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Showing papers on "Frequency response published in 1979"


Journal ArticleDOI
TL;DR: In this article, a unified study of the applications of Volterra functional series to nonlinear-system analysis is presented with special emphasis on frequency-domain results which either have not been published before, or where rigour had been lacking.
Abstract: A unified study of the applications of Volterra functional series to nonlinear-system analysis is presented with special emphasis on frequency-domain results which either have not been published before, or where rigour had been lacking. In particular, an in-depth analysis of the harmonic and intermodulation frequency components due to each Volterra kernel of a given order will be presented and explicit formulas which complement those already published will be given. The effects of manipulating various kernels, which need not be symmetric, on the overall response, as well as on the composite kernels will be investigated. These results are then applied to the analysis of dynamical systems described by a system of nonlinear state equations and a read-out map

156 citations


Journal ArticleDOI
TL;DR: The behaviour of a three-level system consisting of two ground-state sub-levels optically coupled to a common excited state is analyzed in this article, where exact steady solution of the semi-classical equations of motion for the density matrix is obtained (within the RWA) and numerically investigated when the frequency difference of the two applied fields becomes equal to the frequency splitting of the lower levels, a mechanism of transverse optical pumping takes place that accumulates all the atoms in a coherent superposition state of the ground sublevels, in which they are no longer able to
Abstract: The behaviour of a three-level system consisting of two ground-state sublevels optically coupled to a common excited state is analysed An exact steady solution of the semi-classical equations of motion for the density matrix is obtained (within the RWA) and then numerically investigated When the frequency difference of the two applied fields becomes equal to the frequency splitting of the lower levels, a mechanism of transverse optical pumping takes place that accumulates all the atoms in a coherent superposition state of the ground sublevels, in which they are no longer able to absorb the pumping fields The effect is due to nonlinear effects of coherence and is responsible for the appearance of a very strong and narrow resonance in the system response Moreover, if the interaction energies of the two transitions have different magnitude, another resonance appears which corresponds to the power-shifted two-photon transition between the lower sublevels The reported results are in agreement with experimental phenomena recently observed

155 citations


Journal ArticleDOI
TL;DR: The results emphasize the need to test the response characteristics of any transducer with specific connectors and fittings that are to be used to make the actual measurements of pressure, volume, or flow.
Abstract: A device and methodology is presented for testing the frequency response of pressure, volume, or flow transducers. Also reported are responses of selected transducers of all three types over the range of 2--120 Hz. Several pressure transducers tested had good frequency response when connected to the test system with a minimum of interconnecting fittings; others did not. Use of additional connectors degraded the response as did the addition of air-filled catheters. The frequency response of the pneumotachometers tested were influenced largely by the response characteristics of the associated pressure transducer and interconnecting fittings. These results emphasize the need to test the response characteristics of any transducer with specific connectors and fittings that are to be used to make the actual measurements of pressure, volume, or flow.

102 citations


PatentDOI
TL;DR: In this paper, a plurality of carrier signals are modulated by pulses corresponding to signals in audio frequency bands, which are applied to electrodes on a prosthetic device implanted in the cochlea.
Abstract: A plurality of carrier signals are modulated by pulses corresponding to signals in audio frequency bands. The carrier signals are transmitted to a receiver having independent channels for receiving and demodulating the transmitted signals. The detected pulses are applied to electrodes on a prosthetic device implanted in the cochlea with the electrodes selectively positioned in the cochlea to stimulate regions having a desired frequency response. The pulses have a frequency which corresponds to the frequency of signals in an audio band and a pulse width which corresponds to the amplitude of signals in the audio band.

100 citations


Journal ArticleDOI
TL;DR: Re receptive field properties of cat retinal ganglion cells with visual stimuli which were sinusoidal spatial gratings amplitude modulated in time by a sum of sinusoids imply that the receptive field center and surround mechanisms are physiologically quite different in Y cells from those in X cells, and that the Y cells also receive excitatory drive from an additional nonlinear receptive field mechanism.
Abstract: We investigated receptive field properties of cat retinal ganglion cells with visual stimuli which were sinusoidal spatial gratings amplitude modulated in time by a sum of sinusoids. Neural responses were analyzed into the Fourier components at the input frequencies and the components at sum and difference frequencies. The first-order frequency response of X cells had a marked spatial phase and spatial frequency dependence which could be explained in terms of linear interactions between center and surround mechanisms in the receptive field. The second-order frequency response of X cells was much smaller than the first-order frequency response at all spatial frequencies. The spatial phase and spatial frequency dependence of the first-order frequency response in Y cells in some ways resembled that of X cells. However, the Y first-order response declined to zero at a much lower spatial frequency than in X cells. Furthermore, the second-order frequency response was larger in Y cells; the second-order frequency components became the dominant part of the response for patterns of high spatial frequency. This implies that the receptive field center and surround mechanisms are physiologically quite different in Y cells from those in X cells, and that the Y cells also receive excitatory drive from an additional nonlinear receptive field mechanism.

99 citations


Journal ArticleDOI
A.M. Vural1
TL;DR: In this article, the effects of system and medium perturbations, and deviations of signal field statistics from usual assumptions, on the performance of adaptive arrays are investigated, and the emphasis is placed on the determination of the sensitivity of the adaptive processors to perturbation, rather than its overall performance in a representative background.
Abstract: An investigation of the effects of system and medium perturbations, and the deviations of signal field statistics from usual assumptions, on the performance of adaptive arrays is presented. The emphasis is placed on the determination of the sensitivity of the adaptive processors to perturbations, rather than its overall performance in a representative background. The numerical results are limited to CW signals, and a frequency domain element space adaptive beam-former is modeled for the majority of the results. Representative comparative results including frequency domain beam space, time domain element space, and matched array processors are also given.

94 citations


Journal ArticleDOI
TL;DR: In this paper, the exact analysis of networks containing capacitors, independent and dependent voltage sources, and switches is presented for both transient response and frequency response, and solutions for both continuous and piecewiseconstant arbitrary inputs are handled, and the switching pattern can be periodic (with any number of subintervals per period) or nonperiodic.
Abstract: An efficient method is presented for the exact analysis of networks containing capacitors, independent and dependent voltage sources, and switches. Both continuous and piecewise-constant arbitrary inputs are handled, and solutions are presented for both transient response and frequency response. The switching pattern can be periodic (with any number of subintervals per period) or nonperiodic. The formulation proposed can be efficiently implemented on the computer and provides for user convenience; only one network topology and the switching schedule must be specified (as opposed to specifying as many topologies as there are switch position combinations). The method is especially well suited for the analysis of the recently introduced switched capacitor filters and charge redistribution circuits.

93 citations


Journal ArticleDOI
TL;DR: In this article, a method is described for designing linear multivariable control schemes which have a closed-loop frequency response as close as possible, in a least squares sense, to a desired response.
Abstract: In this paper a method is described for designing linear multivariable control schemes which have a closed-loop frequency response as close as possible, in a least squares sense, to a desired response. After using characteristic gain loci to ensure system stability, the closed-loop Bode array gives easily understood information about the controlled system in terms of bandwidth, speed of response, resonance and interaction. The closed-loop Nyquist array indicates the robustness of the control scheme for sensor failures ; it also indicates the extent to which state and input noise will be suppressed, since the feedback just multiplies the open-loop disturbances by a unit matrix minus the closed-loop frequency response. Bands of Gershgorin and Ostrowski circles are used to indicate the behaviour for changes in the characteristics of more than one sensor at a time. A similar frequency-response array, obtained by breaking the feedback loops next to the actuators instead of next to the sensors, can be used to p...

88 citations


Journal ArticleDOI
TL;DR: In this paper, the reflection coefficient versus frequency of symmetrical crossed-dipole arrays exhibits two distinct resonances, which occur when the dipole elements are on the order of a half-wavelength long.
Abstract: An analysis is presented for calculating the scattering from periodic arrays of symmetrical crossed dipoles. It is shown that in general the reflection coefficient versus frequency of symmetrical crossed-dipole arrays exhibits two distinct resonances, which occur when the dipole elements are on the order of a half-wavelength long. The analysis reveals also the presence of an antiresonance, which occurs at a frequency between the two resonances. At the antiresonant frequency the array reflection coefficient is zero. Thus, within a relatively narrow frequency band, the array reflection characteristics traverse the extremes of complete reflection followed by no reflection, and finally by complete reflection again. The anomalous reflection versus frequency behavior in such arrays is shown to be directly attributable to two distinct resonances excited in the crossed elements. For an isolated crossed dipole, it is shown that the total induced current can be approximately represented by two uncoupled current components. The current components induced on the same elements in an array, however, are coupled to one another through interaction with neighboring elements. The coupling results in complete cancellation of the total bistatic array scattering, at a frequency which lies between the two component current resonant frequencies.

79 citations


Journal ArticleDOI
TL;DR: The filter is designed so that binary changes in the sampling frequency provide new sets of center frequencies which smoothly continue the logarithmic progression, and the accuracy and reproducibility inherent in the switched capacitor approach are retained.
Abstract: Techniques are presented for the design of a second-order switched capacitor filter which has its frequency response parameters programmed by the application of digital control signals. Two different types of weighted capacitor arrays are used to achieve programmability in the center frequency, peak gain, and selectivity. Experimental results are given for an integrated NMOS version with eight logarithmically-spaced center frequencies programmed by a 3 bit digital word, and 64 Q and gain values programmed by two 6 bit words. The filter is designed so that binary changes in the sampling frequency provide new sets of center frequencies which smoothly continue the logarithmic progression. Since the response depends on monolithic MOS capacitor ratios, the accuracy and reproducibility inherent in the switched capacitor approach are retained.

76 citations


Journal ArticleDOI
TL;DR: In this paper, a quasi-static device model is proposed to predict nonlinear performance of microwave GaAs field effect transistors in arbitrary circuit embedding, based on measured bias and frequency dependence of the small-signal device parameters.
Abstract: A technique is described for accurately predicting nonlinear performance of microwave GaAs field-effect transistors in arbitrary circuit embedding. The approach is based on a quasi-static device model which is derived from measured bias and frequency dependence of the small-signal device S parameters. Excellent agreement is demonstrated between experimental and predicted "load-pull" characteristics at X band.

Patent
17 Sep 1979
TL;DR: A frequency adaptive power-energy re-scheduler (FAPER) as mentioned in this paper is a frequency transducer that notes frequency or frequency deviations of an electrical system and logic means which controls and reschedules power flow to a load unit in part on the basis of the deviations in frequency from a nominal frequency and in part based on the needs to the load unit as expressed by an external sensor signal obtained from the physical system affected by the load units.
Abstract: A frequency adaptive, power-energy re-scheduler (FAPER) that includes a frequency transducer that notes frequency or frequency deviations of an electrical system and logic means which controls and re-schedules power flow to a load unit in part on the basis of the deviations in frequency from a nominal frequency and in part on the needs to the load unit as expressed by an external sensor signal obtained from the physical system affected by the load unit



Journal ArticleDOI
TL;DR: Preliminary results, like frequency response and amplitude and phase measurements, are presented to illustrate the ability of the electronic speckle pattern interferometry to vibration measurements on the human ear drum in vivo.
Abstract: This paper describes the application of electronic speckle pattern interferometry to vibration measurements on the human ear drum in vivo. The technique makes use of a continuous wave laser, reference wave phase modulation, and videorecording of interferograms for subsequent analysis. Preliminary results, like frequency response and amplitude and phase measurements, are presented to illustrate the ability of this technique.

Journal ArticleDOI
TL;DR: In this article, a random binary calibration signal and cross-spectral techniques were used to calibrate seismic systems to an accuracy of better than 1 per cent in amplitude and 1° in phase.
Abstract: We present a rapid and accurate method of calibrating seismic systems using a random binary calibration signal and cross-spectral techniques. The complex transfer function obtained from the cross spectrum is least-squares fit to the ratio of two polynomials in s(s = iω) whose degrees are determined by a linear systems analysis. This provides a compact representation of the system frequency response. We demonstrate its application to two seismic systems, the IDA and SRO seismomenters. This method yields calibrations to an accuracy of better than 1 per cent in amplitude and 1° in phase.

Journal ArticleDOI
TL;DR: In this article, a method for analyzing microwave class-C amplifiers is proposed which satisfies the requirements of a wide application field, and, at the same time, operates with a fast run-time and without convergence problems.
Abstract: A method for analyzing microwave class-C amplifiers is proposed which satisfies the requirements of a wide application field, and, at the same time, operates with a fast runing time and without convergence problems. It is based on the partitioning of the circuit into linear and nonlinear subnetworks for which, respectively, frequency-domain and time-domain equations are written. Then, taking into account that the time-domain and frequency-domain representations are related by the Fourier series, the circuit behavior is described by means of a system of nonlinear equations whose unknowns are the harmonic components of the incident waves at all the connections. To overcome the numerical problems arising in the search for the solution of this system when strong nonlinearities are involved, a special step-by-step procedure is adopted. The problem is transformed into the search for the solution of a sequence of well-conditioned systems of equations corresponding to a sequence of well-chosen circuits obtained from the original one through progressive changes of the input signal starting from 0 up to the nominal value. The program which implements the method is also described and the results of the analysis relative to a class-C amplifier are compared with measured values.

Journal ArticleDOI
01 Jan 1979
TL;DR: In this paper, the authors present an overview of surface-acoustic-wave (SAW) resonator filter technology, including a general analysis and design formalism based on wave-scattering theory, and experimental results from a number of device prototypes.
Abstract: This paper presents an overview of surface-acoustic-wave (SAW) resonator filter technology. Given the current state of the art, these filters promise reproducible low-loss (≲6 dB) narrow-bandwidth (500 ≲ f/Δf ≲ 50 000) responses in the VHF and UHF ranges. Devices that contain one or a number of sections, each consisting of a resonant cavity between two grating reflectors and an input and output coupling mechanism, are considered. The initial discussion describes the layout, theoretical characteristics, and typical experimental responses of singlesection two-port filters. The subsequent discussion focuses on multisection devices using any of various intercavity coupling techniques. A generalized analysis and design formalism based on wave-scattering theory is reviewed, and experimental results from a number of device prototypes are given. Finally, practical design and fabrication trade-offs and performance ranges are summarized for a number of configurations.

Journal ArticleDOI
TL;DR: In this paper, it was shown that for random additive coefficient errors with variance σ2, the error ΔH(ω) in frequency response for targe n is such that where log denotes the natural logarithm.
Abstract: Coefficient inaccuracy in transversal filters is known to degrade the frequency response, particularly in stopband regions. The magnitude of the stopband degradation increases with the number of stages n, the length of the impulse response. A widely used formula for the error in frequency response is proportional to √n. By extending recent results on random trigonometric polynomials, we show that for random additive coefficient errors with variance σ2, the error ΔH(ω) in frequency response for targe n is such that where log denotes the natural logarithm This result leads to an absolute bound on attainable stopband rejection for any band-select transversal filter with given coefficient inaccuracy. In particular, the result places a definite limitation on the quality of band-select filtering that can be achieved using a ccd split-electrode filter. It also implies bounds for the peak sidelobes of random radar arrays.

Journal ArticleDOI
TL;DR: In this article, a nonlinear macromodel for integrated circuit operational amplifiers has been developed for frequency-domain analysis, which considers the influence of frequency and amplitude on the transfer function of the operational amplifier and also includes the slew-rate effect on the open-loop frequency response and output-voltage distortion computed from the Fourier coefficients.
Abstract: A nonlinear macromodel for integrated circuit operational amplifiers has been developed for frequency-domain analysis. The main difference between this macromodel and those previously reported in the literature is that this model considers the influence of frequency and amplitude on the transfer function of the operational amplifier. The macromodel also includes the slew-rate effect on the open-loop frequency response and output-voltage distortion computed from the Fourier coefficients. The benefits of the developed macromodel are demonstrated by several examples, showing that the simulation is in good agreement with the experimental results. One important application of this macromodel is suggested to be in the computation of the dynamic range of active filters.

Journal ArticleDOI
TL;DR: In this paper, the authors describe a theoretical basis and supporting experimental evidence from tests performed at a power plant, for tuning power system stabilizers using frequency response techniques, where the tie-line power was used as a feedback signal to the stabilizer.
Abstract: During the past ten years a number of authors have put forward techniques for tuning power system stabilizers (PSS) in the literature. Some of these techniques have been tested in on-site applications and others have been evaluated using simulation techniques. This paper describes a theoretical basis, and supporting experimental evidence from tests performed at a power plant, for tuning power system stabilizers using frequency response techniques. By using the method described in this paper, the power system analyst is able to obtain an approximate measure of the amount of damping that can be expected from the stabilizer in damping out tie- line power oscillations. The tests were conducted on the inter- tie between the Alberta and British Columbia Hydro power pools. Test results indicated a direct correlation between the improvement in the electric power damping as observed by field tests and that predicted by theoretical means. Although the method suggested in this paper has general application to power system stabilization for local mode damping and inter- tie damping it was applied to the specific case where the tie- line power was used as a feedback signal to the stabilizer.

Journal ArticleDOI
TL;DR: In this article, a study of the transfer of frequency stability from an atomic reference to a quartz-crystal oscillator is presented, and the results obtained from numerical calculations are presented under the form of graphs.
Abstract: This paper presents a study of the transfer of frequency stability from an atomic reference to a quartz-crystal oscillator. The study is done for the cases of active and passive atomic frequency standards in which one makes use of a phase-lock loop and of a frequency-lock loop, respectively. The analysis is made in both the frequency and time domains and covers the cases of the hydrogen and rubidium masers and the passive cesium-and rubidium-frequency standards. The results obtained from numerical calculations are presented under the form of graphs. These results include the fractional frequency spectral density Sy(f) as a function of the Fourier frequency f, and the two sample variance ?2(?) as a function of ?, the sampling time.

Journal ArticleDOI
TL;DR: In this paper, it was shown that the nonlinear electric polarization density that is third order in the propagating electric fields in the guide medium generates the replica by the process of four-wave mixing.
Abstract: We show that one can generate the time-reversed replica of an "input" monochromatic, image-bearing beam by coupling it into a waveguide where it interacts with counterpropagating multimode "pump" waves of the same frequency. The nonlinear electric polarization density that is third order in the propagating electric fields in the guide medium generates the replica by the process of "four-wave mixing." We show also that the input beam can serve simultaneously as its own pump beam. If the frequency ν of the backward pump beam is different from the frequency ω to of the input beam, then the "phase-conjugate" to the input is generated at the entrance plane to the guide, and this radiates a replica of the input field, magnified by \omega/ u , back along the input beam. The pump power required per resolution element to phase-conjugate a beam in a waveguide is orders-of-magnitude less than for the corresponding process with free (unguided) waves interacting in an infinite medium. Unlike the requirements for free waves, the pump waves do not need to be well aligned or single-mode to produce high fidelity in the replication process. Neither does the guiding structure or enclosed medium have to be precise in dimension or uniformity; the main requirements on the guiding structure being that it not attenuate the waves too heavily. Formulas are derived for the replication efficiency and fidelity in the various guided configurations. We also show how the process can be used: 1) to make a narrowband optical filter with a large acceptance solid angle; 2) to perform image-frequency conversion; 3) to obtain Raman and two-photon spectra of small samples; and 4) to achieve broadband optical amplification. We examine the conditions under which phase conjugation and these applications can be performed at several frequencies simultaneously. Limitations placed by the power-dependence of propagation constants are derived.

Journal ArticleDOI
01 Jan 1979
TL;DR: In this paper, the authors present an introduction to Surface-Acoustic-Wave (SAW) devices, their operation, advantages, and applications, and the process of design and realization of high-performance SAW filters is examined from initial specifications to final device operation.
Abstract: An introduction to Surface-Acoustic-Wave (SAW) devices-their operation, advantages, and applications--is presented. The process of design and realization of high-performance SAW filters is examined from initial specifications to final device operation. Several techniques drawn from a variety of disciplines illustrate the implementation of finite impulse response SAW frequency functions. Material properties, transducer weighting, and computer-aided design are treated. An example of the design and testing of a 321-MHz 0.35-percent bandwidth, 65-dB sidelobe, 15-dB insertion loss filter is presented.

Journal ArticleDOI
TL;DR: In this article, an analysis of an end-launcher type, coaxial-to-rectangular waveguide transition, exciting dominant TE/sub 01/mode in X-band rectangular waveguide is presented.
Abstract: The analysis of an end-launcher type, coaxial-to-rectangular waveguide transition, exciting dominant TE/sub 01/ mode in X-band rectangular waveguide is presented. Expressions for the real and imaginary parts of the input impedance seen by the coaxial line are derived for the general case of an offset launcher using self-reaction of an assumed current over the loop. The dimensions of the combined electric and magnetic loops having low input VSWR in the coaxial line are determined. There is satisfactory agreement between theoretical and experimental results.

Journal ArticleDOI
TL;DR: In this article, the tropospheric limitations of accuracy of coordinate measurements, using phase and fringe frequency, were investigated in the framework of power-model of the structure function, and the general formulae, numerical estimates and a comparison between absolute and differential methods were given.
Abstract: In the framework of power-model of the structure function, the tropospheric limitations of accuracy of coordinate measurements, using phase and fringe frequency are shown. The general formulae, numerical estimates and a comparison between absolute and differential methods are given. It is shown that the tropospheric limitations are especially considerable for coordinate measurements, using fringe frequency.

Journal ArticleDOI
TL;DR: In this article, an external system equivalent for on-line generator outage simulation is presented. The proposed method is an extension to the Ward equivalent, which models the steady state MW response of the external system after primary speed control actions.
Abstract: This paper describes an external system equivalent for on-line generator outage simulation. The equivalent models the steady- state MW response of the external system after primary speed control actions. The proposed method is an extension to the Ward equivalent. Starting with the frequency response characteristics of the individual units and loads in the external system, equivalent frequency response characteristics for each boundary bus have been developed. These equivalent frequency response characteristics model not only the total in-rush, but also the distribution among the individual tie lines. In addition to the data required for branch outage simulations the incremental speed regulations and rated powers of all external units on the line are assumed to be known. No real-time measurement data from the external control areas are required. The suggested equivalent has been verified by off-line simulations of 10 severe generator outages in three European 380/220 kV networks.

Journal ArticleDOI
TL;DR: In this paper, the mean square response of a linear system to nonstationary random excitation is expressed as a product of a deterministic envelope function and a Gaussian stationary non-white noise.

Journal ArticleDOI
TL;DR: It is shown how compensation can be applied using classical graphical design methods to avoid critical regions in the frequency domain and a new computational method is outlined for the determination of limit cycle operation.

Journal ArticleDOI
TL;DR: This work investigates the rate at which the parameter space in the approximate model can be increased as sample size increases, in such a way that these estimates will provide consistent estimates of the underlying system.
Abstract: An infinite distributed lag system is approximated by a truncated one, which can be consistently estimated. We investigate the rate at which the parameter space in the approximate model can be increased as sample size increases, in such a way that these estimates will provide consistent estimates of the underlying system.