Showing papers on "Fundamental frequency published in 1980"

Magnetic surveillance system with odd-even harmonic and phase discrimination

Abstract: Apparatus for detecting the presence within a surveillance zone of a body of high permeability material creates a surveillance field varying sinusoidally at a fundamental frequency. Parallel filter channels select the second and third harmonic components of the perturbations created by said material when present in the field and the phase of the second harmonic relative to a reference signal is compared. The signal level of each of the second and third harmonic components as well as the aforesaid phase congruency cooperatively control an alarm circuit. Rhomboid shaped transmitter coils surrounding figure "8" receiver coils improve coupling to the high permeability body.

A comparison of contact microphone and electroglottograph for the measurement of vocal fundamental frequency.

Abstract: Signals from a throat contact microphone or an electroglottograph often are more suited for fundamental frequency measurements with simple analog circuits than the radiated speech signal. This report compares a contact (accelerometer) microphone placed on the neck below the cricoid cartilage and an electroglottograph for measurement of fundamental frequency in connected speech. The advantages and drawbacks of the two methods are discussed.

Frequency measuring and monitoring apparatus, methods and systems

Abstract: Waveform frequency measuring apparatus and methods utilizing zero-crossing triggered analog-to-digital conversion apparatus combined with Discrete Fourier Transform (DFT) digital computing apparatus accomplish measurement of waveform fundamental frequency using hitherto disadvantageous leakage of the Discrete Fourier Transform. In an example, the frequency measuring apparatus and methods are used in an alternating current (AC) electrical power system for measuring and monitoring frequency deviation Δf from the nominal system frequency f and actuating protective relaying when the frequency deviation is excessive.

Auditory-nerve fiber encoding of two-tone approximations to steady-state vowels.

Abstract: Responses to two harmonically related tones, approximating the lowest formants of nine American English vowels, were recorded from single auditory‐nerve fibers. Data were compiled as period histograms for tones presented singly and in combination using the fundamental frequency of the two‐tone complex as the time base. The amplitudes of the primary frequency components present in a histogram were estimated by least squares fitting a half‐wave rectified sum of the stimulating sinusoids plus a constant. Nonlinear interactions resulted for most two‐tone stimuli: one tone dominated the response. When one tone was equal to best frequency, that tone always controlled discharge timing, usually suppressing the response to the second tone. Complicated interactions took place when the stimulating frequencies bracketed best frequency. The tone nearest best frequency was most effective near threshold, while higher stimulus levels usually favored the low‐frequency tone. Nevertheless, the suppression mechanisms appear to provide an effective spatial separation in the cochlea for the response components to each vowel approximation. Fourier analysis of the period histograms yielded qualitatively similar results.

Digital frequency follower for electronic musical instruments

Abstract: In an electronic musical instrument apparatus is provided for generating musical sounds having a fundamental frequency which tracks the fundamental frequency of a time varying external control signal. A matched filter is used to generate frequency control signals which are determined by a closeness criterion between the external control signal and an internally generated test signal. Provision is made for offsetting the generated musical sounds for a preselected musical interval from the fundamental frequency of the external control signal.

Method and apparatus for frequency doubling a laser beam

Abstract: A method and apparatus for providing coincident orthogonally-polarized laser beams having twice the frequency of a fundamental frequency emitted by a laser source is disclosed. A second harmonic generator within a laser resonator cavity causes frequency-doubled laser beams to travel in opposite directions along an axis thereon. One of the beams undergoes a polarization change of substantially 90° and is returned for travel along the laser axis in the same direction as a second frequency-doubled beam which has not undergone a polarization change. The orthogonally-polarized beams are then emitted through an output mirror designed for transmitting beams of twice the frequency of the fundamental beam.

Automatic apparatus, based upon a nickel-tube resonator, for measuring the complex shear modulus of liquids in the kHz range

Abstract: An apparatus for the measurement of liquid-shear impedance in the frequency range 11–170 kHz using a thin-walled nickel-tube resonator is described. The working principle of the method used has been previously published. Compared with the prototype the most important advances in the design concern the suspension of the resonator and complete automatization of the measurements and data handling. At the cost of not measuring at the fundamental frequency accuracy and ease of operation are greatly improved. Results for Newtonian and viscoelastic liquids are presented. Comparison with other types of apparatus is made.

Narrow-band-pass switching follower filter having n switched paths

Abstract: In a switching follower filter of the narrow-band-pass type having n switched paths for filtering a signal having a useful component of variable frequency associated with a high background noise, the fundamental frequency of the input signal is captured and then followed by collecting a pre-filtered switching synchronization signal so that part of the input signal remains in the pre-filtered signal.

Phased array sonar

Abstract: PURPOSE:To markedly simplify a transmission beam former, by separately performing the delay of an envelope and the setting of the local phase of each element assuming the band limitedness of a probe without performing the delay of each channel of a delay map in a high frequency signal stage. CONSTITUTION:The data of the pulse width, delay quantity or the like of the output signal of each channel are successively inputted as control words. An oscillator 2 oscillates a high frequency signal having a frequency f1 sixteen times of the fundamental frequency f0 at the same time when a power supply is turned ON and a frequency divider 3 divides the frequency of said signal to output the fundamental frequency. When a transmission trigger is inputted, an MV1 generates an envelope pulse having a pulse width prescribed by control word input at every transmission trigger. A SIPU SSR 6 outputs the control words to a VLSR 5 as parallel words with respect to the serial input of said control words to give the data delaying the output pulse of the MV on the basis of the output clock phiE of a clock generator 4 to the VLSR 5 and the output signal E thereof becomes a signal coupled with the signal input having the fundamental frequency by an AND circuit 7 to be outputted. A VLSR 8 delays a signal B in the same way as the VLSR 5 to output a signal B'.

Apparatus for harmonic oscillation analysis

Abstract: Apparatus for harmonic oscillation analysis includes a detector for taking up, as electric oscillation, mechanical vibration generated during the operation of a rotary machine system, a comb filter for extracting from the detector's output signal having a composite periodic oscillation wave form only fundamental wave component of a determined fundamental frequency fo and its harmonic wave component, and a clock pulse generator for generating clock pulses to drive the comb filter by the clock pulse having the fundamental frequency fo and a discriminator for evaluating abnormality of the rotary machine system depending upon the particular signal components extracted through the comb filter.

Method of minimizing resonance in stepping motor and improved driver therefor

Abstract: A stepping motor driver is adjusted to minimize resonance by adjusting a variable frequency source to adjust the fundamental frequency of the drive to the frequency of a filter, driving the driver and motor with the adjusted frequency source, sensing the motion of the motor and providing the sensed motion to an indicator through the filter. The driver is adjusted to minimize the indication. Adjustment at various harmonics are performed by using 1/N the adjusted frequency, where N is the harmonic of interest. The improved driver includes a plurality of voltage sources adjustable for resonance compensation at the fundamental frequency and 1/N thereof. DC offset, relative gain and orthogonality of the motor driver signal adjustments are provided.

Beamed microwave power transmitting and receiving subsystems radiation characteristics

Abstract: Measured characteristics of the spectrum of typical converters and the distribution of radiated Radio Frequency (RF) energy from the terminals (transmitting antenna and rectenna) of a beamed microwave power subsystem are presented for small transmitting and receiving S-band (2.45 GHz) subarrays. Noise and harmonic levels of tube and solid-state RF power amplifiers are shown. The RF patterns and envelope of a 64 element slotted waveguide antenna are given for the fundamental frequency and harmonics through the fifth. Reflected fundamental and harmonic patterns through the fourth for a 42 element rectenna subarray are presented for various dc load and illumination conditions. Bandwidth measurements for the waveguide antenna and rectenna are shown.

Speech Transformation System (Spectrum and/or Excitation) without Pitch Extraction.

Abstract: : A new speech analysis-synthesis system has been developed which is capable of independent manipulation of the fundamental frequency and spectral envelope of a speech waveform. The system deconvolves the original speech with the spectral-envelope estimate to obtain a model for the excitation. Hence, explicit pitch extraction is not required. As a consequence, the transformed speech is more natural sounding than would be the case if the excitation were modeled as a sequence of pulses. The system has applications in the areas of voice modification, baseband-excited vocoders, time-scale modification, and frequency compression as an aid to the partially deaf. (Author)

Interaction effects in marine seismic source arrays

Abstract: Past design of marine source arrays has been based on one or more of the following principles: (i) simultaneous operation of multiple identical sources to increase radiated signal strength by simple addition; (ii) superposition of wavelets of different fundamental frequency to achieve a total pulse of desired, front-loaded form (e.g. mixed volume air-gun arrays); (iii) horizontal spacing of units or groups to achieve spatial filtering effects. The phenomenon of interaction between sources, affecting the loading experienced by each, has usually been ignored, or else avoided by wide spacing of units. However, interactions can significantly affect the efficiency and frequency response, in a way that can be favourable. Calculations are presented for sources emitting continuous or long duration signals, showing the energy efficiency as a function of frequency for arrays in a variety of configurations. Interaction effects are significant for inter-source spacings smaller than or comparable with the wavelength—not, as is often stated, up to a distance related to the radii of the sources. The results show that potential exists for tailoring the frequency response of a source system, according to the application, by simple spatial rearrangement of units. Similar effects occur with interacting impulsive sources, but it is shown that different criteria apply for the optimum arrangements of units.

Sinusoidal output generator

Abstract: In the disclosed device, a square wave generator drives a network composed of a parallel resonant circuit in series with a series resonant circuit. The resonant frequency of the parallel resonant circuit is substantially equal to the fundamental frequency of the square wave voltage generator and lower than the resonant frequency of the series resonant circuit. The resonant frequency of the series resonant circuit is lower than the frequency of the third harmonic of the square wave voltage generator. A load coupleable to the parallel resonant circuit has a complex impedance which shifts the current at the fundamental frequency about 30° relative to the fundamental square wave voltage.

Inverter control circuit

Abstract: PURPOSE:To retain equal radio waveforms of respective phases and readily switch the waveform shape of an inverter by synthesizing symmetrical triangular wave repeated in front and rear half periods and a standard value with a gate signal and controlling the number of pulses to the number of standard value CONSTITUTION:A signal 3072f obtained by the 3072 times of the inverter fundamental frequency f if applied to a 1/512 frequency divider 1 and an up and down counter 2 The frequency divider 1 thus produces its output signal of six times of the inverter fundamental frequency f, which is applied to a sexenary ring counter 3 and to the up and down counter 2 as an up and down instruction The counter 2 produces upon reception of the input a triangular wave TRI This wave TRI is applied to one input of a digital comparator 4 The comparator 4 receives at its other input information from a memory 5 to comapare the wave TRI with the information The address of the memory 5 is determined by the output F of a frequency detecting circuit 6 The output of the comparator 4 is processed in a logic processor 7, which thereupon produces a modulation control signal L, which is then applied to a waveform synthesizer 8, which synthesizes the signal L with the input to the counter 3 to thereby produce a gate signal

Maximum likelihood detection and estimation for harmonic sets

Abstract: Starting from first principles, the optimum receiver for the detection of a harmonic set embedded in white Gaussian noise is derived. The receiver obtained also provides the maximum likelihood estimate of the fundamental frequency of the harmonic set. Three signal conditions are studied: (1) the harmonic amplitudes are known exactly, (2) the harmonic amplitudes are unknown, but have known, independent probability distributions, and (3) the harmonic amplitudes are unknown and have unknown, independent probability distributions. For cases (1) and (2) the optimum receivers are derived. For case (3) the receiver obtained cannot be claimed to be optimum; however, it does have intuitive appeal. In each case the receiver cross correlates the (transformed) spectral estimates with a periodic impulse train whose period corresponds to each possible fundamental frequency of the harmonic set. The receiver for case (3) has an additional interesting property in that it discards all spectral estimates less than a certain value. Some extensions to these results are discussed for situations where (a) the spectral estimates are obtained from data lengths much shorter than the observation interval, and (b) multiple similar harmonic sets may be present.

Optical fiber dispersion measuring unit

Abstract: PURPOSE:To improve a measuring precision by using a continuous light or a light near it as an incident light to observing the small pulsation of an approximate gigahertz in the output light. CONSTITUTION:The light from continuous oscillation laser 1 is subjected to phase modulation by optical phase modualtor 3 which is driven by micro wave power source 2 of frequency fm. Most of the modulated light is injected to optical fiber 7 of a tested object and is transferred. The output optical waveform is analyzed by high- speed photo detector 8 and frequency analyzer 9 or other waveform analyzing units, and modulation degree M or the ratio of fluctuation components P1 to DC components P0 of fundamental frequency fm is obtained and is inputted to dispersion conversion circuit 6. Transmission dispersion is calculated by dispersion conversion circuit 6 and is outputted and displayed.

Frequency-matched signal device for persons with impaired hearing

Abstract: A frequency-matched signal device for persons with impaired hearing, including an activating member (1,2,3), a signal generator (4) activated thereby for producing an electrical signal with a fundamental frequency which is within the range of audibility of a person having a normal sense of hearing, and an amplifier (10) having a loudspeaker (6) connected after it for amplifying the signal into an acoustic signal A first device (P1) permits an optional setting of the fundamental frequency of the signal generator; a second device (P3, R1; 13,14,15) permits an optional setting of the signal generator so that it will deliver at least one additional electrical signal of at least one second frequency which is optionally adjustable and related to the fundamental frequency The additional second signal or signals, respectively, is (are) amplified in the amplifier and an alternator (8) which is connected to the signal generator causes the electrical output signal of the signal generator to alternate between said frequencies at a predetermined slow rate

Hum reduction circuit

Abstract: Apparatus for reducing the fundamental and harmonic frequencies of hum in a signal comprising means for placing a plurality of signal storage means between an input to which the signal is applied and an output in repeated sequence that is synchronous with the fundamental frequency of hum in such manner as to subtract the amount of signal stored from the signal passing between the input and output. The storage means are in a charging circuit having a time constant such that it requires a number of sequences to build the signal stored to its full amplitude.

Logarithmic voltage generative circuit

Abstract: PURPOSE:To generate a logarithmic voltage with extreme ease by providing a counter circuit, several frequency dividers, a priority encoder, a decoder, and a digital-analog converter. CONSTITUTION:A fundamental frequency (f) outputted from an oscillator 1 is supplied to frequency dividers 3 and 4. The outout f1 of the frequency dividers is supplied to a counter 7. The counter 7 counts pulses of a frequency f1 in binary mode until the most significant digit bit MSB of an eight-bit ouput goes to a high level. A priority encoder 8 selects only the 1st pulse of each eight-bit outut from the counter 7 effectively and encodes each pulse into a three-bit output. A decoder 9 decodes encoded signals D0-D2 into an eight-bit output reversely. The decoded signal is supplied to a programmable frequency divider 10. The frequency divider 10 divides the frequency of the pulses of a frequency (f') at a frequency-division ratio determined by the bits, and then supplies the resulting pulse to a counter 12. The output of the counter 12 is applied to a DA converter 13 to obtain a logarithmic voltage.

Speed control unit

Abstract: PURPOSE:To obtain DC output corresponding to the amplitude of the tachogenerator independently of the fundamental frequency of the tachognerator and to perform control by detecting the speed variation in fluctuating at the frequencies of 0 to infinity for the control variable. CONSTITUTION:When the control variable 24 is operated, the tachognerators 31a and 31b output the fundamental waves in sinusoidal shape in which the amplitude is in proportional to the speed of the control variable 24 and the phases are different by 90 deg. each other. The output of the tachogenerators 31a and 31b is squared at the square circuits 32a and 32b connected respectively with the 31a and 31b. The outputs of the square circuits 32a and 32b are added at the addition circuit 33. The output of the circuit 33 is made to 1/2 power at the 1/2 power circuit 34. The output is DC speed signal in proportional to the speed of the control variable 24. The output is compared with the reference signal s at the comparison circuit 22 to output a signal having a deviation with s. The drive circuit 23 amplifies the output of the comparison circuit 22 and feeds it to 24.

Easy displacement versus time graphs for a vibrating string: Tuning a guitar by television

Abstract: When a vertical, vibrating string is silhouetted against a television screen, a wavelike shape may be seen. The shape will appear distinct and stationary if the ratio of the string’s fundamental frequency to 60 Hz is the ratio of small integers. The vertical scan of the (horizontally sweeping) electron beam is responsible for this shape, which amounts to a displacement versus time graph for the string. The effect can be used to tune stringed musical instruments to absolute pitch.

Wideerange acoustic wave flow speed measuring unit

Abstract: PURPOSE:To make it possible to measure a flow speed in a wide range by a sensor which is small- size and has no movable part, by transmitting the acoustic wave obtained by subjecting oscillation frequency f of a fundamental frequency oscillator to amplitude modulation by the frequency of f/n and by detecting the phase difference by receivers in the upper stream and the lower stream CONSTITUTION:Acoustic wave generator A is provided in pipe P where fluid flows, and receivers B and C are provided in the upper stream and the lower stream of generator A respectively, and the phase difference between their receiving signals is detected, thereby measuring the flow speed In this case, the frequency of f/n is generated from oscillation frequency f of fundamental frequency oscillator 1 by frequency divider 2, and fundamental frequency f is subjected to amplitude modulation in modulator circuit 3 by this generated frequency, and this modulated frequency is transmitted to transmitter A The receiving signal is received by receivers B and C and is caused to pass through amplifiers 4 and 5, and after that, the receiving signal is separated into the system where fundamental frequency f is taken out through limiters 6 and 6' and the system where modulated frequency f/n is taken out by detection amplifiers 8 and 8', and the phase difference between both receivers B and C is measured and is displayed on low-speed display equipment 7 and high- speed display equipment 9 As a result, the flow speed measure range can be extended n-number times in comparison with the range for fundamental frequency f