Showing papers on "Fundamental frequency published in 1969"

High efficiency klystron amplifier

Abstract: A klystron amplifier yielding above 65 percent efficiency at the 100 kW power level at a frequency of 800 MHz will be described. The high efficiency is obtained by using a novel combination of second harmonic and fundamental frequency cavities in the buncher system.

MICROWAVE FREQUENCY ACOUSTIC SURFACE WAVE PROPAGATION LOSSES IN LiNbO3

Abstract: Deflection of laser light has been used to measure room‐temperature acoustic surface wave propagation losses in LiNbO3 at both 1 and 2 GHz. In addition, surface wave delay lines operating at 1 GHz using fundamental frequency interdigital transducers and at 2 and 3 GHz using 3rd and 5th harmonic frequencies are described.

Pitch Control and Pitch Paradoxes Demonstrated with Computer‐Synthesized Sounds

Abstract: Using computer‐generated sounds, R. N. Shepard has demonstrated circularity in judgments of relative pitch [J. Acoust. Soc. Amer. 36, 2346–2353 (1964)]. Other unusual sounds will be presented, including endlessly descending glissandi; a succession of periodic tones that are perceived as going down in pitch although the final pitch is perceived as higher than the original pitch; successions of periodic tones that are perceived as going both up and down in pitch. Most of these sounds consist of octave components; the fundamental frequency can be varied and the spectral envelope can be shifted, independently of the fundamental frequency, along the frequency axis. The way some of these sounds are perceived supports the view that pitch perception cannot always be adequately represented by a linear scale, but rather implies a circular component (“tonality”) and a linear component (“tone height”), which can vary independently for specially contrived stimuli. [Work supported by the Delegation Generale a la Recher...

Digital Walsh-Fourier Analysis of Periodic Waveforms

Abstract: A digital process is described for obtaining the Walsh-Fourier series of a periodic waveform, which requires at most two cycles of the waveform under measurement The first cycle of the periodic waveform is required for the determination of period The coefficients of the Walsh-Fourier series are obtained during the second cycle only, and they are available at the end of the cycle Given the Walsh-Fourier coefficients of the periodic wave, the individual sine and cosine components of its Fourier series may be obtained using conversion formulas Special features of the process are that there are no theoretical low-frequency limitations, and for an instrument with an internal clock whose frequency lies in the range 1 Hz to 1 MHz, the fundamental frequency component of a signal that can be analyzed would be in the range 1 cycle in 116 days to 60 Hz Also, whereas the digital processes required to obtain a Fourier series directly are complicated by the need to multiply sample values of voltage by sines and cosines, which are themselves functions of time, determination of Walsh-Fourier coefficients is achieved very simply by using gating circuits Generation of the required Walsh functions for a periodic signal of any fundamental frequency within the design range has been achieved

Acoustic detection apparatus

Abstract: 1,268,640. Acoustic detection of gas bubbles in blood. NATIONAL RESEARCH DEVELOPMENT CORP. 29 May, 1969 [31 May, 1968], No. 26072/68. Heading H4D. Apparatus for detecting decompression bubbles in a diver's blood comprises a transducer for application to his skin to transmit an acoustic wave of predetermined frequency through the blood, and acoustic detection means tuned to respond to acoustic waves of a related frequency generated in the blood due to non-linearity of its acoustic propagation characteristics. In one arrangement, a transmitting transducer coupled to the liquid is energized by an oscillator via an amplifier and a narrow-band filter tuned to the oscillator fundamental frequency. The same or a spaced separate skincontacting transducer is used as a receiver and is connected to an amplifier and amplitudeindicating device via a filter tuned to a harmonic (e.g. the second) or sub-harmonic of the transmitted frequency. The amplitude of the received acoustic signal at the fundamental frequency may additionally be monitored. Spurious pick-up at the desired harmonic or sub-harmonic frequency, due to non-linearity of the transducer or transducers, can be cancelled by initial adjustment of a phase-shifter and attenuator connected across the transmitter filter, the transducer(s) being arranged in air or applied to a person with bubble-free blood. In a modification the transmitted acoustic signal has two distinct frequency components and the receiver arrangement is tuned to detect the sum or difference frequency generated by the non-linearity.

Steady-state analysis and stability of a magnetic frequency tripler

Abstract: A magnetic frequency tripler is a nonlinear device that is used to produce third-harmonic frequency output from a three-phase fundamental frequency source. Previous analyses of triplers assumed that the undesired harmonic currents generated by the magnetic cores could be returned to the input lines. In order to improve the performance of a frequency tripler, input-line filters are required. The presence of line filters influences profoundly the behavior of the device since harmonic voltage components other than the fundamental are allowed to exist at the frequency tripler terminals. In this paper a method is presented to analyze a line-filtered magnetic frequency tripler, and to investigate its stability.

Error reduction logic network for harmonic measurement system

Abstract: The fundamental period of a complex periodic signal may be determined by measuring the periods of individual harmonics of the periodic signal and finding their smallest common multiple. A useful display of harmonics and their submultiples is called a period histogram. Since the fundamental period in a period histogram is an integral multiple of a number of harmonics and is characterized by a maximum amplitude pulse, the time of occurrence of the first maximum pulse may be taken to represent the fundamental period of the complex periodic signal. However, because the largest peak of the histogram does not always correspond to the fundamental frequency of a wave, occasional errors in the indication of pitch may result. Such errors may be obviated by examining the pitch signal developed from a histogram measurement, applying logical tests to determine its acceptability and, if the indicated pitch is found to be unacceptable, by substituting a more acceptable value.

Thermo-elastic Rayleigh waves in transversely isotropic solids

Abstract: The frequency equation of the thermo-elastic Rayleigh waves in a semi-infinite transversely isotropic solid has been obtained. The form of the frequency equation for small values of the reduced frequency has also been deduced, and it is found that, as in the isotropic medium, the velocity does not depend on the frequency. But unlike the isotropic case, the velocity depends upon the thermal constants as well.

Mode-locked frequency doubled laser

Abstract: This laser comprises an intracavity nonlinear crystal that converts fundamental frequency laser light to second harmonic light and is also modulated to mode lock the laser The modulation voltage, and thus the modulation depth, is varied to optimize the magnitude of the second harmonic power produced by the crystal

Fm receiver self-test circuit

Abstract: A self-testing equipment for a frequency-modulated receiver includes a pulse generator rich in harmonics and having a repetition frequency chosen such that the fundamental frequency is substantially equal to the channel spacing of the FM receiver being tested. The supply voltage for the pulse generator is derived from a power supply generator which produces a pulsating voltage varying periodically at a relatively slow rate. This voltage is applied to the pulse generator and serves to modulate the frequency of the pulse generator at the same rate. The accompanying harmonics of the pulse generator are also modulated but at a correspondingly high rate lying within the audio bandwidths of each receiver channel. Inserted between the power supply generator and the pulse generator is a time constant network which permits the supply voltage to vary exponentially during each power supply period. In this way, the frequency deviation of the pulse generator is controlled.

Fundamental-frequency eddy-current loss due to rotating magnetic field. Part 1: Eddy-current loss in solid rotors

Abstract: The flux penetration in solid ferromagnetic cores is analysed without using the simplifying assumption that the B/H curve is a straight line, or a limiting step function. The nonlinear variation of the fundamental B1/H curve is included in its entirety by substituting the equation B1 = KH1–2/n, which fits the magnetisation curve very well, especially beyond the knee portion. The theory is applied to induction motors with solid-iron secondaries, and solutions are obtained for flux and current densities, rotor power factor and eddy-current loss. Simplified expressions are given for easy numerical calculation. Substitution of n = 2 in the equations leads to results which have already been obtained in previous literature using the limiting B/H curve. Results of experimental work carried out on a solid-rotor induction motor are also presented. Curves are given to obtain the eddy-current loss per unit surface of any given solid rotor, operating at any given slip, and with any surface magnetising force. This virtually eliminates numerical calculations when the theory is applied to a new solid-rotor machine.

Analysis of Fundamental Frequency Contours

Abstract: Fundamental frequency contours for several simple declarative sentences were estimated using a computer‐simulated pitch extractor. Measurements were obtained for three American male speakers repeating each of three sentences three times. The speakers were instructed as to which syllables should be emphasized in each sentence. The purpose of the experiment was to determine which aspects of the fundamental frequency contour reflect vowel stress and which aspects reflect characteristics of individual speakers. The stressed vowel regions of the fundamental frequency contours were found to be easily identifiable across speakers and replications. In addition, the variability of the contours during unstressed regions appeared to be greater than that for the stressed vowel regions. This result suggests that in modeling fundamental frequency contours greater weight should be attached to deviations between observed and predicted values in the stressed vowel regions.

Vibration of a Symmetric Tuning-Fork

Abstract: The paper records an investigation of the vibration of a symmetric tuning-fork, with particular reference to the effects of the fork mounting. The relation between flexural vibration of the tines and longitudinal vibration of the fork as a whole is analysed in terms of the coupling induced by unbalanced inertia forces directed parallel to the axis of the stem. It is shown theoretically and confirmed experimentally that longitudinal oscillations can occur at fork frequency and twice fork frequency, and that the fundamental frequency of the fork is affected by the mounting characteristics if there is primary longitudinal unbalance. A method is described whereby the primary component of longitudinal unbalance may be eliminated.

Use of an interactive laboratory computer to study an acoustic-oscillator model of the vocal cords

Abstract: A Honeywell DDP-516 computer is used with an interactive program to study an acoustic-oscillator model of the vocal cords. The program includes a simulated vocal tract. Iterative solutions are obtained to difference equations which describe the acoustic volume velocity through the cords and the sound pressure output at the mouth. The results can be printed, displayed on a scope, or D/A converted for auditory assessment. A fast Fourier transform provides spectral analysis of the synthesized signals. Parameters that the experimenter can specify from the console include, 1) subglottal pressure, 2) vocal cord tension, 3) vocal tract shape, 4) air density and 5) sound velocity. Results show that tract configuration, and hence acoustic load on the cords, substantially influences fundamental frequency of voicing. Fundamental frequency is also found to be a monotonic function of sub-glottal pressure and cord tension, other factors being constant. Increasing air density tends to reduce fundamental frequency, while changes in sound velocity affect it negligibly.

Phase shift circuit for phase controlled rectifiers

Abstract: A phase shift circuit for use with a controllable three-phase rectifier system wherein a frequency of 3 times the fundamental is generated, clipped, passed through an integrator to make a sinusoidal voltage and then amplified and limited to provide an alternating square wave at 3 times the fundamental frequency. Ramp voltages are developed with reset to zero at intervals in accordance with the square wave of voltage and these ramp voltages are compared with a variable DC voltage to achieve a phase shiftable initiation point for rectangular blocks of voltage to control the gating of the thyristors in the rectifier system.

A device for automatic modification of vocal frequency and intensity

Abstract: A system for automatic control of fundamental vocal frequency and intensity is described. The system is essentially a frequency and intensity discriminating circuit which provides immediate feedback information regarding vocal performance in connected speech. Vocal fundamental frequency target areas appropriate to the age and sex of subjects may be selected and varied at will. Applications to the speech of the deaf and to individuals with voice disorders are discussed.

Electromechanical oscillator including a dual vibrator for producing a bent frequency

Abstract: A member whose expansion and elastic properties are minimally affected by temperature, such as invar, is caused to longitudinally vibrate at its fundamental frequency, at a harmonic frequency, or at two frequency modes simultaneously. The vibrations induce corresponding pulses of the two frequencies in tuned circuits to effect a low frequency beat note usable to drive a mechanical output such as a ratchet and pawl for chronometric purposes. A beat frequency of optimum utility is achieved by altering the natural frequencies so that the various harmonics are not exact multiples of the fundamental said alteration being achieved by making the vibratory member nonuniform in section, unit mass, or composition of matter per unit length. A single vibratory member in which two frequencies are generated maintains a constant relationship therebetween despite temperature changes.

Digital speech signal synthesizer

Abstract: Disclosed is an electrical-signal synthesizer for converting digitally coded information associated with at least one electrical signal, whose frequency, amplitude or phase may vary, to analog signals whose frequency, amplitude or phase varies in substantially the same manner as that of the at least one electrical signal. More specifically, the synthesizer is operative to convert a digital signal representative of a first analog signal, such as a voice signal, having varying parameters, such as frequency or amplitude, into an analog output signal which varies in substantially the same manner as the first signal, and where the digital signal is composed of consecutive frames of words, and one word of each frame is representative of a fundamental frequency associated with the first signal at an instant of time, and successive words in the respective frame are representative of the energy associated with at least one of a plurality of successive bands or spectrum segments of the first signal to be reproduced, at the given instant in time, each of the successive bands bearing a predetermined frequency relationship and wherein the synthesis of the output signal is accomplished by generating from the word representative of the fundamental frequency in each respective frame, a stream of digital words representative of the frequency and each of its harmonics at each instant of time and producing therefrom a second stream of digital words which is indicative of the frequency components of the original sound and modulating the second stream with amplitude data corresponding to discrete periods of time and adding the respective digital signals so produced for a discrete period of time and converting the same to an analog signal which is representative of the original voice signal.

Proportional acoustic transducer

Abstract: A proportional acoustic transducer and fluid demodulator. Proportionality of fluid output to acoustic input is achieved by causing a power jet to attach to a semicircular sidewall and directing acoustic signals at the power jet. The angle of deflection of the power jet provides a measure of the amplitude of frequency of the acoustic signal. Sensitivity of the system is greatest when the frequency of the acoustic input is close to the fundamental frequency of the settling chamber from which the power jet is derived.

Fundamental Frequency Estimation by Harmonic Identification

Abstract: A novel method of fundamental frequency estimation is presented utilizing the inherent line spectrum characteristic of the speech signal. After finding the strongest harmonic in a limited frequency range, a computer program determines and examines the expected positions of lower and higher harmonics and assigns the proper harmonic number. An array of previously measured filter responses provides a frequency estimation of the identified harmonic. Two adjacent harmonics are necessary for proper identification, but the fundamental component need not be present in the limited filter bank range. The range of frequency estimation is limited only by hardware and is 75

Harmonic generation using the non-linearity in the hot carrier characteristics of GaAs

Abstract: An approximate theory has been developed for third harmonic generation in GaAs under the application of a large high frequency sinusoidal electric field. The ratio of the third harmonic to the fundamental frequency currents is found to be 0-22 and 015 at fundamental frequencies of 100 GHZ and 450 GHZ respectively, for a field amplitude of 6-7 kv/ cm.

Apparatus and method

Abstract: A method of and an apparatus for cancelling second harmonics in electrical signals resulting from nonlinear devices within electrical networks. The signal applied to the network includes not only the fundamental frequency of interest, but also a component at a frequency equal to the third harmonic of that fundamental frequency. If a nonlinear device is included in the network, energy at new frequencies is generated including components at the frequency of the second harmonic of the fundamental frequency of interest. These second harmonic components are adjusted to cancel each other so that the output has no component at that second harmonic frequency. This cancellation is usable in a broad range of applications including, for example, acoustic couplers utilized in data transmission over telephone networks in which the telephone microphone is nonlinear, causing second harmonics of the transmitted signal which if uncancelled would interfere with received signals during full-duplex operation.

Bridge circuit having plural compensating arms

Abstract: An AC bridge circuit which provides a means for compensating for both in and out of phase components of a fundamental frequency, as well as for harmonics of the fundamental frequency, is disclosed. The bridge utilizes a number of parallel branches (arm pairs) in a compensating leg, each branch having different impedance-versus-frequency characteristics thereby providing for separately compensating for a disparate component or harmonic. Applicable to systems for detection and measurement of a wide variety of electrical, magnetic and optical properties, the circuit is especially useful in conjunction with measurement of very weak magnetic materials, wherein the harmonics resulting from the primary excitation field are of comparable or greater magnitude than the signal generated as a result of exciting the magnetic material. The bridge circuit is shown in a system for displaying hysteresis loops of weakly magnetic materials.

Vibration analyzing apparatus

Abstract: VIBRATION ANALYZING APPARATUS OF THE WATTMETER TYPE, BUT WHEREIN THE WATTMETER IS REPLACED B Y A DEMODULATOR CIRCUIT WHICH DOES NOT REQUIRE CALIBRATION FOR DIFFERENT OPERATING SPEEDS OF A BODY TO BE BALANCED. THE APPARATUS ADDITIONALLY INCORPORATES MEANS INCLUDING A UNIQUE SQUARE WAGE GENERATOR FOR ELIMINATING HARMONICS OTHER THAN THE FUNDAMENTAL FREQUENCY CORRESPONDING TO THE SPEED OF THE BODY BEING BALANCED. THE MEANS FOR ELIMINATING HARMONICS IS NOT A FILTER IN THE TRUE SENSE OF THE WORD, BUT RATHER IS BASED UPON GATING HARMONIC SIGNALS WITH SQUARE WAVE SIGNALS WHEREBY THE AVERAGE DIRECT CURRENT OUTPUT DUE TO HARMONICS WILL ALWAYS BE ZERO.

Nonlinear Interaction of a Microwave Field with a Plasma Slab in a Waveguide

Abstract: The nonlinear interaction of the dominant TE(10) waveguide mode of a fundamental frequency with a plasma slab in an infinitely long rectangular waveguide is analyzed utilizing an approximate technique. Explicit expressions for the first three harmonic components of the electron density and current density in the plasma are given. General expressions for the nonlinearly generated second‐harmonic electric fields are derived. Numerical results show that the second‐harmonic power generated in the TM(11) wave‐guide mode is more than ten times that generated in the TE(11) waveguide mode.

Gas laser exciter

Abstract: A gas laser having a power supply consisting of an overdriven oscillator of relatively low fundamental frequency with an output rich in harmonics. The harmonic content of the power supply output helps to initiate the excitation of the laser; after the gas has been excited the waveform of the power supply output becomes more nearly sinusoidal.

Low-frequency operation of avalanche diodes under large-signal conditions

Abstract: Application of basic Read theory to the operation of avalanche diodes at frequencies of fractions of the transit frequency is found to predict high-efficiency oscillations when a waveform consisting of a low-amplitude fundamental and a larger second harmonic in the appropriate phase is applied. The resultant-circuit current is such that the power output is essentially at the fundamental frequency.