Showing papers on "Linear phase published in 1969"

360/spl deg/ Varactor Linear Phase Modulator

Abstract: Theory is presented which 1) derives the circuit impedance requirements to match the nonlinearity of the varactor reactance-versus-voltage curve to the tangent /spl theta/ curve to obtain 180/spl deg/ linear phase modulation from one diode; 2) gives the value and position of a resistor to make insertion loss invariant with phase; and 3) derives the circuit requirements for combining two 180/spl deg/ diode phase moduIators in an admittance adding network to obtain 360/spl deg/ phase modulation. Experiments are disclosed rising series tuning at 1 GHz providing 360/spl deg/ phase modulation within /spl plusmn/ 3.0 percent of linearity, and using shunt tuning at 5 GHz providing 360/spl deg/ phase modulation within /spl plusmn/ 3.3 percent of linearity. A discussion is given of the application of the modulators to the serrodyne function.

The Design and Synthesis of a Class of Microwave Bandpass Linear Phase Filters

Abstract: This paper is concerned with the design procedure and synthesis of a class of microwave bandpass linear phase filters which simultaneously exhibit a maximally flat amplitude and delay response about band center. In the first part of the paper a systematic procedure is developed for the construction of a nonminimum phase transfer function which exhibits a maximally flat delay and maximally flat amplitude characteristic. In the second part, a synthesis procedure is presented for the realization of the general nth-ordered transfer function by a generalized interdigital network. To simplify the design and construction of this filter, typical characteristics for filters of degree n = 3,4,5,6,7 are graphically presented together with a tabular representation of the polynomials which are required to design the filter. Finally, the results of an experimental filter of degree 3 are incorporated to illustrate that this class of nonminimum phase filters may readily be constructed in practice.

Effects of multipath transmission on the measured propagation delay of an FM signal

Abstract: Position location techniques based on propagation delay have been proposed previously. A narrow-band version of this technique involves the transmission of RF carrier, modulated by a single audio frequency. At a receiver, the audio phase is a measure of distance provided the propagation delay is less than one quarter cycle. The transmission medium introduces multipath distortion and the received signal consists of a set of signals, each an attenuated and delayed replica of the transmitted signal, having traversed a different path. When FM is employed, the phase of the demodulated composite is a nonlinear function of the parameters of the multipath structure of the channel. In this paper, this functional relationship is derived.

Frequency modulated phase-locked oscillator having a low- and high-frequency response

Abstract: In a phase-locked loop frequency modulator, the signal applied to the reference input of the phase comparator is a frequencymodulated signal, modulated at the same rate as the output signal, for low-modulating frequencies. For higher modulating frequencies, the signal applied to the reference input of the phase comparator is a constant frequency source.

General expression for the group delay of digital filters

Abstract: An expression for the group delay of a digital filter is derived in terms of the numerator and denominator polynomials of the transfer function H(z) The application of this expression to three cases is shown, and an important theorem relating to the exact realisability of linear phase digital filters is given

Digital differential angle demodulator

Abstract: A digital differential angle demodulator for use in a high bit rate digital data transmission system utilizing randomly selected voice grade telephone lines is disclosed The demodulator derives a clock signal from an information-representing phase shifted intermediate frequency modulated signal This clock signal is employed to synchronously gate a high frequency counter output into a detector circuit which samples a precise portion of an intermediate frequency signal containing the phase shift information to be ascertained The high speed counter is phase locked to the intermediate frequency carrier so that the zero crossing of the squared intermediate frequency signal will occur at an odd multiple of 225* in the phase value of the output of the binary counter Two separate storage registers in the detector circuit receive the most significant bits of successive counter output values depending upon the phase sampled from the precise portion of the information-containing signal A parallel adder determines the difference between successive counts, each count of which is characteristic of the information-representing phase change originally received during the interval in question Phase locking of the high speed counter assures that random phase changes caused by system noise will not adversely affect the detection operation An encoder converts the phase change signal as emitted by the parallel adder back to its original digital data level format

Pull-In Performance of a Piecewise Linear Phase-Locked Loop

Abstract: This is part of a study concerned with the analysis of phase-locked loops (PLL's). The broad objective throughout this work is to improve upon our general understanding in this important area. More particularly, ly, we are seeking quantitative results indicative of the pull-in behavior of PLL's. In the present paper, we point out some results in foreign publications and focus attention on a paper by Kapranov [1] which is devoted to the study of the pull-in frequency of second-order PLL's with a symmetric phase comparator. We apply the same approach and present results, in closed form, in the more general case where the phase comparator possesses an asymmetric triangular characteristic. Special cases of this phase comparator are the sawtooth and symmetric triangular comparators. It can also be viewed as an approximation to the Tanlock phase comparator. The RC filter case is treated.

Frequency modulator including selectively controllable delay line

Abstract: A frequency modulated HF wave is obtained by applying a HF carrier wave of preselected frequency to a variable phase shifter consisting of a delay line made up of a plurality of switchable delay units controlled by a pulse counter to effect a periodic phase shift of 360*, wide band operation being ensured by correction of the effective capacity of the counter depending on the value of high frequency selected.

Linear phase demodulator

Abstract: A PHASE DEMODULATOR INCLUDING A DUAL CHANNEL QUADRATURE PHASE MODULATOR FOR MODULATING AN INCOMING PHASE MODULATED SIGNAL, A FILTER IN EACH CHANNEL, A FREQUENCY MIXER FOR COMBINING THE PROCESSED SIGNALS FROM THE TWO CHANNELS, A FREQUENCY DISCRIMINATOR, AND AN INTEGRATOR. THE CIRCUIT DOUBLES THE PHASE ARGUMENT OF THE INPUT SIGNAL PRIOR TO DEMODULATION SO THAT THE RESOLUTION OF THE PHASE INFORMATION CAN BE INCREASED, AND THE ACCURACY ENHANCED.

Linear phase digital filter design

Abstract: The results of an investigation of linear phase digital filters are presented. It was determined that stable filters of this type are necessarily nonrecursive. The corresponding transfer function is presented in a general form in terms of basic z-plane pole and zero configurations. The design of digital filters of this form is accomplished by approximating a desired frequency function by one of four types of Fourier series. The types of series correspond to the forms of the z transfer function polynomial, which is either a mirror-image polynomial or a negative mirror-image polynomial, and either even or odd order.

Phase detection and comparison apparatus for determining the phase derivative with respect to frequency of an eddy current test signal

Abstract: An electronic eddy current apparatus for detecting and displaying the phase derivative with respect to frequency of an eddy current flux responsive coil signal A frequency modulated input is applied to a phase detection and comparison system, the output of which is filtered to separate the carried phase component from the phase modulation component, and the phase modulation component is applied to a suitable indicating device to display the phase derivative with respect to frequency This signal is indicative of electrical properties of a test piece which are affected by microstructure, alloy, and so forth of the test piece

Instrumentation for Analog Differentiator at Low Frequencies

Abstract: Sources of errors and noise in analog differentiators are reviewed, together with techniques for minimizing signal distortion. A modified basic operational differentiator is augmented with a linear phase filter. Accurate derivatives are obtained over the range spanning dc to 1 Hz. An inexpensive instrument is presented which reduces noise to a low level while minimizing delay distortion of the signal.

Method of measuring time delay

Abstract: The propagation time of a linear system, defined as the group delay at zero frequency, is given by the time centroid of its response to unit impulse. Based on this, a method of measurement is described which is independent of the shape of either the input or output time functions.

A study of phase advance networks for A.C. control system stabilisation

Abstract: The M;bs oarriet dOnrd± system is discussed and varioUs methods Of applying stabilisation are considered The brldged-T neIWOrk Is designed to produce the characteristic notch response and the resulting modulating frequency characterlston is discussed; The filter is considered from a pole-zero aporoach and the limitations and effects caused by temnerature, component tolerances and carrier frequency drift are considered in detail In chapter 3 an active filter that will produce a symmetrical response is discussed and this provides an improved phase advance chtracteristic when compared to that of the asymmetrical notch response of the bridged-T filter It is also shown that the modulating frequency characteristics of a network which has a linear phase and constant-amplitude characteristic will be virtually unaffected by temperature, component tolerances and significant changes- in carrier frequency; a cascaded filter is designed to produce this type of response The cascaded filter is designed by considering the locations of the poles, and zeros, and a dominant zero analysis technique is developed to obtain an optimum filter response Chapter 4 considers in detail the experimental results for this filter In chapter 5 the response of the cascaded and bridged-P networks to frequency changes is analysed and the theoretical and experimental results compared These networks are then senarately included in a com -olete ac servo system and the response of the system analysed The thesis concludes with a general discussion of the project and analyses the significance of the results

On the wide-band RC phase shifter

Abstract: The design procedure is discussed for an RC phase-shift network which is the same in phase and magnitude over wide frequency bands.

Measurement of Ultrasonic Attenuation and Phase Shift in the Presence of Noise

Abstract: For measuring attenuation by the ultrasonic pulse‐echo method, a selected echo—obtained by pulse modulating a very stable CW carrier—is directly heterodyned to produce a video signal with a beat frequency of a few hertz. This signal is then sampled at the repetition rate and filtered to give a low‐frequency CW output with a signal‐to‐noise ratio some 30 dB greater than for the selected echo. Phase shift at the wave frequency produces an equal phase shift at the beat frequency, and can be measured with a phase meter. The detection system is sensitive for weak signals and is linear. Readout of amplitude and phase can be made on standard recorders. In a second arrangement, the selected echo is added algebraically to a reference signal having a slightly different frequency. with the CW beat frequency resulting processed as before. Because of the good phase stability, this method can be used at frequencies in the high megahertz range.

Two-channel frequency converter with quartz filters

Abstract: The method described for reproducing phase shifts between two voltages at elevated and high frequencies can be recommended as a beginning in constructing standard phase measuring apparatus.

Measurement of Nonlinear Phase Distortion in Microwave Limiters under Dynamic Conditions

Abstract: Nonlinear phase distortion (amplitude-modulation to phase-modulation conversion) in microwave limiters can be different under static and dynamic conditions. A technique for measurement of dynamic phase distortion is described in which a two-tone test signal is used to simulate amplitude modulation with modulating frequencies of the order of megahertz. The two-tone test signal is generated by linearly summing two equal-amplitude sine waves. The result is a constant-frequency amplitude-modulated signal whose envelope varies as a rectified cosine wave at the beat frequency of the two sine waves. There is no phase deviation except at the envelope zeros, where the phase jumps 180°. Measurements are made by splitting the output signal from the limiter into two identical signals and delaying one relative to the other by approximately an odd multiple of one-half the envelope period. The two signals, when displayed on an X-Y cathode-ray tube, produce a pair of filled-in ellipses with major axes at 45° and and 135°. Peak phase deviation is obtained by direct measurement of either ellipse. Measurement data in E band are given for two tunnel-diode amplifier-limiters, a balanced mixer-limiter, and a traveling-wave-tube amplifier followed by a balanced mixer-limiter.

An improvement of the phase stabilization of a simple microwave interferometer

Abstract: In order to obtain a good phase stabilization of the output signal of a simple microwave interferometer for plasma electron density measurements, it has been suggested that both paths of the interferometer should have the same electrical length. It can be shown, both theoretically and experimentally, that by deriving the output signal from the point where the first derivative of the phase to the frequency is equal to zero, a much better phase stabilization can be reached. In a 70 GHz device with an open path, having a length of 960 mm, a change of 100 MHz in the frequency and an uncertainty of 1 mm in the length of the path, cause a calculated phase alteration of 0·4°. In the point, given by the principle of equal electrical length, the same change in the frequency would cause a phase alteration of about 100°.

State equations for delay systems

Abstract: It is demonstrated that feedback delay in a linear system leads naturally to a state formulation with delays in the control variable. Equations that reduce to 'normal form' equations for the nondelay case are given for a single-input single-output system with a single delay. The system coefficient matrices are given as solutions of linear equations involving the coefficients in the input-output representation.