interactions that shape the nature of plate tectonics, and to be a step towards improved tomographic models of strongly scale-dependent earth properties, such as attenuation and anisotropy. The inversion for detailed regional earth structure consistently embedded within a large-scale model requires locally refined numerical meshes that allow us to (1) model regional wave propagation at high frequencies, and (2) capture the inferred fine-scale heterogeneities. The smallest local grid spacing sets the upper bound of the largest possible time step used to iteratively advance the seismic wave field. This limitation leads to extreme computational costs in the presence of fine-scale structure, and it inhibits the construction of full waveform tomographic models that describe earth structure on multiple scales. To reduce computational requirements to a feasible level, we design a multigrid approach based on the decomposition of a multiscale earth model with widely varying grid spacings into a family of single-scale models where the grid spacing is approximately uniform. Each of the single-scale models contains a tractable number of grid points, which ensures computational efficiency. The multi-to-single-scale decomposition is the foundation of iterative, gradient-based optimization schemes that simultaneously and consistently invert data on all scales for one multi-scale model. We demonstrate the applicability of our method in a full waveform inversion for Eurasia, with a special focus on Anatolia where coverage is particularly dense. Continental-scale structure is constrained by complete seismic waveforms in the 30-200 s period range. In addition to the well-known structural elements of the Eurasian mantle, our model reveals a variety of subtle features, such as the Armorican Massif, the Rhine Graben and the Massif Central. Anatolia is covered by waveforms with 8-200 s period, meaning that the details of both crustal and mantle structure are resolved consistently. The final model contains numerous previously undiscovered structures, including the extension-related updoming of lower-crustal material beneath the Menderes Massif in western Anatolia. Furthermore, the final model for the Anatolian region confirms estimates of crustal depth from receiver function analysis, and it accurately explains cross-correlations of ambient seismic noise at 10 s period that have not been used in the tomographic inversion. This provides strong independent evidence that detailed 3-D structure is well resolved.

Fichtner, Andreas; Trampert, Jeannot; Cupillard, Paul; Saygin, Erdinc; Taymaz, Tuncay; Capdeville, Yann; Villaseñor, Antonio

2013-07-01

129

Optimal chirped probe pulse length for terahertz pulse measurement.  

PubMed

A detailed analysis of the relationship between the duration of the chirped probe pulse and the bipolar terahertz (THz) pulse length in the spectral encoding technique is carried out. We prove that there is an optimal chirped probe pulse length (or an optimal chirp rate of the chirped probe pulse) matched to the input THz pulse length and derive a rigorous relationship between them. We find that only under this restricted condition the THz signal can be correctly retrieved. PMID:18679511

Peng, Xiao-Yu; Willi, Oswald; Chen, Min; Pukhov, Alexander

2008-08-01

130

All-Optical High-Frequency Electrical Chirped Pulse Generation using a Nonlinearly Chirped Fiber Bragg Grating  

Microsoft Academic Search

In this paper, two novel approaches to optically generating high-frequency chirped electrical pulses with tunable chirp rate using a tunable nonlinearly chirped fiber Bragg grating (NL-CFBG) are proposed. In the first approach, a high-frequency electrical chirped pulse is generated based on optical spectral shaping and nonlinear wavelength-to-time conversion using a tunable NL-CFBG. In the second approach, two ultrashort pulses at

Chao Wang; Jianping Yao

2007-01-01

131

Rotational spectroscopy of iodobenzene and iodobenzene–neon with a direct digital 2–8 GHz chirped-pulse Fourier transform microwave spectrometer  

Microsoft Academic Search

The design of a chirped-pulse Fourier transform microwave spectrometer operating in the 2–8GHz frequency range is presented. The linear frequency sweep is generated by an arbitrary waveform generator with a sampling rate of 20 GS\\/s. After amplification, the microwave pulse is broadcast into a vacuum chamber where it interacts with a supersonically expanded molecular sample. The resulting molecular free induction

Justin L. Neill; Steven T. Shipman; Leonardo Alvarez-Valtierra; Alberto Lesarri; Zbigniew Kisiel; Brooks H. Pate

2011-01-01

132

Advanced transient waveform digitizers  

NASA Astrophysics Data System (ADS)

A series of multi-channel transient waveform digitization integrated circuits with up to 5 GHz sample rates and parallel 10-bit digitization has been designed, tested, and fabricated in large quantities. The current CMOS circuit uses four arrays of 128 fast switched capacitors per channel to record four parallel analog transient inputs. Triggering and clocking is provided by a current-mode adjustable asynchronous active delay line that uses look-ahead to generate 128 4-way interleaved clocks without the need for external high-speed clocking. After transient capture, each channel is fed into 128 parallel 10-bit analog to digital converters for fast, channel-parallel digitization, followed by digital readout. The fast triggering and waveform capture, channel-parallel digitization and convenient word-parallel digital readout results in a responsive and low dead-time system. Acquisition sample rates range from ~50 kHz to ~3 GHz. Analog input bandwidth is approximately 350 MHz. Fixed-pattern spatial noise, after on-chip digitization, is equivalent to ~5 mV RMS. Temporal noise is typically equivalent to ~1 mV RMS, for a signal to noise ratio of ~2,500:1, RMS. This integrated circuit, the "Analog Transient Waveform Digitizer," has been successfully used to instrument the AMANDA and KamLAND neutrino physics experiments, and has been selected for use in the IceCube neutrino observatory. Current efforts to improve this technology will yield larger array sizes, sample rates in excess of 10 GHz, analog bandwidth exceeding 1 GHz, higher conversion rates, lower dead-time, greater uniformity and enhanced flexibility and ease of use.

Kleinfelder, Stuart

2003-02-01

133

Reflection seismic waveform tomography  

NASA Astrophysics Data System (ADS)

In seismic waveform tomography, if using reflection data with limited source-receiver offsets, it is difficult to reconstruct the deep part of the subsurface velocity model. We present two approaches to tackle this problem: layer stripping and weighted updating. In a layer-stripping procedure, we replace the top portion of seismic data with synthetics generated from the previous-layer inversion and make the current inversion focus on the minimization of the data misfit corresponding to the deep part of the model. To improve efficiency, we use only sparsely sampled frequency data in the deeper-layer inversions, unlike the first-layer inversion where we use densely sampled frequency data as usual. The sparsely sampled frequencies together have the full wave number coverage for effective imaging. Combined use of dense and sparse sampling in frequency is a compromise between resolution and efficiency, as it reduces the number of iterations needed in layer-stripping inversion while still producing a good image. In the second scheme, we apply depth-dependent weights to model updates in order to improve the convergence in an iterative solution. The weighting is inversely proportional to the ray density variation along the depth and is mathematically equivalent to the application of an inverse Hessian matrix which sharpens the gradient vector for model updating. For real seismic data, we transfer point source shot records to line source records, by partial amplitude compensation and phase adjusting, before inputting it to the waveform tomography. We perform traveltime inversion to generate a reliable layered velocity model and then waveform tomography to produce a high-resolution image of the subsurface model through frequency domain iteration.

Wang, Yanghua; Rao, Ying

2009-03-01

134

High precision triangular waveform generator  

DOEpatents

An ultra-linear ramp generator having separately programmable ascending and descending ramp rates and voltages is provided. Two constant current sources provide the ramp through an integrator. Switching of the current at current source inputs rather than at the integrator input eliminates switching transients and contributes to the waveform precision. The triangular waveforms produced by the waveform generator are characterized by accurate reproduction and low drift over periods of several hours. The ascending and descending slopes are independently selectable.

Mueller, Theodore R. (Oak Ridge, TN)

1983-01-01

135

Improved transmission performance resulting from the reduced chirp of a semiconductor laser coupled to an external high-Q resonator  

SciTech Connect

The coupling of a Fabry--Perot laser to an external high-{ital Q} resonator, whose resonance frequencies are not altered by changes in the carrier density, yields a dynamic single-longitudinal-mode laser with a significantly reduced transient frequency chirp. The improvement in the receiver sensitivity due to the reduced chirp is examined for NRZ and RZ intensity modulation, direct detection systems operating in the 1.55-{mu}m wavelength region with conventional single-mode optical fiber. The methodology involves a solving modified rate equations numerically for the optical power and phase of the external resonator laser in response to an injected current waveform, modeling the signal transmission properties of single-mode optical fibers by convolution and modulus squared operations, and using a truncated pulse train approximation to evaluate the probability of error in the presence of intersymbol interference, shot noise, APD multiplication noise, and preamplifier circuit noise.

Cartledge, J.C. (Bellcore, Red Bank, NJ (US))

1990-05-01

136

Chirp excitation of ultrasonic probes and algorithm for filtering transit times in high-rangeability gas flow metering.  

PubMed

The signal processing used in an ultrasonic high-rangeability gas flow meter using times of flight is presented. The flow meter under discussion uses a combination of continuous wave and chirp signals to measure at low flow velocities, below 20 m/s, and chirp signals alone to measure high flow velocities, above 20 m/s. Because of the need for a pulse compression technique in the signal waveform design the technique of pulse compression and the choice of signal waveforms are discussed. The advantages and disadvantages of amplitude weighting vis-a-vis frequency domain manipulations of the waveforms are also discussed. To eliminate spurious times of flight, a special filtering technique is used, based on assessing the gradient of ascendingly ordered time series of time-of-flight measurements. A summary of user experience with high-rangeability gas flow meters in use on different offshore platforms and in refineries is given. Long-term tests that examined the accuracy of the high-rangeability flow meter are also described. PMID:18263174

Folkestad, T; Mylvaganam, K S

1993-01-01

137

Automatic frequency control for FM transmitter  

NASA Technical Reports Server (NTRS)

An automatic frequency control circuit for an FM television transmitter is described. The frequency of the transmitter is sampled during what is termed the back porch portion of the horizontal synchronizing pulse which occurs during the retrace interval, the frequency sample compared with the frequency of a reference oscillator, and a correction applied to the frequency of the transmitter during this portion of the retrace interval.

Honnell, M. A. (inventor)

1974-01-01

138

Separation model for multipath FM signals transmission  

Microsoft Academic Search

In this paper, it is assumed that the channel without noise and the proposed algorithm based on phase-locked-loop (PLL) and amplitude-locked-loop (ALL) systems, which separated the FM multipath cosine signals. It can be represented as an autoregressive (AR) process under channel without noise. We adopted the discrete state-space procedure for searching the optimal weight coefficients value by updating Kalman gain

Gwo-Jia Jong; Jing-Zu Chen; Te-Jen Su

2005-01-01

139

Above-threshold ionization by chirped laser pulses  

SciTech Connect

We theoretically investigate above-threshold ionization by chirped laser pulses. By comparing the photoelectron energy spectra and the photoelectron angular distributions of Na for the laser pulses with different chirp rates but with the identical spectral profile, we find that the ionization processes have a clear dependence on the chirp rate. Further calculations without excited bound states during the time propagation of the wave function reveal practically no chirp dependence, which is clear evidence that the origin of the chirp dependence in above-threshold ionization is the excited bound states.

Nakajima, Takashi [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)

2007-05-15

140

Time reversed photonic beamforming of arbitrary waveform ladar arrays  

NASA Astrophysics Data System (ADS)

Herein is described a novel approach of performing adaptive photonic beam forming of an array of optical fibers with the expressed purpose of performing laser ranging. The beam forming technique leverages the concepts of time reversal, previously implemented in the sonar community, and wherein photonic implementation has recently been described for use by beamforming of ultra-wideband radar arrays. Photonic beam forming is also capable of combining the optical output of several fiber lasers into a coherent source, exactly phase matched on a pre-determined target. By implementing electro-optically modulated pulses from frequency chirped femtosecond-scale laser pulses, ladar waveforms can be generated with arbitrary spectral and temporal characteristics within the limitations of the wide-band system. Also described is a means of generating angle/angle/range measurements of illuminated targets.

Cox, Joseph L.; Zmuda, Henry; Bussjaeger, Rebecca J.; Erdmann, Reinhard K.; Fanto, Michael L.; Hayduk, Michael J.; Malowicki, John E.

2007-04-01

141

Photonic Generation of Chirped Microwave Pulses Using Superimposed Chirped Fiber Bragg Gratings  

Microsoft Academic Search

A novel approach to generating linearly chirped microwave pulses in the optical domain based on spectral shaping and linear frequency-to-time mapping is proposed and experimentally demonstrated. In the proposed system, the spectrum of a femtosecond pulse generated by a mode-locked fiber laser is spectrum-shaped by an optical filter that consists of two superimposed chirped fiber Bragg gratings (SI-CFBGs) with different

Chao Wang; Jianping Yao

2008-01-01

142

47 CFR 73.597 - FM stereophonic sound broadcasting.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false FM stereophonic sound broadcasting. 73.597 Section 73...Stations § 73.597 FM stereophonic sound broadcasting. A noncommercial educational...authority from the FCC, transmit stereophonic sound programs upon installation of...

2013-10-01

143

47 CFR 73.322 - FM stereophonic sound transmission standards.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false FM stereophonic sound transmission standards. 73.322 Section...Stations § 73.322 FM stereophonic sound transmission standards. (a) An...one channel of a two channel (biphonic) sound transmission, modulation of the...

2013-10-01

144

47 CFR 73.515 - NCE FM transmitter location.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 2009-10-01 false NCE FM transmitter location. 73.515 Section...COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.515...

2009-10-01

145

47 CFR 73.599 - NCE-FM engineering charts.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 2009-10-01 false NCE-FM engineering charts. 73.599 Section...COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.599...

2009-10-01

146

Extension of harmonic cutoff in a multicycle chirped pulse combined with a chirp-free pulse  

SciTech Connect

We demonstrate high-order harmonic generation in a wave form synthesized by a multicycle 800-nm chirped laser pulse and a chirp-free laser pulse. Compared with the case of using only a chirped pulse, both the harmonic cutoff and the extreme ultraviolet supercontinuum can be extended when a weak chirp-free pulse is combined with the chirped pulse. When chirp-free pulse intensity grows, the cutoff energy and bandwidth of the supercontinuum grow as well. It is found that the broad supercontinuum can be achieved for a driving pulse with long duration even though the driving pulse reaches 10 optical cycles. An isolated attosecond pulse with duration of about 59 as is obtained, and after appropriate phase compensation with a duration of about 11 as. In addition, by performing time-frequency analyses and the classical trajectory simulation, the difference in supercontinuum generation between the preceding wave form and a similar wave form synthesized by an 800-nm fundamental pulse and a 1600-nm subharmonic pulse is investigated.

Xu Junjie; Zeng Bin; Yu Yongli [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, P.O. Box 800-211, Shanghai 201800 (China)

2010-11-15

147

Radar/sonar acceleration estimation with linear-period modulated waveforms  

NASA Astrophysics Data System (ADS)

Doppler and acceleration tolerance of wideband LPM/HFM (linear period-modulated, hyperbolic frequency-modulated) and linear FM signals are compared. A bank of filters matched to frequency-shifted versions of a wideband LPM/HFM transmission system yields a joint maximum-likelihood estimate of range and acceleration and avoids acceleration-induced degradation in detection performance. Analytical and neurophysiological results suggest that such processing can be used in bat echolocation for detection and classification of insect wing motion, since wideband LFM waveforms are much less Doppler-tolerant than HFM waveforms but have greater acceleration tolerance.

Altes, Richard A.

1990-11-01

148

Superconductive chirp-transform spectrum analyzer  

SciTech Connect

Spectral analysis over an instantaneous bandwidth of 2.4 GHz was demonstrated, utilizing superconductive dispersive delay lines in a chirp-transform configuration. Two-tone resolution of 43 MHz and + or - 1.2 dB amplitude uniformity was achieved.

Withers, R.S.; Reible, S.A.

1985-06-01

149

Cr4+ : YAG chirped-pulse oscillator  

PubMed Central

We demonstrate chirped-pulse operation of a Cr : YAG passively mode-locked laser. Different operation regimes of the laser are extensively investigated in the vicinity of zero dispersion both experimentally and numerically. It is shown that for a given laser configuration, transition to the positive dispersion regime allows a 5-fold increase in the output pulse energy, which is otherwise limited by the onset of the multipulsing or ‘chaotic’ mode-locking. The output pulses have 1.4 ps duration and are compressible down to 120 fs in a 3 m piece of silica fiber, enabling supercontinuum generation in a nonlinear fiber. The spectrum shape and operation stability of the chirped-pulse regime depend strongly on the amount and shape of the intracavity dispersion. The numerical model predicts the existence of the minimum amount of the positive dispersion, above which the chirped-pulse regime can be realized. Once located, the chirped-pulse regime can be reliably reproduced and is sufficiently stable for applications.

Sorokin, Evgeni; Kalashnikov, Vladimir L; Mandon, Julien; Guelachvili, Guy; Picque, Nathalie; Sorokina, Irina T

2010-01-01

150

Superconductive Chirp-Transform Spectrum Analyzer.  

National Technical Information Service (NTIS)

Spectral analysis over an instantaneous bandwidth of 2.4 GHz has been demonstrated utilizing superconductive dispersive delay lines in a chirp-transform configuration. Two-tone resolution of 43 MHz and + or - 1.2 dB amplitude uniformity was achieved.

R. S. Withers S. A. Reible

1985-01-01

151

Parameter estimation for superimposed chirp signals  

Microsoft Academic Search

Parameter estimation for superimposed chirp signals is a difficult signal processing problem that shows up in many applications. Cramer-Rao lower bounds are derived here for the error variance in the parameter estimates. The approach reported uses global Hankel rank reduction to estimate instantaneous frequencies followed by total least squares fitting to obtain initial estimates of the parameters. These estimates are

R. M. Liang; K. S. Arun

1992-01-01

152

Compression of amplified chirped optical pulses  

Microsoft Academic Search

A system is reported which transposes a short-pulse amplification technique employed in radar to the optical regime and that, in principle, should be capable of producing short (1 pc or less) pulses with energies at the Joule level. The technique involves stretching a chirped optical pulse and then amplifying it before recompression. To date, 2-ps pulses with an energy of

D. Strickland; G. Mourou

1985-01-01

153

MIMO Radar - Waveforms and Applications  

Microsoft Academic Search

This paper describes two applications suited to the particular characteristics of MIMO radar. We provide a brief description of the MIMO radars which could meet these applications and present a detailed analysis of two candidate waveform types suited to these applications. Each of the waveform types are shown to have different characteristics that make them better suited to one application

B. J. Donnet; I. D. Longstaff

154

EMG burst waveform recognition procedure  

Microsoft Academic Search

A fast, simple EMG (electromyogram) burst waveform recognition algorithm has been developed for a personal computer. Raw EMG data are detrended, squared, and filtered. A sample EMG waveform segment, known as a template, is drawn from this data. A recognition signal is constructed as the convolution of the template and the prepared EMG data. This recognition signal is interpreted to

G. Dwyer; Y. Noguchi; H. H. Szeto

1989-01-01

155

STRS Compliant FPGA Waveform Development  

NASA Technical Reports Server (NTRS)

The Space Telecommunications Radio System (STRS) Architecture Standard describes a standard for NASA space software defined radios (SDRs). It provides a common framework that can be used to develop and operate a space SDR in a reconfigurable and reprogrammable manner. One goal of the STRS Architecture is to promote waveform reuse among multiple software defined radios. Many space domain waveforms are designed to run in the special signal processing (SSP) hardware. However, the STRS Architecture is currently incomplete in defining a standard for designing waveforms in the SSP hardware. Therefore, the STRS Architecture needs to be extended to encompass waveform development in the SSP hardware. The extension of STRS to the SSP hardware will promote easier waveform reconfiguration and reuse. A transmit waveform for space applications was developed to determine ways to extend the STRS Architecture to a field programmable gate array (FPGA). These extensions include a standard hardware abstraction layer for FPGAs and a standard interface between waveform functions running inside a FPGA. A FPGA-based transmit waveform implementation of the proposed standard interfaces on a laboratory breadboard SDR will be discussed.

Nappier, Jennifer; Downey, Joseph; Mortensen, Dale

2008-01-01

156

47 CFR 73.599 - NCE-FM engineering charts.  

Code of Federal Regulations, 2013 CFR

... 4 2013-10-01 2013-10-01 false NCE-FM engineering charts. 73.599 Section 73.599 Telecommunication...Educational FM Broadcast Stations § 73.599 NCE-FM engineering charts. This section consists of the following...

2013-10-01

157

Waveform Sampler CAMAC Module  

SciTech Connect

A Waveform Sampler Module (WSM) for the measurement of signal shapes coming from the multi-hit drift chambers of the SLAC SLC detector is described. The module uses a high speed, high resolution analog storage device (AMU) developed in collaboration between SLAC and Stanford University. The AMU devices together with high speed TTL clocking circuitry are packaged in a hybrid which is also suitable for mounting on the detector. The module is in CAMAC format and provides eight signal channels, each recording signal amplitude versus time in 512 cells at a sampling rate of up to 360 MHz. Data are digitized by a 12-bit ADC with a 1 ..mu..s conversion time and stored in an on-board memory accessible through CAMAC.

Freytag, D.R.; Haller, G.M.; Kang, H.; Wang, J.

1985-09-01

158

Gaussian and click noise in an FM/FM multiplex receiver.  

NASA Technical Reports Server (NTRS)

An FM/FM system is one in which the signal information frequency modulates a subcarrier, which, in turn, frequency modulates a main carrier for transmission. The detection process then involves two frequency demodulators in sequence. Using Rice's click model for both FM demodulators, we obtain the average click rate and an approximate output spectrum that include the effect of the impulses generated by the carrier demodulator on the subcarrier demodulation at and below threshold. We then focus on the threshold behavior of these systems and the proportioning of their modulation parameters so as to provide certain desired characteristics. We find that due to the filtering action of the second demodulator, the number of output clicks from carrier generated spikes can be orders of magnitude smaller, yet their contribution to the output noise can be much greater than that produced by the first demodulation.

Stochel, N. H.; Schilling, D. L.

1972-01-01

159

The Climate Hazards group InfraRed Precipitation (CHIRP) with Stations (CHIRPS): Development and Validation  

NASA Astrophysics Data System (ADS)

CHIRP and CHIRPS are new quasi-global precipitation products with daily to seasonal time scales, a 0.05° resolution, and a 1981 to near real-time period of record. Developed by the Climate Hazards Group at UCSB and scientists at the U.S. Geological Survey Earth Resources Observation and Science Center specifically for drought early warning and environmental monitoring, CHIRPS provides moderate latency precipitation estimates that place observed hydrologic extremes in their historic context. Three main types of information are used in the CHIRPS: (1) global 0.05° precipitation climatologies, (2) time-varying grids of satellite-based precipitation estimates, and (3) in situ precipitation observations. CHIRP: The global grids of long-term (1980-2009) average precipitation were estimated for each month based on station data, averaged satellite observations, and physiographic parameters. 1981-present time-varying grids of satellite precipitation were derived from spatially varying regression models based on pentadal cold cloud duration (CCD) values and TRMM V7 training data. The CCD time-series were derived from the CPC and NOAA B1 datasets. Pentadal CCD-percent anomaly values were multiplied by pentadal climatology fields to produce low bias pentadal precipitation estimates. CHIRPS: The CHG station blending procedure uses the satellite-observed spatial covariance structure to assign relative weights to neighboring stations and the CHIRP values. The CHIRPS blending procedure is based on the expected correlation between precipitation at a given target location and precipitation at the locations of the neighboring observation stations. These correlations are estimated using the CHIRP fields. The CHG has developed an extensive archive of in situ daily, pentadal and monthly precipitation totals. The CHG database has over half a billion daily rainfall observations since 1980 and another half billion before 1980. Most of these observations come from four sets of global climate observations: the monthly Global Historical Climate Network version 2 archive, the daily Global Historical Climate Network archive, the Global Summary of the Day dataset (GSOD), and the daily Global Telecommunication System (GTS) archive provided by NOAA's Climate Prediction Center (CPC). A screening procedure was developed to flag and remove potential false zeros from the daily data, since these potentially spurious data can artificially suppress rainfall totals. Validation: Our validation focused on precipitation products with global coverage, long periods of record and near real-time availability: CHIRP, CHIRPS, CPC-Unified, CFS Reanalysis and ECMWF datasets were compared to GPCC and high quality datasets from Uganda, Colombia and the Sahel. The CHIRP and CHIRPS are shown to have low systematic errors (bias) and low mean absolute errors. Analyses in Uganda, Colombia and the Sahel indicate that the ECMWF, CPC-Unified and CFS-Reanalysis have large inhomogeneities, making them unsuitable for drought monitoring. The CHIRPS performance appears quite similar to research quality products like the GPCC and GPCP, but with higher resolution and lower latency.

Peterson, P.; Funk, C. C.; Husak, G. J.; Pedreros, D. H.; Landsfeld, M.; Verdin, J. P.; Shukla, S.

2013-12-01

160

FM-MRR analog audio system  

NASA Astrophysics Data System (ADS)

In this work, we describe a hybrid free-space infrared communications link that supports audio transmission. The technique combines conventional frequency modulation (FM) techniques with optical amplitude modulation (AM) with a Multiple Quantum Well (MQW) Modulating Retroreflector (MRR) technology. The method has produced a robust, low power system capable of transmitting high quality audio information over a free space infrared link extending to multiple kilometers, depending on the characteristics of the Transmit/Receiver (interrogator) and the sensor/ MRR unit at the data source.

Murphy, J. L.; Gilbreath, G. C.; Rabinovich, W. S.; Sepantaie, M. M.; Goetz, P. G.

2005-08-01

161

A fine resolution multifrequency polarimetric FM radar  

NASA Astrophysics Data System (ADS)

A fine resolution polarimetric FM SAR was developed for optimization of polarimetric SARs and interpretation of SAR data via controlled experiments with surface-base sensors. The system is designed for collecting polarimetric data at 5.3 and 10 GHz over incidence angles from 0 to 60 deg. Features of the system include broad bandwidth to obtain fine range resolution, phase stabilization and linearization loop circuitry, and digital signal processing capability. The system is used in a research program to collect polarimetric backscatter data from artificial sea ice research and design trade-offs, laboratory and field evaluation, as well as results from experiments on artificial sea ice are presented.

Bredow, J.; Gogineni, S.; Leung, T.; Moore, R. K.

1988-08-01

162

Microscopic analysis of the fission barriers in 256Fm and 258Fm  

NASA Astrophysics Data System (ADS)

The fission barriers of 256Fm and 258Fm have been analyzed in the HFB theory. The potential energy and the effective inertia parameter have been calculated in the two-dimensional deformation space of quadrupole and octupole moments. Fission paths for various octupole moments of the exit point from the fission barrier have been determined. The half-life along each path has been calculated. The shortest half-lives have been obtained for the paths with reflection symmetric shapes of nuclei in both the considered isotopes.

Warda, M.

2009-12-01

163

Zeptosecond high harmonic keV x-ray waveforms driven by midinfrared laser pulses.  

PubMed

We demonstrate theoretically that the temporal structure of high harmonic x-ray pulses generated with midinfrared lasers differs substantially from those generated with near-infrared pulses, especially at high photon energies. In particular, we show that, although the total width of the x-ray bursts spans femtosecond time scales, the pulse exhibits a zeptosecond structure due to the interference of high harmonic emission from multiple reencounters of the electron wave packet with the ion. Properly filtered and without any compensation of the chirp, regular subattosecond keV waveforms can be produced. PMID:23909315

Hernández-García, C; Pérez-Hernández, J A; Popmintchev, T; Murnane, M M; Kapteyn, H C; Jaron-Becker, A; Becker, A; Plaja, L

2013-07-19

164

Design constraints of optical parametric chirped pulse amplification based on chirped quasi-phase-matching gratings.  

PubMed

Chirped quasi-phase-matching (QPM) gratings offer efficient, ultra-broadband optical parametric chirped pulse amplification (OPCPA) in the mid-infrared as well as other spectral regions. Only recently, however, has this potential begun to be realized [1]. In this paper, we study the design of chirped QPM-based OPCPA in detail, revealing several important constraints which must be accounted for in order to obtain broad-band, high-quality amplification. We determine these constraints in terms of the underlying saturated nonlinear processes, and explain how they were met when designing our mid-IR OPCPA system. The issues considered include gain and saturation based on the basic three-wave mixing equations; suppression of unwanted non-collinear gain-guided modes; minimizing and characterizing nonlinear losses associated with random duty cycle errors in the QPM grating; avoiding coincidentally-phase-matched nonlinear processes; and controlling the temporal/spectral characteristics of the saturated nonlinear interaction in order to maintain the chirped-pulse structure required for OPCPA. The issues considered place constraints both on the QPM devices as well as the OPCPA system. The resulting experimental guidelines are detailed. Our results represent the first comprehensive discussion of chirped QPM devices operated in strongly nonlinear regimes, and provide a roadmap for advancing and experimentally implementing OPCPA systems based on these devices. PMID:24787850

Phillips, C R; Mayer, B W; Gallmann, L; Fejer, M M; Keller, U

2014-04-21

165

Coherent Stark nonlinear spectroscopy with chirped pulses  

NASA Astrophysics Data System (ADS)

Quantum control of the four-wave mixing produced by two-color ?-3? femtosecond laser pulses propagating in a two-level system is accomplished by varying the relative phase between the two laser pulses. The phase sensitivity of the spectral 5? anti-Stokes component is cancelled when the ac Stark shift produced by the ? and 3? pulses is compensated. We apply perturbation theory and provide simple analytical formulas for the phase-sensitivity cancellation in the 5? anti-Stokes component. We demonstrate that this quantum interference effect is robust against chirping of the pulses and show that asymmetric chirping results in phase-sensitive shaping of the four-wave mixing spectra.

Serrat, C.; Loiko, Yu.; de La Cruz, R.; Cela, J. M.

2007-01-01

166

Coherent control of ultracold collisions with chirped light: Direction matters  

SciTech Connect

We demonstrate the ability to coherently control ultracold atomic Rb collisions using frequency-chirped light on the nanosecond time scale. For certain center frequencies of the chirp, the rate of inelastic trap-loss collisions induced by negatively chirped light is dramatically suppressed compared to the case of a positive chirp. We attribute this to a fundamental asymmetry in the system: an excited wave packet moves inward on the attractive molecular potential. For a positive chirp, the resonance condition moves outward in time, while for a negative chirp, it moves inward, in the same direction as the excited wave packet; this allows multiple interactions between the wave packet and the light, enabling the wave packet to be returned coherently to the ground state. Classical and quantum calculations support this interpretation.

Wright, M. J.; Pechkis, J. A.; Carini, J. L.; Gould, P. L. [Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States); Kallush, S.; Kosloff, R. [Department of Physical Chemistry and the Fritz Haber Research Center for Molecular Dynamics, The Hebrew University, 91094, Jerusalem (Israel)

2007-05-15

167

A Segmented Chirped-Pulse Fourier Transform Mm-Wave Spectrometer (260-295 Ghz) with Real-Time Signal Averaging Capability  

NASA Astrophysics Data System (ADS)

The design and performance of a 260-295 GHz segmented chirped-pulse Fourier transform mm-wave spectrometer is presented. The spectrometer uses an arbitrary waveform generator to create an excitation and detection waveform. The excitation waveform is a series of chirped pulses with 720 MHz bandwidth at mm-wave and about 200 ns pulse duration. The excitation pulses are produced using an x24 active multiplier chain with a peak power of 30 mW. Following a chirped pulse excitation, the molecular emission from all transitions in the excitation bandwidth is detected using heterodyne detection. The free induction decay (FID) is collected for about 1.5 microseconds and each segment measurement time period is 2 microseconds. The local oscillator for the detection in each segment is also created from the arbitrary waveform generator. The full excitation waveform contains 50 segments that scan the chirped pulse frequency and LO frequency across the 260-295 GHz frequency range in a total measurement time of 100 microseconds. The FID from each measurement segment is digitized at 4 GSamples/s, for a record length of 400 kpts. Signal averaging is performed by accumulating the FID signals from each sweep through the spectrum in a 32-bit FPGA. This allows the acquisition of 16 million sequential 260-295 GHz spectra in real time. The final spectrum is produced from fast Fourier transform of the FID in each measurement segment with the frequency calculated using the segment's LO frequency. The agility of the arbitrary waveform generator light source makes it possible to perform several coherent spectroscopic measurements to speed the analysis of the spectrum. In particular, high-sensitivity double-resonance measurements can be performed by applying a "pi-pulse" to a selected molecular transition and observing the changes to all other transitions in the 260-295 GHz frequency range of the spectrometer. In this mode of operation, up to 50 double-resonance frequencies can be used in each segment with the double-resonance signal collection taking place in real time.

Harris, Brent J.; Steber, Amanda L.; Pate, Brooks H.

2013-06-01

168

Recent EISCAT heating results using chirped ISR  

Microsoft Academic Search

The chirp technique has recently become fully operational on the EISCAT UHF radar system and has been used for daytime observations of the HF-modified ionosphere over Ramfjordmoen in November 1992 and March 1993. During certain periods the UHF observations show a difference in the frequencies of the photoelectron-enhanced plasma line and the HF-enhanced plasma line (HFPL) similar to the one

B. Isham; C. La Hoz; H. Kohl; T. Hagfors; T. B. Leyser; M. T. Rietveld

1996-01-01

169

Precision SAR processing using chirp scaling  

Microsoft Academic Search

A space-variant interpolation is required to compensate for the migration of signal energy through range resolution cells when processing synthetic aperture radar (SAR) data, using either the classical range\\/Doppler (R\\/D) algorithm or related frequency domain techniques. In general, interpolation requires significant computation time, and leads to loss of image quality, especially in the complex image. The new chirp scaling algorithm

R. Keith Raney; H. Runge; Richard Bamler; Ian G. Cumming; Frank H. Wong

1994-01-01

170

Spectral shaping in chirped-pulse amplification  

SciTech Connect

The role of spectral shaping in the production of subpicosecond, high-contrast pulses using chirped-pulse amplification in Nd:glass lasers is described. Spectral shaping has been used to produce 3.2-TW pulses at 750 fsec with an energy contrast of better than 10{sup 3}:1. In the absence of shaping, compression of the 1053-nm pulses yielded only 1.5 psec and a contrast ratio of approximately 10:1.

Perry, M.D.; Patterson, F.G. (Lawrence Livermore National Laboratory, P.O. Box 808, L-473, Livermore, California 94550 (USA)); Weston, J.; Pax, P. (Continuum, 3150 Central Expressway, Santa Clara, California 95051 (USA))

1990-04-01

171

Doppler-Tolerant Signal Waveforms.  

National Technical Information Service (NTIS)

When Doppler distortions of radar signals can be neglected, correlation or marched-filter processing is relatively simple. In those applications where high resolution requirements and high target speeds combine, the distortions in the waveform lead to sev...

A. W. Rihaczek

1966-01-01

172

Reduced chirping in coupled-cavity-semiconductor lasers  

Microsoft Academic Search

Chirping in coupled-cavity lasers is studied experimentally and theoretically. Using a conventional and a cleaved-coupled-cavity (C3) laser obtained from the same wafer, we find that the chirp for a C3 laser is typically reduced by a factor of 2. A simple rate equation model is presented to account for reduced chirping. Mode selectivity arising from the cavity coupling is incorporated

G. P. Agrawal; N. A. Olsson; N. K. Dutta

1984-01-01

173

Reduced chirping in coupled-cavity-semiconductor lasers  

Microsoft Academic Search

Chirping in coupled-cavity lasers is studied experimentally and theoretically. Using a conventional and a cleaved-coupled-cavity (C³) laser obtained from the same wafer, we find that the chirp for a C³ laser is typically reduced by a factor of 2. A simple rate equation model is presented to account for reduced chirping. Mode selectivity arising from the cavity coupling is incorporated

G. P. Agrawal; N. A. Olsson; N. K. Dutta

1984-01-01

174

Reduced chirping in coupled-cavity-semiconductor lasers  

SciTech Connect

Chirping in coupled-cavity lasers is studied experimentally and theoretically. Using a conventional and a cleaved-coupled-cavity (C/sup 3/) laser obtained from the same wafer, we find that the chirp for a C/sup 3/ laser is typically reduced by a factor of 2. A simple rate equation model is presented to account for reduced chirping. Mode selectivity arising from the cavity coupling is incorporated through wavelength-dependent cavity-loss variations.

Agrawal, G.P.; Olsson, N.A.; Dutta, N.K.

1984-07-15

175

Coherent Control of Stimulated Raman Scattering Using Chirped Laser Pulses  

Microsoft Academic Search

A novel method for the control of stimulated Raman scattering in short-pulse laser-plasma interactions is proposed. Linear frequency chirp in a non-bandwidth limited pulse is used to selectively increase or decrease the instability growth rate, depending on the sign of the chirp. Theoretical calculations show that a chirped pulse with 12% bandwidth is needed to eliminate forward Raman scattering. The

Evan Dodd; Donald Umstadter

1999-01-01

176

The effect of laser chirping on lightwave system performance  

Microsoft Academic Search

Directly modulated semiconductor lasers exhibit a dynamic wavelength shift (chirping) arising from gain-induced variations of the laser refractive index. The effect of laser chirping on the performance of multi-Gb\\/s lightwave systems operating at a wavelength of 1550 nm is investigated. Models suitable for computer-aided analysis are used to describe the dynamic response of the laser and the propagation of chirped

J. C. Cartledge; G. S. Burley

1989-01-01

177

Mechanism of electron acceleration by chirped laser pulse  

SciTech Connect

We studied the mechanism of electron acceleration by a chirped laser pulse. We found that, because of the chirp effect, a region exists where the laser wave phase experienced by the electron varies slowly, so that the electron can be accelerated for a long time. The mechanism of chirped laser acceleration is different to that of the capture and acceleration scenario, although both of them have a main acceleration stage in which the electrons are trapped for long periods.

Wu, X. Y.; Wang, P. X. [Department of Nuclear Science and Technology, Institute of Modern Physics, Fudan University, Shanghai 200433, China and Applied Ion Beam Physics Laboratory, Key Laboratory of the Ministry of Education (China); Kawata, S. [Department of Advanced Interdisciplinary Science, Center for Optical Research and Education, Graduate School of Engineering, Utsunomiya University, Utsunomiya 321-8585 (Japan)

2012-05-28

178

Fast matching pursuit with a multiscale dictionary of Gaussian chirps  

Microsoft Academic Search

We introduce a modified matching pursuit algorithm, called fast ridge pursuit, to approximate N-dimensional signals with M Gaussian chirps at a computational cost O(MN) instead of the expected O(MN2 logN). At each iteration of the pursuit, the best Gabor atom is first selected, and then, its scale and chirp rate are locally optimized so as to get a “good” chirp

Rémi Gribonval

2001-01-01

179

pathChirp: Efficient Available Bandwidth Estimation for Network Paths  

Microsoft Academic Search

This paper presents pathChirp, a new active probing tool for estimating the available bandwidth on a communication network path. Based on the concept of ''self-induced congestion,'' pathChirp features an exponential flight pattern of probes we call a chirp. Packet chips offer several significant advantages over current probing schemes based on packet pairs or packet trains. By rapidly increasing the probing

Les

2003-01-01

180

Multiple mechanisms shape FM sweep rate selectivity: complementary or redundant?  

PubMed Central

Auditory neurons in the inferior colliculus (IC) of the pallid bat have highly rate selective responses to downward frequency modulated (FM) sweeps attributable to the spectrotemporal pattern of their echolocation call (a brief FM pulse). Several mechanisms are known to shape FM rate selectivity within the pallid bat IC. Here we explore how two mechanisms, stimulus duration and high-frequency inhibition (HFI), can interact to shape FM rate selectivity within the same neuron. Results from extracellular recordings indicated that a derived duration-rate function (based on tonal response) was highly predictive of the shape of the FM rate response. Longpass duration selectivity for tones was predictive of slowpass rate selectivity for FM sweeps, both of which required long stimulus durations and remained intact following iontophoretic blockade of inhibitory input. Bandpass duration selectivity for tones, sensitive to only a narrow range of tone durations, was predictive of bandpass rate selectivity for FM sweeps. Conversion of the tone duration response from bandpass to longpass after blocking inhibition was coincident with a change in FM rate selectivity from bandpass to slowpass indicating an active inhibitory component to the formation of bandpass selectivity. Independent of the effect of duration tuning on FM rate selectivity, the presence of HFI acted as a fastpass FM rate filter by suppressing slow FM sweep rates. In cases where both mechanisms were present, both had to be eliminated, by removing inhibition, before bandpass FM rate selectivity was affected. It is unknown why the auditory system utilizes multiple mechanisms capable of shaping identical forms of FM rate selectivity though it may represent distinct but convergent modes of neural signaling directed at shaping response selectivity for important biologically relevant sounds.

Williams, Anthony J.; Fuzessery, Zoltan M.

2012-01-01

181

Wavelets And Adapted Waveform Analysis  

Microsoft Academic Search

, scientist or engineer to choose the appropriate analysis method in thiscatalogue of tools and apply it to practical problems.In the adapted waveform transform (AWT) method the user is provided with a collectionof standard libraries of waveforms---wavelets, wavelet-packets, windowed trigonometricwaveforms---which can be chosen to fit specific classes of signals. These libraries comeequipped with fast numerical algorithms, enabling real-time implementation of

Ronald R. Coifman; M. Victor Wickerhauser

1992-01-01

182

Bright chirp-free and chirped nonautonomous solitons under dispersion and nonlinearity management  

NASA Astrophysics Data System (ADS)

We present a series of chirp-free and chirped analytical nonautonomous soliton solutions to the generalized nonlinear Schrodinger equation (NLSE) with distributed coefficients by Darboux transformation from a trivial seed. For chirpfree nonautonomous soliton, the dispersion management term can change the motion of nonautonomous soliton and do not affect its shape at all. Especially,the classical optical soliton can be presented with variable dispersion term and nonlinearity when there is no gain. For chirped nonautonomous soliton, dispersion management can affect the shape and motion of nonautonomous solitons meanwhile. The periodic dispersion term can be used to control its "breathing" shape, and it does not affect the trajectory of nonautonomous soliton center with a certain condition.

Yang, Zhan-Ying; Zhao, Li-Chen; Zhang, Tao; Yue, Rui-Hong

2011-02-01

183

Information theory and radar waveform design  

Microsoft Academic Search

The use of information theory to design waveforms for the measurement of extended radar targets exhibiting reso- nance phenomena is investigated. The target impulse response is introduced to model target scattering behavior. Two radar waveform design problems with constraints on waveform energy and duration are then solved. In the first, a deterministic target impulse response is used to design waveform\\/receiver-filter

Mark R. Bell

1993-01-01

184

STRS Compliant FPGA Waveform Development  

NASA Technical Reports Server (NTRS)

The Space Telecommunications Radio System (STRS) Architecture Standard describes a standard for NASA space software defined radios (SDRs). It provides a common framework that can be used to develop and operate a space SDR in a reconfigurable and reprogrammable manner. One goal of the STRS Architecture is to promote waveform reuse among multiple software defined radios. Many space domain waveforms are designed to run in the special signal processing (SSP) hardware. However, the STRS Architecture is currently incomplete in defining a standard for designing waveforms in the SSP hardware. Therefore, the STRS Architecture needs to be extended to encompass waveform development in the SSP hardware. A transmit waveform for space applications was developed to determine ways to extend the STRS Architecture to a field programmable gate array (FPGA). These extensions include a standard hardware abstraction layer for FPGAs and a standard interface between waveform functions running inside a FPGA. Current standards were researched and new standard interfaces were proposed. The implementation of the proposed standard interfaces on a laboratory breadboard SDR will be presented.

Nappier, Jennifer; Downey, Joseph

2008-01-01

185

Analysis of intrapulse chirp in CO2 oscillators  

NASA Technical Reports Server (NTRS)

Pulsed single-frequency CO2 laser oscillators are often used as transmitters for coherent lidar applications. These oscillators suffer from intrapulse chirp, or dynamic frequency shifting. If excessive, such chirp can limit the signal-to-noise ratio of the lidar (by generating excess bandwidth), or limit the velocity resolution if the lidar is of the Doppler type. This paper describes a detailed numerical model that considers all known sources of intrapulse chirp. Some typical predictions of the model are shown, and simple design rules to minimize chirp are proposed.

Moody, Stephen E.; Berger, Russell G.; Thayer, William J., III

1987-01-01

186

A Modified Subpulse SAR Processing Procedure Based on the Range-Doppler Algorithm for Synthetic Wideband Waveforms  

PubMed Central

Synthetic wideband waveforms (SWW) combine a stepped frequency CW waveform and a chirp signal waveform to achieve high range resolution without requiring a large bandwidth or the consequent very high sampling rate. If an efficient algorithm like the range-Doppler algorithm (RDA) is used to acquire the SAR images for synthetic wideband signals, errors occur due to approximations, so the images may not show the best possible result. This paper proposes a modified subpulse SAR processing algorithm for synthetic wideband signals which is based on RDA. An experiment with an automobile-based SAR system showed that the proposed algorithm is quite accurate with a considerable improvement in resolution and quality of the obtained SAR image.

Lim, Byoung-Gyun; Woo, Jea-Choon; Lee, Hee-Young; Kim, Young-Soo

2008-01-01

187

Quantum cascade laser FM spectroscopy of explosives  

NASA Astrophysics Data System (ADS)

Polyisobutylene is an industrial polymer that is widely used in a number of applications including the manufacture of military grade explosives. We have examined the vapor emanating from a series of different molecular weight samples of polyisobutylene using high resolution Quantum Cascade Laser FM spectroscopy. The vapor phase spectra all exhibit a rovibrational structure similar to that for the gas phase isobutylene molecule. We have assigned the structure in the 890 cm-1 and 1380 cm-1 regions to the isobutylene ?28 and ?7 fundamental bands respectively. These spectroscopic signatures may prove useful for infrared sensing applications. Here we will present the infrared signatures along with recent GCMS data from a sample of C4, utilizing solid-phase microextraction vapor collection fibers, which confirm the presence of isobutylene as one of the volatile bouquet species in RDX-based explosives.

Gutmann, Zach; Clasp, Trocia; Lue, Chris; Johnson, Tiffani; Ingle, Taylor; Jamison, Janet; Buchanan, Roger; Reeve, Scott

2013-05-01

188

Noncircular waveforms exploitation for Radar Signal processing: Survey and study for agile radar waveform  

Microsoft Academic Search

With new generation of Active Digital Radar Antenna, there is a renewal of waveform generation and processing approaches, and new strategies can be explored to optimize waveform design and waveform analysis and to benefit of all potential waveform diversity. Among these strategies, building and exploitation of the Noncircularity of waveforms is a promising issue. Up to the middle of the

F. Barbaresco; P. Chevalier

2009-01-01

189

a KA-BAND Chirped-Pulse Fourier Transform Microwave Spectrometer.  

NASA Astrophysics Data System (ADS)

The design and performance of a new chirped-pulse Fourier transform microwave (CP-FTMW) spectrometer operating from 25-40 GHz will be discussed. A 10.5-3 GHz linear frequency sweep, generated by a 24 GS/s arbitrary waveform generator, is upconverted by a 23.00 GHz phase-locked oscillator, then fed into an active doubler to create a 25-40 GHz chirped pulse. After amplification with a 60-80 W pulsed traveling wave tube amplifier, the pulse is broadcast across a molecular beam chamber where it interacts with a molecular sample. The molecular FID signal is downconverted with the 23 GHz oscillator so that it can be digitized on a 50 GS/s oscilloscope with 16 GHz hardware bandwidth. The sensitivity and phase stability of this spectrometer is comparable to that of the previously reported 6.5-18.5 CP-FTMW spectrometer. On propyne (?=0.78 D), a single-shot signal to noise ratio of approximately 200:1 is observed on the J=2-1 rotational transition at 34183 MHz when the full bandwidth is swept; optimal excitation is observed for this transition with a 250 MHz bandwidth sweep. The emission has a T_2 lifetime of 4 ?s. Early results from this spectrometer, particularly in the study of species of astrochemical interest, will be presented. G.G. Brown et al., Rev. Sci. Instrum. 79 (2008) 053103.

Zaleski, Daniel P.; Neill, Justin L.; Muckle, Matthew T.; Pate, Brooks H.; Carroll, P. Brandon; Weaver, Susanna L. Widicus

2010-06-01

190

Discrete chirp-Fourier transform and its application to chirp rate estimation  

Microsoft Academic Search

The discrete Fourier transform (DFT) has found tremendous applications in almost all fields, mainly because it can be used to match the multiple frequencies of a stationary signal with multiple harmonics. In many applications, wideband and nonstationary signals, however, often occur. One of the typical examples of such signals is chirp-type signals that are usually encountered in radar signal processing,

Xiang-Gen Xia

2000-01-01

191

A portable CW/FM-CW Doppler radar for local investigation of severe storms  

NASA Astrophysics Data System (ADS)

During the 1987 spring storm season we used a portable 1-W X-band CW Doppler radar to probe a tornado, a funnel cloud, and a wall cloud in Oklahoma and Texas. This same device was used during the spring storm season in 1988 to probe a wall cloud in Texas. The radar was battery powered and highly portable, and thus convenient to deploy from our chase vehicle. The device separated the receding and approaching Doppler velocities in real time and, while the radar was being used, it allowed convenient stereo data recording for later spectral analysis and operator monitoring of the Doppler signals in stereo headphones. This aural monitoring, coupled with the ease with which an operator can be trained to recognize the nature of the signals heard, made the radar very easy to operate reliably and significantly enhanced the quality of the data being recorded. At the end of the 1988 spring season, the radar was modified to include FM-CW ranging and processing. These modifications were based on a unique combination of video recording and FM chirp generation, which incorporated a video camera and recorder as an integral part of the radar. After modification, the radar retains its convenient portability and the operational advantage of being able to listen to the Doppler signals directly. The original mechanical design was unaffected by these additions. During the summer of 1988, this modified device was used at the Langmuir Laboratory at Socorro, New Mexico in an attempt to measure vertical convective flow in a thunderstorm.

Unruh, Wesley P.; Wolf, Michael A.; Bluestein, Howard B.

192

A portable CW/FM-CW Doppler radar for local investigation of severe storms  

SciTech Connect

During the 1987 spring storm season we used a portable 1-W X-band CW Doppler radar to probe a tornado, a funnel cloud, and a wall cloud in Oklahoma and Texas. This same device was used during the spring storm season in 1988 to probe a wall cloud in Texas. The radar was battery powered and highly portable, and thus convenient to deploy from our chase vehicle. The device separated the receding and approaching Doppler velocities in real time and, while the radar was being used, it allowed convenient stereo data recording for later spectral analysis and operator monitoring of the Doppler signals in stereo headphones. This aural monitoring, coupled with the ease with which an operator can be trained to recognize the nature of the signals heard, made the radar very easy to operate reliably and significantly enhanced the quality of the data being recorded. At the end of the 1988 spring season, the radar was modified to include FM-CW ranging and processing. These modifications were based on a unique combination of video recording and FM chirp generation, which incorporated a video camera and recorder as an integral part of the radar. After modification, the radar retains its convenient portability and the operational advantage of being able to listen to the Doppler signals directly. The original mechanical design was unaffected by these additions. During the summer of 1988, this modified device was used at the Langmuir Laboratory at Socorro, New Mexico in an attempt to measure vertical convective flow in a thunderstorm. 2 refs., 2 figs.

Unruh, W.P.; Wolf, M.A.; Bluestein, H.B.

1988-01-01

193

Fractals and the analysis of waveforms.  

PubMed

Waveforms are planar curves--ordered collections of (x, y) point pairs--where the x values increase monotonically. One technique for numerically classifying waveforms assesses their fractal dimensionality, D. For waveforms: D = log(n)/(log(n) + log(d/L], with n = number of steps in the waveform (one less than the number of (x, y) point pairs), d = planar extent (diameter) of the waveform, and L = total length of the waveform. Under this formulation, fractal dimensions range from D = 1.0, for straight lines through approximately D = 1.15 for random-walk waveforms, to D approaching 1.5 for the most convoluted waveforms. The fractal characterization may be especially useful for analyzing and comparing complex waveforms such as electroencephalograms (EEGs). PMID:3396335

Katz, M J

1988-01-01

194

Frequency chirping in semiconductor-optical fiber ring laser  

SciTech Connect

In this letter, a complete small-signal analysis for frequency chirping in the semiconductor-optical fiber ring laser is presented. It shows that chirp-to-power ratio (CPR) strongly depends on the junction phase shift, the optical coupling, and the phase detuning between two cavities, especially if the modulation frequency is below the gigahertz range. 7 refs.

Zhang, Jiangping; Ye, Peida (Beijing Univ. of Posts and Telecommunications (China))

1990-01-01

195

Some focusing properties of chirped gratings at microwave frequencies  

Microsoft Academic Search

The paper presents theoretical and experimental analyses of the focusing properties of metallic chirped gratings. It is shown that chirped gratings can be used to focus microwave energy at a predetermined position. The focal point depends on the exact width and space variations of the grating, as well as on the angle of incidence.

C. G. Christodoulou; J. C. Schmidt

1993-01-01

196

Phase-Locking Transition in a Chirped Superconducting Josephson Resonator  

Microsoft Academic Search

We observe a sharp threshold for dynamic phase locking in a high-Q transmission line resonator embedded with a Josephson tunnel junction, and driven with a purely ac, chirped microwave signal. When the drive amplitude is below a critical value, which depends on the chirp rate and is sensitive to the junction critical current I0, the resonator is only excited near

O. Naaman; J. Aumentado; L. Friedland; J. S. Wurtele; I. Siddiqi

2008-01-01

197

Electron acceleration by a chirped Gaussian laser pulse in vacuum  

SciTech Connect

Electron acceleration by a chirped Gaussian laser pulse is investigated numerically. A linear and negative chirp is employed in this study. At first, a simple analytical description for the chirp effect on the electron acceleration in vacuum is provided in one-dimensional model. The chirp mechanism is then extended to the interaction of a femtosecond laser pulse and electron. The electron final energy is obtained as a function of laser beam waist, laser intensity, chirp parameter, and initial phase of the laser pulse. It is shown that the electron final energy depends strongly on the chirp parameter and the initial phase of the laser pulse. There is an optimal value for the chirp parameter in which the electron acceleration takes place effectively. The energy gain increases with laser beam waist and intensity. It is also shown that the electron is accelerated within a few degrees to the axial direction. Emphasis is on the important aspect of the chirp effect on the energy gained by an electron from the electromagnetic wave.

Sohbatzadeh, F.; Mirzanejhad, S.; Ghasemi, M. [Physics Department, Science Faculty, Mazandaran University, Babolsar (Iran, Islamic Republic of)

2006-12-15

198

Beam homogenizers based on chirped microlens arrays.  

PubMed

Lens array arrangements are commonly used for the homogenization of highly coherent laser beams. These fly's eye condenser configurations can be used to shape almost arbitrary input intensity distributions into a top hat. Due to the periodic structure of regular arrays the output intensity distribution is modulated by equidistant sharp intensity peaks which are disturbing the homogeneity. As a new approach we apply chirped microlens arrays to the beam shaping system. These are non-regular arrays consisting of individually shaped lenses defined by a parametric description which can be derived completely from analytical functions. The advantages of the new concept and design rules are presented. PMID:19546927

Wippermann, Frank; Zeitner, Uwe-D; Dannberg, Peter; Bräuer, Andreas; Sinzinger, Stefan

2007-05-14

199

CHIRPED PULSE AMPLIFICATION OF HGHG-FEL FACILITY AT BNL.  

SciTech Connect

The DUV-FEL facility has been in operation in High Gain Harmonic Generation (HGHG) mode for one year producing 266 nm output from 177 MeV electrons. In this paper we present preliminary results of the Chirped Pulse Amplification (CPA) of HGHG radiation. In the normal HGHG process, a 1 ps electron beam is seeded by chirped 9 ps long 800 nm Ti:Sapphire laser. The electron beam sees only a narrow fraction of the seed laser bandwidth. However, in the CPA case the seed laser pulse length is reduced to 1 ps, and the electron beam sees the full bandwidth. We introduce an energy chirp on electron beam to match the chirp of the seed pulse, enabling the resonant condition for the whole beam. We present measurements of the spectrum bandwidth for various chirp conditions.

DOYURAN,A.ET AL.

2003-09-08

200

Raman forward scattering of high-intensity chirped laser pulses  

SciTech Connect

Raman forward scattering of a high-intensity, short-duration, frequency-chirped laser pulse propagating in an underdense plasma is examined. The growth of the direct forward scattered light is calculated for a laser pulse with a linear frequency chirp in various spatio-temporal regimes. This includes a previously undescribed regime of strongly-coupled four-wave nonresonant interaction, which is important for relativistic laser intensities. In all regimes of forward scattering, it is shown that the growth rate increases (decreases) for positive (negative) frequency chirp. The effect of chirp on the growth rate is relatively minor, i.e., a few percent chirp yields few percent changes in the growth rates. Relation of these results to recent experiments is discussed.

Schroeder, C.B.; Esarey, E.; Shadwick, B.A.; Leemans, W.P.

2002-06-23

201

Optical fringe reduction technique for FM laser spectroscopy  

NASA Technical Reports Server (NTRS)

A simple fringe reduction method for FM diode laser spectroscopy is discussed. The fringes can be effectively suppressed by using a modulation frequency that is an integral multiple of the free spectral range of the fringes. The technique is experimentally confirmed by two-tone FM spectroscopy of water vapor absorption lines. A factor of 20 fringe reduction is observed.

Chou, Nee-Yin; Sachse, Glen W.; Wang, Liang-Guo; Gallagher, Thomas F.

1989-01-01

202

47 CFR 73.4108 - FM transmitter site map submissions.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false FM transmitter site map submissions. 73.4108 Section 73.4108 Telecommunication...to All Broadcast Stations § 73.4108 FM transmitter site map submissions. See Memorandum Opinion and Order and...

2013-10-01

203

Basic examination of the FM ultrasonic flowmeter for gas  

Microsoft Academic Search

The construction of an ultrasonic gas flowmeter is difficult because the attenuation of ultrasonic waves and the effects of acoustic noises are considerably higher for gas than for liquid. The sound field of the proposed meter is stabilized by FM ultrasonic wave; however, the receiver eliminates the FM components. Therefore, the flow rate can be measured using a single frequency

T. Saitou; S. Tanisawa; H. Hirose

2002-01-01

204

Hearing Aid Accessories for Adults: The Remote FM Microphone  

Microsoft Academic Search

Objective: The primary goal was to determine the benefits and limitations of a remote FM microphone as a hearing aid accessory. A secondary goal was to determine the predictors of aided and FM-assisted speech perception by adults with hearing loss, in quiet and in noise, using methods derived from Articulation Index theory. Design: Twelve adults with mild to severe hearing

Arthur Boothroyd

2004-01-01

205

Automating seismic waveform analysis for full 3-D waveform inversions  

NASA Astrophysics Data System (ADS)

We present a semi-automatic seismic waveform selection algorithm that can be used in full 3-D waveform inversions for earthquake source parameters and/or earth structure models. The algorithm is applied on pairs of observed and synthetic seismograms. A pair of observed and synthetic seismograms are first segmented in the wavelet domain into a number of wave packets using a topological watershed algorithm. A set of user-adjustable criteria based on waveform similarities is then applied to match each wave packet obtained from the observed seismogram with the corresponding wave packet obtained from the synthetic seismogram. The selected wave packet pairs are then used for extracting frequency-dependent phase and amplitude misfit measurements, which can be used in seismic source and/or structural inversions. The algorithm takes advantage of time-frequency representations of seismograms and is able to separate seismic phases in both time and frequency domains. We demonstrate the flexibility of this algorithm using examples of full 3-D waveform inversions for earthquake centroid moment tensors and earth structure models at different geographic scales.

Lee, En-Jui; Chen, Po

2013-07-01

206

Convolutional coding/Viterbi decoding of PCM/FM  

NASA Astrophysics Data System (ADS)

Tests were run with a binary PCM/FM transmission channel using limiter/discriminator detection, and (7, 1/2) convolutional coding with Viterbi decoding. In all cases, soft decision decoding showed little or no improvement relative to hard-decision, evidently because of the pops in the FM demodulator. Under optimum PCM/FM conditions, namely p-p deviation = 0.7 f(s) and IFBW = f(s), the coding improvement at BER = 10 to the -6th was about 2.2 dB. The binary symbol rate in the transmission channel is f(s). In the course of the test, it was discovered that with PCM/FM under optimum conditions, channel errors frequently occurred in pairs. This severely reduces the value of parity bit when used with uncoded PCM/FM, and also degrades the Viterbi decoder performance by about 1 dB.

Cox, T. F.; Nichols, M. H.

207

Chirped fiber Bragg grating detonation velocity sensing  

NASA Astrophysics Data System (ADS)

An all optical-fiber-based approach to measuring high explosive detonation front position and velocity is described. By measuring total light return using an incoherent light source reflected from a linearly chirped fiber Bragg grating sensor in contact with the explosive, dynamic mapping of the detonation front position and velocity versus time is obtained. We demonstrate two calibration procedures and provide several examples of detonation front measurements: PBX 9502 cylindrical rate stick, radial detonation front in PBX 9501, and PBX 9501 detonation along curved meridian line. In the cylindrical rate stick measurement, excellent agreement with complementary diagnostics (electrical pins and streak camera imaging) is achieved, demonstrating accuracy in the detonation front velocity to below the 0.3% level when compared to the results from the pin data. Finally, an estimate on the linear spatial and temporal resolution of the system shows that sub-mm and sub-?s levels are attainable with proper consideration of the recording speed, detection sensitivity, spectrum, and chirp properties of the grating.

Rodriguez, G.; Sandberg, R. L.; McCulloch, Q.; Jackson, S. I.; Vincent, S. W.; Udd, E.

2013-01-01

208

Radar Waveform Design and the Heisenberg Group  

Microsoft Academic Search

This paper presents a number of constructions based on the Heisenberg group that are relevant to the problem of radar waveform design. All of the constructions are based on the modification of the Weil transform of a waveform.

L. Auslander; F. Geshwind; F. Warner

1995-01-01

209

Fiber Bragg gratings with various chirp profiles made in etched tapers  

NASA Astrophysics Data System (ADS)

We have studied, both theoretically and experimentally, fiber Bragg gratings with a number of different chirp profiles. These chirp profiles can easily be achieved by a recently demonstrated technique involving a taper of desired profile etched into the cladding of a fiber. The performances of gratings with linear, quadratic, periodically modulated, and step-chirp profiles are analyzed numerically. The versatility of the technique was demonstrated when linearly and quadratically chirped gratings were made as examples of continuous chirp, and gratings with step chirps were made as examples of discontinuously chirped structures.

Cruz, J. L.; Dong, L.; Barcelos, S.; Reekie, L.

1996-12-01

210

Parameter Biases Introduced by Approximate Gravitational Waveforms  

NASA Astrophysics Data System (ADS)

The production of the most accurate gravitational waveforms from compact binary mergers require Einstein's equations to be solved numerically, a process far too expensive to produce the ˜10^7 waveforms necessary to estimate the parameters of a measured gravitational wave signal. Instead, parameter estimation depends on approximate or phenomenological waveforms to characterize measured signals. As part of the Ninja collaboration, we study the biases introduced by these methods when estimating the parameters of numerically produced waveforms.

Farr, Benjamin; Coughlin, Scott; Le, John; Skeehan, Connor; Kalogera, Vicky

2013-04-01

211

Orthogonal waveforms for FMCW MIMO radar  

Microsoft Academic Search

Multiple input\\/multiple output (MIMO) radar system performance benefits from the capability to simultaneously transmit and receive multiple orthogonal waveforms. For pulse radars fitting orthogonal waveforms have been developed. These waveforms are however not necessarily suitable for frequency- modulated continuous-wave (FMCW) radar. The major benefit of the FMCW radar principle is that the bandwidth of the beat signal is generally much

J. J. M. de Wit; W. L. van Rossum; A. J. de Jong

2011-01-01

212

Phenomenological gravitational waveforms from spinning coalescing binaries  

Microsoft Academic Search

An accurate knowledge of the coalescing binary gravitational waveform is crucial for experimental searches as the ones performed by the LIGO-Virgo collaboration. Following an earlier paper by the same authors we refine the construction of analytical phenomenological waveforms describing the signal sourced by generically spinning binary systems. The gap between the initial inspiral part of the waveform, described by spin-Taylor

R. Sturani; S. Fischetti; L. Cadonati; G. M. Guidi; J. Healy; D. Shoemaker; A. Vicere

2010-01-01

213

Chirped pulse amplification in single mode Tm:fiber using a chirped Bragg grating  

NASA Astrophysics Data System (ADS)

We report femtosecond pulse generation and chirped pulse amplification in Tm:fiber. A mode-locked oscillator operating in the soliton regime produced 800 fs pulses with 5 nm spectral bandwidth, at 40 pJ pulse energy. This oscillator seeded a pre-amplifier that utilizes a Raman soliton self-frequency shift to produce wavelength tunable pulses with 3 nJ energy, reduced pulse duration of 150 fs, and increased bandwidth of 30 nm. For further amplification, the pulses were stretched up to 160 ps using a chirped Bragg grating (CBG). Stretched pulses were amplified to 85 nJ after compression in single-mode Tm:fiber and recompressed with the CBG as short as 400 fs. Compressed pulses were coupled into a highly nonlinear tellurite fiber to investigate the potential of this ultrashort pulse 2-?m fiber source as a pump for mid-IR supercontinuum generation.

Sims, R. Andrew; Kadwani, Pankaj; Ebendorff-Heideprem, Heike; Shah, Lawrence; Monro, Tanya M.; Richardson, Martin

2013-05-01

214

Propagation of chirped laser pulses in a plasma channel  

SciTech Connect

Propagation of an initially chirped, Gaussian laser pulse in a preformed parabolic plasma channel is analyzed. A variational technique is used to obtain equations describing the evolution of the phase shift and laser spot size. The effect of initial chirp on the laser pulse length and intensity of a matched laser beam propagating in a plasma channel has been analyzed. The effective pulse length and chirp parameter of the laser pulse due to its interaction with plasma have been obtained and graphically depicted. The resultant variation in laser frequency across the laser pulse is discussed.

Jha, Pallavi; Malviya, Amita; Upadhyay, Ajay K. [Department of Physics, University of Lucknow, Lucknow 226007 (India)

2009-06-15

215

Three-Dimensional Analysis of Frequency-Chirped FELs  

SciTech Connect

Frequency-chirped free-electron lasers (FELs) are useful to generate a large photon bandwidth or a shorter x-ray pulse duration. In this paper, we present a three-dimensional analysis of a high-gain FEL driven by the energy-chirped electron beam. We show that the FEL eigenmode equation is the same for a frequency-chirped FEL as for an undulator-tapered FEL. We study the transverse effects of such FELs including mode properties and transverse coherence.

Zhirong, Huang

2010-09-14

216

Chirped-Superlattice, Blocked-Intersubband QWIP  

NASA Technical Reports Server (NTRS)

An Al(x)Ga(1-x)As/GaAs quantum-well infrared photodetector (QWIP) of the blocked-intersubband-detector (BID) type, now undergoing development, features a chirped (that is, aperiodic) superlattice. The purpose of the chirped superlattice is to increase the quantum efficiency of the device. A somewhat lengthy background discussion is necessary to give meaning to a brief description of the present developmental QWIP. A BID QWIP was described in "MQW Based Block Intersubband Detector for Low-Background Operation" (NPO-21073), NASA Tech Briefs Vol. 25, No. 7 (July 2001), page 46. To recapitulate: The BID design was conceived in response to the deleterious effects of operation of a QWIP at low temperature under low background radiation. These effects can be summarized as a buildup of space charge and an associated high impedance and diminution of responsivity with increasing modulation frequency. The BID design, which reduces these deleterious effects, calls for a heavily doped multiple-quantum-well (MQW) emitter section with barriers that are thinner than in prior MQW devices. The thinning of the barriers results in a large overlap of sublevel wave functions, thereby creating a miniband. Because of sequential resonant quantum-mechanical tunneling of electrons from the negative ohmic contact to and between wells, any space charge is quickly neutralized. At the same time, what would otherwise be a large component of dark current attributable to tunneling current through the whole device is suppressed by placing a relatively thick, undoped, impurity-free AlxGa1 x As blocking barrier layer between the MQW emitter section and the positive ohmic contact. [This layer is similar to the thick, undoped Al(x)Ga(1-x)As layers used in photodetectors of the blocked-impurity-band (BIB) type.] Notwithstanding the aforementioned advantage afforded by the BID design, the responsivity of a BID QWIP is very low because of low collection efficiency, which, in turn, is a result of low electrostatic- potential drop across the superlattice emitter. Because the emitter must be electrically conductive to prevent the buildup of space charge in depleted quantum wells, most of the externally applied bias voltage drop occurs across the blocking-barrier layer. This completes the background discussion. In the developmental QWIP, the periodic superlattice of the prior BID design is to be replaced with the chirped superlattice, which is expected to provide a built-in electric field. As a result, the efficiency of collection of photoexcited charge carriers (and, hence, the net quantum efficiency and thus responsivity) should increase significantly.

Gunapala, Sarath; Ting, David; Bandara, Sumith

2004-01-01

217

The Gurvich waveform has lower defibrillation threshold than the rectilinear waveform and the truncated exponential waveform in the rabbit heart.  

PubMed

Implantable cardioverter defibrillator studies have established the superiority of biphasic waveforms over monophasic waveforms. However, external defibrillator studies of biphasic waveforms are not as widespread. Our objective was to compare the defibrillation efficacy of clinically used biphasic waveforms, i.e., truncated exponential, rectilinear, and quasi-sinusoidal (Gurvich) waveforms in a fibrillating heart model. Langendorff-perfused rabbit hearts (n = 10) were stained with a voltage-sensitive fluorescent dye, Di-4-ANEPPS. Transmembrane action potentials were optically mapped from the anterior epicardium. We found that the Gurvich waveform was significantly superior (p < 0.05) to the rectilinear and truncated exponential waveforms. The defibrillation thresholds (mean +/- SE) were as follows: Gurvich, 0.25 +/- 0.01 J; rectilinear-1, 0.34 +/- 0.01 J; rectilinear-2, 0.33 +/- 0.01 J; and truncated exponential, 0.32 +/- 0.02 J. Using optically recorded transmembrane responses, we determined the shock-response transfer function, which allowed us to predict the cellular response to waveforms at high accuracy. The passive parallel resistor-capacitor model (RC-model) predicted polarization superiority of the Gurvich waveform in the myocardium with a membrane time constant (taum) of less than 2 ms. The finding of a lower defibrillation threshold with the Gurvich waveform in an in vitro model of external defibrillation suggests that the Gurvich waveform may be important for future external defibrillator designs. PMID:15791288

Qu, Fujian; Zarubin, Fidel; Wollenzier, Brian; Nikolski, Vladimir P; Efimov, Igor R

2005-02-01

218

Wide-band superconductive Chirp filters  

SciTech Connect

Chirp filters are described that consist of miniature tapped superconductive stripline. The stripline consists of 40-micron-wide niobium thin films in a spiral pattern on 125-micron-thick silicon wafers, and tapping is effected by backward-wave couplers between neighboring lines. Sophisticated fabrication and packaging techniques have led to a now mature technology. Devices with 2.6-GHz bandwidth and time-bandwidth products of 98 are routinely fabricated that exhibit amplitude errors within a few tenths of a decibel and phase errors within a fractions of a degree of theoretical. In pulse-compression tests, matched amplitude-weighted devices yield peak relative side-lobe levels of -32 dB.

DiIorio, M.S.; Withers, R.S.; Anderson, A.C.

1989-04-01

219

76. Credit FM. Detail showing belts running from water wheel ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

76. Credit FM. Detail showing belts running from water wheel to governor and from water wheel to tachometer (foreground). - Battle Creek Hydroelectric System, Battle Creek & Tributaries, Red Bluff, Tehama County, CA

220

Diode-quad bridge for reactive transducers and FM discriminators  

NASA Technical Reports Server (NTRS)

Diode-quad bridge circuit was developed for use with pressure-sensitive capacitive transducers, liquid-level measuring devices, proximity deflection sensors, and inductive displacement sensors. It may also be used as FM discriminator and as universal impedance bridge.

Harrison, D. R.; Dimeff, J.

1972-01-01

221

47 CFR 73.295 - FM subsidiary communications services.  

Code of Federal Regulations, 2013 CFR

...FM subsidiary communications services that are common carrier in nature are subject...c) Subsidiary communications services are of a secondary nature under the authority...to provide such communications services...

2013-10-01

222

47 CFR 73.295 - FM subsidiary communications services.  

Code of Federal Regulations, 2010 CFR

...FM subsidiary communications services that are common carrier in nature are subject...c) Subsidiary communications services are of a secondary nature under the authority...to provide such communications services...

2009-10-01

223

68. Credit FM. Detail showing operators. Note cooling duct (now ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

68. Credit FM. Detail showing operators. Note cooling duct (now removed), governor (now removed), hand-operated needle valve controls (now removed). - Battle Creek Hydroelectric System, Battle Creek & Tributaries, Red Bluff, Tehama County, CA

224

59. Credit FM. Flood waters on South Battle Creek next ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

59. Credit FM. Flood waters on South Battle Creek next to powerhouse. Note height of water in relation to tailraces. - Battle Creek Hydroelectric System, Battle Creek & Tributaries, Red Bluff, Tehama County, CA

225

72. Credit FM. Overview of powerhouse from gallery. Notice cooling ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

72. Credit FM. Overview of powerhouse from gallery. Notice cooling duct on generator (now removed) and spare gate valve in far corner. - Battle Creek Hydroelectric System, Battle Creek & Tributaries, Red Bluff, Tehama County, CA

226

56. Credit FM. East elevation taken from along penstock. Note ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

56. Credit FM. East elevation taken from along penstock. Note additions to the east side and the north side of the building. - Battle Creek Hydroelectric System, Battle Creek & Tributaries, Red Bluff, Tehama County, CA

227

FM Correlator Spectral Data Transfer by Scrambled Transmission System.  

National Technical Information Service (NTIS)

This report presents design consideration for a Spectral Data Transfer System. FM correlators are proposed as cost-effective spectral detectors. The spectral data are scrambled and transmitted via satellite channel to a remote center for processing. A uni...

J. S. Lee S. Tsai L. E. Miller

1980-01-01

228

47 CFR 73.201 - Numerical designation of FM broadcast channels.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 2009-10-01 false Numerical designation of FM broadcast channels... FM Broadcast Stations § 73.201 Numerical designation of FM broadcast channels...educational broadcasting) are given numerical designations which are shown in the...

2009-10-01

229

47 CFR 73.201 - Numerical designation of FM broadcast channels.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Numerical designation of FM broadcast channels... FM Broadcast Stations § 73.201 Numerical designation of FM broadcast channels...educational broadcasting) are given numerical designations which are shown in the...

2010-10-01

230

Automated Analysis, Classification, and Display of Waveforms  

NASA Technical Reports Server (NTRS)

A computer program partly automates the analysis, classification, and display of waveforms represented by digital samples. In the original application for which the program was developed, the raw waveform data to be analyzed by the program are acquired from space-shuttle auxiliary power units (APUs) at a sampling rate of 100 Hz. The program could also be modified for application to other waveforms -- for example, electrocardiograms. The program begins by performing principal-component analysis (PCA) of 50 normal-mode APU waveforms. Each waveform is segmented. A covariance matrix is formed by use of the segmented waveforms. Three eigenvectors corresponding to three principal components are calculated. To generate features, each waveform is then projected onto the eigenvectors. These features are displayed on a three-dimensional diagram, facilitating the visualization of the trend of APU operations.

Kwan, Chiman; Xu, Roger; Mayhew, David; Zhang, Frank; Zide, Alan; Bonggren, Jeff

2004-01-01

231

Coded Modulation Scheme with CPPC Codes for FM IBOC Broadcasting  

Microsoft Academic Search

Hybrid in-band on-channel (IBOC) broadcasting system is a method of digital audio radio, which could transmit analog FM and digital audio simultaneously. Due to the existence of fading and interference in FM bands, however, the signal receiving for the hybrid IBOC system is very challenging. In this work, a type of coded modulation scheme was proposed in hybrid in-band on-channel

Feng Yunfei; Li Jianping; Dong Yue; Sha Shi

2009-01-01

232

Real-time chirp diagnostic for ultrashort laser pulses.  

PubMed

Using a real-time Fourier-transform algorithm, we present a simple technique for measuring the chirp of femtosecond laser pulses. We demonstrate significantly enhanced sensitivity compared with standard autocorrelation measurements. PMID:18007952

Hirayama, Toshiyuki; Sheik-Bahae, Mansoor

2002-05-15

233

CHIRP Versus BURST Sonar Resolution Techniques for Classification during Detection.  

National Technical Information Service (NTIS)

A previous Dalmo Victor report, R-2850-2931, proposed the CHIRP pulse compression technique as most adequately resolving detection range, classification and range rate problems for search sonars. This report qualitatively evaluates the effects of propagat...

R. E. Baker

1969-01-01

234

Giant-chirp oscillators for short-pulse fiber amplifiers.  

PubMed

A new regime of pulse parameters in a normal-dispersion fiber laser is identified. Dissipative solitons exist with remarkably large pulse duration and chirp, along with large pulse energy. A low-repetition-rate oscillator that generates pulses with large and linear chirp can replace the standard oscillator, stretcher, pulse-picker, and preamplifier in a chirped-pulse fiber amplifier. The theoretical properties of such a giant-chirp oscillator are presented. A fiber laser designed to operate in the new regime generates approximately 150 ps pulses at a 3 MHz repetition rate. Amplification of these pulses to 1 microJ energy with pulse duration as short as 670 fs demonstrates the promise of this new approach. PMID:19079529

Renninger, William H; Chong, Andy; Wise, Frank W

2008-12-15

235

Giant-chirp oscillators for short-pulse fiber amplifiers  

PubMed Central

A new regime of pulse parameters in a normal-dispersion fiber laser is identified. Dissipative solitons exist with remarkably large pulse duration and chirp, along with large pulse energy. A low-repetition-rate oscillator that generates pulses with large and linear chirp can replace the standard oscillator, stretcher, pulse-picker, and pre-amplifier in a chirped-pulse fiber amplifier. The theoretical properties of such a giant-chirp oscillator are presented. A fiber laser designed to operate in the new regime generates ~150-ps pulses at 3-MHz repetition rate. Amplification of these pulses to 1-?J energy with pulse duration as short as 670 fs demonstrates the promise of this new approach.

Renninger, William H.; Chong, Andy; Wise, Frank W.

2011-01-01

236

Determinism in synthesized chaotic waveforms.  

PubMed

The output of a linear filter driven by a randomly polarized square wave, when viewed backward in time, is shown to exhibit determinism at all times when embedded in a three-dimensional state space. Combined with previous results establishing exponential divergence equivalent to a positive Lyapunov exponent, this result rigorously shows that such reverse-time synthesized waveforms appear equally to have been produced by a deterministic chaotic system. PMID:18517561

Corron, Ned J; Blakely, Jonathan N; Hayes, Scott T; Pethel, Shawn D

2008-03-01

237

Effects of Pulse Shaping and Soft Decisions on the Performance of Digital FM with Discriminator Detection  

Microsoft Academic Search

Band-limited digital FM systems employing discriminator detection are analyzed. The error-rate performance of binary FM with premodulation shaping and duobinary FM with the same occupied bandwidth are compared. At bandwidths above 1.1 times the bit rate, it is found that binary FM gives a lower error rate than duobinary FM. For binary FM to meet lower bandwidth requirements, frequency deviation

T. T. Tjhung; K. K. Yeo; P. Wittke

1986-01-01

238

The NINJA-2 Waveform Catalog  

NASA Astrophysics Data System (ADS)

Two important advances have occurred in recent years which have brought us closer to the goal of observing and interpreting gravitational waves from coalescing compact objects: the successful construction and operation of a world-wide network of ground-based gravitational-wave detectors and the impressive success of numerical relativity in successfully simulating the merger phase of Binary Black Hole (BBH) coalescence. The aim of the NINJA project is to study the sensitivity of gravitational-wave analysis pipelines to numerical simulations of waveforms and foster close collaboration between numerical relativists and data analysts. NINJA-1 was a huge success, over 75 numerical relativists and data analysis participated in the contribution of a simulated data set containing numerical waveforms, analysis of this data and interpreting the results of this analysis. The follow-up project, NINJA-2 is currently underway. We present some of the goals of NINJA-2 and discuss aspects of the construction of the catalog of waveforms which will be used.

Pekowsky, Larne

2012-03-01

239

Chirped Microwave Pulse Generation Based on Optical Spectral Shaping and Wavelength-to-Time Mapping Using a Sagnac Loop Mirror Incorporating a Chirped Fiber Bragg Grating  

Microsoft Academic Search

In this paper, we propose and demonstrate an approach to optically generating chirped microwave pulses with tunable chirp profile based on optical spectral shaping using a Sagnac loop filter incorporating a chirped fiber Bragg grating (CFBG) and linear wavelength-to-time mapping in a dispersive element. In the proposed approach, the optical power spectrum of an ultrashort optical pulse is shaped by

Chao Wang; Jianping Yao

2009-01-01

240

Amplitude-phase coupling and chirp in quantum-dot lasers: influence of charge carrier scattering dynamics.  

PubMed

We investigate the dependence of the amplitude-phase coupling in quantum-dot (QD) lasers on the charge-carrier scattering timescales. The carrier scattering processes influence the relaxation oscillation parameters, as well as the frequency chirp, which are both important parameters when determining the modulation performance of the laser device and its reaction to optical perturbations. We find that the FM/AM response exhibits a strong dependence on the modulation frequency, which leads to a modified optical response of QD lasers when compared to conventional laser devices. Furthermore, the frequency response curve changes with the scattering time scales, which can allow for an optimization of the laser stability towards optical perturbations. PMID:24663826

Lingnau, Benjamin; Chow, Weng W; Lüdge, Kathy

2014-03-10

241

Microwave multiphoton transitions between Rydberg states driven by chirped pulses  

Microsoft Academic Search

We observe microwave multiphoton transitions in Rydberg states of potassium using intense pulses of chirped microwave radiation. Pulses of microwaves with frequencies between 0.6 and 0.9 GHz with frequency chirp times from 5 ns (4 cycles) to 200 ns (150 cycles) are generated with peak fields of 15 V\\/cm. We are able to drive high order multiphoton transitions using these

C. W. S. Conover; M. C. Doogue; D. A. Perry

1998-01-01

242

Pulse-front tilt caused by spatial and temporal chirp.  

PubMed

Pulse-front tilt in an ultrashort laser pulse is generally considered to be a direct consequence of, and equivalent to, angular dispersion. We show, however, that, while this is true for certain types of pulse fields, simultaneous temporal chirp and spatial chirp also yield pulse-front tilt, even in the absence of angular dispersion. We verify this effect experimentally using GRENOUILLE. PMID:19483989

Akturk, Selcuk; Gu, Xun; Zeek, Erik; Trebino, Rick

2004-09-20

243

Dispersion penalty reduction using an optical modulator with adjustable chirp  

Microsoft Academic Search

Using a unique Ti:LiNbO3 modulator, the value of the modulation chirp parameter that minimizes the transmission power penalty caused by fiber chromatic dispersion was experimentally identified. System experiments at 5 Gb\\/s using nonreturn-to-zero (NRZ) amplitude-shift-keyed (ASK) transmission with direct detection reception are discussed, and the optimum values of the modulation chirp parameter versus distance for transmission at 1.5 mu m

A. H. Gnauck; S. K. Korotky; J. J. Veselka; J. Nagel; C. T. Kemmerer; W. J. Minford; D. T. Moser

1991-01-01

244

Low chirp observed in directly modulated quantum dot lasers  

Microsoft Academic Search

We have examined the dynamic properties of high-aspect-ratio InAs-quantum-dot (QD) lasers at room temperature. A novel characteristic of low chirp in the lasing wavelength under 1-GHz current modulation was found in the quantum dot lasers. This is more than one order of magnitude less than the typical chirp (0.2-nm) found in a conventional quantum well laser that we used as

Hideaki Saito; Kenichi Nishi; Akio Kamei; Shigeo Sugou

2000-01-01

245

Single attosecond pulse generation from multicycle nonlinear chirped pulses  

SciTech Connect

We present a method of producing single attosecond pulses by high-order harmonic generation with multicycle nonlinear chirped driver laser pulses. The symmetry of the laser field in several optical cycles near the pulse center is broken, and then the photons near the cutoff burst only in half optical cycle. By selecting out the harmonics near the cutoff, an isolated attosecond pulse could be obtained. The results are almost independent of the length and chirp form of the driver laser pulse.

Niu Yueping; Qi Yihong; Gong Shangqing [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Science, Shanghai 201800 (China); Xiang Yang [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Science, Shanghai 201800 (China); College of Computer Science and Technology, Henan Polytechnic University, Jiaozuo 454000 (China)

2009-12-15

246

Measuring optically thick molecular samples using chirped laser dispersion spectroscopy.  

PubMed

In this Letter, a dispersion-based gas sensing method applied to detection of optically thick samples is presented. We show that chirped laser dispersion spectroscopy (CLaDS) technique provides perfectly linear signal response over a wide range of target analyte concentrations. Using the most convenient chirp-modulated CLaDS detection scheme, it enables spectroscopic measurements in a line-locked mode from the minimum detection limit up to >99% peak molecular absorption. PMID:24081065

Nikodem, Michal; Wysocki, Gerard

2013-10-01

247

Sampled chirped fiber gratings as distributed pressure sensors  

NASA Astrophysics Data System (ADS)

Fiber gratings have been studied for their applications in sensing and communications. Many sensing applications of the uniform fiber Bragg grating, chirped fiber grating and long period grating have been studied, proposed and commercialized. Sampled chirped gratings have been studied for multichannel dispersion compensation in DWDM systems. In this paper, we show that the sampled chirped fiber grating can be used as a distributed pressure sensor. The chirp provides ease of manufacture of many gratings. The sampling results in many small, uniform grating-like structures. This fact can be used to simulate a distributed sensor over the length of the sampled chirped grating. When a surface comes into contact with the sensor, the distribution of the pressure determines the shift in central wavelength of the various sub-gratings. The sub-grating that experiences the maximum pressure will show maximum wavelength shift whereas adjacent sub-gratings will show less shift. This can also give the location of the pressure. The sensor design comprises of a sampled chirped grating embedded in unidirectional fiber-reinforced composite prepreg. The prepreg enhances the mechanical strength and the unidirectional embedding reduces birefringence. The number of layers in the prepreg stack varies the sensitivity. Such distributed pressure sensors can be applied in robotics, ergonomics, and in the biomedical field.

Tjin, Swee Chuan; Mohanty, Lipi; Ngo, Nam Quoc

2004-09-01

248

Techniques for High-Bandwidth (?30 GHz) Chirped-Pulse Submillimeter-Wave Spectroscopy  

NASA Astrophysics Data System (ADS)

Due to the increased availability of active multiplier chains for converting microwave pulses into the millimeter/submillimeter with reasonably high power (?1 mW), chirped pulses with high phase stability and complete arbitrary waveform generator (AWG) frequency agility can be created and employed for high-sensitivity molecular spectroscopy, as demonstrated at the Symposium in the past few years. The bandwidths of multiplier chains, however, can exceed the current limitations on digitizer bandwidth. Therefore, in order to obtain ?30 GHz spectra in ~1 ms or less, techniques are being developed in which a two-channel AWG creates both the chirped pulses for molecular irradiation and a local oscillator pulse for heterodyne detection. These approaches reduce the digitizer bandwidths to 500 MHz or less to collect a high-bandwidth spectrum. A single instrument design can be used to measure both absorption and emission spectra, only requiring that the AWG pulses are changed. Due to the phase stability of the pulse generation and detection, coherent time-domain signal averaging can be performed to enhance sensitivity as desired. Preliminary results from prototype instruments designed at UVa and NIST will be presented, with sensitivity, frequency accuracy, and measurement speed comparisons to current millimeter/submillimeter-wave spectrometers. G.B. Park, A.H. Steeves, K. Kuyanov-Prozument, A.P. Colombo, R.W. Field, J.L. Neill, and B.H. Pate, RH07, 64th International Symposium on Molecular Spectroscopy (2009) K.O. Douglass, D.F. Plusquellic, and E. Gerecht, WH09, 65th International Symposium on Molecular Spectroscopy (2010).

Neill, Justin L.; Steber, Amanda L.; Harris, Brent J.; Pate, Brooks H.; Douglass, Kevin O.; Plusquellic, David F.; Gerecht, Eyal

2011-06-01

249

Filtering in the joint time/chirp-rate domain for separation of quadratic and cubic phase chirp signals  

NASA Astrophysics Data System (ADS)

This article investigates the possibility and convenience of a filtering operation in the joint time/chirp-rate (TCR) domain, and proposes a novel linear TCR filter for decomposing multicomponent signals into their quadratic and/or cubic phase chirp components with monotonic instantaneous chirp-rate (ICR) laws only. The TCR domain mask of the filter is selected on a display of a TCR representation of an input signal to isolate the desired chirp component. Projecting the input signal onto the phase signal associated with the TCR mask and approximating the phase difference in this projection operation in terms of ICR values result in the proposed TCR filter that recovers the selected component. Simulations illustrate the proposed filtering in recovery of undersampled cubic phase signals and in resolving back-to-back objects from in-line holograms for which cases it is easier to design filter masks in the TCR domain than in the time-frequency domain.

Özgen, Mehmet Tankut

2012-12-01

250

Ion-beam sputtering deposition and magnetoelectric properties of layered heterostructures (FM/PZT/FM)n, where FM - Co or Ni78Fe22  

NASA Astrophysics Data System (ADS)

Magnetoelectric properties of layered heterostructures (FM/PZT/FM)n (n? 3) obtained by ion-beam sputtering deposition of ferromagnetic metal (FM), where FM is the cobalt (Co) or permalloy Ni78Fe22, onto ferroelectric ceramic based on lead zirconate titanate (PZT) have been studied. The polished ferroelectric plates in thickness from 400 to 20 ?m were subjected to finished treatment by ion-beam sputtering. After plasma activation they were covered by the ferromagnetic films from 1 to 6 ?m in thickness. Enhanced characteristics of these structures were reached by means of both the thickness optimization of ferroelectric and ferromagnetic layers and obtaining of ferromagnetic/ferroelectric interfaces being free from defects and foreign impurities. Assuming on the basis of analysis of elastic stresses in the ferromagnetic film that the magnetoelectric effect forms within ferromagnetic/ferroelectric interface, the structures with 2-3 ferromagnetic layers were obtained. In layered heterostructure (Py/PZT/Py)3, the optimal thickness of ferromagnetic film was 2 ?m, and outer and inner ferroelectric layers had 20 ?m and 80 ?m in thickness, respectively. For such structure the maximal magnetoelectric voltage coefficient of 250 mV/(cm Oe) was reached at a frequency 100 Hz in magnetic field of 0.25 T at room temperature. The structures studied can serve as energy-independent elements detecting the change of magnetic or electric fields in electronic devices based on magnetoelectric effect.

Stognij, Alexander; Novitskii, Nikolai; Sazanovich, Andrei; Poddubnaya, Nadezhda; Sharko, Sergei; Mikhailov, Vladimir; Nizhankovski, Viktor; Dyakonov, Vladimir; Szymczak, Henryk

2013-08-01

251

High-precision triangular-waveform generator  

DOEpatents

An ultra-linear ramp generator having separately programmable ascending and decending ramp rates and voltages is provided. Two constant current sources provide the ramp through an integrator. Switching of the current at current source inputs rather than at the integrator input eliminates switching transients and contributes to the waveform precision. The triangular waveforms produced by the waveform generator are characterized by accurate reproduction and low drift over periods of several hours. The ascending and descending slopes are independently selectable.

Mueller, T.R.

1981-11-14

252

FD-CHIRP: hosted payload system engineering lessons  

NASA Astrophysics Data System (ADS)

The Commercially Hosted Infrared Payload (CHIRP) Flight Demonstration (FD-CHIRP) launched 21 Sept 2011 was designated a "resounding success" as the first Wide Field-of-View (WFOV) staring infrared (IR) sensor flown in geostationary earth orbit (GEO) with a primary mission of Missile Warning (MW). FD-CHIRP was an Air Force research and development project initiated in July 2008 via an unsolicited industry proposal aimed to mature and reduce the risk of WFOV sensors and ground processing technologies. Unlike the Defense Support Program (DSP) and the Space Based Infrared System (SBIRS) which were acquired via traditional integrated sensor and satellite design, FDCHIRP was developed using the "commercially hosted" approach. The FD-CHIRP host spacecraft and sensor were independently designed, creating significant development risk to the industry proposer, especially under a Firm Fixed Price contract. Yet, within 39 months of contract initiation, FD-CHIRP was launched and successfully operated in GEO to 30 June 2012 at a total cost of 111M including the 82.9M CHIRP commercial-hosting contract and a $28M sensor upgrade. The commercial-hosting contract included sensor and spacecraft modifications, integration and test, design and development of secure Mission Operations and Analysis Centers, launch, and nearly a year of GEO operations with 70 Mbps secure data acquisition. The Air Force extended the contract for six months to continue operations through the end of calendar 2012. This paper outlines system engineering challenges FD-CHIRP overcame and key lessons to smooth development of future commercially hosted missions.

Schueler, Carl F.

2012-10-01

253

Fast Quantum Gates Using Chirped Pulses  

NASA Astrophysics Data System (ADS)

A common method to implement quantum gates is based on the Rabi solution regime of a two-level system excited by external field. To construct a quantum gate one uses the exact form of evolution operator of the qubit under the external excitation. In the case of Rabi solution the qubit evolution has very simple and easily interpreted form. In essence, the whole dynamics of the qubit wave function is governed by the pulse area and it exhibits Rabi oscillations for the time less than the decoherence time. Various implementations of the quantum gates employ relatively weak pulses that results in slow gate operations of order microseconds. To make quantum gates faster one may use strong femtosecond pulses. However, direct implementation schemes are not so obvious because of strong field effects and large bandwidth of the pulses might give rise to unwanted excitations. Here we propose a scheme which provides a possibility to utilize strong pulses while keeps all advantages of Rabi solution regime. We design fast quantum gates (picosecond time scale) by choosing proper parameters of the chirped pulses as a way to control nonadiabatic terms and to satisfy the adiabaticity conditions. Proposed Hadamard and phase-shift gate allow us to construct universal set of single qubit gates by controlling the effective pulse area and two-photon detuning. The proposed excitation scheme can be also used to implement CNOT gate.

Malinovsky, Vladimir

2008-05-01

254

Combining full waveform inversion and traveltime tomography  

NASA Astrophysics Data System (ADS)

By alternating full waveform inversion and traveltime tomography we attempt to merge their complementary merits and produce models of the European continent explaining both waveform and traveltime data sets. Technological developments and advances in theoretical and numerical seismology allow us to assimilate complete waveforms for the solution of full waveform tomographic problems. However, due to computational limitations, full waveform inversion is and will, in the long term, be limited to an intermediate period band. Valuable information contained in high-frequency P and S wave traveltimes cannot be exploited. Consequently, full waveform inversion only yields excellent results in the upper 300 km, where surface wave sensitivity is large. P and S velocity heterogeneities at greater depth are less well resolved. On the contrary, classical traveltime tomography intrinsically incorporates information from high-frequency body waves. As an initial step to combine both methods and extend the spectrum of exploited information, we test an inversion scheme, where full waveform inversion and ray tomography alternate, thereby avoiding an explicit coupling of both methods and data sets. We put special emphasis on the convergence properties of this scheme and its ability to produce 3D models that explain both waveform and traveltime data sets. We test our approach starting with a full waveform tomographic model of Europe and Western Asia in conjunction with the traveltime tomography package FMTOMO and the teleseismic data set used for the construction of the global model S40RTS.

Sager, Korbinian; Fichtner, Andreas

2014-05-01

255

FM Technologies: Enhancing Language and Learning in Home and School Environments.  

ERIC Educational Resources Information Center

This article discusses why FM technologies and a remote microphone should be used to assist students with hearing impairments in inclusive classrooms, lists factors governing the selection of FM coupling arrangements and performance, and describes types of FM systems. Cochlear implants and FM technology are also addressed. (Contains six references…

Flexer, Carol

2000-01-01

256

Automatic target recognition using waveform diversity in radar sensor networks  

Microsoft Academic Search

In this paper, we perform a number of theoretical studies on constant frequency (CF) pulse waveform design and diversity in radar sensor networks (RSN): (1) the conditions for waveform co-existence, (2) interferences among waveforms in RSN, (3) waveform diversity combining in RSN. As an application example, we apply the waveform design and diversity to automatic target recognition (ATR) in RSN

Qilian Liang

2008-01-01

257

High-resolution imaging with advanced chirp optical coherence tomography  

NASA Astrophysics Data System (ADS)

Chirp optical coherence tomography (Chirp OCT) has been introduced as an alternative solution for imaging scattering media or biotissues. The basic principle of Chirp OCT is well-known by the FMCW radar technique and is adapted to the optical regime. This method uses a frequency modulated laser source in the near IR frequency range. Fast imaging can be performed by an electrical tuned diode laser without the disadvantage of any mechanical moved elements but retaining the properties of optical tomographic tools for contact less, non-ionizing, non-invasive and high depth resolved scanning. The demand of high resolution imaging for media application requires a large frequency tuning range. Covering the whole lasing bandwidth of an external cavity laser by the frequency Chirp, non-linear terms as well as mode-hopping reduce the depth resolution and the dynamic range, if equidistant sampling in the time domain is performed. To restore the resolution given by the Chirp bandwidth a reference detector has been implemented, which allows the detection of mode-hopping quantitatively and the correction of the non-linearity. The reference detector can be used for real-time laser frequency measurements and offers the possibility to determine the location of discrete reflectors more accurate. Images with a high dynamic range demonstrate an increased penetration depth.

Hoelscher, Dominik; Kemmer, Claude; Rupp, Florian; Blazek, Vladimir

2000-04-01

258

Goldstone Solar System Radar Waveform Generator  

NASA Technical Reports Server (NTRS)

Due to distances and relative motions among the transmitter, target object, and receiver, the time-base between any transmitted and received signal will undergo distortion. Pre-distortion of the transmitted signal to compensate for this time-base distortion allows reception of an undistorted signal. In most radar applications, an arbitrary waveform generator (AWG) would be used to store the pre-calculated waveform and then play back this waveform during transmission. The Goldstone Solar System Radar (GSSR), however, has transmission durations that exceed the available memory storage of such a device. A waveform generator capable of real-time pre-distortion of a radar waveform to a given time-base distortion function is needed. To pre-distort the transmitted signal, both the baseband radar waveform and the RF carrier must be modified. In the GSSR, this occurs at the up-conversion mixing stage to an intermediate frequency (IF). A programmable oscillator (PO) is used to generate the IF along with a time-varying phase component that matches the time-base distortion of the RF carrier. This serves as the IF input to the waveform generator where it is mixed with a baseband radar waveform whose time-base has been distorted to match the given time-base distortion function producing the modulated IF output. An error control feedback loop is used to precisely control the time-base distortion of the baseband waveform, allowing its real-time generation. The waveform generator produces IF modulated radar waveforms whose time-base has been pre-distorted to match a given arbitrary function. The following waveforms are supported: continuous wave (CW), frequency hopped (FH), binary phase code (BPC), and linear frequency modulation (LFM). The waveform generator takes as input an IF with a time varying phase component that matches the time-base distortion of the carrier. The waveform generator supports interconnection with deep-space network (DSN) timing and frequency standards, and is controlled through a 1 Gb/s Ethernet UDP/IP interface. This real-time generation of a timebase distorted radar waveform for continuous transmission in a planetary radar is a unique capability.

Quirk, Kevin J.; Patawaran, Ferze D.; Nguyen, Danh H.; Nguyen, Huy

2012-01-01

259

Quasimonoenergic collimated electrons from the ionization of nitrogen by a chirped intense laser pulse  

SciTech Connect

A scheme is proposed for quasimonoenergic collimated GeV electrons generated during ionization of nitrogen by a chirped intense laser pulse. The electrons accelerated by a laser pulse without a frequency chirp are known for poor-quality beams. If a suitable frequency chirp is introduced, then the energy of the electrons increases significantly. It is shown that quasimonoenergic collimated GeV electrons can be produced using a right choice of laser spot size, frequency chirp, and pulse duration.

Singh, Kunwar Pal [Singh Simutech Pvt. Ltd., Bharatpur, Rajasthan 321201 (India); Sajal, Vivek [Department of Physics, Jaypee Institute of Information Technology University, Noida 201 307, Uttar Pradesh (India)

2009-04-15

260

Wideband chirp modulation for FH-CDMA wireless systems: coherent and non-coherent receiver structures  

Microsoft Academic Search

In this paper, we propose a novel signaling scheme based on wideband time-varying chirp signals for frequency-hopped code division multiple access (FH-CDMA) techniques. Our new method has been motivated by the inherent resistance of chirp signals against channel imposed distortions as chirps are bandwidth efficient and robust to fading. Specifically, we combine FH-CDMA with chirp modulation such that every user

C. Gupta; T. Mumtaz; M. Zaman; A. Papandreou-Suppappola

2003-01-01

261

Optical arbitrary waveform characterization using linear spectrograms  

PubMed Central

We demonstrate the first application of linear spectrogram methods based on electro-optic phase modulation to characterize optical arbitrary waveforms generated under spectral line-by-line control. This approach offers both superior sensitivity and self-referencing capability for retrieval of periodic high repetition rate optical arbitrary waveforms.

Jiang, Zhi; Leaird, Daniel E.; Long, Christopher M.; Boppart, Stephen A.; Weiner, Andrew M.

2010-01-01

262

Radar waveform design for detection of weapons  

Microsoft Academic Search

We present waveform design based on signature exploitation techniques for improved detection of weapons in urban sensing applications. We consider a single-antenna monostatic radar system. Under the assumption of exact knowledge of the target orientation and, hence, known impulse response, matched illumination approach is used for optimal target detection. For the case of unknown target orientation, we propose waveform design

Fauzia Ahmad; Moeness G. Amin

2010-01-01

263

Migration Velocity Analysis and Waveform Inversion  

Microsoft Academic Search

Waveform (output least squares) inversion of seismic reflection data can recon- struct remarkably detailed models of subsurface structure, and take into account es- sentially any physics of seismic wave propagation that can be modeled. However the waveform inversion objective has many spurious local minima, hence convergence of descent methods (mandatory because of problem size) to useful Earth models requires accurate

William W. Symes

2007-01-01

264

Accelerated Waveform Methods for Parallel Transient Simulation  

Microsoft Academic Search

In this paper we compare accelerated waveform relaxation algorithms to pointwise direct and iterative methods for the parallel transient simulation of semiconductor device s on parallel machines. Experimental results are presented for simulations on single (serial) workstations, clusters of workstations, and an IBM SP-2. The results show that ac- celerated waveform methods are competitive with standard pointwise methods on serial

Andrew Lumsdaine; Mark W. Reichelt; Jeffrey M. Squyres; Jacob K. White

265

Arbitrary waveform DDFS utilizing Chebyshev polynomials interpolation  

Microsoft Academic Search

A new technique of arbitrary waveform direct digital frequency synthesis (DDFS) is introduced. In this method, one period of the desired periodic waveform is divided into m sections, and each section is approximated by a series of Chebyshev polynomials up to degree d. By expanding the resultant Chebyshev polynomials, a power series of degree d is produced. The coefficients of

Ashkan Ashrafi; Reza Adhami; Laurie Joiner; Parisa Kaveh

2004-01-01

266

Orthogonal waveform set design for netted radar  

Microsoft Academic Search

Orthogonal netted radar system requires the transmitted waveforms with a very low autocorrelation and cross-correlation sidelobe peak level. Pseudo-random Phase Coded Modulation (PCM) waveform is suitable for orthogonal design in this sense. In this paper, the correlation properties of Gold sequences as binary phase codes are discussed. Numerical examples are presented to demonstrate the desired orthogonal properties of the coded

Long Cai; Xiaochuan Ma; Shefeng Yan; Qi Xu

2010-01-01

267

Waveform Analysis and Display System (WADS).  

National Technical Information Service (NTIS)

The report describes the design and implementation of a Waveform Analysis and Display System (WADS). WADS was implemented on the HIS-635 computer with a remote Tektronix 4002A graphic storage tube terminal. It serves as an interim Waveform Processing Syst...

D. D. White D. F. Roberts

1973-01-01

268

Waveform and spectral analysis of crackles  

Microsoft Academic Search

Crackles were recorded from six patients, four with tuberculosis and two with chronic bronchitis. It was observed by waveform and spectral analysis that most of the frequency components of a crackle were limited within a range of 0.1 to 1 kHz. Characteristically, waveforms of crackles were separable into two segments, initial \\

M Mori; K Kinoshita; H Morinari; T Shiraishi; S Koike; S Murao

1980-01-01

269

A novel radar waveform compatible with communication  

Microsoft Academic Search

Multifunctional radar is a trend in the future. Employing radar system for high data rate, long range, anti-intercepted communication by making use of its wide bandwidth, high power and directing property has been a research hotspot nowadays. Hereinto, radar-communication compatible waveforms design is a key technique. This paper proposes a novel compatible waveform produced by modulating LFM signal by MSK

Xingbo Chen; Xiaomo Wang; Shanfeng Xu; Jing Zhang

2011-01-01

270

Optical generation of linearly chirped microwave pulses using fiber Bragg gratings  

Microsoft Academic Search

We demonstrate a new method to generate broad spectrum chirped microwave pulses using an electrooptical system. Two fiber Bragg gratings and a mode-locked fiber laser were used to generate pulses with a linear frequency chirp. The bandwidth of the microwave pulses can be significantly broader than the bandwidth that can be obtained using electronic systems. The parameters of the chirp

Avi Zeitouny; Sander Stepanov; Oren Levinson; Moshe Horowitz

2005-01-01

271

Application of chirped fiber Bragg grating sensors for identification of crack locations in composites  

Microsoft Academic Search

Chirped fiber Bragg grating (FBG) sensors were applied for the identification of crack locations in carbon fiber reinforced plastic (CFRP) laminates since the reflection spectrum from a chirped FBG was expressed as a function of the position along the grating. For the crack identification in the 90° ply of a cross-ply laminate, a chirped FBG sensor, whose grating length and

Yoji Okabe; Ryohei Tsuji; Nobuo Takeda

2004-01-01

272

Chirped soliton interaction in strongly dispersion-managed wavelength-division-multiplexing systems.  

PubMed

We theoretically analyze nonlinear interactions between chirped solitons in dispersion-managed wavelength-division-multiplexing (WDM) systems. We employ the perturbation method to evaluate frequency and chirp shifts caused by collisions among different WDM channels. It is shown that a chirped soliton suffers less frequency shift and time displacement than an ideal soliton, indicating its potential applicability for WDM systems. PMID:18087336

Hirooka, T; Hasegawa, A

1998-05-15

273

Simulation and experimental characterization of dual chirped long period fiber gratings  

NASA Astrophysics Data System (ADS)

We demonstrate a novel device consisting of two concatenated chirped long period fiber gratings (LPG) that exhibit multiple pass bands. Transmission spectra of single and dual chirped LPG were simulated theoretically and investigated experimentally show a qualitatively good match. The dual chirped LPGs with multiple pass bands in the transmission spectrum could find applications as WDM channel isolation filter.

Tiwari, Umesh; Singla, Nidhi; Mishra, Vandana; Shenoy, M. R.; Thyagarajan, K.; Jain, Subhash C.; Singh, Nahar; Kapur, Pawan

2010-12-01

274

A digital dispersive matching network for SAW devices in chirp transform spectrometers  

Microsoft Academic Search

The performance of a chirp transform spectrometer can be significantly improved through a digital dispersive matching network. In this paper, we present the development of a new design, the adaptive digital chirp processor (ADCP), which generates an expander chirp signal with dispersive characteristics matching those of the surface acoustic wave filter behaving as a compressor\\/convolver. This matching signal (i.e., the

Geronimo Luis Villanueva; Paul Hartogh; Leonhard M. Reindl

2006-01-01

275

Rainbow trapping using chirped all-dielectric periodic structures  

NASA Astrophysics Data System (ADS)

We report a numerical investigation of rainbow trapping (light of different wavelengths) at different spatial locations in a newly designed two-dimensional photonic structure that is formed using chirping parameters in two-dimensional photonic crystals. Chirped parameters ensure trapping of certain light wavelengths inside these structures. To achieve broadband electromagnetic wave trapping, we properly adjust and chirp the position and dielectric filling factor of each unit cell within a photonic crystal structure. The low group velocity regions of the dielectric continuum bands at the Brillouin zone edge enable different wavelengths to be slowed and stopped along the propagation direction. The all-dielectric transparent material nature of the proposed structure realizes light trapping in different electromagnetic regions by spatially varying the effective refractive index of the structure.

Kurt, H.; Yilmaz, D.

2013-03-01

276

Chirped pulse inverse free-electron laser vacuum accelerator  

DOEpatents

A chirped pulse inverse free-electron laser (IFEL) vacuum accelerator for high gradient laser acceleration in vacuum. By the use of an ultrashort (femtosecond), ultrahigh intensity chirped laser pulse both the IFEL interaction bandwidth and accelerating gradient are increased, thus yielding large gains in a compact system. In addition, the IFEL resonance condition can be maintained throughout the interaction region by using a chirped drive laser wave. In addition, diffraction can be alleviated by taking advantage of the laser optical bandwidth with negative dispersion focusing optics to produce a chromatic line focus. The combination of these features results in a compact, efficient vacuum laser accelerator which finds many applications including high energy physics, compact table-top laser accelerator for medical imaging and therapy, material science, and basic physics.

Hartemann, Frederic V. (Dublin, CA); Baldis, Hector A. (Pleasanton, CA); Landahl, Eric C. (Walnut Creek, CA)

2002-01-01

277

A direct digital synthesis chirped pulse Fourier transform microwave spectrometer  

NASA Astrophysics Data System (ADS)

Chirped pulse Fourier transform microwave (CP-FTMW) spectrometers have become the instrument of choice for acquiring rotational spectra, due to their high sensitivity, fast acquisition rate, and large bandwidth. Here we present the design and capabilities of a recently constructed CP-FTMW spectrometer using direct digital synthesis (DDS) as a new method for chirped pulse generation, through both a suite of extensive microwave characterizations and deep averaging of the 10-14 GHz spectrum of jet-cooled acetone. The use of DDS is more suited for in situ applications of CP-FTMW spectroscopy, as it reduces the size, weight, and power consumption of the chirp generation segment of the spectrometer all by more than an order of magnitude, while matching the performance of traditional designs. The performance of the instrument was further improved by the use of a high speed digitizer with dedicated signal averaging electronics, which facilitates a data acquisition rate of 2.1 kHz.

Finneran, Ian A.; Holland, Daniel B.; Carroll, P. Brandon; Blake, Geoffrey A.

2013-08-01

278

Phase-locking transition in a chirped superconducting Josephson resonator.  

PubMed

We observe a sharp threshold for dynamic phase locking in a high-Q transmission line resonator embedded with a Josephson tunnel junction, and driven with a purely ac, chirped microwave signal. When the drive amplitude is below a critical value, which depends on the chirp rate and is sensitive to the junction critical current I0, the resonator is only excited near its linear resonance frequency. For a larger amplitude, the resonator phase locks to the chirped drive and its amplitude grows until a deterministic maximum is reached. Near threshold, the oscillator evolves smoothly in one of two diverging trajectories, providing a way to discriminate small changes in I0 with a nonswitching detector, with potential applications in quantum state measurement. PMID:18851320

Naaman, O; Aumentado, J; Friedland, L; Wurtele, J S; Siddiqi, I

2008-09-12

279

40-MHz Ultrasound Imaging with Chirps and Annular Arrays  

PubMed Central

High-frequency ultrasound (HFU) shows promise for fine-resolution imaging. However, the depth of field (DOF) and penetration depth of HFU waves limit clinical significance. In a previous study using a 17-MHz annular array, we established that chirp coded excitation and synthetic focusing can improve penetration depth and DOF simultaneously. In this study, we evaluated the same approach using two five-element annular arrays with focal lengths of 12 mm, total apertures of 6 mm. The annular arrays had center frequencies of ?35 MHz and were excited by a 4-?s chirp signal spanning the frequency range 15–65 MHz. Results demonstrated that DOF could be increased by a factor of about 3, SNR could be increased by more than 10 dB, and penetration depth into an attenuating phantom could be increased by 1.8 mm. The chirp imaging method was then evaluated on low-contrast phantoms and mouse embryos.

Mamou, Jonathan; Aristizabal, Orlando; Silverman, Ronald H.; Ketterling, Jeffrey A.

2011-01-01

280

Optical parametric chirped pulse amplification based on photonic crystal fibre  

NASA Astrophysics Data System (ADS)

A compact two-stage optical parametric chirped pulse amplifier based on photonic crystal fibre is demonstrated. A 1064-nm soliton pulse is obtained in a home-made photonic crystal fibre (PCF) with femtosecond pulse pumping and then amplified to 2 mJ in an Nd:YAG regenerative amplifier. After the amplified pulses pass through the LBO crystal, the 532-nm double-frequency light with an energy of 0.8 mJ and a duration of over 100 ps at 10-Hz repetition rate is generated as a pump source in the following two-stage optical parametric amplification (OPA). The 850-nm chirped signal light gain from the stretcher is 1.5×104 in the first-stage OPA while it is 120 in the second-stage OPA. The total signal gain of optical parametric chirped pulse amplification (OPCPA) can reach 1.8×106.

Wang, He-Lin; Yang, Ai-Jun; Leng, Yu-Xin; Wang, Cheng; Xu, Zhi-Zhan; Hou, Lan-Tian

2011-08-01

281

Schwinger vacuum pair production in chirped laser pulses  

SciTech Connect

The recent developments of high intensity ultrashort laser pulses have raised the hopes of observing Schwinger vacuum pair production which is one of the important nonperturbative phenomena in QED. The quantitative analysis of realistic high intensity laser pulses is vital for understanding the effect of the field parameters on the momentum spectrum of the produced particles. In this study, we analyze chirped laser pulses with a subcycle structure, and investigate the effects of the chirp parameter on the momentum spectrum of the produced particles. The combined effect of the chirp and carrier phase of the laser pulse is also analyzed. These effects are qualitatively explained by investigating the turning-point structure of the potential within the framework of the complex WKB scattering approach to pair production.

Dumlu, Cesim K. [Department of Physics, University of Connecticut, Storrs Connecticut 06269-3046 (United States)

2010-08-15

282

Phase-sensitive amplification of chirped optical pulses in fibers.  

PubMed

In this paper a detailed analysis is made of the phase-sensitive amplification (PSA) of optical pulses by degenerate four-wave mixing (phase-conjugation) in fibers. Formulas are derived, which show that the amplification level and phase sensitivity depend strongly on the phase of the signal pulse, but weakly on its chirp, and the difference between its carrier frequency and the average pump frequency. Solitons, which are unchirped, and dispersion-managed solitons, which are weakly chirped, are suitable for in-line and post-transmission PSA. Pseudo-linear pulses, which are strongly chirped, are unsuitable for in-line PSA, but post-transmission dispersion compensation makes them suitable for PSA prior to detection. PMID:19532620

McKinstrie, C J; Moore, R O; Radic, S; Jiang, R

2007-04-01

283

Beam energy chirp effects in seeded free-electron lasers  

NASA Astrophysics Data System (ADS)

Seeded free-electron lasers (FELs) hold great promise for generating high brilliance radiation pulses with a narrow bandwidth, which typically requires an electron bunch with relatively uniform energy distribution. However, it has been pointed out that the beam energy curvature generated in the acceleration process may degrade the output radiation pulse quality of seeded FELs. In this paper, we studied the beam energy chirp effects in various seeded FEL configurations. The theoretical and simulation results show that the performance degradation of high gain harmonic generation scheme is proportional to the beam energy chirp, while the advanced seeding schemes, e.g. echo-enabled harmonic generation and phase merging enhanced harmonic generation, are capable of eliminating the effect of the electron beam energy chirp.

Wang, Guanglei; Feng, Chao; Deng, Haixiao; Zhang, Tong; Wang, Dong

2014-07-01

284

Effects of collisions on energetic particle-driven chirping bursts  

SciTech Connect

In the presence of an energetic particle population in a dissipative plasma, self-trapped structures in phase-space (holes and clumps) emerge from nonlinear wave-particle interactions. Their dynamics can lead to a nonlinear continuous shifting of the wave frequency (chirping). The effects of collisions on chirping characteristics are investigated, with a one-dimensional kinetic model. Existing analytic theory is extended to account for Krook-like collisions, which quantitatively explains a significant departure from widely accepted square-root time dependency. Relaxation oscillations, associated with chirping bursts, are investigated in the presence of dynamical friction and velocity-diffusion. The period increases with decreasing drag and weakly increases with decreasing diffusion. The mechanism is clarified with a simple semi-analytic model of hole/clump pair, which satisfies a Fokker-Planck equation. The model shows that the linear growth rate cannot be obtained simply by fitting an exponential to the amplitude time-series.

Lesur, M. [Itoh Research Center for Plasma Turbulence, Kyushu University, Kasuga, Kasuga Koen 6-1, Fukuoka 816-8580 (Japan)] [Itoh Research Center for Plasma Turbulence, Kyushu University, Kasuga, Kasuga Koen 6-1, Fukuoka 816-8580 (Japan)

2013-05-15

285

Wallops Waveform Analysis of Seasat-1 Radar Altimeter Data.  

National Technical Information Service (NTIS)

Fitting a six parameter model waveform to over ocean experimental data from the waveform samplers in the SEASAT-1 radar altimeter is described. The fitted parameters include a waveform risetime, skewness, and track point; from these can be obtained estima...

G. S. Hayne

1980-01-01

286

Range-Doppler imaging of moving target with chirped AM ladar  

NASA Astrophysics Data System (ADS)

As the result of the synthetic aperture radar technique applied to laser band, SAIL (synthetic aperture imaging ladar) can provide range-Doppler image of targets with much more high-resolution than its counterpart in microwave band. However, the complicated structure of coherent heterodyne detection and the significant impacts of laser atmospheric effect, target depolarization, phase error arising from platform vibration on heterodyne detection efficiency degrades its performance. In this paper, an APD and semiconductor laser based range-Doppler imaging ladar is presented. The ladar combines the (inverse) synthetic aperture technique and direct detection and can obtain the high-resolution image at a relative low cost and complexity. In the meanwhile, owing to the poor coherence of semiconductor laser, the impact of atmospheric effect on laser pattern can be released to some extent. Firstly, the system diagram is presented and the components are briefly introduced; Secondly, the operation principle and performance are formulated detailedly; and then the parameters determination of the chirped AM waveform is analyzed considering the extraction of the range and velocity and the fine resolution. Finally, the 1-D range and 2-D range-Doppler imaging procedure are numerically simulated based on the given target model, which shows that the proposed imaging ladar is effective and feasible.

Liu, Chun-Bo; Lu, Fang; Zhao, Yanjie; Han, Xiang'e.

2011-06-01

287

Conformationally restricted analogs of the direct thrombin inhibitor FM 19.  

PubMed

The serine protease thrombin plays several key roles in the clotting cascade within the hemostatic system, such as in fibrin formation and platelet activation. Thus, development of an inhibitor that binds to the enzyme's active site (a direct thrombin inhibitor) offers an approach for the treatment of thrombus-associated diseases. Previous structure-activity relationship studies originally based on the bradykinin breakdown product Arg-Pro-Pro-Gly-Phe (RPPGF) led to the development of lead compound FM 19 (d-Arg-Oic-Pro-d-Ala-Phe(p-Me)-NH(2)). The recently determined X-ray structure of FM 19 in the active site of thrombin has revealed sites of modification to potentially improve inhibition. In this study, we report the synthesis and biological characterization of nine peptides that replace only the d-Arg residue of the FM 19 sequence, investigating ways to add conformational restriction, modification of the basic moiety at the end of the side chain, and removal of the charge from the N-terminus. Two of these peptides, 6 and 7 (IC(50) values of 0.51 and 0.45 ?M, respectively), show similar potency to the best compounds in the FM 19 series reported thus far. PMID:22055408

Girnys, Elizabeth A; Porter, Vanessa R; Mosberg, Henry I

2011-12-15

288

“History is bunk”: considerations on the future of FM  

Microsoft Academic Search

Purpose – The last 25 years have seen facilities management established as an internationally recognised and valued function. However, the organisational changes that created the original demand for FM services are accelerating and will ensure that it will need to constantly adapt itself to new demands if it is to thrive. This article seeks to examine the nature of these

Bob Grimshaw

2007-01-01

289

Convective Activity Observed by FM-CW Radar.  

National Technical Information Service (NTIS)

Data taken in San Diego by the fixed and mobile FM-CW (frequency-modulated, continuous-wave) radars reveal characteristic echo structures created by forced and free convection. Echoes produced by forced convection are not structured and are observed over ...

V. R. Noonkester

1974-01-01

290

75 FR 65521 - FM Approvals; Expansion of Recognition  

Federal Register 2010, 2011, 2012, 2013

...Each NRTL's scope of recognition has three elements...2007, to expand its recognition to include 31 additional...standards. The NRTL Program staff deferred action on 20...and Order NRTL Program staff examined FM's application...for expansion of its recognition, subject to the...

2010-10-25

291

Waveform digitizing at 500 MHz  

SciTech Connect

Experiment E787 at Brookhaven National Laboratory is designed to study the decay K/sup +/ ..-->.. ..pi../sup +/..nu../bar /nu// to a sensitivity of 2 /times/ 10/sup -10/. To achieve acceptable muon rejection it is necessary to couple traditional methods (range/energy/momentum correlation) with observation of the (..pi../sup +/ ..-->.. ..mu../sup +/..nu.., ..mu../sup +/ ..-->.. e/sup +/..nu../bar /nu//) decay sequence in scintillator. We report on the design and construction of 200 channels of relatively low cost solid state waveform digitizers. The distinguishing features are: 8 bits dynamic range, 500 MHz sampling, zero suppression on the fly, deep memory (up to .5 msec), and fast readout time (100 ..mu..sec for the entire system). We report on data obtained during the February-May 1988 run showing performance of the system for the observation of the above decay. 8 figs.

Atiya, M.; Ito, M.; Haggerty, J.; Ng, C.; Sippach, F.W.

1988-01-01

292

Effects of noise reduction on AM and FM perception.  

PubMed

The goal of noise reduction (NR) algorithms in digital hearing aid devices is to reduce background noise whilst preserving as much of the original signal as possible. These algorithms may increase the signal-to-noise ratio (SNR) in an ideal case, but they generally fail to improve speech intelligibility. However, due to the complex nature of speech, it is difficult to disentangle the numerous low- and high-level effects of NR that may underlie the lack of speech perception benefits. The goal of this study was to better understand why NR algorithms do not improve speech intelligibility by investigating the effects of NR on the ability to discriminate two basic acoustic features, namely amplitude modulation (AM) and frequency modulation (FM) cues, known to be crucial for speech identification in quiet and in noise. Here, discrimination of complex, non-linguistic AM and FM patterns was measured for normal hearing listeners using a same/different task. The stimuli were generated by modulating 1-kHz pure tones by either a two-component AM or FM modulator with patterns changed by manipulating component phases. Modulation rates were centered on 3 Hz. Discrimination of AM and FM patterns was measured in quiet and in the presence of a white noise that had been passed through a gammatone filter centered on 1 kHz. The noise was presented at SNRs ranging from -6 to +12 dB. Stimuli were left as such or processed via an NR algorithm based on the spectral subtraction method. NR was found to yield small but systematic improvements in discrimination for the AM conditions at favorable SNRs but had little effect, if any, on FM discrimination. A computational model of early auditory processing was developed to quantify the fidelity of AM and FM transmission. The model captured the improvement in discrimination performance for AM stimuli at high SNRs with NR. However, the model also predicted a relatively small detrimental effect of NR for FM stimuli in contrast with the average psychophysical data. Overall, these results suggest that the lack of benefits of NR on speech intelligibility is partly caused by the limited effect of NR on the transmission of narrowband speech modulation cues. PMID:23180229

Ives, D Timothy; Calcus, Axelle; Kalluri, Sridhar; Strelcyk, Olaf; Sheft, Stanley; Lorenzi, Christian

2013-02-01

293

Speech Processing Applications Using AN Am-Fm Modulation Model.  

NASA Astrophysics Data System (ADS)

In this thesis, the AM-FM modulation speech model and multiband demodulation are applied to speech analysis and coding. The AM-FM model represents the speech signal as a sum of amplitude modulated (AM) and frequency modulated (FM) signals, each AM-FM signal models a single speech resonance (formant). The model is able to describe a wide range of nonlinear and time-varying phenomena during speech production. Multiband demodulation is the proposed speech analysis method in the context of the AM-FM model. A bank of Gabor filters is used to filter the speech signal and, then, a demodulation algorithm is applied on each band to obtain the amplitude envelope and instantaneous frequency signals. The energy separation algorithm (ESA) and the Hilbert transform approach are compared for signal and speech resonance demodulation, and the ESA is found to have better time-resolution and to be computationally more efficient. Next, we apply multiband demodulation analysis (MDA) to formant and pitch tracking. Using the amplitude envelope and instantaneous frequency signals short-time estimates are proposed for the formant frequency and the fundamental frequency. The merits of the estimates are evaluated and it is concluded that the amplitude weighted mean instantaneous frequency and the short-time phase slope perform best for formant and pitch estimation respectively. Finally, decision algorithms are provided for the formant and pitch contours. Both speech analysis algorithms provide very smooth and accurate estimates and have attractive time -domain parallel implementations. Next, we use time-varying MDA for a speech coding application. A time-varying Gabor filterbank extracts four formant bands from the signal and, then, each resonance is demodulated to amplitude envelope and instantaneous frequency signals. Efficient modeling and coding schemes are proposed for the information signals that exploit the correlation between the formant bands. Finally, speech is synthesized as the sum of the reconstructed formant bands. The AM-FM analysis-synthesis system produces speech of very natural quality. Currently, the vocoder operates in the 4.8-9.6 kbits/sec range. Future applications of these modeling/coding ideas include text-to-speech synthesis and speaker identification. Overall, the AM-FM modulation model and multiband demodulation analysis are a general nonlinear approach to speech processing with a wide range of successful applications.

Potamianos, Alexandros

1995-01-01

294

Dense Monoenergetic Proton Beams from Chirped Laser-Plasma Interaction  

NASA Astrophysics Data System (ADS)

Interaction of a frequency-chirped laser pulse with single protons and a hydrogen gas target is studied analytically and by means of particle-in-cell simulations, respectively. The feasibility of generating ultraintense (107 particles per bunch) and phase-space collimated beams of protons (energy spread of about 1%) is demonstrated. Phase synchronization of the protons and the laser field, guaranteed by the appropriate chirping of the laser pulse, allows the particles to gain sufficient kinetic energy (around 250 MeV) required for such applications as hadron cancer therapy, from state-of-the-art laser systems of intensities of the order of 1021W/cm2.

Galow, Benjamin J.; Salamin, Yousef I.; Liseykina, Tatyana V.; Harman, Zoltán; Keitel, Christoph H.

2011-10-01

295

Effects of frequency chirp on magnetron injection locking  

SciTech Connect

The injection locking of a magnetron is theoretically analyzed when either the free running oscillator or the drive signal has a frequency chirp. It is found that complete phase locking of the signal cannot be achieved in either case. However, as long as the locking condition of Adler is well-satisfied instantaneously, a high degree of locking occurs during a major duration of the frequency chirps. The expected output phase variation is computed in terms of the noise in the free-running magnetron oscillator for the case of constant drive frequency.

Pengvanich, P.; Lau, Y. Y.; Luginsland, J. W.; Gilgenbach, R. M.; Cruz, E. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan 48109-2104 (United States); Schamiloglu, E. [Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, New Mexico 87131 (United States)

2008-07-15

296

Effects of frequency chirp on magnetron injection locking  

NASA Astrophysics Data System (ADS)

The injection locking of a magnetron is theoretically analyzed when either the free running oscillator or the drive signal has a frequency chirp. It is found that complete phase locking of the signal cannot be achieved in either case. However, as long as the locking condition of Adler is well-satisfied instantaneously, a high degree of locking occurs during a major duration of the frequency chirps. The expected output phase variation is computed in terms of the noise in the free-running magnetron oscillator for the case of constant drive frequency.

Pengvanich, P.; Lau, Y. Y.; Luginsland, J. W.; Gilgenbach, R. M.; Cruz, E.; Schamiloglu, E.

2008-07-01

297

Monolithic optical parametric oscillator using chirped quasi-phase matching  

NASA Astrophysics Data System (ADS)

We describe a highly efficient monolithic, Q-switched, nanosecond optical parametric oscillator based on a magnesium-oxide-doped periodically poled lithium niobate crystal and containing multiple quasi-phase-matched gratings. The crystal consisted of a single unchirped grating and five gratings containing progressively increasing amounts of longitudinal chirp. The monolithic design makes the device highly compact, stable, and robust, and it demonstrated a pump-to-signal conversion efficiency of around 50%, generating 50 ?J pulses at 1.55 ?m with a spectral bandwidth of 20 nm. Sonogram traces are presented showing the effect of crystal chirp on the temporal and spectral performance.

Tillman, Karl A.; Reid, Derryck T.

2007-06-01

298

Temperature insensitive accelerometer based on a strain-chirped FBG  

NASA Astrophysics Data System (ADS)

A novel accelerometer based on a strain-chirped optical fiber Bragg grating (FBG) is proposed. The FBG is glued in a slanted direction onto the lateral side of a right-angled triangle cantilever beam with a mass bonded on its free end. Vertical acceleration applied to the cantilever beam leads to a uniform bending along the beam length. As a result, the FBG is chirped and its reflection bandwidth changes linearly with the applied acceleration. A high sensitivity of 0.684 nm/g has been achieved in the experiment. This sensor is temperature insensitive, owning to the temperatureindependence nature of reflection bandwidth of the FBG.

Zhou, Wenjun; Dong, Xinyong; Ni, Kai; Chan, C. C.; Shum, P.

2009-10-01

299

Measurement and control of the frequency chirp rate of high-order harmonic pulses  

SciTech Connect

We measure the chirp rate of harmonics 13 to 23 in argon by cross correlation with a 12 femtosecond probe pulse. Under low ionization conditions, we directly measure the negative chirp due to the atomic dipole phase, and show that an additional chirp on the pump pulse is transferred to the qth harmonic as q times the fundamental chirp. Our results are in accord with simulations using the experimentally measured 815 nm pump and probe pulses. The ability to measure and manipulate the harmonic chirp rate is essential for the characterization and optimization of attosecond pulse trains.

Mauritsson, J.; Johnsson, P.; Lopez-Martens, R.; Varju, K.; L'Huillier, A. [Department of Physics, Lund Institute of Technology, P. O. Box 118, SE-221 00 Lund (Sweden); Kornelis, W.; Biegert, J.; Keller, U. [Physics Department, Swiss Federal Institute of Technology (ETH Zuerich), CH-8093 Zurich (Switzerland); Gaarde, M.B.; Schafer, K.J. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803-4001 (United States)

2004-08-01

300

Analysis in the instantaneous frequency forms of a chirped laser pulse  

SciTech Connect

We analyze two forms of the instantaneous frequency of a linearly chirped laser pulse. Using a 3D test particle simulation, numerical results are presented for electrons accelerated by a chirped laser pulse with these two linearly chirped forms of the instantaneous frequency. We summarize that the linearly chirped frequency, {omega}(t)={omega}{sub 0}[1-{alpha}(t-z/c)] is reasonable, {omega}{sub 0} is laser frequency at z=0 and t=0, and {alpha} is the frequency chirp parameter.

Yuan, C. J.; Wu, X. Y.; Wang, P. X. [Applied Ion Beam Physics Laboratory, Key Laboratory of the Ministry of Education, China and Institute of Modern Physics, Department of Nuclear Science and Technology, Fudan University, Shanghai 200433 (China); Wang, J. X. [State Key Laboratory of Precision Spectroscopy and Department of Physics, East China Normal University, Shanghai 200062 (China)

2011-10-15

301

All-optical electrical chirped pulse generation based on nonlinear wavelength-to-time conversion in a chirped fiber Bragg grating  

Microsoft Academic Search

In this paper, we propose and demonstrate a novel approach to optically generating chirped microwave pulse with tunable chirp rate based on spectral shaping and nonlinear wavelength-to-time conversion using a tunable nonlinearly chirped fiber Bragg grating (NL-CFBG). In our approach, the optical power spectrum of a ultrashort pulse from a femtosecond pulsed laser (FSPL) is shaped by a two-tap Sagnac

Chao Wang; Jianping Yao

2007-01-01

302

Quasi-simultaneous measurements of scattering matrix elements in polarimetric radar with continuous waveforms providing high-level isolation in radar channels  

Microsoft Academic Search

This paper presents a new type of sounding signals for polarimetric FM-CW radar and corresponding de-ramping technique for processing, which provide the possibility for simultaneous measurement of all backscattering matrix elements and have high-level isolation between branches of the polarimetric receiver. The radar transmitter forms sounding signal, which has orthogonally-polarized components with orthogonal waveforms. The radar receiver is splitting orthogonally-polarized

Galina P. Babur; Oleg A. Krasnov; Leo P. Ligthart

2009-01-01

303

Power losses of Finemet using nonsinusoidal waveforms  

NASA Astrophysics Data System (ADS)

Though many practical applications preferably take advantage of nonsinusoidal induction waveforms the characterisation of soft magnetic materials is performed under sinusoidal induction waveforms. Therefore, it would be useful if results from magnetic measurements could be transformed to be valid for applications using different waveforms. This also enables to compare results obtained from measurements where sinusoidal waveforms could not be realised and thus makes them independent of the measuring device used. The dynamic hysteresis loops of differently prepared Finemet ribbons were measured with a computer controlled device at different frequencies and polarisations using sinusoidal and triangular waveforms of the magnetic field which leads to induction waveforms varying with frequency, amplitude of polarisation, waveform of the magnetising field and preparation of specimen material. The samples measured were strips of Fe 73.5Si 13.5Cu 1Nb 3B 9 nanocrystallised at 580°C for 1 h. Different types of samples were used which includes specimens surface treated prior to heat treatment in order to achieve domain refinement. A one to one functional dependency between power loss, frequency, and k-factor was found that enables the comparison of power losses for different induction signals characterised by their form factor as it is already known for grain oriented silicon steel sheets. This dependency is valid for all types of specimen investigated regardless of their different magnetic properties.

Ramin, D.; Riehemann, W.

1999-08-01

304

Chirp and Click Evoked Auditory Steady State Responses.  

National Technical Information Service (NTIS)

In this study, Auditory Steady State Responses (ASSR) to 100 microsec clicks and 4 msec cochlear chirps are recorded in adult subjects at repetition rates of 20 to 100Hz in 10 Hz increments, Response characteristics of ASSRs are compared in the frequency ...

Y. Hekimoglu O. Ozdamar R. E. Delgado

2001-01-01

305

Chirped microwave photonic filter with high frequency tuning capability  

Microsoft Academic Search

A chirped single-bandpass photonic filter is proposed improving the delay performance achieved by microstrip structures. Frequency range is extended up to tens of GHz since carrier- suppression-effect is avoided although double-side-band is employed. OCIS codes: (000.0000) General;

Mario Bolea; Jose Mora; Beatriz Ortega; Jose Capmany

2011-01-01

306

Photonic microwave matched filters for chirped microwave pulse compression  

Microsoft Academic Search

In this paper, a technique to design and implement a photonic microwave matched filter for chirped microwave pulse compression is presented. To realize matched filtering, the filter should have a spectral response that is matched to that of the input pulse, which is implemented in this paper using a photonic system that consists of an optical single-sideband (SSB) modulator and

Chao Wang; Jianping Yao

2008-01-01

307

Amplification of optical pulse signal using chirped fiber grating  

Microsoft Academic Search

These chirped fiber Bragg gratin is an attractive and practical element in particular context of dense wavelength- division multiplexing. We introduce a structure to realize working mode of the optical pulse's high power amplification. Also we analyze the variation of pulse signal after broaden or compression together with the variation in frequency domain and the peak intensity of pulse signal

Weihai Ni; Li Zhan; YuXing Xia

2002-01-01

308

Coherent control of stimulated Raman scattering using chirped laser pulses  

Microsoft Academic Search

A novel method for the control of stimulated Raman scattering and hot electron production in short-pulse laser-plasma interactions is proposed. It relies on the use of a linear frequency chirp in nonbandwidth limited pulses. Theoretical calculations show that a 12% bandwidth will eliminate Raman forward scattering for a plasma density that is 1% of the critical density. The predicted changes

Evan S. Dodd; Donald Umstadter

2001-01-01

309

Habituation analysis of chirp vs. tone evoked auditory late responses  

Microsoft Academic Search

We have recently shown that tone evoked auditory late responses are able to proof that habituation is occurring. The sweep to sweep analysis using time scale coherence method from is used. Where clear results using tone evoked ALRs were obtained. Now it is of interest how does the results behave using chirp evoked ALRs compared to tone evoked ALRs so

Kevin Kern; Vladislav Royter; Farah I. Corona-Strauss; Mai Mariam; Daniel J. Strauss

2010-01-01

310

Optimization of apodized linearly chirped fiber gratings for optical communications  

Microsoft Academic Search

The dispersion characteristics of apodized, linearly chirped fiber Bragg gratings and their potential as dispersion compensators have been studied systematically. It is shown that the positive hyperbolic-tangent profile results in an overall superior performance, as it provides highly linearized time-delay characteristics with minimum reduction in the linear dispersion. To compensate for the linear dispersion of 100 km of standard telecom

Karin Ennser; N. Zervas; Richard I. Laming

1998-01-01

311

Spectral analysis using the CCD Chirp Z-transform  

NASA Technical Reports Server (NTRS)

The charge coupled device (CCD) Chirp Z transformation (CZT) spectral analysis techniques were reviewed and results on state-of-the-art CCD CZT technology are presented. The CZT algorithm was examined and the advantages of CCD implementation are discussed. The sliding CZT which is useful in many spectral analysis applications is described, and the performance limitations of the CZT are studied.

Eversole, W. L.; Mayer, D. J.; Bosshart, P. W.; Dewit, M.; Howes, C. R.; Buss, D. D.

1978-01-01

312

On the Utility of Chirp Modulation for Digital Signaling  

Microsoft Academic Search

The issue of signal selection in binary data transmission is presented. The question of the relative utility of linear frequency sweeping (LFS or chirp), compared to PSK and FSK, in terms of error probability and spectrum usage, is discussed. The transmission media considered are the coherent, partially coherent, Rayleigh, and Rician channel models. Theoretically, LFS has unconditionally superior characteristics in

A. Berni; W. Gregg

1973-01-01

313

Influence of nonideal chirped fiber grating characteristics on dispersion cancellation  

Microsoft Academic Search

The effect of nonideal dispersion and reflection characteristics of chirped fiber gratings on the performance of 10-Gb\\/s nonreturn-to-zero-transmission systems operating over standard fiber is investigated. The system penalty for different amplitude and period ripples are quantified. Analyses of an experimental grating confirm that current fabrication technology can meet the requirements for <1-dB-penalty operation

K. Ennser; M. Ibsen; M. Durkin; M. N. Zervas; R. I. Laming

1998-01-01

314

Design of apodized linearly chirped fiber gratings for dispersion compensation  

Microsoft Academic Search

We investigate and compare the equalization performance of various apodization functions in linearly chirped fiber gratings, with a view of determining an optimum profile for the design and fabrication of chromatic dispersion compensators. A discussion concerning the relation of these apodization functions with the group delay characteristic of the equalizer is presented yielding important results connected with the grating design.

Daniel Pastor; J. Capmany; D. Ortega; V. Tatay; J. Marti

1996-01-01

315

Effects of frequency chirp on magnetron injection locking  

Microsoft Academic Search

In this paper, effects of time-varying frequencies on the injection locking behavior are explored. Of interest is when the driver frequency is linearly swept (chirp) in time, e.g., for frequency search when the oscillator frequency is not known. It is found that complete locking similar to the constant frequency case can no longer occur. Instead, frequency of the oscillator \\

P. Pengvanich; Yue Ying Lau; J. W. Luginsland; R. M. Gilgenbach; E. Cruz; E. Schamiloglu

2008-01-01

316

Effects of frequency chirp on magnetron injection locking  

Microsoft Academic Search

The injection locking of a magnetron is theoretically analyzed when either the free running oscillator or the drive signal has a frequency chirp. It is found that complete phase locking of the signal cannot be achieved in either case. However, as long as the locking condition of Adler is well-satisfied instantaneously, a high degree of locking occurs during a major

P. Pengvanich; Y. Y. Lau; J. W. Luginsland; R. M. Gilgenbach; E. Cruz; E. Schamiloglu

2008-01-01

317

Carrier-Compatible Chirp-Z Transform Device.  

National Technical Information Service (NTIS)

The patent application relates to a surface acoustic wave (SAW) device useful in band-limited TV systems, and suitable for carrier-compatible chirp-Z transform Fourier analysis. It includes apparatus for taking the discrete Fourier transform of a complex ...

J. M. Alsup H. J. Whitehouse

1976-01-01

318

Chirped fiber Bragg gratings for electrically tunable time delay lines  

Microsoft Academic Search

In this paper, a continuously variable delay line for phased array antennas is presented. The proposed delay line operates at a single wavelength and is based on properly designed linearly chirped fiber Bragg gratings. Continuous true time delay can be achieved by changing the temperature or strain along the grating region. Numerical results show that the delay line can be

Vincenzo Italia; Marco Pisco; Stefania Campopiano; Andrea Cusano; Antonello Cutolo

2005-01-01

319

Chirped frequency transfer: a tool for synchronization and time transfer.  

PubMed

We propose and demonstrate the phase-stabilized transfer of a chirped frequency as a tool for synchronization and time transfer. Technically, this is done by evaluating remote measurements of the transferred, chirped frequency. The gates of the frequency counters, here driven by a 10-MHz oscillation derived from a hydrogen maser, play a role analogous to the 1-pulse per second (PPS) signals usually employed for time transfer. In general, for time transfer, the gates consequently must be related to the external clock. Synchronizing observations based on frequency measurements, on the other hand, only requires a stable oscillator driving the frequency counters. In a proof of principle, we demonstrate the suppression of symmetrical delays, such as the geometrical path delay. We transfer an optical frequency chirped by around 240 kHz/s over a fiber link of around 149 km. We observe an accuracy and simultaneity, as well as a precision (Allan deviation, 18 000 s averaging interval) of the transferred frequency of around 2 × 10-19. We apply chirped frequency transfer to remote measurements of the synchronization between two counters' gate intervals. Here, we find a precision of around 200 ps at an estimated overall uncertainty of around 500 ps. The measurement results agree with those obtained from reference measurements, being well within the uncertainty. In the present setup, timing offsets up to 4 min can be measured unambiguously. We indicate how this range can be extended further. PMID:24859656

Raupach, Sebastian; Grosche, Gesine

2014-06-01

320

Dispersion tuning of a linearly chirped fiber Bragg grating without a center wavelength shift by applying a strain gradient  

Microsoft Academic Search

We propose a new method for controlling the chirp of a linearly chirped fiber Bragg grating (FBG) without a center wavelength shift by using beam bending. The beam consists of a plastic sleeve enclosing a 10-cm-long chirped FBG and a metal rod. The grating pitch could be varied to give positive or negative chirp as well as zero chirp (i.e.

T. Imai; T. Komukai; M. Nakazawa

1998-01-01

321

Full Waveform Active Hyperspectral LIDAR  

NASA Astrophysics Data System (ADS)

We have developed a prototype full waveform hyperspectral LiDAR and investigated its potential for remote sensing applications. Traditionally hyperspectral remote sensing is based on passive measurement of sunlit targets. These methods are sensitive to errors in illumination conditions and lack the range information. Our prototype can measure both the range and the spectral information from a single laser pulse. At this stage, the instrument is optimized for short range terrestrial applications. An active hyperspectral LiDAR opens up new possibilities for LiDAR data analysis. The lack of spectral information in traditional monochrome LiDARs rules out many of the classification techniques available for processing of hyperspectral data. Similarly, passive hyperspectral data does not allow extensive use of the classifications based on 3D shape parameters. With both hyperspectral and range data available in a single dataset, the best of the techniques can be applied to form more reliable classification results. The data also allows the mapping of spectral indices in 3D. As an example a Norway spruce is measured and spatial distribution of several spectral indices is illustrated.

Hakala, T.; Suomalainen, J.; Kaasalainen, S.

2012-08-01

322

Multiscale AM-FM Methods for Diabetic Retinopathy Lesion Detection  

Microsoft Academic Search

In this paper, we propose the use of multiscale amplitude-modulation-frequency-modulation (AM-FM) methods for discriminating between normal and pathological retinal images. The method presented in this paper is tested using standard images from the early treatment diabetic retinopathy study. We use 120 regions of 40 ?? 40 pixels containing four types of lesions commonly associated with diabetic retinopathy (DR) and two

Carla Agurto; Víctor Murray; Eduardo S. Barriga; Sergio Murillo; Marios S. Pattichis; Herbert Davis; Stephen R. Russell; Michael D. Abràmoff; Peter Soliz

2010-01-01

323

New Approach to Radar Waveform Design.  

National Technical Information Service (NTIS)

We have extended Wilcox's classical result to address an issue of acceptable approximation of the 'ideal' ambiguity surface in the area of interest. We have considered a problem of constructing a waveform with minimal volume under the ambiguity surface in...

I. Gladkova

2007-01-01

324

Comparative Waveform Analysis of Multisensor Imagery.  

National Technical Information Service (NTIS)

Video conversion of imagery to sampling scan lines which generate waveforms measuring gray tones (or thermal variation) in the distribution pattern demonstrates a basis for instrumented comparative analyses. Distribution patterns are sampled by parallel s...

J. P. Latham R. E. Witmer

1967-01-01

325

High-Voltage, Asymmetric-Waveform Generator  

NASA Technical Reports Server (NTRS)

The shapes of waveforms generated by commercially available analytical separation devices, such as some types of mass spectrometers and differential mobility spectrometers are, in general, inadequate and result in resolution degradation in output spectra. A waveform generator was designed that would be able to circumvent these shortcomings. It is capable of generating an asymmetric waveform, having a peak amplitude as large as 2 kV and frequency of several megahertz, which can be applied to a capacitive load. In the original intended application, the capacitive load would consist of the drift plates in a differential-mobility spectrometer. The main advantage to be gained by developing the proposed generator is that the shape of the waveform is made nearly optimum for various analytical devices requiring asymmetric-waveform such as differential-mobility spectrometers. In addition, this waveform generator could easily be adjusted to modify the waveform in accordance with changed operational requirements for differential-mobility spectrometers. The capacitive nature of the load is an important consideration in the design of the proposed waveform generator. For example, the design provision for shaping the output waveform is based partly on the principle that (1) the potential (V) on a capacitor is given by V=q/C, where C is the capacitance and q is the charge stored in the capacitor; and, hence (2) the rate of increase or decrease of the potential is similarly proportional to the charging or discharging current. The proposed waveform generator would comprise four functional blocks: a sine-wave generator, a buffer, a voltage shifter, and a high-voltage switch (see Figure 1). The sine-wave generator would include a pair of operational amplifiers in a feedback configuration, the parameters of which would be chosen to obtain a sinusoidal timing signal of the desired frequency. The buffer would introduce a slight delay (approximately equal to 20 ns) but would otherwise leave the fundamental timing signal unchanged. The buffered timing signal would be fed as input to the level shifter. The output of the level shifter would serve as a timing and control signal for the high-voltage switch, causing the switch to alternately be (1) opened, allowing the capacitive load to be charged from a high-voltage DC power supply; then (2) closed to discharge the capacitive load to ground. Hence, the output waveform would closely approximate a series of exponential charging and discharging curves (see Figure 2).

Beegle, Luther W.; Duong, Tuan A.; Duong, Vu A.; Kanik, Isik

2008-01-01

326

Analysis and Application of LIDAR Waveform Data Using a Progressive Waveform Decomposition Method  

NASA Astrophysics Data System (ADS)

Due to rich information of a full waveform of airborne LiDAR (light detection and ranging) data, the analysis of full waveform has been an active area in LiDAR application. It is possible to digitally sample and store the entire reflected waveform of small-footprint instead of only discrete point clouds. Decomposition of waveform data, a key step in waveform data analysis, can be categorized to two typical methods: 1) the Gaussian modelling method such as the Non-linear least-squares (NLS) algorithm and the maximum likelihood estimation using the Exception Maximization (EM) algorithm. 2) pulse detection method—Average Square Difference Function (ASDF). However, the Gaussian modelling methods strongly rely on initial parameters, whereas the ASDF omits the importance of parameter information of the waveform. In this paper, we proposed a fast algorithm—Progressive Waveform Decomposition (PWD) method to extract local maxims and fit the echo with Gaussian function, and calculate other parameters from the raw waveform data. On the one hand, experiments are implemented to evaluate the PWD method and the results demonstrate its robustness and efficiency. On the other hand, with the PWD parametric analysis of the full-waveform instead of a 3D point cloud, some special applications are investigated afterward.

Zhu, J.; Zhang, Z.; Hu, X.; Li, Z.

2011-09-01

327

Waveform inversion using a logarithmic wavefield  

Microsoft Academic Search

Although waveform inversion has been studied extensively since its beginning 20 years ago, applications to seismic field data have been limited, and most of those applications have been for global-seismology- or engineering-seismology-scale problems, not for exploration-scale data. As an alternative to classical waveform inversion, we propose the use of a new, ob- jective function constructed by taking the logarithm of

Changsoo Shin; Dong-Joo Min

2006-01-01

328

Arbitrary waveform synthesis for communication applications  

NASA Astrophysics Data System (ADS)

For optical wireless laser transmissions we take advantage of a specific comblike structure of the spectrum of mode-locked laser ultrashort pulse trains and present a pulse-shaping technique for arbitrary waveform synthesis. The shaped pulses are free of space-time coupling effects and high-order spatial modes. As examples, we provide simulation results for the synthesis of waveforms that are of particular interest for optical communications, namely, square-root-raised cosines and Meyer wavelets.

Hamzeh, B.; Jivkova, S.; Kavehrad, Mohsen

2005-10-01

329

GRC GSFC TDRSS Waveform Metrics Report  

NASA Technical Reports Server (NTRS)

The report presents software metrics and porting metrics for the GGT Waveform. The porting was from a ground-based COTS SDR, the SDR-3000, to the CoNNeCT JPL SDR. The report does not address any of the Operating Environment (OE) software development, nor the original TDRSS waveform development at GSFC for the COTS SDR. With regard to STRS, the report presents compliance data and lessons learned.

Mortensen, Dale J.

2013-01-01

330

Waveform analysis for Geosat day 96  

NASA Technical Reports Server (NTRS)

A detailed model waveform function has been least-squares-fitted to 10-second averages of waveform sampler data from selected over-ocean portions of day 96 of the Geosat mission. The results confirm that the height corrections already applied in the routine Geosat data processing are generally good to well within 10 centimeters. Additional height corrections are provided that can refine height estimates to within the several-centimeter level.

Hayne, George S.; Hancock, David W., III

1987-01-01

331

Radar waveform design and target detection using wavelets  

Microsoft Academic Search

The projection of the conventional radar waveform in wavelet space is comparatively complex, which complicated the wavelet decomposition of the radar waveform. A novel radar waveform design method is proposed. The proposed approach uses the wavelet function of a specific scale as the waveform and thus the inter-dependency of the wavelet coefficients in different subspaces is reduced. Better detection performance

Naiwei Wang; Yingguang Zhang; Shunjun Wu

2001-01-01

332

STAP performance analysis for MIMO radar with waveform diversity  

Microsoft Academic Search

This paper studies the waveform effect on the space time adaptive processing (STAP) of multiple-input multiple-output (MIMO) radar systems. A general signal model based on waveform diversity is constructed for MIMO STAP. System sensitivity and optimal adapted pattern are investigated according to waveform diversity. These studies show how the MIMO STAP performance is affected by waveform diversity, based on which

Guohua Wang; Yilong Lu; Jinping Sun

2009-01-01

333

78 FR 9915 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2013-03218 Filed 2-11-13; 8:45 am] BILLING CODE...

2013-02-12

334

76 FR 50732 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2011-20828 Filed 8-15-11; 8:45 am] BILLING CODE...

2011-08-16

335

77 FR 57086 - Radio Broadcasting Services; AM or FM Proposals To Change The Community of License.  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change The Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2012-22753 Filed 9-14-12; 8:45 am] BILLING CODE...

2012-09-17

336

78 FR 23565 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License.  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2013-09276 Filed 4-18-13; 8:45 am] BILLING CODE...

2013-04-19

337

77 FR 66839 - Radio Broadcasting Services; AM or FM Proposals To Change The Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change The Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2012-27194 Filed 11-6-12; 8:45 am] BILLING CODE...

2012-11-07

338

76 FR 55388 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License.  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2011-22745 Filed 9-6-11; 8:45 am] BILLING CODE...

2011-09-07

339

78 FR 41062 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2013-16360 Filed 7-8-13; 8:45 am] BILLING CODE...

2013-07-09

340

77 FR 8869 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2012-3561 Filed 2-14-12; 8:45 am] BILLING CODE...

2012-02-15

341

75 FR 31437 - Radio Broadcasting Services; AM or FM Proposals To Change The Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change The Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2010-13383 Filed 6-2-10; 8:45 am] BILLING CODE...

2010-06-03

342

75 FR 6395 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2010-2774 Filed 2-8-10; 8:45 am] BILLING CODE...

2010-02-09

343

78 FR 55075 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2013-21774 Filed 9-6-13; 8:45 am] BILLING CODE...

2013-09-09

344

75 FR 66098 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2010-27209 Filed 10-26-10; 8:45 am] BILLING CODE...

2010-10-27

345

75 FR 20597 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

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2010-04-20

346

76 FR 14394 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2011-6147 Filed 3-15-11; 8:45 am] BILLING CODE...

2011-03-16

347

78 FR 69086 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2013-27576 Filed 11-15-13; 8:45 am] BILLING CODE...

2013-11-18

348

75 FR 74732 - Radio Broadcasting Services; AM or FM Proposals To Change The Community of License  

Federal Register 2010, 2011, 2012, 2013

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2010-12-01

349

78 FR 13670 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2013-04717 Filed 2-27-13; 8:45 am] BILLING CODE...

2013-02-28

350

77 FR 75434 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2012-30594 Filed 12-19-12; 8:45 am] BILLING CODE...

2012-12-20

351

76 FR 72705 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2011-30395 Filed 11-23-11; 8:45 am] BILLING CODE...

2011-11-25

352

47 CFR 73.4015 - Applications for AM and FM construction permits, incomplete or defective.  

Code of Federal Regulations, 2013 CFR

...4 2013-10-01 2013-10-01 false Applications for AM and FM construction permits, incomplete or defective. 73...Applicable to All Broadcast Stations § 73.4015 Applications for AM and FM construction permits, incomplete or defective....

2013-10-01

353

76 FR 22704 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2011-9859 Filed 4-21-11; 8:45 am] BILLING CODE...

2011-04-22

354

77 FR 45352 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2012-18584 Filed 7-30-12; 8:45 am] BILLING CODE...

2012-07-31

355

77 FR 24954 - Radio Broadcasting Services; AM or FM Proposals to Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals to Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2012-10131 Filed 4-25-12; 8:45 am] BILLING CODE...

2012-04-26

356

75 FR 51812 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2010-20912 Filed 8-20-10; 8:45 am] BILLING CODE...

2010-08-23

357

77 FR 4817 - Radio Broadcasting Services; AM or FM Proposals To Change The Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change The Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2012-2067 Filed 1-30-12; 8:45 am] BILLING CODE...

2012-01-31

358

76 FR 2382 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2011-563 Filed 1-12-11; 8:45 am] BILLING CODE...

2011-01-13

359

76 FR 65192 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2011-27107 Filed 10-19-11; 8:45 am] BILLING CODE...

2011-10-20

360

77 FR 18815 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2012-7468 Filed 3-27-12; 8:45 am] BILLING CODE...

2012-03-28

361

75 FR 36393 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2010-15473 Filed 6-24-10; 8:45 am] BILLING CODE...

2010-06-25

362

77 FR 33217 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2012-13495 Filed 6-4-12; 8:45 am] BILLING CODE...

2012-06-05

363

75 FR 1621 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2010-330 Filed 1-11-10; 8:45 am] BILLING CODE...

2010-01-12

364

76 FR 6788 - Radio Broadcasting Services; AM or FM Proposals To Change The Community of License.  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change The Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2011-2764 Filed 2-7-11; 8:45 am] BILLING CODE...

2011-02-08

365

76 FR 46294 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2011-19521 Filed 8-1-11; 8:45 am] BILLING CODE...

2011-08-02

366

75 FR 13761 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2010-6328 Filed 3-22-10; 8:45 am] BILLING CODE...

2010-03-23

367

76 FR 31961 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2011-13745 Filed 6-1-11; 8:45 am] BILLING CODE...

2011-06-02

368

75 FR 63475 - Radio Broadcasting Services; AM or FM Proposals To Change The Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change The Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2010-25928 Filed 10-14-10; 8:45 am] BILLING CODE...

2010-10-15

369

75 FR 47596 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2010-19457 Filed 8-5-10; 8:45 am] BILLING CODE...

2010-08-06

370

77 FR 38631 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community...SUMMARY: The following applicants filed AM or FM proposals to change the community...2012-15757 Filed 6-27-12; 8:45 am] BILLING CODE...

2012-06-28

371

76 FR 81932 - Auction of FM Broadcast Construction Permits; Revised Construction Permit Number in Auction 93  

Federal Register 2010, 2011, 2012, 2013

...DA 11-2046] Auction of FM Broadcast Construction Permits; Revised Construction Permit Number in Auction 93 AGENCY: Federal...This document announces a change to the construction permit number for one of the FM...

2011-12-29

372

47 CFR 73.506 - Classes of noncommercial educational FM stations and channels.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Classes of noncommercial educational FM stations and channels. 73.506...COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.506...

2010-10-01

373

47 CFR 73.513 - Noncommercial educational FM stations operating on unreserved channels.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 2009-10-01 false Noncommercial educational FM stations operating on unreserved...COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.513...

2009-10-01

374

47 CFR 73.506 - Classes of noncommercial educational FM stations and channels.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 false Classes of noncommercial educational FM stations and channels. 73.506...COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.506...

2009-10-01

375

47 CFR 73.513 - Noncommercial educational FM stations operating on unreserved channels.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Noncommercial educational FM stations operating on unreserved...COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.513...

2010-10-01

376

Waveform design for compressively sampled ultrawideband radar  

NASA Astrophysics Data System (ADS)

Compressive sensing makes it possible to recover sparse target scenes from under-sampled measurements when uncorrelated random-noise waveforms are used as probing signals. The mathematical theory behind this assertion is based on the fact that Toeplitz and circulant random matrices generated from independent identically distributed (i.i.d) Gaussian random sequences satisfy the restricted isometry property. In real systems, waveforms have smooth, nonideal autocorrelation functions, thereby degrading the performance of compressive sensing algorithms. Compressive sensing requires the system matrix to have particular properties. Incorporating prior information into the target scene either to enhance imaging or to mitigate nonidealities can result in system matrices that are not suitable for compressive sensing. We can overcome this problem by designing appropriate transmit waveforms. We extend the existing theory to incorporate such nonidealities into the analysis of compressive recovery. As an example we consider the problem of tailoring waveforms to image extended targets. Extended targets make the target scene denser, causing random transmit waveforms to be suboptimal for recovery. We propose to incorporate extended targets by considering them to be sparsely representable in redundant dictionaries. We demonstrate that a low complexity algorithm to optimize the transmit waveform leads to improved performance.

Shastry, Mahesh C.; Narayanan, Ram M.; Rangaswamy, Muralidhar

2013-04-01

377

Calculation and manipulation of the chirp rates of high-order harmonics  

SciTech Connect

We calculate the linear chirp rates of high-order harmonics in argon, generated by intense, 810 nm laser pulses, and explore the dependence of the chirp rate on harmonic order, driving laser intensity, and pulse duration. By using a time-frequency representation of the harmonic fields we can identify several different linear chirp contributions to the plateau harmonics. Our results, which are based on numerical integration of the time-dependent Schroedinger equation, are in good agreement with the adiabatic predictions of the strong field approximation for the chirp rates. Extending the theoretical analysis in the recent paper by Mauritsson et al. [Phys. Rev. A 70, 021801(R) (2004)], we also manipulate the chirp rates of the harmonics by adding a chirp to the driving pulse. We show that the chirp rate for harmonic q is given by the sum of the intrinsic chirp rate, which is determined by the new duration and peak intensity of the chirped driving pulse, and q times the external chirp rate.

Murakami, M.; Mauritsson, J.; Schafer, K.J.; Gaarde, M.B. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803-4001 (United States); L'Huillier, A. [Department of Physics, Lund Institute of Technology, P. O. Box 118, S-22100 Lund (Sweden)

2005-01-01

378

75 FR 9530 - FM TABLE OF ALLOTMENTS, French Lick, Indiana, and Irvington, Kentucky.  

Federal Register 2010, 2011, 2012, 2013

...RM-11412] FM TABLE OF ALLOTMENTS, French Lick, Indiana, and Irvington, Kentucky...modifies the license of Station WFLQ(FM), French Lick, Indiana, to specify operation...the licensee of Station WFLQ(FM), French Lick, Indiana, to show cause why...

2010-03-03

379

75 FR 63402 - FM Table of Allotments, Culebra, PR, Charlotte Amalie, and Christiansted, VI  

Federal Register 2010, 2011, 2012, 2013

...vacant Channel 271B at Charlotte Amalie, Virgin Islands to enable Station WNVE-FM to...224B for Channel 236B at Christiansted, Virgin Islands and modifying the license of FM...b), the Table of FM Allotments under Virgin Islands, is amended by adding...

2010-10-15

380

Platform for Postprocessing Waveform-Based NDE  

NASA Technical Reports Server (NTRS)

Taking advantage of the similarities that exist among all waveform-based non-destructive evaluation (NDE) methods, a common software platform has been developed containing multiple- signal and image-processing techniques for waveforms and images. The NASA NDE Signal and Image Processing software has been developed using the latest versions of LabVIEW, and its associated Advanced Signal Processing and Vision Toolkits. The software is useable on a PC with Windows XP and Windows Vista. The software has been designed with a commercial grade interface in which two main windows, Waveform Window and Image Window, are displayed if the user chooses a waveform file to display. Within these two main windows, most actions are chosen through logically conceived run-time menus. The Waveform Window has plots for both the raw time-domain waves and their frequency- domain transformations (fast Fourier transform and power spectral density). The Image Window shows the C-scan image formed from information of the time-domain waveform (such as peak amplitude) or its frequency-domain transformation at each scan location. The user also has the ability to open an image, or series of images, or a simple set of X-Y paired data set in text format. Each of the Waveform and Image Windows contains menus from which to perform many user actions. An option exists to use raw waves obtained directly from scan, or waves after deconvolution if system wave response is provided. Two types of deconvolution, time-based subtraction or inverse-filter, can be performed to arrive at a deconvolved wave set. Additionally, the menu on the Waveform Window allows preprocessing of waveforms prior to image formation, scaling and display of waveforms, formation of different types of images (including non-standard types such as velocity), gating of portions of waves prior to image formation, and several other miscellaneous and specialized operations. The menu available on the Image Window allows many further image processing and analysis operations, some of which are found in commercially-available image-processing software programs (such as Adobe Photoshop), and some that are not (removing outliers, Bscan information, region-of-interest analysis, line profiles, and precision feature measurements).

Roth, Don

2008-01-01

381

75 FR 61752 - Auction of FM Broadcast Construction Permits Scheduled for March 29, 2011; Comment Sought on...  

Federal Register 2010, 2011, 2012, 2013

...10-1711] Auction of FM Broadcast Construction Permits Scheduled for March 29, 2011...announces the auction of certain FM construction permits scheduled to commence on March...an auction of certain FM Broadcast construction permits. This auction, which is...

2010-10-06

382

The Waveform Suite: A robust platform for accessing and manipulating seismic waveforms in MATLAB  

NASA Astrophysics Data System (ADS)

The Waveform Suite, developed at the University of Alaska Geophysical Institute, is an open-source collection of MATLAB classes that provide a means to import, manipulate, display, and share waveform data while ensuring integrity of the data and stability for programs that incorporate them. Data may be imported from a variety of sources, such as Antelope, Winston databases, SAC files, SEISAN, .mat files, or other user-defined file formats. The waveforms being manipulated in MATLAB are isolated from their stored representations, relieving the overlying programs from the responsibility of understanding the specific format in which data is stored or retrieved. The waveform class provides an object oriented framework that simplifies manipulations to waveform data. Playing with data becomes easier because the tedious aspects of data manipulation have been automated. The user is able to change multiple waveforms simultaneously using standard mathematical operators and other syntactically familiar functions. Unlike MATLAB structs or workspace variables, the data stored within waveform class objects are protected from modification, and instead are accessed through standardized functions, such as get and set; these are already familiar to users of MATLAB’s graphical features. This prevents accidental or nonsensical modifications to the data, which in turn simplifies troubleshooting of complex programs. Upgrades to the internal structure of the waveform class are invisible to applications which use it, making maintenance easier. We demonstrate the Waveform Suite’s capabilities on seismic data from Okmok and Redoubt volcanoes. Years of data from Okmok were retrieved from Antelope and Winston databases. Using the Waveform Suite, we built a tremor-location program. Because the program was built on the Waveform Suite, modifying it to operate on real-time data from Redoubt involved only minimal code changes. The utility of the Waveform Suite as a foundation for large developments is demonstrated with the Correlation Toolbox for MATLAB. This mature package contains 50+ codes for carrying out various type of waveform correlation analyses (multiplet analysis, clustering, interferometry, …) This package is greatly strengthened by delegating numerous book-keeping and signal processing tasks to the underlying Waveform Suite. The Waveform Suite’s built-in tools for searching arbitrary directory/file structures is demonstrated with matched video and audio from the recent eruption of Redoubt Volcano. These tools were used to find subsets of photo images corresponding to specific seismic traces. Using Waveform’s audio file routines, matched video and audio were assembled to produce outreach-quality eruption products. The Waveform Suite is not designed as a ready-to-go replacement for more comprehensive packages such as SAC or AH. Rather, it is a suite of classes which provide core time series functionality in a MATLAB environment. It is designed to be a more robust alternative to the numerous ad hoc MATLAB formats that exist. Complex programs may be created upon the Waveform Suite’s framework, while existing programs may be modified to take advantage of the Waveform Suites capabilities.

Reyes, C. G.; West, M. E.; McNutt, S. R.

2009-12-01

383

Design of pulse waveform for waveform division multiple access UWB wireless communication system.  

PubMed

A new multiple access scheme, Waveform Division Multiple Access (WDMA) based on the orthogonal wavelet function, is presented. After studying the correlation properties of different categories of single wavelet functions, the one with the best correlation property will be chosen as the foundation for combined waveform. In the communication system, each user is assigned to different combined orthogonal waveform. Demonstrated by simulation, combined waveform is more suitable than single wavelet function to be a communication medium in WDMA system. Due to the excellent orthogonality, the bit error rate (BER) of multiuser with combined waveforms is so close to that of single user in a synchronous system. That is to say, the multiple access interference (MAI) is almost eliminated. Furthermore, even in an asynchronous system without multiuser detection after matched filters, the result is still pretty ideal and satisfactory by using the third combination mode that will be mentioned in the study. PMID:24672294

Yin, Zhendong; Wang, Zhirui; Liu, Xiaohui; Wu, Zhilu

2014-01-01

384

PREFACE: Functional materials and nanotechnologies (FM&NT-2007)  

NASA Astrophysics Data System (ADS)

The International Baltic Sea Region conference Functional Materials and Nanotechnologies (FM&NT-2007) was held in Riga, 2-4 April 2007 in the Institute of Solid State Physics, University of Latvia (ISSP LU). The conference was organized in co-operation with projects ERANET 'MATERA' and EUREKA 'BIONANOCOMPOSITE'. The purpose of the conference was to bring together scientists, engineers and students from universities, research institutes and related industrial companies active in the field of advanced material science and materials technologies trends and future activities. Scientific themes covered in the conference are:

  • advanced inorganic materials for photonics, energetics and microelectronics
  • organic materials for photonics and nanoelectronics
  • advanced methods for investigation of nanostructures
  • perspective biomaterials and medicine technologies
  • development of technologies for design of nanostructured materials, nanoparticles, and thin films
  • design of functional materials and nanocomposites and development of their technologies
  • The number of registered participants from 14 countries was nearly 110. During three days of the conference 70 oral reports and 58 posters were presented, 50 papers, based on these reports, are included in this volume of Journal of Physics: Conference Series. Additional information about FM&NT-2007 is available in its homepage http://fmnt.lu.lv and http://www.fmnt.lv . The Organizing Committee would like to thank all speakers, contributors, session chairs, referees and meeting staff for their efforts in making the FM&NT-2007 successful. The local Organization Committee would like to acknowledge and thank our sponsors - Latvian Council of Science and the Institute of Solid State Physics, University of Latvia. Andris Sternberg Inta Muzikante Guest editors

    Sternberg, Andris; Muzikante, Inta

    2007-06-01

    385

    Short-pulse chirped adiabatic population transfer in diatomic molecules  

    NASA Astrophysics Data System (ADS)

    Using the concept of light-induced potentials introduced by Garraway and Suominen [Phys. Rev. Lett. 80, 932 (1998)], we study alternative schemes of adiabatic population transfer in a diatomic molecule from the lowest vibrational level of the ground electronic state to the lowest vibrational level of a third electronic state via allowed optical transitions from the ground and third electronic states to a second electronic state. Our chirped-pulse rapid adiabatic passage scheme is implemented with short-duration optical pulses, and can be understood in terms of ``road design engineering'' of the light-induced time-dependent adiabatic potential upon which the dynamics occurs. We explicitly show that complete adiabatic vibronic population transfer occurs using chirped picosecond-duration pulses in the sodium dimer example.

    Kallush, S.; Band, Y. B.

    2000-04-01

    386

    Excitation of the Morse oscillator by an ultrashort chirped pulse  

    SciTech Connect

    The excitation of the classic Morse oscillator by an ultrashort electromagnetic pulse with a linear frequency chirp is studied theoretically. Formulas are derived for the oscillation amplitude and the radiation power averaged over a period as functions of the excitation energy for free oscillations of the Morse oscillator. Analytical expressions for describing the oscillator motion after the end of the pulse are obtained in the harmonic limit. In the general case of arbitrary parameters of the problem, the specific features of an excited Morse oscillator are analyzed numerically. Prominence is given to the effect of chirp on the excitation energy. The consideration is performed in terms of dimensionless variables, which makes it possible to apply the results obtained to a wide range of molecular systems and exciting-pulse parameters.

    Astapenko, V. A., E-mail: astval@mail.ru; Romadanovskii, M. S. [Moscow Institute of Physics and Technology (Russian Federation)

    2010-03-15

    387

    Interaction of strongly chirped pulses with two-level atoms  

    SciTech Connect

    We study the effect of ultrachirped pulses on the population inversion of two-level atoms. Ultrachirped pulses are defined as those for which the frequency chirp is of the order of the transition frequency of the two-level atom. When the chirp is large enough, the resonance may be crossed twice, for positive and negative frequencies. In fact the decomposition of the field into amplitude and phase factors, and the corresponding definition of the instantaneous frequency, are not unique. The interaction pictures for different decomposition are strictly equivalent, but only as long as approximations are not applied. The domain of validity of the formal rotating wave approximation is dramatically enhanced by a suitable choice, the so-called analytic signal representation.

    Ibanez, S.; Peralta Conde, A.; Muga, J. G. [Departamento de Quimica Fisica, Universidad del Pais Vasco - Euskal Herriko Unibertsitatea, Apdo. 644, Bilbao (Spain); Guery-Odelin, D. [Laboratoire Collisions Agregats Reactivite, CNRS UMR 5589, IRSAMC, Universite Paul Sabatier, 118 Route de Narbonne, F-31062 Toulouse CEDEX 4 (France)

    2011-07-15

    388

    Measuring spatial chirp in ultrashort pulses using single-shot Frequency-Resolved Optical Gating.  

    PubMed

    We show that the spatio-temporal distortion, spatial chirp, is naturally and easily measured by single-shot versions of second-harmonic generation frequency-resolved optical gating (SHG FROG) (including the extremely simple version, GRENOUILLE);. While SHG FROG traces are ordinarily symmetrical, a pulse with spatial chirp yields a trace with a shear that is approximately twice the pulse spatial chirp. As a result, the trace shear unambiguously reveals both the magnitude and sign of the pulse spatial chirp. The effects of spatial chirp can then be removed from the trace and the intensity and phase vs. time also retrieved, yielding a full description of the spatially chirped pulse in space and time. PMID:19461707

    Akturk, Selcuk; Kimmel, Mark; O'Shea, Patrick; Trebino, Rick

    2003-01-13

    389

    Frequency-chirp rates of harmonics driven by a few-cycle pulse  

    SciTech Connect

    We present numerical calculations of the time-frequency characteristics of cutoff harmonics generated by few-cycle laser pulses. We find that for driving pulses as short as three optical cycles, the adiabatic prediction for the harmonic chirp rate is very accurate. This negative chirp is so large that the resulting bandwidth causes substantial overlap between neighboring harmonics, and the harmonic phase therefore appears to not vary in time or frequency. By adding a compensating positive chirp to the driving pulse, which reduces the harmonic bandwidth and allows for the appearance of the negative chirp, we can measure the harmonic chirp rates. We also find that the positive chirp on the driving pulse causes the harmonics to shift down in frequency. We show that this counterintuitive result is caused by the change in the strong field continuum dynamics introduced by the variation of the driving frequency with time.

    Murakami, M.; Mauritsson, J.; Gaarde, M.B. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803-4001 (United States)

    2005-08-15

    390

    Studies relating to FM television and telemetry transmitters  

    NASA Technical Reports Server (NTRS)

    The Auburn University Model S-2 FM television transmitter was examined to determine if the performance and reliability could be improved by application of new techniques and devices developed since completion of the original design work. In particular this study examined the possibility of increased use of integrated circuits. It was determined that improvements in both performance and reliability were possible. In addition a study was conducted to determine the feasibility of converting the transmitter to handle telemetry signals. The study revealed that this conversion was feasible and the modifications were made to the prototype model for verification.

    Albritton, W. P.; Honnell, M. A.

    1972-01-01

    391

    Pulsing dynamics in Ytterbium based chirped-pulse oscillators.  

    PubMed

    The properties of passively mode-locked laser oscillators based on Ytterbium doped gain media are studied theoretically along with experimental data. Based on the chirped-pulse approach limitations due to excessive non-linearities are avoided, opening up new routes for energy scaling of mode-locked solid-state oscillators. Predictions about potential future pulse energies are made and possible experimental problems are discussed. PMID:18794966

    Siegel, Martin; Palmer, Guido; Emons, Moritz; Schultze, Marcel; Ruehl, Axel; Morgner, Uwe

    2008-09-15

    392

    Development of a Reduced-Cost Chirped Pulse Microwave Spectrometer  

    NASA Astrophysics Data System (ADS)

    Chirped pulse Fourier transform microwave (CP-FTMW) spectroscopy has become a ubiquitous technique in the high-resolution molecular spectroscopy community. Unfortunately, many components of CP-FTMW spectrometers are extremely expensive. Here we report of the development of an inexpensive microwave circuit and we present spectra of tetrahydrofuran and methanol collected between 8-16 GHz. Possible applications in remote sensing will also be discussed.

    Finneran, Ian A.; Holland, Daniel B.; Carroll, P. Brandon; Blake, Geoffrey A.

    2013-06-01

    393

    Chirped nonlinear cavity for digital quantum state readout without switching  

    Microsoft Academic Search

    We observe a new phase-locking effect in a high-Q cavity embedding a Josephson junction driven with a chirped microwave signal. Above a critical drive amplitude, the cavity phase-locks to the drive and its oscillation amplitude grows with time. Below threshold, the cavity dephases from the drive and its amplitude remains small. The transition to phase-locking is associated with a sharp

    Ofer Naaman; José. Aumentado; Lazar Friedland; Jonathan Wurtele; Irfan Siddiqi

    2009-01-01

    394

    Excitation and control of chirped nonlinear ion-acoustic waves  

    NASA Astrophysics Data System (ADS)

    Large-amplitude ion acoustic waves are excited and controlled by a chirped frequency driving perturbation. The process involves capturing into autoresonance (a continuous nonlinear synchronization) with the drive by passage through the linear resonance in the problem. The transition to autoresonance has a sharp threshold on the driving amplitude. The theory of this transition is developed beyond the Korteweg-de Vries limit by using the Whitham's averaged variational principle within the water bag model and compared with Vlasov-Poisson simulations.

    Friedland, L.; Shagalov, A. G.

    2014-05-01

    395

    Compact multi-pass amplifier for chirped-pulse amplification  

    NASA Astrophysics Data System (ADS)

    A compact and simple multi-pass amplifier configuration suited for chirped-pulse amplification that can fit about 16 passes is presented. This configuration uses a pair of spherical mirrors with a diameter of two inches, and a sapphire window to shift the path of the seed beam and allow easy extraction from the amplifier. We present experimental results obtained using eight passes with this configuration, together with calculations for the gain achievable with the presented configuration.

    Ruiz-de-La-Cruz, A.; Rangel-Rojo, R.

    2006-03-01

    396

    Generation of ultrahigh peak power pulses by chirped pulse amplification  

    Microsoft Academic Search

    Single picosecond pulses have been amplified to the terawatt level by a table-top-size Nd:glass amplifier by using the technique of chirped pulse amplification (CPA). The divergence of the beam is twice the diffraction limit, making the brightness of this source equal to 2 x 10 to the 18th W\\/(cm-sr), which is thought to be the highest brightness yet reported. The

    P. Maine; D. Strickland; P. Bado; M. Pessot; G. Mourou

    1988-01-01

    397

    Generalized chirp-like polyphase sequences with optimum correlation properties  

    Microsoft Academic Search

    A new general class of polyphase sequences with ideal periodic autocorrelation function is presented. The new class of sequences is based on the application of Zadoff-Chu polyphase sequences of length N=sm2, where s and m are any positive integers. It is shown that the generalized chirp-like sequences of odd length have the optimum crosscorrelation function under certain conditions. Finally, recently

    Branislav M. Popovic

    1992-01-01

    398

    Advanced sounding. II - First results from an advanced chirp ionosonde  

    NASA Astrophysics Data System (ADS)

    A BR Communications 'chirp' ionosonde has been modified to allow the measurement of the phase of ionospherically reflected echoes. The use of a dual-channel receiver and microprocessor-based control allows phase comparisons of temporally and spatially diverse echoes from which Doppler velocity, angle of arrival, and polarization mode can be evaluated, in addition to group range and amplitude. A test study of the ionosphere at Grahamstown is described.

    Poole, A. W. V.; Evans, G. P.

    1985-12-01

    399

    Identification of biological tissue using chirped probe THz imaging  

    Microsoft Academic Search

    We consider the application of pulsed THz imaging systems in biomedical diagnostics and mail\\/packaging inspection. The sub-millimetre spectroscopic measurements obtained from T-ray systems contain a wealth of information about the sample under test. We demonstrate that different types of tissue can be classified based on their terahertz response measured with the chirped probe pulse technique. We demonstrate the performance of

    B. Ferguson; S. Wang; D. Gray; D. Abbott; X.-C Zhang

    2002-01-01

    400

    SCA Waveform Development for Space Telemetry  

    NASA Technical Reports Server (NTRS)

    The NASA Glenn Research Center is investigating and developing suitable reconfigurable radio architectures for future NASA missions. This effort is examining software-based open-architectures for space based transceivers, as well as common hardware platform architectures. The Joint Tactical Radio System's (JTRS) Software Communications Architecture (SCA) is a candidate for the software approach, but may need modifications or adaptations for use in space. An in-house SCA compliant waveform development focuses on increasing understanding of software defined radio architectures and more specifically the JTRS SCA. Space requirements put a premium on size, mass, and power. This waveform development effort is key to evaluating tradeoffs with the SCA for space applications. Existing NASA telemetry links, as well as Space Exploration Initiative scenarios, are the basis for defining the waveform requirements. Modeling and simulations are being developed to determine signal processing requirements associated with a waveform and a mission-specific computational burden. Implementation of the waveform on a laboratory software defined radio platform is proceeding in an iterative fashion. Parallel top-down and bottom-up design approaches are employed.

    Mortensen, Dale J.; Kifle, Multi; Hall, C. Steve; Quinn, Todd M.

    2004-01-01

    401

    Frequency range extension of actively mode-locked lasers integrated with electroabsorption modulators using chirped gratings  

    Microsoft Academic Search

    We have fabricated actively mode-locked lasers integrated with electroabsorption modulators and chirped gratings. A chirped grating with a large chirp rate of 1.45 Å\\/?m can be realized by using multiphase-shifted patterns. Short pulses of 4-6 ps were generated over a wide frequency range from 18.9-19.8 GHz. We observed jumps in the wavelength during detuning. These jumps arise from multiple lobes

    Kenji Sato; Hiroyuki Ishii; Isamu Kotaka; Yasuhiro Kondo; Mitsuo Yamamoto

    1997-01-01

    402

    All-fiber devices for chromatic dispersion compensation based on chirped distributed resonant coupling  

    Microsoft Academic Search

    We review the principle of operation and characteristics of all-fiber devices for dispersion compensation based on chirped distributed resonant coupling. These devices are the chirped Bragg grating, the chirped intermodal coupler, and the tapered two-dissimilar-core fiber. We discuss the use of a figure of merit to characterize equalizing filters. Based on a specific example, filter responses are computed and their

    Francois Ouellette; Jean-Francois Cliche; Stephane Gagnon

    1994-01-01

    403

    A Novel Real-Time Chirp Measurement Method for Ultrashort Optical Pulses  

    NASA Astrophysics Data System (ADS)

    Rapid measurements of ultrashort optical pulse chirping were realized with a newly developed real-time chirp monitor. The application of a moving coil translator and electrical filters enabled the rapid measurement and decoding of fringe-resolved second-harmonic-generation (FRSHG) autocorrelation. The prototype system displayed chirping characteristics at a repetition rate higher than a few hertz, which demonstrates the usefulness of this monitor for dye laser system alignment.

    Mogi, Kazuo; Naganuma, Kazunori; Yamada, Hajime

    1988-11-01

    404

    Measuring spatial chirp in ultrashort pulses using single-shot Frequency-Resolved Optical Gating  

    Microsoft Academic Search

    We show that the spatio-temporal distortion, spatial chirp, is naturally and easily measured by single-shot versions of second-harmonic generation frequency-resolved optical gating (SHG FROG) (including the extremely simple version, GRENOUILLE)`. While SHG FROG traces are ordinarily symmetrical, a pulse with spatial chirp yields a trace with a shear that is approximately twice the pulse spatial chirp. As a result, the

    Selcuk Akturk; Mark Kimmel; Patrick O'Shea; Rick Trebino

    2003-01-01

    405

    Auditory brainstem responses to chirps delivered by different insert earphones  

    PubMed Central

    The frequency response and sensitivity of the ER-3A and ER-2 insert earphones are measured in the occluded-ear simulator using three ear canal extensions. Compared to the other two extensions, the DB 0370 (Brüel & Kjær), which is recommended by the international standards, introduces a significant resonance peak around 4500?Hz. The ER-3A has an amplitude response like a band-pass filter (1400?Hz, 6?dB/octave –?4000?Hz, ?36?dB/octave), and a group delay with “ripples” of up to ±0.5?ms, while the ER-2 has an amplitude response, and a group delay which are flat and smooth up to above 10000?Hz. Both earphones are used to record auditory brainstem responses, ABRs, from 22 normal-hearing ears in response to two chirps and a click at levels from 20 to 80?dB nHL. While the click-ABRs are slightly larger for ER-2 than for ER-3A, the chirp-ABRs are much larger for ER-2 than for ER-3A at levels below 60?dB nHL. With a simulated amplitude response of the ER-3A and the smooth group delay of the ER-2 it is shown that the increased chirp-ABR amplitude with the ER-2 is caused by its broader amplitude response and not by its smoother group delay.

    Elberling, Claus; Kristensen, Sinnet G. B.; Don, Manuel

    2012-01-01

    406

    Coherent chirped pulse laser network with Mickelson phase conjugator.  

    PubMed

    The mechanisms of nonlinear phase-locking of a large fiber amplifier array are analyzed. The preference is given to the most suitable configuration for a coherent coupling of thousands of fundamental spatial mode fiber beams into a single smooth beam ready for chirped pulse compression. It is shown that a Michelson phase-conjugating configuration with double passage through an array of fiber amplifiers has the definite advantage compared to a one-way fiber array coupled in a Mach-Zehnder configuration. Regardless of the amount of synchronized fiber amplifiers, the Michelson phase-conjugating interferometer is expected to do a perfect compensation of the phase-piston errors and collimation of backwardly amplified fiber beams on an entrance/output beam splitter. In both configurations, the nonlinear transformation of the stretched pulse envelope, due to gain saturation, is capable of randomizing the position of chirp inside an envelope; thus it may reduce the visibility of the interference pattern at an output beam splitter. Certain advantages are inherent to the sech-form temporal envelope because of the exponential precursor and self-similar propagation in gain medium. The Gaussian envelope is significantly compressed in a deep gain saturation regime, and the frequency chirp position inside pulse envelope is more deformed. PMID:24787398

    Okulov, A Yu

    2014-04-10

    407

    A direct digital synthesis chirped pulse Fourier transform microwave spectrometer.  

    PubMed

    Chirped pulse Fourier transform microwave (CP-FTMW) spectrometers have become the instrument of choice for acquiring rotational spectra, due to their high sensitivity, fast acquisition rate, and large bandwidth. Here we present the design and capabilities of a recently constructed CP-FTMW spectrometer using direct digital synthesis (DDS) as a new method for chirped pulse generation, through both a suite of extensive microwave characterizations and deep averaging of the 10-14 GHz spectrum of jet-cooled acetone. The use of DDS is more suited for in situ applications of CP-FTMW spectroscopy, as it reduces the size, weight, and power consumption of the chirp generation segment of the spectrometer all by more than an order of magnitude, while matching the performance of traditional designs. The performance of the instrument was further improved by the use of a high speed digitizer with dedicated signal averaging electronics, which facilitates a data acquisition rate of 2.1 kHz. PMID:24007050

    Finneran, Ian A; Holland, Daniel B; Carroll, P Brandon; Blake, Geoffrey A

    2013-08-01

    408

    Progress Towards Chirped-Pulse Fourier Transform Thz Spectroscopy  

    NASA Astrophysics Data System (ADS)

    New opportunities are provided by the development of higher power THz frequency multiplier sources, the development of a broadband Chirped-Pulse FTMW spectroscopy technique at microwave and mm Wave frequencies, and recently demonstrated heterodyne hot electron bolometer detection technology in the THz frequency region with near quantum noise-limited performance and high spectral resolution. Combining these three technologies and extending the chirped-pulse technique to 0.85 THz enables a host of new applications. NIST is currently pursing applications as a point sensor for greenhouse gases, volatile organic compounds, and potentially human breath. The generation and detection of phase stable chirped pulses at 850 GHz will be demonstrated. A description of the experimental setup and preliminary data will be presented for nitrous oxide. G.G. Brown, B.C. Dian, K.O. Douglass, S.M. Geyer, S. Shipman and B.H. Pate, Rev.Sci.Instrum. 79 (2008) 053103. E. Gerecht, D. Gu, L. You, K.S. Yngvesson, IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES. 56, (2008) 1083.

    Douglass, Kevin O.; Plusquellic, David F.; Gerecht, Eyal

    2010-06-01

    409

    An improved processing sequence for uncorrelated Chirp sonar data  

    NASA Astrophysics Data System (ADS)

    Chirp sonar systems can be used to obtain high resolution seismic reflection images of the sub-seafloor during marine surveys. The exact knowledge of the Chirp signature allows the use of deterministic algorithms to process the data, similarly to that applied to Vibroseis data on land. Here, it is described an innovative processing sequence to be applied to uncorrelated Chirp data, which can improve vertical and lateral resolution compared to conventional methods. It includes application of a Wiener filter to transform a frequency-modulated sweep into a minimum-phase pulse sequence. In this way, the data become causal and can undergo predictive deconvolution to reduce ringing and enhance vertical resolution. Afterwards, FX-deconvolution and Stolt migration can be applied to obtain an improved imaging of the subsurface. The result of this procedure is a seismic reflection image with higher resolution than traditional ones, which are normally represented using the envelope function of the signal. This technique can be particularly useful for engineering-geotechnical surveys and archaeological investigations that require a fine detail imaging of the uppermost meters of the sub-seafloor.

    Baradello, Luca

    2014-03-01

    410

    Chirp Z-transform spectral zoom optimization with MATLAB.  

    SciTech Connect

    The MATLAB language has become a standard for rapid prototyping throughout all disciplines of engineering because the environment is easy to understand and use. Many of the basic functions included in MATLAB are those operations that are necessary to carry out larger algorithms such as the chirp z-transform spectral zoom. These functions include, but are not limited to mathematical operators, logical operators, array indexing, and the Fast Fourier Transform (FFT). However, despite its ease of use, MATLAB's technical computing language is interpreted and thus is not always capable of the memory management and performance of a compiled language. There are however, several optimizations that can be made within the chirp z-transform spectral zoom algorithm itself, and also to the MATLAB implementation in order to take full advantage of the computing environment and lower processing time and improve memory usage. To that end, this document's purpose is two-fold. The first demonstrates how to perform a chirp z-transform spectral zoom as well as an optimization within the algorithm that improves performance and memory usage. The second demonstrates a minor MATLAB language usage technique that can reduce overhead memory costs and improve performance.

    Martin, Grant D.

    2005-11-01

    411

    Chirped-pulse millimeter-wave spectroscopy: Spectrum, dynamics, and manipulation of Rydberg-Rydberg transitions  

    NASA Astrophysics Data System (ADS)

    We apply the chirped-pulse millimeter-wave (CPmmW) technique to transitions between Rydberg states in calcium atoms. The unique feature of Rydberg-Rydberg transitions is that they have enormous electric dipole transition moments (~5 kiloDebye at n* ~ 40, where n* is the effective principal quantum number), so they interact strongly with the mm-wave radiation. After polarization by a mm-wave pulse in the 70-84 GHz frequency region, the excited transitions re-radiate free induction decay (FID) at their resonant frequencies, and the FID is heterodyne-detected by the CPmmW spectrometer. Data collection and averaging are performed in the time domain. The spectral resolution is ~100 kHz. Because of the large transition dipole moments, the available mm-wave power is sufficient to polarize the entire bandwidth of the spectrometer (12 GHz) in each pulse, and high-resolution survey spectra may be collected. Both absorptive and emissive transitions are observed, and they are distinguished by the phase of their FID relative to that of the excitation pulse. With the combination of the large transition dipole moments and direct monitoring of transitions, we observe dynamics, such as transient nutations from the interference of the excitation pulse with the polarization that it induces in the sample. Since the waveform produced by the mm-wave source may be precisely controlled, we can populate states with high angular momentum by a sequence of pulses while recording the results of these manipulations in the time domain. We also probe the superradiant decay of the Rydberg sample using photon echoes. The application of the CPmmW technique to transitions between Rydberg states of molecules is discussed.

    Colombo, Anthony P.; Zhou, Yan; Prozument, Kirill; Coy, Stephen L.; Field, Robert W.

    2013-01-01

    412

    Chirped holographic grating used as the dispersive element in an optical spectrometer  

    SciTech Connect

    We have developed a new design of optical spectrometer based on the use of a chirped holographic grating inscribed on a flat substrate. This type of grating has a surface modulation with a spatially varying period. The ability of the chirped grating to focus a beam is exploited to reduce significantly the physical dimensions of the instrument. Wavelength selection is achieved by a pure translation of the chirped grating. The properties of the chirped grating spectrometer have been characterized with different lasers and arc lamps and compared with those of two commercial spectrometers. A performance parameter has been defined, enabling the various instruments to be compared.

    Fortin, Gilles; McCarthy, Nathalie

    2005-08-10

    413

    Propagation dependence of chirp in Gaussian pulses and beams due to angular dispersion.  

    PubMed

    The chirp acquired by a Gaussian ultrashort pulse due to angular dispersion, unlike that of plane waves, increases nonlinearly with propagation distance and eventually asymptotes to a constant. However, this interesting result has never been directly measured. In this Letter, we use two-dimensional spectral interferometry to measure the propagation dependence of the chirp for Gaussian ultrashort pulses and beams with angular dispersion. The measured chirp as a function of propagation distance agreed well with theory. This work verifies both an equation and a measurement technique that will be useful for predicting or determining the pulse's chirp in ultrafast optics experiments that contain angular dispersion. PMID:19340185

    Li, Derong; Zeng, Shaoqun; Luo, Qingming; Bowlan, Pamela; Chauhan, Vikrant; Trebino, Rick

    2009-04-01

    414

    Information content of time domain reflectometry waveforms  

    NASA Astrophysics Data System (ADS)

    The possibility to link model parameters with soil properties is obstructed if identification problems in inverse modeling of time domain reflectometry (TDR) waveforms occur. Therefore multiple objective functions, each associated with one model parameter, are sought for identification of probe (resistance and length) and Debye (static permittivity, high-frequency permittivity, relaxation frequency, and bulk electrical conductivity) parameters in TDR waveforms. An objective function could be defined for all six model parameters. Some of the defined objective functions correspond with theoretical and experimental observations of earlier work. Other new insights have been obtained. For instance, it is possible to obtain estimates of high-frequency permittivity even when the reflection of the end of the probe has vanished because of high salinity. Application of the found objective functions on measured TDR waveforms yielded parameter values that compared well with values obtained from several references. However, identification of a parameter is only possible if its true value lies within the frequency bandwidth of TDR.

    Weerts, A. H.; Huisman, J. A.; Bouten, W.

    2001-05-01

    415

    Wavelet analysis of the impedance cardiogram waveforms  

    NASA Astrophysics Data System (ADS)

    Impedance cardiography has been used for diagnosing atrial and ventricular dysfunctions, valve disorders, aortic stenosis, and vascular diseases. Almost all the applications of impedance cardiography require determination of some of the characteristic points of the ICG waveform. The ICG waveform has a set of characteristic points known as A, B, E ((dZ/dt)max) X, Y, O and Z. These points are related to distinct physiological events in the cardiac cycle. Objective of this work is an approbation of a new method of processing and interpretation of the impedance cardiogram waveforms using wavelet analysis. A method of computer thoracic tetrapolar polyrheocardiography is used for hemodynamic registrations. Use of original wavelet differentiation algorithm allows combining filtration and calculation of the derivatives of rheocardiogram. The proposed approach can be used in clinical practice for early diagnostics of cardiovascular system remodelling in the course of different pathologies.

    Podtaev, S.; Stepanov, R.; Dumler, A.; Chugainov, S.; Tziberkin, K.

    2012-12-01

    416

    Timing detection and seismocardiography waveform extraction.  

    PubMed

    Described herein is a new and robust method to extract heart-beat timing from seismocardiogram (SCG). This timing indicates the precise time location of each heart beat and therefore directly conveys heart rate information. Knowledge of the time location of each occurrence of the underlying SCG waveform allows us to obtain a clean SCG waveform estimate by time averaging noisy segments of an SCG time series. The algorithm can be implemented in wearable SCG-based devices to provide heart monitoring or diagnosis capabilities without relying on any other methodology, such as electrocardiography, as a timing reference. PMID:23366694

    Nguyen, Hoang; Zhang, Jianzhong; Nam, Young-Han

    2012-01-01

    417

    Temperature dependent exchange bias effect in polycrystalline BiFeO3/FM (FM = NiFe, Co) bilayers  

    NASA Astrophysics Data System (ADS)

    Extensive studies on the temperature (T) dependent exchange bias effect were carried out in polycrystalline BiFeO3(BFO)/NiFe and BFO/Co bilayers. In contrast to single-crystalline BFO/ferromagnet (FM) bilayers, sharp increase of the exchange bias field (HE) below 50 K were clearly observed in both of these two bilayers. However, when T is higher than 50 K, HE increases with T and decreases further when T is larger than 230 K (for BFO/NiFe) or 200 K (for BFO/Co), which is similar to those reported in single-crystalline BFO/FM bilayers. After the exploration of magnetic field cooling, the temperature dependent exchange bias can be explained considering two contributions from both the interfacial spin-glass-like frustrated spins and the polycrystalline grains in the BFO layer. Moreover, obvious exchange bias training effect can be observed at both 5 K and room temperature and the corresponding results can be well fitted based on a recently proposed theoretical model taking into account the energy dissipation of the AFM layer.

    Xue, Xiaobo; Yuan, Xueyong; Rui, Wenbin; Xu, Qingyu; You, Biao; Zhang, Wei; Zhou, Shiming; Du, Jun

    2013-04-01

    418

    Utilizing a Chirp Sonar to Accurately Characterize Newly Deposited Material at the Calcasieu Ocean Dredged Material Disposal Site, Louisiana.  

    National Technical Information Service (NTIS)

    The distribution of dredged sediments is measured at the Calcasieu Ocean Dredged Material Disposal Site (ODMDS) using a chirp sonar immediately after disposal and two months later. Subbottom reflection data, generated by a chirp sonar transmitting a 4 to ...

    S. G. Schock D. J. Keith D. L. Debruin E. Dettmann G. Tracey

    1992-01-01

    419

    Radar altimeter waveform modeled parameter recovery. [SEASAT-1 data  

    NASA Technical Reports Server (NTRS)

    Satellite-borne radar altimeters include waveform sampling gates providing point samples of the transmitted radar pulse after its scattering from the ocean's surface. Averages of the waveform sampler data can be fitted by varying parameters in a model mean return waveform. The theoretical waveform model used is described as well as a general iterative nonlinear least squares procedures used to obtain estimates of parameters characterizing the modeled waveform for SEASAT-1 data. The six waveform parameters recovered by the fitting procedure are: (1) amplitude; (2) time origin, or track point; (3) ocean surface rms roughness; (4) noise baseline; (5) ocean surface skewness; and (6) altitude or off-nadir angle. Additional practical processing considerations are addressed and FORTRAN source listing for subroutines used in the waveform fitting are included. While the description is for the Seasat-1 altimeter waveform data analysis, the work can easily be generalized and extended to other radar altimeter systems.

    1981-01-01

    420

    Analysis of Chaotic Waveforms for Application to Active Sonar Systems.  

    National Technical Information Service (NTIS)

    This report evaluates the feasibility of using a new class of chaotic waveforms in low-frequency active acoustic scenarios. These waveforms are generated by nonlinear processes and therefore have characteristics that differ from their linear counterparts....

    N. K. Alapati R. H. Kirklin P. C. Etter

    1993-01-01

    421

    JTRS/SCA and Custom/SDR Waveform Comparison  

    NASA Technical Reports Server (NTRS)

    This paper compares two waveform implementations generating the same RF signal using the same SDR development system. Both waveforms implement a satellite modem using QPSK modulation at 1M BPS data rates with one half rate convolutional encoding. Both waveforms are partitioned the same across the general purpose processor (GPP) and the field programmable gate array (FPGA). Both waveforms implement the same equivalent set of radio functions on the GPP and FPGA. The GPP implements the majority of the radio functions and the FPGA implements the final digital RF modulator stage. One waveform is implemented directly on the SDR development system and the second waveform is implemented using the JTRS/SCA model. This paper contrasts the amount of resources to implement both waveforms and demonstrates the importance of waveform partitioning across the SDR development system.

    Oldham, Daniel R.; Scardelletti, Maximilian C.

    2007-01-01

    422

    FMCW Radar Waveforms in the HF Band  

    Microsoft Academic Search

    The HF band is used for various communications and radar requirements. Australian users of the band are required to adhere to spectrum management recommendations set by the Australian ACMA based on regulations set by the International Telecommunications Union (ITU). Here we exam- ine the applicability of the ITU recommendations on Linear Frequency Modulated Continuous Waveforms (LFMCW) and amplitude modulated LFMCW

    Mike D. E. Turley

    423

    ADVANCED WAVEFORM SIMULATION FOR SEISMIC MONITORING EVENTS  

    SciTech Connect

    Earthquake source parameters underpin several aspects of nuclear explosion monitoring. Such aspects are: calibration of moment magnitudes (including coda magnitudes) and magnitude and distance amplitude corrections (MDAC); source depths; discrimination by isotropic moment tensor components; and waveform modeling for structure (including waveform tomography). This project seeks to improve methods for and broaden the applicability of estimating source parameters from broadband waveforms using the Cut-and-Paste (CAP) methodology. The CAP method uses a library of Green’s functions for a one-dimensional (1D, depth-varying) seismic velocity model. The method separates the main arrivals of the regional waveform into 5 windows: Pnl (vertical and radial components), Rayleigh (vertical and radial components) and Love (transverse component). Source parameters are estimated by grid search over strike, dip, rake and depth and seismic moment or equivalently moment magnitude, MW, are adjusted to fit the amplitudes. Key to the CAP method is allowing the synthetic seismograms to shift in time relative to the data in order to account for path-propagation errors (delays) in the 1D seismic velocity model used to compute the Green’s functions. The CAP method has been shown to improve estimates of source parameters, especially when delay and amplitude biases are calibrated using high signal-to-noise data from moderate earthquakes, CAP+.

    Helmberger, Donald V.; Tromp, Jeroen; Rodgers, Arthur J.

    2008-06-17

    424

    GRC GSFC TDRSS Waveform Metrics Report.  

    National Technical Information Service (NTIS)

    The report presents software metrics and porting metrics for the GGT Waveform. The porting was from a ground-based COTS SDR, the SDR-3000, to the CoNNeCT JPL SDR. The report does not address any of the Operating Environment (OE) software development, nor ...

    D. J. Mortensen

    2013-01-01

    425

    A transformer of closely spaced pulsed waveforms  

    NASA Technical Reports Server (NTRS)

    Passive circuit, using diodes, transistors, and magnetic cores, transforms the voltage of repetitive positive or negative pulses. It combines a pulse transformer with switching devices to effect a resonant flux reset and can transform various pulsed waveforms that have a nonzero average value and are relatively cosely spaced in time.

    Niedra, J.

    1970-01-01

    426

    Wave: interactive color graphics for waveform analysis  

    Microsoft Academic Search

    WAVE, an interactive color graphics software system for Waveform Analysis Visualization and Edification, is an evolving software interface between an Anagraph Color Graphics System, a CDC 6400\\/7600 computer configuration, and User Application programs coded in standard FORTRAN source language.WAVE, when mated with the user application modules provides a complete specialized interactive graphical analysis system. The system features:• Full interaction of

    Fred E. Robbins; William G. Green

    1975-01-01

    427

    Waveform analysis for HF ground wave radar  

    Microsoft Academic Search

    According to general radar designing principles, this paper discusses the concepts and pro- cessing techniques concerning the radar waveform analysis. For the need in developing HF ground wave system, as requested by a key oceanic project in the national 863 plans, basic theories and parameter de- sign techniques on Frequency Modulated Interrupted Continuous Wave (FMICW) have been studied. This study

    Wu Shi-cai; Yang Zi-jie; Wen Bi-yang; Shi Zhen-hua; Tian Jian-sheng

    2001-01-01

    428

    A radar waveform processing utilization of wavelets  

    Microsoft Academic Search

    The scaling and delay features of the continuous wavelet transform occur naturally in the radar problem. It is shown how the classical matched filtering approach employed in radar processing is compatible with the continuous wavelet transform for waveforms based on wavelet shapes. Examples are provided to illustrate the concept

    Greg Lester

    1994-01-01

    429

    Pareto-optimal radar waveform design  

    Microsoft Academic Search

    This paper deals with the problem of Pareto-optimal waveform design in the presence of colored Gaussian noise, under a similarity and an energy constraint. At the design stage, we determine the optimal radar code according to the following criterion: joint constrained maximization of the detection probability and constrained minimization of the Cramer Rao Lower Bound (CRLB) on the Doppler estimation

    A. De Maio; M. Piezzo; A. Farina; M. Wicks

    2010-01-01

    430

    Servo-operated respiratory waveform simulator  

    Microsoft Academic Search

    An apparatus for the generation of typical respiratory patterns is described. Two pistons are driven by a half horse-power servomotor operated by a Velodyne speed control system. The desired waveform is produced by means of a cam or photoelectric function generator.

    D W Hill; J R Hook; E G Bell

    1961-01-01

    431

    A comparison of waveform fractal dimension algorithms  

    Microsoft Academic Search

    The fractal dimension of a waveform represents a powerful tool for transient detection. In particular, in analysis of electroencephalograms and electrocardiograms, this feature has been used to identify and distinguish specific states of physiologic function. A variety of algorithms are available for the computation of fractal dimension. In this study, the most common methods of estimating the fractal dimension of

    Rosana Esteller; George Vachtsevanos; Javier Echauz; Brian Litt

    2001-01-01

    432

    Parameter Estimation using Numerical Merger Waveforms  

    NASA Technical Reports Server (NTRS)

    Results: Developed parameter estimation model integrating complete waveforms and improved instrumental models. Initial results for equal-mass non-spinning systems indicate moderate improvement in most parameters, significant improvement in some Near-term improvement: a) Improved statistics; b) T-channel; c) Larger parameter space coverage. Combination with other results: a) Higher harmonics; b) Spin precession; c) Instrumental effects.

    Thorpe, J. I.; McWilliams, S.; Kelly, B.; Fahey, R.; Arnaud, K.; Baker, J.

    2008-01-01

    433

    Waveform Tomography of the Salzach Valley  

    NASA Astrophysics Data System (ADS)

    A 3-km-long refraction survey near Zell-am-See, Austria, provides a detailed characterization of the sedimentary structure and the depth to bedrock of the Salzach Valley. A low resolution first-arrival tomography model was derived from the data that served as a starting model for a full waveform inversion in the 4-26-Hz-band. The waveforms are modeled in the acoustic approximation, and the inversion is performed in the frequency domain. The final data fit is excellent in the central parts of the valley, but it degrades significantly towards the edges. In addition to the differing subsurface coverage, we interpret this as a result of the acoustic approximation being well suited for the largely unconsolidated valley fill. In contrast, the sediment-bedrock interface creates strong converted phases that prevent reconstruction of detailed features in the underlying crystalline crust. The resulting waveform model shows an up to 0,5 km thick sedimentary fill over bedrock, which is surprisingly large compared to the much larger, but shallower, Salzburg Basin. The P-wave structure of the sediments shows a significant velocity inversion, which is interpreted as a pressured aquifer overlying a 150-m-thick unsaturated zone. Near the surface, the seismic model is controlled by coincident deep GPR and ERT profiles. The good structural agreement emphasizes the quality of the results. From the comparison with other 2D waveform-inversion studies from a variety of scales, we conclude that refraction surveys at this scale are ideal candidates for full waveform inversion because of the typically relatively low signal frequencies.

    Bleibinhaus, Florian; Hilberg, Sylke

    2013-04-01

    434

    Simulation of optical pulse compression using parabolic pulse with linear chirp  

    NASA Astrophysics Data System (ADS)

    It is the key of realizing high speed, large capacity fiber information transmission that achieve ultrashort optical pulse by optical pulse compression. At present, the compression method that is achieving parabolic pulse with linear chirp and compensating the linear chirp is paid more attention. Based on the two schemes for the parabolic pulse with linear chirp by the normal dispersion decreasing fiber or the fiber amplifier with a normal dispersion, more study on the characteristics of the parabolic pulse with linear chirp in the different dispersion decreasing profiles (such as cosine, Gaussian, linear, exponential and hyperbolic) is showed; the results show that, for different dispersion decreasing profiles, the good linear chirp and parabolic shapes that are good for pulse compression can be generated. Moreover, a novel scheme for the parabolic pulse, which is achieved by a dispersion decreasing fiber amplifier with a normal dispersion, is presented. Numerical simulations show that, compared with the parabolic pulses generated in the normal dispersion decreasing fiber or the fiber amplifier, the parabolic pulse generated by the novel scheme has the better linear chirp and the more pulse energy; the gain has an obviously effect on the intensity and quality of the linear chirp, which is that the output pulse has a smaller pulse width and higher pulse power after the chirp is compensated.

    Wang, Zun-zhi

    2013-08-01

    435

    Reconfigurable optical fiber-based microwave dispersive line for single-shot chirped microwave pulse compression  

    Microsoft Academic Search

    A fiber-based approach for reconfigurable and single-shot chirped microwave pulse compression is proposed and demonstrated based on a time-spectrum convolution system. Different nanosecond-long, GHz-bandwidth linearly chirped microwave pulses are successfully compressed using the same platform.

    Ming Li; Antonio Malacarne; Nezih Belhadj; Sophie LaRochelle; Jianping Yao; Jose Azana

    2012-01-01

    436

    Chirped Microwave Pulse Compression Using a Photonic Microwave Filter With a Nonlinear Phase Response  

    Microsoft Academic Search

    Chirped microwave pulse compression using a photonic microwave filter with nonlinear phase response to implement matched filtering is proposed and investigated. The photonic microwave filter with the required phase response is realized based on optical phase to microwave phase conversion through single-sideband modulation and heterodyne detection. A detailed theoretical analysis on the photonic microwave filter design and the linearly chirped

    Chao Wang; Jianping Yao

    2009-01-01

    437

    Photonic generation of linearly chirped millimeter wave based on comb-spacing tunable optical frequency comb  

    NASA Astrophysics Data System (ADS)

    We demonstrated a photonic approach to generate a phase-continuous frequency-linear-chirped millimeter-wave (mm-wave) signal with high linearity based on continuous-wave phase modulated optical frequency comb and cascaded interleavers. Through linearly sweeping the frequency of the radio frequency (RF) driving signal, high-order frequency-linear-chirped optical comb lines are generated and then extracted by the cascaded interleavers. By beating the filtered high-order comb lines, center frequency and chirp range multiplied linear-chirp microwave signals are generated. Frequency doubled and quadrupled linear-chirp mm-wave signals of range 48.6 to 52.6 GHz and 97.2 to 105.2 GHz at chirp rates of 133.33 and 266.67 GHz/s are demonstrated with the ±1st and ±2nd optical comb lines, respectively, while the RF driving signal is of chirp range 24.3 to 26.3 GHz and chirp time 30 ms.

    Xia, Zongyang; Xie, Weilin; Sun, Dongning; Shi, Hongxiao; Dong, Yi; Hu, Weisheng

    2013-12-01

    438

    Wideband true-time-delay beam former that employs a tunable chirped fiber grating prism.  

    PubMed

    A fiber grating prism that consists of four tunable chirped-grating delay lines for wideband true-time-delay beam forming is proposed and demonstrated. The chirped gratings are produced by use of the grating bending technique in which a uniform grating is surface mounted on a simply supported beam. We obtained chirped gratings with different chirp rates by bending the uniform gratings with different beam deflections. Four linear chirped fiber gratings with identical spectral width but linearly increased grating length are fabricated. The spectra and time-delay responses of the tunable chirped gratings are measured. A chirped-grating prism for wideband true-time-delay beam forming by use of four chirped gratings is constructed and tested experimentally. We obtained different time delays by tuning the wavelength of the optical carrier. The proposed true-time-delay beam former with a four-element phased-array steerer is suitable for continuous beam forming at microwave frequencies up to 20 GHz. PMID:12737457

    Liu, Yunqi; Yao, Jianping; Yang, Jianliang

    2003-05-01

    439

    An attempt of high-speed imaging of the chirp radar-type microwave computed tomography  

    Microsoft Academic Search

    Methods for high speed imaging of the chirp radar-type microwave computed tomography have been investigated to show the feasibility of biological imaging. Electronic scan of the array antennas is a major scheme to reduce the data acquisition time. However, quick sweep of the chirp pulse microwave signal and data acquisition in time domain are also useful for the purpose. By

    Michio Miyakawa; Toyohiko Hayashi

    1997-01-01

    440

    Temperature-insensitive displacement sensing using the chirp effect of fiber Bragg grating  

    Microsoft Academic Search

    A new approach for displacement sensing based on chirp effect of fiber Bragg under strain-gradient is proposed and demonstrated in this paper. Strain gradient chirp of fiber Brag grating is realized by attaching the grating slant ways on a side face of a simple cantilever beam. The strain gradient, which is formed along the gratin when the free of the

    Zhengrong Tong; Yonglin Huang; Hongyun Meng; Xinyong Dong; Guiyun Kai; Xiaoyi Dong

    2002-01-01

    441

    High channel-count comb filter based on chirped sampled fiber Bragg grating and phase shift  

    Microsoft Academic Search

    Based on strongly chirped sampled fiber Bragg grating and phase shifts, a novel approach to obtain high channel-count comb filters is proposed in this letter. Various channel spacing can be achieved by a single strongly chirped phase mask where the required phase shifts can be gained by a precise translation stage. Comb filters with channel spacing of 50, 100, and

    Yitang Dai; Xiangfei Chen; Ximing Xu; Chongcheng Fan; Shizhong Xie

    2005-01-01

    442

    Effect of pulse profile and chirp on a laser wakefield generation  

    SciTech Connect

    A laser wakefield driven by an asymmetric laser pulse with/without chirp is investigated analytically and through two-dimensional particle-in-cell simulations. For a laser pulse with an appropriate pulse length compared with the plasma wavelength, the wakefield amplitude can be enhanced by using an asymmetric un-chirped laser pulse with a fast rise time; however, the growth is small. On the other hand, the wakefield can be greatly enhanced for both positively chirped laser pulse having a fast rise time and negatively chirped laser pulse having a slow rise time. Simulations show that at the early laser-plasma interaction stage, due to the influence of the fast rise time the wakefield driven by the positively chirped laser pulse is more intense than that driven by the negatively chirped laser pulse, which is in good agreement with analytical results. At a later time, since the laser pulse with positive chirp exhibits opposite evolution to the one with negative chirp when propagating in plasma, the wakefield in the latter case grows more intensely. These effects should be useful in laser wakefield acceleration experiments operating at low plasma densities.

    Zhang Xiaomei; Shen Baifei; Ji Liangliang; Wang Wenpeng; Xu Jiancai; Yu Yahong; Yi Longqing; Wang Xiaofeng [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Hafz, Nasr A. M. [Key Laboratory for Laser Plasmas (Ministry of Education) and Department of Physics, Shanghai Jiao Tong University, Shanghai 200240 (China); Kulagin, V. [Sternberg Astronomical Institute of Moscow State University, Moscow 119992 (Russian Federation); Moscow Institute of Physics and Technology, Dolgoprudny, Moscow region, 141700 (Russian Federation)

    2012-05-15

    443

    Airborne SAR processing of highly squinted data using a chirp scaling approach with integrated motion compensation  

    Microsoft Academic Search

    Proposes a new approach for high-resolution airborne SAR data processing, which uses a modified chirp scaling algorithm to accommodate the correction of motion errors, as well as the variations of the Doppler centroid in range and azimuth. By introducing a cubic phase term in the chirp scaling phase, data acquired with a squint angle up to 30° can be processed

    A. Moreira; Yonghong Huang

    1994-01-01

    444

    Simple measurement of fiber dispersion and of chirp parameter of intensity modulated light emitter  

    Microsoft Academic Search

    We report a novel method to measure two important parameters for optical fiber intensity modulated transmission systems: dispersion of optical fibers and chirp parameter of modulated light emitters. The method is easy, quick, and accurate for chirp parameter in the -10-to-10 range

    F. Devaux; Y. Sorel; J. F. Kerdiles

    1993-01-01

    445

    Effects of Energy Chirp on Echo-Enabled Harmonic Generation Free-Electron Lasers  

    SciTech Connect

    We study effects of energy chirp on echo-enabled harmonic generation (EEHG). Analytical expressions are compared with numerical simulations for both harmonic and bunching factors. We also discuss the EEHG free-electron laser bandwidth increase due to an energy-modulated beam and its pulse length dependence on the electron energy chirp.

    Huang, Z.; Ratner, D.; Stupakov, G.; Xiang, D.; /SLAC

    2009-02-23

    446

    Effects of auditory selective attention on chirp evoked auditory steady state responses  

    Microsoft Academic Search

    Auditory steady state responses (ASSRs) are frequently used to assess auditory function. Recently, the interest in effects of attention on ASSRs has increased. In this paper, we investigated for the first time possible effects of attention on AS-SRs evoked by amplitude modulated and frequency modulated chirps paradigms. Different paradigms were designed using chirps with low and high frequency content, and

    Andreas Bohr; Corinna Bernarding; Daniel J. Strauss; Farah I. Corona-Strauss

    2011-01-01

    447

    A series of notched-noise embedded chirps for objective frequency specific hearing examinations  

    Microsoft Academic Search

    Chirp-evoked auditory brainstem responses (ABRs) have shown a better performance compared to click-evoked ABRs, due to their temporal organization which compensates for the traveling wave delay achieving a synchronous discharge of the cochlea. In this paper we present the development and evaluation, in healthy subjects, of a series of notched noise embedded frequency specific chirps to evoke ABRs. Results of

    Farah I. Corona-Strauss; Daniel J. Strauss; Bernhard Schick; Wolfgang Delb

    2009-01-01

    448

    Analytical solutions for a two-level system driven by a class of chirped pulses  

    SciTech Connect

    We present analytical solutions for the problem of a two-level atom driven by a class of chirped pulses. The solutions are given in terms of Heun functions. By use of the appropriate chirping parameters, an enhancement of four orders of magnitude in the population transfer is obtained.

    Jha, Pankaj K. [Institute for Quantum Science and Engineering and Department of Physics, Texas A and M University, College Station, Texas 77843 (United States); Rostovtsev, Yuri V. [Institute for Quantum Science and Engineering and Department of Physics, Texas A and M University, College Station, Texas 77843 (United States); Department of Physics, University of North Texas, 1155 Union Circle 311427, Denton, Texas 76203 (United States)

    2010-07-15

    449

    Chirped Pulse Adiabatic Passage in CARS for Imaging of Biological Structure and Dynamics  

    SciTech Connect

    We propose the adiabatic passage control scheme implementing chirped femtosecond laser pulses to maximize coherence in a predetermined molecular vibrational mode using two-photon Raman transitions. We investigate vibrational energy relaxation and collisional dephasing as factors of coherence loss, and demonstrate the possibility for preventing decoherence by the chirped pulse train. The proposed method may be used to advance noninvasive biological imaging techniques.

    Malinovskaya, Svetlana A. [Department of Physics and Engineering Physics, Stevens Institute of Technology Hoboken, NJ 07030 (United States)

    2007-12-26

    450

    In silico estimates of cell electroporation by electrical incapacitation waveforms  

    Microsoft Academic Search

    We use a system model of a cell and approximate magnitudes of electrical incapacitation (EI) device waveforms to estimate conditions that lead to responses with or without electroporation (EP) of cell membranes near electrodes. Single pulse waveforms of Taser X26 and Aegis MK63 devices were measured using a resistive load. For the present estimates the digitized waveforms were scaled in

    T. R. Gowrishankar; A. T. Esser; K. C. Smith; S. K. Burns; J. C. Weaver

    2009-01-01

    451

    ACF-based classification of phase modulated waveforms  

    Microsoft Academic Search

    Classification of radar waveform phase modulation based on a sequence of observations is a simple problem complicated by a number of nuisance parameters. Without prior knowledge of waveform carrier frequency, time offset, amplitude, initial phase, and bandwidth, application of a matched filter classifier is not achievable. One must instead rely on waveform features that are invariant to these parameters. This

    Brian D. Rigling; Craig Roush

    2010-01-01

    452

    Generation and performance analysis of wideband radar waveforms  

    Microsoft Academic Search

    Coherent wide bandwidth waveforms, as used in high resolution radar, can accurately be generated by a digital waveform generator followed by a single sideband modulator and frequency multiplier. To fully exploit high resolution waveforms weighting must be applied to lower the sidelobe level, but the signals must have sufficiently small errors to support the required sidelobe level. This paper analyzes

    G. B. Postema

    1987-01-01

    453

    Wallops waveform analysis of SEASAT1 radar altimeter data  

    Microsoft Academic Search

    Fitting a six parameter model waveform to over ocean experimental data from the waveform samplers in the SEASAT-1 radar altimeter is described. The fitted parameters include a waveform risetime, skewness, and track point; from these can be obtained estimates of the ocean surface significant waveheight, the surface skewness, and a correction to the altimeter's on board altitude measurement, respectively. Among

    G. S. Hayne

    1980-01-01

    454

    Chirped Microwave Pulse Generation Using a Photonic Microwave Delay-Line Filter With a Quadratic Phase Response  

    Microsoft Academic Search

    We propose an optical approach to generating chirped microwave pulses using a photonic microwave delay-line filter (PMDLF) with a quadratic phase response. If a chirp-free broadband microwave pulse is inputted into the filter, a chirped microwave pulse is generated thanks to the quadratic phase response of the filter. To design a PMDLF with a quadratic phase response, complex tap coefficients

    Yitang Dai; Jianping Yao

    2009-01-01

    455

    The relation of line narrowing and chirp reduction resulting from the coupling of a semiconductor laser to passive resonator  

    Microsoft Academic Search

    The authors present a theory of adiabatic chirp reduction and narrowing of the Lorentzian laser line that occurs when a laser is coupled to an external passive resonator. Chirp reduction and line narrowing are simply related. They show that the reduction in the Lorentzian line width is equal to the square of the reduction in adiabatic chirp. Both are strongly

    R. F. Kazarinov; C. H. Henry

    1987-01-01

    456

    In-beam gamma ray and conversion electron study of 250Fm  

    Microsoft Academic Search

    We report on a set of in-beam studies of excited states in 250Fm. We detected prompt gamma rays by using the JUROSPHERE IV array and conversion electrons by using the SACRED spectrometer. Both devices were used in conjunction with the RITU gas-filled recoil separator located at the University of Jyväskylä. 250Fm nuclei were produced through the 204Hg(48Ca,2n)250Fm fusion-evaporation reaction. An

    J. E. Bastin; R.-D. Herzberg; P. A. Butler; G. D. Jones; R. D. Page; D. G. Jenkins; N. Amzal; P. M. Brew; N. J. Hammond; R. D. Humphreys; P. J. Ikin; T. Page; P. T. Greenlees; P. M. Jones; R. Julin; S. Juutinen; H. Kankaanpää; A. Keenan; H. Kettunen; P. Kuusiniemi; M. Leino; A. P. Leppänen; M. Muikku; P. Nieminen; P. Rahkila; C. Scholey; J. Uusitalo; E. Bouchez; A. Chatillon; A. Hürstel; W. Korten; Y. Le Coz; Ch. Theisen; D. Ackermann; J. Gerl; K. Helariutta; F. P. Hessberger; Ch. Schlegel; H. J. Wollerscheim; M. Lach; A. Maj; W. Meczynski; J. Styczen; T. L. Khoo; C. J. Lister; A. V. Afanasjev; H. J. Maier; P. Reiter; P. Bednarczyc; K. Eskola; K. Hauschild

    2006-01-01

    457

    Chirped-pulse amplification system based on chirp reversal and near-field spatial reversal with common tiled grating pair as stretcher and compressor.  

    PubMed

    Chirped-pulse amplification system based on chirp reversal in optical parametric chirped-pulse amplification is proposed and experimentally demonstrated. The operation of this system can be described as negative stretching-temporal chirp reversal-energy amplification-negative compression, in which the pulse is stretched and compressed with the same gratings. Stand-alone stretcher adopting lenses or concave mirrors with large aperture can be omitted. Simulations showed that this work mode can also increase the cut-off band-pass of the whole system and increase the output energy by 15-17%. In addition, the stability of a tiled-grating compressor can be improved with this work mode. PMID:22885574

    Wang, Xiao; Wei, Xiaofeng; Hu, Yao; Zeng, Xiaoming; Zuo, Yanlei; Hao, Xin; Zhou, Kainan; Xie, Na; Zhang, Ying

    2012-08-10

    458

    Experimental demonstration of a multi-wavelength distributed feedback semiconductor laser array with an equivalent chirped grating profile based on the equivalent chirp technology.  

    PubMed

    We report, to the best of our knowledge, the first realization of a multi-wavelength distributed feedback (DFB) semiconductor laser array with an equivalent chirped grating profile based on equivalent chirp technology. All the lasers in the laser array have an identical grating period with an equivalent chirped grating structure, which are realized by nonuniform sampling of the gratings. Different wavelengths are achieved by changing the sampling functions. A multi-wavelength DFB semiconductor laser array is fabricated and the lasing performance is evaluated. The results show that the equivalent chirp technology is an effective solution for monolithic integration of a multi-wavelength laser array with potential for large volume fabrication. PMID:24105542

    Li, Wangzhe; Zhang, Xia; Yao, Jianping

    2013-08-26

    459

    First-harmonic approximation in nonlinear chirped-driven oscillators.  

    PubMed

    Nonlinear classical oscillators can be excited to high energies by a weak driving field provided the drive frequency is properly chirped. This process is known as autoresonance (AR). We find that for a large class of oscillators, it is sufficient to consider only the first harmonic of the motion when studying AR, even when the dynamics is highly nonlinear. The first harmonic approximation is also used to relate AR in an asymmetric potential to AR in a "frequency equivalent" symmetric potential and to study the autoresonance breakdown phenomenon. PMID:24580292

    Uzdin, Raam; Friedland, Lazar; Gat, Omri

    2014-01-01

    460

    Seed Laser Chirping for Enhanced Backward Raman Amplification in Plasmas  

    NASA Astrophysics Data System (ADS)

    Backward Raman compression in plasma enables pulse compression to intensities not available using material gratings. Mediating the compression with higher density plasma generally produces shorter and therefore more intense output pulses. However, very high density plasma, even if sufficiently tenuous to be transparent to the laser, also produces group velocity dispersion of the amplified pulse, deleteriously affecting the interaction. What is shown here is that, by chirping the seed pulse, the group velocity dispersion may in fact be used advantageously, achieving the maximum intensities over the shortest distances while minimizing unwanted effects.

    Toroker, Z.; Malkin, V. M.; Fisch, N. J.

    2012-08-01

    461

    Chirped-Pulse Fourier Transform Microwave Spectroscopy of 3-VINYLBENZALDEHYDE  

    NASA Astrophysics Data System (ADS)

    The pure rotational spectrum of 3-vinylbenzaldehyde (3VBA) has been measured and assigned. Coker College's chirped-pulse Fourier transform microwave (CP-FTMW) spectrometer was used to measure the rotational spectrum of 3VBA in the 7.5 - 18.5 GHz region of the microwave spectrum. The results have been analyzed to discover the rotational constants and centrifugal distortion constants of four distinct conformations of 3VBA: cis,cis-, cis,trans-, trans,cis-, and trans,trans-3VBA. The experimental rotational constants have been compared to the results of ab initio calculations. The performance of Coker's CP-FTMW spectrometer will also be discussed.

    Smith, Miranda; Brown, Gordon G.

    2013-06-01

    462

    Amplification of optical pulse signal using chirped fiber grating  

    NASA Astrophysics Data System (ADS)

    These chirped fiber Bragg gratin is an attractive and practical element in particular context of dense wavelength- division multiplexing. We introduce a structure to realize working mode of the optical pulse's high power amplification. Also we analyze the variation of pulse signal after broaden or compression together with the variation in frequency domain and the peak intensity of pulse signal amplified by EDFA and subsequently compressed, in which these influence caused by the discrepancy of two optical paths and two dispersion parameters are considered.

    Ni, Weihai; Zhan, Li; Xia, YuXing

    2002-08-01

    463

    Control of laser induced molecular fragmentation of n-propyl benzene using chirped femtosecond laser pulses  

    PubMed Central

    We present the effect of chirping a femtosecond laser pulse on the fragmentation of n-propyl benzene. An enhancement of an order of magnitude for the relative yields of C3H3+ and C5H5+ in the case of negatively chirped pulses and C6H5+ in the case of positively chirped pulses with respect to the transform-limited pulse indicates that in some fragmentation channel, coherence of the laser field plays an important role. For the relative yield of all other heavier fragment ions, resulting from the interaction of the intense laser field with the molecule, there is no such enhancement effect with the sign of chirp, within experimental errors. The importance of the laser phase is further reinforced through a direct comparison of the fragmentation results with the second harmonic of the chirped laser pulse with identical bandwidth.

    Goswami, Tapas; Karthick Kumar, S.K.; Dutta, Aveek; Goswami, Debabrata

    2009-01-01

    464

    Manipulation of ro-vibronic wave packet composition using chirped ultrafast laser pulses  

    NASA Astrophysics Data System (ADS)

    Linearly chirped femtosecond laser pulses are used to excite ro-vibrational wave packets in lithium dimers from a single well-prepared launch state. Two-photon resonant Raman transitions excite a manifold of rotational states in a coherent superposition. Excitation with positively chirped laser pulses is shown to enhance a quantum beat involving states with lower rotational quantum numbers, whereas negatively chirped pulses enhance a quantum beat between states with higher rotational quantum numbers, thus steering the rotational coherences to higher or lower rotational states. Time-dependent perturbation theory calculations verify the magnitudes and directions of the enhancement as a function of the applied chirp. The quantitative calculations and experimental results demonstrate that excitation with chirped pulses is an effective method for enhancing specific rotational coherences involving higher or lower rotational states.

    Lerch, Eliza-Beth W.; Dai, Xingcan; Torres, Elva A.; Ballard, Joshua B.; Stauffer, Hans U.; Leone, Stephen R.

    2008-04-01

    465

    Isolated short attosecond pulse generation in an orthogonally polarized multicycle chirped laser field  

    SciTech Connect

    We theoretically demonstrate the generation of a high-order harmonic and isolated attosecond pulse in an orthogonally polarized laser field, which is synthesized by an 800-nm chirped laser pulse and an 800-nm chirp-free laser pulse. Owing to the instantaneous frequency increasingly reducing close to the center of the driving pulse, the extreme ultraviolet supercontinuum for the chirped synthesized field is even broader than that for an orthogonal chirp-free two-color laser field. It is found that the broadband supercontinuum spectrum can be achieved for the driving pulse with ten and above optical cycles. After phase compensation an isolated attosecond pulse with a duration of {approx}16 as is produced. Furthermore, the optimization of the chirping rate parameters is investigated to achieve cutoff extension and an isolated short attosecond pulse.

    Xu Junjie [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, P.O. Box 800-211, Shanghai 201800 (China)

    2011-03-15

    466

    Chirp of the single attosecond pulse generated by a polarization gating  

    SciTech Connect

    The chirp of the xuv supercontinuum generated by a polarization gating is investigated by comparing three-dimensional nonadiabatic numerical simulations with classical calculations. The origin of the chirp is the dependence of the energy gain by an electron on the return time. The chirp is positive and its value is almost the same as that when a linearly polarized laser is used. Although the 250-eV-wide supercontinuum corresponds to a single attosecond pulse, the shortest duration of the pulse is limited by the chirp. By compensating the positive chirp with the negative group velocity dispersion of a Sn filter, it is predicted that a single 58-as pulse can be generated.

    Chang Zenghu [Department of Physics, Kansas State University, Manhattan, Kansas 66506 (United States)

    2005-02-01

    467

    Perturbation-theory analysis of ionization by a chirped few-cycle attosecond pulse  

    SciTech Connect

    The angular distribution of electrons ionized from an atom by a chirped few-cycle attosecond pulse is analyzed using perturbation theory (PT), keeping terms in the transition amplitude up to second order in the pulse electric field. The dependence of the asymmetry in the ionized electron distributions on both the chirp and the carrier-envelope phase (CEP) of the pulse are explained using a simple analytical formula that approximates the exact PT result. This approximate formula (in which the chirp dependence is explicit) reproduces reasonably well the chirp-dependent oscillations of the electron angular distribution asymmetries found numerically by Peng et al. [Phys. Rev. A 80, 013407 (2009)]. It can also be used to determine the chirp rate of the attosecond pulse from the measured electron angular distribution asymmetry.

    Pronin, E. A.; Starace, Anthony F.; Peng Liangyou [Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588-0299 (United States); State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871 (China)

    2011-07-15

    468

    Transverse-to-longitudinal Emittance-exchange with an Energy Chirped Beam  

    SciTech Connect

    Emittance exchange has been proposed to increase the performance of free electron lasers by tailoring the phase space of an electron beam. The principle of emittance exchange - where the transverse phase space of the electron beam is exchanged with the longitudinal phase space - has been demonstrated recently at the A0 photoinjector. The experiment used a low charge bunch (250 pC) with no energy chirp. Theory predicts an improvement in the emittance exchange scheme when the incoming beam has an energy chirp imparted on it. The energy chirp helps to overcome the thick lens effect of the deflecting mode cavity and other second order effects that might lead to an incomplete emittance exchange at higher charges. In this work, we report experimental and simulation results from operating the emittance exchange beam line using an energy chirped beam with higher charge (500 pC) at different RF-chirp settings.

    Thangaraj, J.; Ruan, J.; Johnson, A.S.; Thurman-Keup, R.; Lumpkin, A.H.; Santucci, J.; Sun, Y.-E; Maxwell, T.; Edwards, H.; /Fermilab

    2012-05-01

    469

    Photonic Generation of Chirped Millimeter-Wave Pulses Based on Nonlinear Frequency-to-Time Mapping in a Nonlinearly Chirped Fiber Bragg Grating  

    Microsoft Academic Search

    A novel approach to optically generating chirped millimeter-wave pulses with tunable chirp rate based on spectral shaping and nonlinear frequency-to-time mapping is proposed and experimentally demonstrated. In the proposed approach, the optical power spectrum of an ultrashort pulse from a femtosecond pulsed laser is shaped by a two-tap Sagnac loop filter that has a sinusoidal frequency response. The spectrum-shaped optical

    Chao Wang; Jianping Yao

    2008-01-01

    470

    The Analytic Signal Representation of Modulated Waveforms  

    Microsoft Academic Search

    This report offers a rather general and mathematically convenient formulation of analog-modulated signals which makes use of the analytic signal concept. Known types of modulation are readily identified as special cases. As a result of examining the various cases which the model embraces, a new type of modulation has been discovered-single sideband frequency modulation (SSB FM)¿which can be derived from

    Edward Bedrosian

    1962-01-01

    471

    Frequency tracking and Doppler shift compensation in response to an artificial CF\\/FM echolocation sound in the CF\\/FM bat, Noctilio albiventris  

    Microsoft Academic Search

    Bats of the speciesNoctilio albiventris emit short-constant frequency\\/frequency modulated (short-CF\\/FM) pulses with a CF component frequency at about 75 kHz. Bats sitting on a stationary platform were trained to discriminate target distance by means of echolocation. Loud, free-running artificial pulses, simulating the bat's natural CF\\/FM echolocation sounds or with systematic modifications in the frequency of the sounds, were presented to

    Roald C. Roverud; Alan D. Grinnell

    1985-01-01

    472

    The role of the FM component in shaping the number of impulses and response latency of inferior collicular neurons of Hipposideros armiger elicited by CF-FM sounds.  

    PubMed

    Previous studies show that when stimulated with constant frequency-frequency modulated (CF-FM) sounds, the inferior collicular neurons of the leaf-nosed bat, Hipposideros armiger, either discharge impulses only to the CF component (single-on, SO neurons) or to both CF and FM components (double-on, DO neurons). In this study, we specifically determine the role of the FM component in shaping the number of impulses and response latency of these two types of neurons in response to CF-FM sounds. Adding the FM component to the CF sounds significantly decreases the number of impulses of both SO and DO neurons but shortens the response latency of DO neurons in response to the CF component of the CF-FM sounds. The possible neural mechanisms underlying these seemingly paradoxical observations are briefly discussed based on our preliminary intracellular recording studies. Biological relevance of these findings in relation to different phases of bats' hunting is also discussed. PMID:24915297

    Fu, Zi-Ying; Xu, Na; Wang, Jing; Tang, Jia; Jen, Philip Hung-Sun; Chen, Qi-Cai

    2014-07-25

    473

    Chirped CPMG for well-logging NMR applications  

    NASA Astrophysics Data System (ADS)

    In NMR well-logging, the measurement apparatus typically consists of a permanent magnet which is inserted into a bore, and the sample is the rock surrounding the borehole. When compared to the conditions of standard NMR experiments, this application is thus challenged by relatively weak and invariably inhomogeneous B0 and B1 fields. Chemical shift information is not generally obtained in these measurements. Instead, diffusivity, porosity and permeability information is collected from multi-echo decay measurements - most often using a Carr-Purcell Meiboom-Gill (CPMG) pulse sequence to enhance the experiment’s limited sensitivity. In this work, we explore the consequences of replacing the hard square pulses used in a typical CPMG sequence with chirped pulses sweeping a range of frequencies. The greater bandwidths that for a maximum B1 level can be excited by chirped pulses translates into marked expansion of the detection volume, and thus significant signal-to-noise improvements when compared to standard CPMG acquisitions using hard pulses. This improvement, usually amounting to signal enhancements ?3, can be used to reduce the experimental time of NMR well-logging measurements, for measuring T2 even when B0 and B1 inhomogenieties complicate the measurements, and opening new opportunities in the determination of diffusional properties.

    Casabianca, Leah B.; Mohr, Daniel; Mandal, Soumyajit; Song, Yi-Qiao; Frydman, Lucio

    2014-05-01

    474

    Coherent chirped pulse laser network with Mickelson phase conjugator  

    NASA Astrophysics Data System (ADS)

    The mechanisms of nonlinear phase-locking of a large fiber amplifier array are analyzed. It is shown that Michelson phase conjugating configuration with double passage through array of fiber amplifiers have the definite advantages compared to one-way fiber array coupled in a Mach-Zehnder configuration. Regardless to amount of synchronized fiber amplifiers Michelson phase-conjugating interferometer is expected to do a perfect compensation of the phase-piston errors and collimation of backwardly amplified fiber beams on entrance/output beamsplitter. In both configurations the nonlinear transformation of the stretched pulse envelope due to gain saturation is capable to randomize the position of chirp inside envelope thus it may reduce the visibility of interference pattern at output beamsplitter. A certain advantages are inherent to the $sech$-form temporal envelope because of exponential precursor and self-similar propagation in gain medium. The Gaussian envelope is significantly compressed in a deep gain saturation regime and frequency chirp position inside pulse envelope is more deformed.

    Okulov, A. Yu.

    2014-04-01

    475

    Chirped fiber Brillouin frequency-domain distributed sensing  

    NASA Astrophysics Data System (ADS)

    A frequency-domain distributed temperature/strain sensor based on a longitudinally graded optical fiber (LGF) is proposed and evaluated. In an LGF, the Brillouin scattering frequency, ?, changes (i.e., is chirped) lengthwise monotonically and thus every position along the fiber has a unique ?. Any change locally (at some position) in the fiber environment will result in a measurable change in the shape of the Brillouin gain spectrum (BGS) near the frequency component mapped to that position. This is demonstrated via measurements and modeling for an LGF with local heating. The LGF is one with ˜100 MHz Brillouin frequency gradient over 16.7 m, with 1.1 and 1.7 m segments heated up to 40 K above ambient. A measurement of the BGS can enable the determination of a thermal (or strain) distribution along a sensor fiber, thus rendering the system one that is in the frequency domain. A sensitivity analysis is also presented for both coherent and pump-probe BGS measurement schemes. The modeling results suggest that the frequency-domain systems based on fibers with a chirped Brillouin frequency are highly suited as inexpensive event sensors (alarms) and have the potential to reach submeter position determination with sub-1-K temperature accuracies at >1 kHz sampling rates. Limitations to the technique are discussed.

    Dragic, Peter D.; Mangognia, Anthony; Ballato, John

    2014-05-01

    476

    Chirped CPMG for well-logging NMR applications.  

    PubMed

    In NMR well-logging, the measurement apparatus typically consists of a permanent magnet which is inserted into a bore, and the sample is the rock surrounding the borehole. When compared to the conditions of standard NMR experiments, this application is thus challenged by relatively weak and invariably inhomogeneous B0 and B1 fields. Chemical shift information is not generally obtained in these measurements. Instead, diffusivity, porosity and permeability information is collected from multi-echo decay measurements - most often using a Carr-Purcell Meiboom-Gill (CPMG) pulse sequence to enhance the experiment's limited sensitivity. In this work, we explore the consequences of replacing the hard square pulses used in a typical CPMG sequence with chirped pulses sweeping a range of frequencies. The greater bandwidths that for a maximum B1 level can be excited by chirped pulses translates into marked expansion of the detection volume, and thus significant signal-to-noise improvements when compared to standard CPMG acquisitions using hard pulses. This improvement, usually amounting to signal enhancements ?3, can be used to reduce the experimental time of NMR well-logging measurements, for measuring T2 even when B0 and B1 inhomogenieties complicate the measurements, and opening new opportunities in the determination of diffusional properties. PMID:24674888

    Casabianca, Leah B; Mohr, Daniel; Mandal, Soumyajit; Song, Yi-Qiao; Frydman, Lucio

    2014-05-01

    477

    Mechanism of inverted-chirp infrasonic radiation from sprites  

    NASA Astrophysics Data System (ADS)

    Farges and Blanc (2010) reported inverted-chirp infrasonic signals with high frequencies arriving before low frequencies, possibly emitted by sprite discharges and observed on the ground at close range (<100 km) from the source. In the present work a parallel version of a 2-D FDTD model of infrasound propagation in a realistic atmosphere is applied to demonstrate that the observed morphology of infrasound signals is consistent with general scaling of diameters of sprite streamers inversely proportionally to the air density. The smaller structures at lower altitudes radiate higher infrasonic frequencies that arrive first at the observational point on the ground, while the low frequency components are delayed because they originate at lower air densities at higher altitudes. The results demonstrate that strong absorption of high frequency infrasonic components at high altitudes (i.e., ˜0.2 dB/km for 8 Hz at 70 km) may also contribute to formation of inverted-chirp signals observed on the ground at close range.

    de Larquier, Sebastien; Pasko, Victor P.

    2010-12-01

    478

    Characterization and compensation of the residual chirp in a Mach-Zehnder-type electro-optical intensity modulator.  

    PubMed

    We utilize various techniques to characterize the residual phase modulation of a waveguide-based Mach-Zehnder electro-optical intensity modulator. A heterodyne technique is used to directly measure the phase change due to a given change in intensity, thereby determining the chirp parameter of the device. This chirp parameter is also measured by examining the ratio of sidebands for sinusoidal amplitude modulation. Finally, the frequency chirp caused by an intensity pulse on the nanosecond time scale is measured via the heterodyne signal. We show that this chirp can be largely compensated with a separate phase modulator. The various measurements of the chirp parameter are in reasonable agreement. PMID:20173940

    Rogers, C E; Carini, J L; Pechkis, J A; Gould, P L

    2010-01-18

    479

    Neutron spectroscopy with fast waveform digitizer  

    NASA Astrophysics Data System (ADS)

    In this paper, we demonstrate the application of a fast waveform digitizer (1 GHz) for neutron spectroscopy. We investigated pulse-shape discrimination between neutrons and ?-rays, timing properties and count rate capabilities of this new experimental method and compared the results with traditional techniques. The present method compares particularly well in the case of particle-type identification in the presence of pulse saturation and in case of high count rate. Excellent timing resolution and good pulse amplitude resolution is demonstrated.

    Kornilov, N. V.; Khriatchkov, V. A.; Dunaev, M.; Kagalenko, A. B.; Semenova, N. N.; Demenkov, V. G.; Plompen, A. J. M.

    2003-02-01

    480

    Asymptotic waveform evaluation via a Lanczos method  

    Microsoft Academic Search

    In this paper we show that the two-sided Lanczos procedure combined with implicitrestarts offers significant advantages over Pad'e approximations used typically for model reduction incircuit simulation.Keywords---Dynamical systems, Model reduction, Numerical methods, Pad'e approximation,Lanczos algorithm..1. INTRODUCTIONAsymptotic Waveform Evaluation (AWE) is a recently developed technique for acquiring loworderapproximations for large, linearized circuits [1, 2, 3]. Such a circuit is...

    E. Grimme; K. Gallivan; P. Van Dooren

    1994-01-01

    481

    Resolution Analysis in Full Waveform Inversion  

    NASA Astrophysics Data System (ADS)

    Full waveform inversion is a tomographic technique that is based on numerical wave propagation through complex media combined with adjoint or scattering integral methods for the computation of Fréchet kernels. While the tomographic method itself has advanced substantially, an essential aspect of the inverse problem has been ignored almost completely: The quantification of resolution and uncertainties. We propose a new method for the quantitative resolution analysis in full seismic waveform inversion that overcomes the limitations of synthetic inversions while being computationally more efficient and applicable to any misfit measure. The method rests on (1) the local quadratic approximation of the misfit functional in the vicinity of an optimal Earth model, (2) the parametrisation of the Hessian in terms of a parent function, and (3) the computation of the space-dependent parameters via Fourier transforms of the Hessian, calculated with the help of adjoint techniques. In the simplest case of a Gaussian approximation we can infer rigorously defined 3D distributions of direction-dependent resolution lengths and the image distortion introduced by the tomographic method. We illustrate these concepts with a realistic full waveform inversion for upper-mantle structure beneath Europe. As a corollary to the method for resolution analysis we propose several improvements to full waveform inversion techniques. These include a pre-conditioner for optimisation schemes of the conjugate-gradient type, a new family of Newton-like methods, an approach to adaptive parametrisation independent from ray theory, and a strategy for objective functional design that aims at maximising resolution. The computational requirements of our approach are less than for a typical synthetic inversion, but yield a much more complete picture of resolution and trade-offs. It allows for adaptations to exploration scenarios and other wave equation based tomography techniques that employ, for instance, georadar or microwave data.

    Fichtner, A.; Trampert, J.

    2011-12-01

    482

    Diversified MIMO SAR waveform analysis and generation  

    Microsoft Academic Search

    Inspired by recent advances in multiple-input and multiple-output (MIMO) radar, which has the potential to dramatically improve the performance of radar systems over single antenna systems. This paper proposes a waveform diversity-based MIMO synthetic aperture radar (SAR) concept. The fundamental difference between MIMO SAR and conventional SAR is that the latter seeks to maximize coherent processing gain, while MIMO SAR

    Wen-Qin Wang; Qicong Peng; Jingye Cai

    2009-01-01

    483

    Bandwidth formula for Linear FMCW radar waveforms  

    Microsoft Academic Search

    The International Telecommunications Union provides recommendations regarding spectral emission bounds for primary radar systems. These bounds are currently in review and are defined in terms of spectral occupancy, necessary bandwidth, 40dB bandwidth and out-of-band roll-off rates. Here we derive out-of-band domain spectral envelopes, bandwidth formula and roll-off rates, for various Linear FMCW radar waveforms including sawtooth (LFMCW), Quadratic Phase Coded

    Michael D. E. Turley

    2009-01-01

    484

    Compression Waveforms for Non-Coherent Radar  

    Microsoft Academic Search

    Non-coherent pulse compression (NCPC) was suggested recently. It was described using on-off keying (OOK) signals based on Manchester-coded binary pulse compression sequences (e.g., Barker, Ipatov). The present paper expands the discussion on waveform choice for both periodic and a-periodic cases, and on detection performances of this method. OOK transmitter and a receiver based on envelope-detection, suggested for the NCPC system,

    Uri Peer; Nadav Levanon

    2007-01-01

    485

    Satellite analog FDMA/FM to digital TDMA conversion  

    NASA Technical Reports Server (NTRS)

    The results of a study which investigated design issues regarding the use of analog to digital (A/D) conversion on board a satellite are presented. The need for A/D, and of course D/A as well, conversion arose from a satellite design which required analog FDMA/FM up and down links to/from a digitally modulated intersatellite link. There are also some advantages when one must interconnect a large number of various spot beams which are using analog, and therefore cannot take advantage of SS/TDMA switching among the beams, thus resulting in low fill factors. Various tradeoffs were performed regarding the implementation of on-board A/D processing, including mass, power, and costs. The various technologies which were considered included flash ADCs, surface acoustic wave (SAW) devices, and digital signal processing (DSP) chips. Impact analyses were also performed to determine the effect on ground stations to convert to digital if the A/D approach were not implemented.

    Driggers, T.; Nguyen, T.; Kolavennu, V.

    1987-01-01

    486

    The Waveform Server: A Web-based Interactive Seismic Waveform Interface  

    NASA Astrophysics Data System (ADS)

    Seismic waveform data has traditionally been displayed on machines that are either local area networked to, or directly host, a seismic networks waveform database(s). Typical seismic data warehouses allow online users to query and download data collected from regional networks passively, without the scientist directly visually assessing data coverage and/or quality. Using a suite of web-based protocols, we have developed an online seismic waveform interface that directly queries and displays data from a relational database through a web-browser. Using the Python interface to Datascope and the Python-based Twisted network package on the server side, and the jQuery Javascript framework on the client side to send and receive asynchronous waveform queries, we display broadband seismic data using the HTML Canvas element that is globally accessible by anyone using a modern web-browser. The system is used to display data from the USArray experiment, a US continent-wide migratory transportable seismic array. We are currently creating additional interface tools to create a rich-client interface for accessing and displaying seismic data that can be deployed to any system running Boulder Real Time Technology's (BRTT) Antelope Real Time System (ARTS). The software is freely available from the Antelope contributed code Git repository. Screenshot of the web-based waveform server interface

    Newman, R. L.; Clemesha, A.; Lindquist, K. G.; Reyes, J.; Steidl, J. H.; Vernon, F. L.

    2009-12-01

    487

    FM1-43 reports plasma membrane phospholipid scrambling in T-lymphocytes.  

    PubMed Central

    We have found using imaging techniques that stimulating Jurkat human leukaemic T-cells with ionomycin in the presence of FM1-43, a dye used to monitor exocytosis and endocytosis, causes large (6--10-fold) increases in FM1-43 fluorescence. These responses are too large to be caused by exocytosis. Instead, three lines of evidence suggest that FM1-43 is responding to phospholipid scrambling. First, ionomycin also stimulates increases in the fluorescence of annexin V, a phosphatidylserine-specific probe, while thapsigargin does not stimulate fluorescence increases of either probe. Secondly, cells that exhibit FM1-43 fluorescence increases after ionomycin stimulation stain with annexin V once FM1-43 is washed out. Thirdly, ionomycin stimulates uptake of 7-nitrobenz-2-oxa-1,3-diazole-labelled phosphatidylcholine, a specific assay for scramblase activity, whereas thapsigargin does not. We find that FM1-43 reports phospholipid scrambling with 'better' kinetics than annexin V, and does require extracellular Ca(2+) to report phospholipid scrambling. We suggest that FM1-43 may be a useful probe to study the dynamics of phospholipid scrambling. The results are the first demonstration that FM1-43 can respond significantly to a biological process other than vesicular trafficking.

    Zweifach, A

    2000-01-01

    488

    47 CFR 73.1570 - Modulation levels: AM, FM, TV and Class A TV aural.  

    Code of Federal Regulations, 2013 CFR

    ...2013-10-01 false Modulation levels: AM, FM, TV and Class A TV aural. 73...Stations § 73.1570 Modulation levels: AM, FM, TV and Class A TV aural...meet the following limitations: (1) AM stations. In no case shall the...

    2013-10-01

    489

    A Dual Channel Correlator for an FM-CW Ranging Radar.  

    National Technical Information Service (NTIS)

    This abstract discloses a method and apparatus for eliminating the sidelobe ambiguity in the range response of an FM-CW radar. An FM-CW signal with a periodic modulation frequency is transmitted and reflected from a target, received and combined with a sa...

    R. A. Parkhurst, D. L. Rodkey, J. O. Wedel

    1980-01-01

    490

    Methods for Detecting Internalized, FM 1-43 Stained Particles in Epithelial Cells and Monolayers  

    Microsoft Academic Search

    The membrane dye FM 1-43 has frequently been used to quantify exocytosis in neurons. In epithelia, intense lateral intracellular space staining and fluctuations in baseline labeling produced inconsistent results. Membrane retrieved in the presence of FM 1-43 retains the dye, however, and cells that undergo compensatory endocytosis during and following evoked exocytosis contain punctate, fluorescent particles after washout of external

    C. A. Bertrand; C. Laboisse; U. Hopfer; R. J. Bridges; R. A. Frizzell

    2006-01-01

    491

    The Effect of Multiple CW and FM Signals Passed Through a Hard Limiter or TWT  

    Microsoft Academic Search

    This study reviews the analysis of the output autocorrelation function and spectral density for two CW signals which are passed through a hard limiter, describes the experimental results for two CW signals passed through a TWT, and analyzes the output autocorrelation function and spectral density for two FM signals, four CW signals, and four FM signals passed through a hard

    J. Sevy

    1966-01-01

    492

    Multidimensional quasi-eigenfunction approximations and multicomponent AM-FM models  

    Microsoft Academic Search

    We develop multicomponent AM-FM models for multidimensional signals. The analysis is cast in a general -di- mensional framework where the component modulating functions are assumed to lie in certain Sobolev spaces. For both contin- uous and discrete LSI systems with AM-FM inputs, powerful new approximations are introduced that provide closed form expressions for the responses in terms of the input

    Joseph P. Havlicek; David S. Harding; Alan Conrad Bovik

    2000-01-01

    493

    47 CFR 73.1210 - TV/FM dual-language broadcasting in Puerto Rico.  

    Code of Federal Regulations, 2013 CFR

    ...2013-10-01 false TV/FM dual-language broadcasting in Puerto Rico. 73...Stations § 73.1210 TV/FM dual-language broadcasting in Puerto Rico. (a) For the purpose of this section, dual-language broadcasting shall be understood...

    2013-10-01

    494

    FM-dyes as experimental probes for dissecting vesicle trafficking in living plant cells  

    Microsoft Academic Search

    Summary FM-dyes are widely used to study endocytosis, vesicle traffick- ing and organelle organization in living eukaryotic cells. The increasing use of FM-dyes in plant cells has provoked much debate with regard to their suitability as endocytosis markers, which organelles they stain and the precise pathways they follow through the vesicle trafficking network. A primary aim of this article is

    S. Bolte; C. Talbot; Y. Boutte; O. Catrice; N. D. Read; B. Satiat-Jeunemaitre

    2004-01-01

    495

    Descriptive Study of Noncommercial FM Radio Stations Affiliated with Colleges and Universities.  

    ERIC Educational Resources Information Center

    Designed to establish a framework for current and future documentation of FM radio in institutions of higher education, this study examined the state of noncommercial FM radio stations affiliated with colleges and universities. Topics investigated included: (1) basic descriptions of institutions housing noncommercial radio stations; (2) operating…

    Leidman, Mary Beth; Lamberski, Richard J.

    496

    Chirp-modulated visual evoked potential as a generalization of steady state visual evoked potential  

    NASA Astrophysics Data System (ADS)

    Visual evoked potentials (VEPs) are of great concern in cognitive and clinical neuroscience as well as in the recent research field of brain-computer interfaces (BCIs). In this study, a chirp-modulated stimulation was employed to serve as a novel type of visual stimulus. Based on our empirical study, the chirp stimuli visual evoked potential (Chirp-VEP) preserved frequency features of the chirp stimulus analogous to the steady state evoked potential (SSVEP), and therefore it can be regarded as a generalization of SSVEP. Specifically, we first investigated the characteristics of the Chirp-VEP in the time-frequency domain and the fractional domain via fractional Fourier transform. We also proposed a group delay technique to derive the apparent latency from Chirp-VEP. Results on EEG data showed that our approach outperformed the traditional SSVEP-based method in efficiency and ease of apparent latency estimation. For the recruited six subjects, the average apparent latencies ranged from 100 to 130 ms. Finally, we implemented a BCI system with six targets to validate the feasibility of Chirp-VEP as a potential candidate in the field of BCIs.

    Tu, Tao; Xin, Yi; Gao, Xiaorong; Gao, Shangkai

    2012-02-01

    497

    Isolated attosecond pulse generation from pre-excited medium with a chirped and chirped-free two-color field.  

    PubMed

    We theoretically investigate the isolated attosecond pulse generation from pre-excited medium with a chirped and chirped-free two-color field. It is found that the large initial population of the excited state can lead to the high density of the free electrons in the medium and the large distortion of the driving laser field after propagation, though it benefits large enhancement of harmonic intensity in single atom response. These effects can weaken the phase-match of the macroscopic supercontinuum. On the contrary, the small initial population of 4% can generate well phase-match intense supercontinuum. We also investigate an isolated attosecond pulse generation by using a filter centered on axis to select the harmonics in the far field. Our results reveal that the radius of the spatial filter should be chosen to be small enough to reduce the duration of the isolated attosecond pulse due to the curvature effect of spatiotemporal profiles of the generated attosecond pulses in the far field. PMID:22535063

    Du, Hongchuan; Luo, Laoyong; Wang, Xiaoshan; Hu, Bitao

    2012-04-23

    498