Showing papers on "Frequency response published in 1985"

Frequency-Dependent Characteristics of Microstrip Discontinuities in Millimeter-Wave Integrated Circuits

Abstract: A theoretical approach for the representation of microstrip discontinuities by equivalent circuits with frequency-dependent parameters is presented. The model accounts accurately for the substrate presence and associated surface-wave effects, strip finite thickness, and radiation losses. The method can also be applied for the solution of microstrip components in the millimeter frequency range.

Generalizations of ‘‘universal dielectric response’’ and a general distribution‐of‐activation‐energies model for dielectric and conducting systems

Abstract: Three empirical equations introduced by Jonscher to represent the imaginary part of the small‐signal frequency response of dielectric materials and termed ‘‘universal dielectric response’’ by him are generalized in three ways. The equations may be applied in normalized form at the impedance level as well as at the usual complex dielectric constant level, defining the response of conducting rather than dielectric materials. They are generalized to include real as well as imaginary parts where possible. A unified dielectric or conductive distribution‐of‐activation‐energies (DAE) physical model is proposed whose predictions agree remarkably well with those of all the Jonscher universal dielectric response equations as well as with many other common dielectric response equations. The new model, unlike previous small‐signal response models, leads to quantitative predictions for the temperature dependence of the power‐law frequency exponent appearing in the ubiquitous constant‐phase‐response frequency region of the total response.

Frequency response of unified dielectric and conductive systems involving an exponential distribution of activation energies

Abstract: When the small‐signal ac frequency response of a dielectric or conductive system is known, either functionally or as data, it is shown that the corresponding response of an associated conductive or dielectric system may be immediately obtained through the use of new duality relations. A specific model is considered which involves thermally activated capacitance and/or resistance, with an activation energy probability density exponentially dependent on energy. Previous frequency response analyses of such a continuously distributed model involve inadequate approximations and lead to erroneous predictions. Correct immittance results are presented in three ways: analytically, by means of complex plane plots, and through the use of three‐dimensional perspective plots. Results are given in general form but apply to both dielectric and conductive systems which involve the same functional dependence on activation energies. Low‐ and high‐frequency‐limiting responses for a given system are found to be associated wi...

Frequency broadening by self-phase modulation in optical fibers

Abstract: We examine the effects of optical nonlinearities that are due to the intensity-dependent index of refraction in optical fibers. The broadening of the frequency spectrum of an optical pulse will combine with the group-velocity dispersion, increasing the temporal pulse spreading, thereby limiting the information transmission rate. We derive an exact formula for the rms frequency width of a Gaussian input pulse after it undergoes self-phase modulation. This new formula gives good agreement with experimental results.

Variable frequency synthesizer with reduced phase noise

Abstract: A reference signal from a reference signal source is supplied to a frequency transformer and a side band signal generator. The frequency transformer is formed mainly by up-converters and produces a frequency m times as high as the frequency f s of the reference signal. The side band signal generator outputs signals of base and harmonic frequencies f s , 2f s , 3f s , . . . and nf s (where n is less than m) and produces less phase noise than does the frequency transformer. The outputs of the frequency transformer and the side band signal generator are frequency mixed by a frequency mixer, and one frequency component in the frequency-mixed output is selected by a variable filter.

The multivariate mode indicator function in modal analysis

Abstract: In the sine dwell school of modal testing, a frequency domain function, most often called the Mode Indicator Function (MIF), has been employed for several years to detect the presence of real normal modes. This function is calculated from Frequency Response Functions from a single exciter location to highlight those frequencies where the global response phase lags the sinusoidal excitation by 90 degrees. Recently, a multivariate mode indicator procedure was presented, that, using FRF's from several exciter locations, can detect repeated roots, as well as providing initial force patterns for the sine dwell tuning of the associated modes. This paper presents a brief outline of the theory of this multivariate mode indicator and then shows how the information generated by this procedure may be used for the extraction of selected modal parameters through function enhancement and frequency domain SDOF techniques. The use of the multivariate mode indicator in the traditional MDOF procedures will also be discussed. Examples will be presented from several tests.

Period-doubling systems as small-signal amplifiers.

Abstract: Near the onset of a period-doubling bifurcation, any dynamical system can be used to amplify perturbations near half the fundamental frequency: The closer the bifurcation point, the greater the amplification. An analytic expression for the frequency response curve is derived explicitly for the driven Duffing oscillator. Results of analog simulations are presented to check the main features of the theory. We propose that the superconducting Josephson parametric amplifier is an example of this amplification process.

Rigorous Hybrid-Mode Analysis of the Transition from Rectangular Waveguide to Shielded Dielectric Image Guide

Abstract: The transition waveguide to shielded and dielectric image guide is analyzed by the rigorous hybrid-mode field expansion technique where higher order mode coupling effects are taken into account directly, also below the corresponding cutoff frequency. The solution of the related eigenvalue problem includes waves with a complex propagation constant although the guide is assumed to be lossless. Calculated diagrams of the propagation constant as a function of frequency, as well as of the permittivity, illustrate the complicated mode conversion between evanescent modes, complex waves, backward waves, and propagating waves. For the three-dimensional scattering problem, the calculated magnitude of the input reflection coefficient agrees well with measurements, whereas the transmission-line theory applied to this structure leads to wrong results.

A Frequency Domain Approach to Water Quality Modeling in Groundwater: Theory

Abstract: A method for the analysis of complex temporal variations of environmental tracers or pollution time series in groundwater is examined using spectral analysis and linear filter theory for stationary stochastic processes. The interpretation of solute fluctuations subject to a time varying source is accomplished via frequency domain solutions to stochastic differential equations for three widely applied transport models: (1) a lumped parameter or linear reservoir model; (2) convective (advective) transport in a curvilinear flow field; and (3) convective-dispersive transport in a uniform flow field. Frequency domain solutions are presented in terms of the theoretical transfer function and phase spectra which describe the amplitude attenuation and phase lag between frequencies in the input and output. A comparison of the frequency response of the three models indicates that the unique filtering characteristics of each may provide a diagnostic tool for matching the appropriate theory to a sampled water quality “signal.” A procedure is suggested for parameter estimation which involves comparison of the theoretical and field estimated transfer function and phase spectra.

Automatic transmission system for vehicles

Abstract: An automatic transmission system for a vehicle in which the gear change operations are carried out in response to a condition signal relating to the speed of an internal combustion engine, which is determined by detecting the operating speed of a brake pedal of the vehicle and a variable filter circuit for receiving the condition signal and for removing any high frequency component of the condition signal, the frequency response characteristics of the variable filter circuit being changeable in response to the operating speed of a brake pedal means. The system is controlled in response to an output signal derived from the variable filter circuit so as to shift the transmission into a gear position determined on the basis of a predetermined map data in response to the operating condition of the vehicle at each instant, whereby the gear change operation can be carried out so as to match the actual operating condition of the vehicle.

Small-Signal Model for the Series Resonant Converter

Abstract: The results of a previous discrete-time model of the series resonant dc-dc converter are reviewed and from these a small signal dynamic model is derived. This model is valid for low frequencies and is based on the modulation of the diode conduction angle for control. The basic converter is modeled separately from its output filter to facilitate the use of these results for design purposes. Experimental results are presented.

Magnitude and phase characteristics of frequency modulation in directly modulated GaAlAs semiconductor diode lasers

Abstract: The magnitude and phase of the small-signal injection current-to-frequency modulation transfer function in GaAlAs semiconductor diode lasers has been measured over the frequency range 100 Hz-1300 MHz using network analyzers. Channeled substrate planar (CSP), buried heterostructure (BH), and crank transverse junction stripe (TJS) laser structures were investigated and will be compared. Approximately 180, 180, and 90° phase differences between the low frequency, thermal frequency modulation (FM), and the high-frequency carrier-density FM was observed for BH, TJS, and CSP laser structures, respectively. The origin of this phase difference and its implications for FM optical communications will be discussed, A rate equation analysis for small-signal injection current modulation (using Mason's flowgraph representation) indicates the presence of a real-axis left half-plane zero in the carrier-density small-signal frequency modulation response. Experimental evidence for this feature has been observed in the measured injection current-to-FM transfer functions.

Steady‐State Dynamic Analysis of Hysteretic Systems

Abstract: A great many hysteretic models have been recently introduced in the analysis of dynamic behavior of structures and structural elements. This paper considers the steady‐state oscillations of single‐degree‐of‐freedom systems with different force‐deflection relationships. Three types of constitutive laws are covered: bilinear, stiffness degrading, and stiffness‐strength degrading. An approximate solution to the equation of motion under sinusoidal excitations is obtained by an analytical procedure and the frequency response curves are drawn. All the models exhibit softening behavior but while the bilinear and the Ramberg‐Osgood type models give stable and single‐valued response curves, the stiffness and the stiffness‐strength degrading models exhibit a multi‐valued curve in a certain frequency range. The results obtained are verified by numerically integrating the equation of motion. Numerical solutions are also used to predict the actual response of systems with unstable frequency response curve to general e...

Frequency domain solutions to multi-degree-of-freedom, dry friction damped systems under periodic excitation

Abstract: The anticipated low damping level in large space structures (LSS) has been a major concern for the designers of these structures. Low damping degrades the free response and complicates the design of shape and attitude controllers for flexible spacecraft. Dry friction damping has been considered as a means of increasing the passive damping of LSS, by placing it in the joints and connecting junctures of structures. However, dry friction is highly nonlinear and, hence, analytical investigations are difficult to perform. Here, a multi-harmonic, frequency domain solution technique is developed and applied to a multi-DOF, dry friction damped system. It is seen that the multi-harmonic method is much more accurate than traditional, one harmonic solution methods. The method also compares well with time integration. Finally, comparisons are made with experimental results.

Gallium arsenide traveling-wave field-effect transistors

Abstract: The design, modeling, and fabrication of a GaAs traveling-wave field-effect transistor (TWF) is reported. The TWF described is a device with a single continuous 1-µm-long gate and a total width of 3 mm which shows flat band gain from 1 to 10 GHz with the potential of much wider band performance (1-40 GHz) and high gains. An advanced theoretical model is presented which performs a full coupled transmission line modal analysis for three lines (source gate and drain) using ab.initio calculations of interelectrode capacitance and inductance matrices. Good agreement is demonstrated between theory and experiment for frequency gain response measurements using balanced feed circuits.

Analysis of Multilayer Interconnection Lines for a High-Speed Digital Integrated Circuit

Abstract: A general method for the analysis of multilayer interconnection lines is presented. This method is capable of predicting frequency dispersion of the transmission-line parameters and is useful for accurately investigating the coupling phenomena among adjacent lines and the input and output impedance relations.

Exact dynamically convergent calculations of the frequency-dependent density response function.

Abstract: A general expression for the response function is derived by the method of recurrence relations. Memory effects appear as corrections to the dynamic random-phase-approximation form. The dynamic structure for the three-dimensional electron gas is calculated to third order and compared with Al data at a large wave vector. Also shown is the dynamic local-field term.

Double Dielectric-Slab-Filled Waveguide Phase Shifter

Abstract: A field theory method based on the orthogonal expansion into eigenmodes is presented for the design of double dielectric-slab-filled waveguide phase shifters with linearly tapered sections. Prototypes of 90° differential phase shift with reference to a corresponding empty waveguide of the same length achieved typically about +-4° phase error and less than -30-dB input reflection within +-5-percent bandwidth, for WR 102-band (7-11 GHz) through WR 28-band (26.5-40 GHz) waveguides. Design curves for differential phase shifts of 12.25°, 22.5°, 45°, 90°, 180°, and 270° are given. Utilizing the differential phase compensation effect of the dispersive behavior of the dielectric-filled and empty reference waveguides, the phase error is only +-1° within +-8.5-percent bandwidth. Further investigations include composite phase shifters, mechanical lateral displacement, and tolerance influences. An experimental 90° phase shifter for 14-GHz midband frequency shows good agreement between theory and measurements.

Optical-fiber diagnosis using optical-frequency-domain reflectometry

Abstract: Temporal signatures (reflection impulse responses) of optical fibers are obtained as the inverse Fourier transforms of the optical-frequency-domain reflectometry (OFDR) data. In this OFDR system, the entire process is automated. The modulation frequency is changed stepwise to obtain an exact inverse Fourier transform. The experimental results are in good agreement with those obtained by computer simulations.

Harmonic Analysis Of Induction Watthour Meter Performance

Abstract: A mathematical nonlinear model is developed to simulate the performance of an induction watthour meter for nonsinusoidal voltage and current waves. The computation results show that for the special case where the voltage is purely sinusoidal, the measurement error causedby the nonlinear magnetic circuits is generally small unless the current wave contains a relatively large third harmonic component. However, when the voltage and current waves are both nonsinusoidal, the registration error can be relatively large even for a small voltage distortion. This is attributed not only to the nonlinearity but also to the drooping frequency response curve of the meter. In both cases, the sign of the registration error depends largely on the phase angles of voltage and current harmonics with respect to their fundamentals. A comparison shows that the computation results are consistent with the experimental ones which are available in the literature.

Frequency-Domain Identification of XV-15 Tilt-Rotor Aircraft Dynamics in Hovering Flight

Abstract: Frequency-domain methods are used to identify the open-loop dynamics of the XV-15 tilt-rotor aircraft from flight tests. Piloting and data analysis techniques are presented to determine frequency response plots and equivalent transfer function models. The open-loop pitch and roll dynamics for the hover flight condition exhibit unstable low-frequency oscillations, whereas the dynamics in the remaining degrees of freedom are lightly damped and generally decoupled. Comparisons of XV-15 flight-test and simulator data are more favorable for high-frequency inputs (omega greater than 1.0 rad/sec) than low-frequency inputs. Time-domain comparisons of the extracted transfer functions with step response flight data are very favorable, even for large amplitude motions. The results presented in this paper demonstrate the utility of the frequency-domain techniques for dynamics identification and simulator fidelity studies.

Microprocessor Implementation of a Fast and Simultaneous Amplitude and Frequency Detector for Sinusoidal Signals

Abstract: A microprocessor-controlled implementation of a fast and simultaneous amplitude and frequency detector for sinusoidal signals is introduced. The method computes the amplitude and frequency from three successive samples of the input signal. A special feature is that the samples are taken within a fraction of the period of the signal being measured, thereby minimizing the measurement time. Automatic selection of the sampling interval is based on the input frequency range.

Optical radar system

Abstract: An optical radar system comprising a transmitter (20), a receiver (22), a signal processor (200) and means (202, 206) for conveying a return signal from the receiver to the signal processor. The transmitter comprises a laser diode (50), an avalanche transistor (52), a capacitor (56) and a trigger generator (58). The laser diode, avalanche transistor and capacitor are arranged so as to minimize the combined effects of self-inductance and stray capacitance, thereby enhancing the speed and power of the optical pulses. The receiver comprises a reverse biased photodiode capacitively coupled to a dual gate GaAsFET. The transmitter and reciever are connected to the signal processor via coaxial cable (206) and cable amplifiers (202). The cable amplifiers are selected to compensate for the high frequency attenuation of the coaxial cable, such that the combined cable/cable amplifier transmission system has an essentially flat frequency response up to 1000 MHz.

Detection of harmonic burst signals

Abstract: The proposed procedure and the corresponding circuits for the recognition of a frequency from a set of possible input frequencies in the frame of a time-window interval seem to be advantageous as they lead to simpler hardware than the well-known energy detector. A unique feature is the single channel processing possibility. In addition the decision on the presence or absence of a given frequency is much faster than with a filter bank of resonators in a nearly lossless resonators. the frequency response is however not monotonic in frequency but has a somewhat periodic shape. the cases of the real lossy or unstable circuits are also dealt with. Some aspects of circuit realizations are given.

Methods and apparatus for measuring relative gain and phase of voltage input signals versus voltage output signals

Abstract: A system for accurately measuring frequency response (phase and gain) in either a wireless or in a wired mode of operation is described. When used in either mode, a multiplexing method is employed which allows the use of a narrow channel bandwidth, with a simultaneous improvement in overall accuracy. Cancellation of all linear and time invariant errors, including those of the analog to digital conversion process, is thus accomplished. As a result, the system error only depends on the differential nonlinearity of the channel.

Low-frequency characterization of PWM converters

Abstract: Low-frequency components of states or outputs in PWM dc and ac converters can be characterized by differential equations called describing equations. These equations are derived by inspection of converter topology and use of switching functions and duty ratios. Their steady-state and small-signal dynamic solution shows how energy-storage elements in a converter/load system shape the frequency response of conversion functions established by the switches.