Showing papers on "Sine wave published in 1973"

Analysis and measurement of ultrasound backscattering from an ensemble of scatterers excited by sine‐wave bursts

Abstract: This paper develops a practical approximation for the backscattering of periodic bursts of sine waves by a volume of randomly distributed scatterers. The approximation is applied to the measurement of a “volumetric backscattering cross section,” using a substitution method in which the rms value of the gated backscattered signal is compared with the rms value of a wave reflected from a target of known coefficient of reflection. It is shown that the signal backscattered from the ensemble depends on the attenuation of the wave in the volume and upon the burst and gate lengths. An equation to obtain the volumetric backscattering cross section from experimental data is derived.

A study of sine-wave contrast sensitivity by two psychophysical methods

Abstract: In the literature on visual contrast thresholds for sine wave gratings, little attention has been paid to the psychophysical methods used to obtain these spatial-frequency response curves. Here we report a comparison of such data obtained by two quite different psychophysical methods, but otherwise under identical conditions, using five Ss. Both experiments were run by computer: (1) In the method of adjustments, the computer program merely controls the order of the stimuli and records S’s contrast settings. (2) In the forced-choice staircase (FCS) technique, the program determines how often S can discriminate the sinusoidal grating from a uniform field, informs S of his accuracy, controls the stimulus contrast on the basis of S’s preceding responses, and brackets his threshold by a series of successive approximations. Method 2 eliminates criterion effects that occur in Method 1, and hence tends to minimize individual differences. However, the FCS technique requires an order of magnitude more observing time to obtain equally smooth contrast sensitivity curves. FCS also increases the/overall sensitivity of some Ss by as much as five times, but it does not significantly change theshape of the contrast sensitivity curve; both methods show strong effects of lateral inhibition at low spatial frequencies.

Quasi-sine-wave fully regenerative invertor

Abstract: The paper shows that, if a cage induction motor is fed with a quasi-square-wave current, the motor terminal voltage is approximately sinusoidal under normal operating conditions. A simple analytical approach, based on the assumption that the motor resistances and inductances do not change with frequency, is shown to describe adequately the motor-terminal voltage. The quasi-square-wave-current supply is derived by modification of a known variable d.c.-link-voltage invertor. These modifications result in numerous advantages. The modified invertor is capable of regeneration back into the mains supply, has only 12 noninvertor-grade thyristors, and is undamaged by short-circuiting of the output terminals or by misfire of the output thyristors. Overall, the invertor lends itself to a simpler electrical and mechanical arrangement.

Quantitative model for the effects of stimulus frequency upon synchronization of auditory nerve discharges.

Abstract: A theory has been developed which can be used to quantify the loss of synchronization in auditory nerve discharges with increasing stimulus frequency.The assumptions for the theory are (1) the probability of discharge versus time position within the period for very low stimulus frequency has the shape of a half‐wave‐rectified sine wave, and (2) travel times for impulses propagating along the acoustic nerve have a Gaussian statistical distribution around some mean travel time. With these two assumptions it is possible to predict the shapes of histograms which arise from higher frequency stimulation. Further, a single quantity (Gt ) may be derived from these fits which characterizes the whole progression from pure half‐sine‐wave distribution at zero frequency to a completely flat distribution at high frequencies.

Statistical properties of two sine waves in Gaussian noise

Abstract: A detailed study is presented of some statistical properties of the stochastic process, that consists of the sum of two sine waves of unknown relative phase and a normal process. Since none of the statistics investigated seem to yield a closed-form expression, all the derivations are cast in a form that is particularly suitable for machine computation. Specifically, results are presented for the probability density function (pdf) of the envelope and the instantaneous value, the moments of these distributions, and the relative cumulative density function (cdf). The analysis hinges on expanding the functions of interest in a way that allows computation by means of recursive relations. Specifically, all the expansions are expressed in terms of sums of products of Gaussian hypergeometric functions and Laguerre polynomials. Computer results obtained on a CDC 6600 are presented. If a and b are the amplitudes of the two sine waves, normalized to the rms noise level, the expansions presented are useful up to values of a,b of about 17 dB, in double precision on the CDC 6600. A different approximation is also given for the case of very high SNR.

Directive harmonic generation in the radiation field of a circular piston

Abstract: An experimental and theoretical investigation is presented of farfield distortion of a finite‐amplitude wave generated by a circular‐piston source. Nearfield distortion is neglected. Thus the boundary condition is that the acoustic signal at the beginning of the farfield is a pure sine wave of amplitude proportional to the small‐signal directivity factor for the piston. The method of applying weak‐shock theory to obtain directivity patterns and propagation curves is outlined. A criterion for the maximum range at which weak‐shock theory is valid is derived for each harmonic. An ad hoc method of matching at this range the small‐signal solution, with absorption included, to the weak‐shock solution is proposed. Data obtained for a fundamental frequency of 450 kHz and source levels of 109 and 127 dB (re 1 μbar at 1 yd) are presented. Theoretical and experimental beam patterns are in good agreement. Propagation data presented for the 127‐dB source level are in poor agreement with the predictions of unmodified w...

Memory switching in SiO films with Ag and Co electrodes

Abstract: Reversible memory switching in evaporated SiO films with one Co and one Ag electrode was investigated. The high-impedance state was more than 109 Ω; the low-impedance state about 300 Ω. A rectified sine wave was used as a switching pulse in one direction and a short square-wave pulse in the other. The switching characteristics at different repetition rates and the properties of the low-impedance state suggest metal diffusion from the electrodes. A model for explaining the memory effect is presented.

Effect of Co-Channel Interference on CPSK Carriers

Abstract: This paper investigates the problem of estimating the effects of interference to a coherent phase-shift-keyed (CPSK) digital carrier. Paralleling Saltzberg [1], the principal tool utilized is the CramerChernoff bounding technique. The interference effects can be characterized by equating the larger interferers to an equivalent coherent canceling sine wave and the remaining interferers to an equivalent incoherent source of thermal noise. Subject to an envelope constraint, any allocation of the interferers between a canceling sine wave and thermal noise is allowed. Conditions are developed for the case: 1) when all the interference should be allocated to thermal noise; and 2) when as much as possible of the interference should be allocated to a canceling sine wave. This provides insight into the formal procedure of equating interference as additional thermal noise.

Circuit for generating a single high voltage subnanosecond pulse from a step recovery diode

Abstract: A series connected electronic circuit including in combination a trigger generator, an impulse generator, a filter circuit having an inductance L, a step recovery diode having a forward resistance RF and a reverse capacitance CR and an optimal bias circuit coupled to the step recovery diode. The trigger generator produces a train of pulses having a relatively long time interval, T, between each pulse; these pulses are then coupled to the impulse generator which produces an impulse having a Fourier component predominant at a frequency omega in response to each trigger pulse. The filter circuit converts each impulse into a damped sine wave having an angular frequency omega and a damping constant delta RF/2L. The sine wave is coupled to the step recovery diode which generates a single high voltage subnanosecond pulse having a half period, tp/ pi square root LCR in response to each damped sine wave.

Digital phase measuring system

Abstract: A system for measuring the phase difference between two signals and having a digital readout. Each of the two signals are fed to Schmitt trigger circuits which convert the sine wave signals to square waves. The two square waves are compared for coincidence in a discriminator, the output thereof being converted by a logic circuit to a form for displaying the digital phase difference of the two signals.

Optical signal reproducing apparatus

Abstract: In optical signal reproducing apparatus for reproducing a signal from a recording medium having a groove in which the signal has been recorded as continuous irregularities of a sine curve having a pitch of the order of microns, there are provided a source of light for emanating a light beam of a definite phase, means for projecting the light beam upon the groove after limiting the width of the beam to be less than the minimum pitch of the irregularities, and means for detecting the diffracted light reflected by the irregularities

Model approximations to visual spatio-temporal sine-wave threshold data

Abstract: Experimental data on visual spatio-temporal sine-wave thresholds obtained by Robson and Kelly are considered. In seeking model approximations to the data it is assumed that the subject's visual threshold to modulation at different spatial and temporal frequencies gives the image of his filter function to within a multiplicative constant. It is further assumed that the data can be approximated by a system with a spatially uniform, isotropic, and temporally invariant response which consists of the difference between an excitatory and an inhibitory term, and that each term is separable into a product of a spatial and a temporal function.

Performance of Apodized Apertures under Partially Coherent Illumination

Abstract: The performance characteristics of optical systems having apodized apertures and employing partially coherent illumination have been investigated. The pupil function has been taken to be of the form f(x y) = 1 m g (x 2 + y 2), where g is the amplitude shading parameter of the filter. The generalized cross-transfer functions for the system have been calculated for different values of the coherence parameter which is the ratio of the numerical aperture of the condenser to that of the objective. The modulations of periodic targets commonly employed, namely, the sine wave, square wave and triangular wave objects, have also been investigated. It has been shown that for the partially coherent and the incoherent illuminations (… S 1) the apodization improves the low frequency response at a cost of the high frequency response of the system. However, for coherent and near coherent illuminations (

Nonlinear Dielectric Constants in Barium Titanate

Abstract: An apparatus for detecting small second and third harmonics due to the dielectric nonlinearity is devised. A reactance filter network is used to obtain pure sine wave voltage and high detection sensitivity. The higher harmonic level applied to the crystal is suppressed to the order of 5×10 -7 times below the fundamental voltage. This apparatus is used for measuring the nonlinear dielectric constants of BaTiO 3 single crystals above and below the Curie point (120°C). The experimental results show that the coefficient of the P 4 term in the Devonshire's equation increases gradually with increasing temperature, which is against the previous result reported by Drougard et al.

Shuttle transfer with sine wave time/velocity acceleration

Abstract: A stacker crane elevator has drive mechanism for exending a two-part load bearing shuttle from centered position on the elevator into a selected pigeonhole of an automated warehouse and vice versa. The drive mechanism accelerates and decelerates the shuttle in a sine curve time/velocity ratio by means of two crank-like drive pins mounted on a rotative head member and interposed one between each of two parallel drive faces. Orbital movement of the crank pins through circular arcs of 180 DEG rotative movement of the head member produces acceleration of the shuttle from zero velocity through maximum and back to zero in a sine wave curve which tends to equalize acceleration throughout shuttle travel and thus to minimize displacement of a load on the shuttle.

Integrated circuit all-harmonic wave organ system including provision for flute tones and pedal notes

Abstract: A bright wave (all harmonic wave) organ system which has direct current (D.C.) keying for all notes, both manual and pedal, and also provides sine wave (flute) notes by filtration. All-harmonic waves are provided by stairstepping octavely related square waves and the flutes by filtration of the complex stairstepped wave minus the square wave component which has its fundamental at twice the frequency of the desired flute note to accommodate octave flute filtering. The present arrangement is such that one integrated circuit package provides for two octavely related groups of adjacent notes, all C''s and all C ''s, for instance, for eight octaves of manual notes and three octaves of 16-, 8- and 4foot pedal notes or the equivalent. Each circuit package requires only one musical frequency input or clock for each of two adjacent note groups, one for C and one for C for instance. The integrated circuit packages are large scale integrations (LSI) and include the frequency dividers, the arrangement for keying and stairstepping the square waves, for collecting and controlling the outputs for octave or half octave sine wave filtration and for formanting, and for providing three pedal outputs, one each for the 16-foot, 8-foot and 4-foot pedal notes or the equivalent for other use. Provision is made for phase synchronization of the frequency dividers.

Relation between vibratory sensibility and electric signal of living body

Abstract: The paper presents psychological experiments carried out using a vibrometer as an acoustical calibration apparatus for triangular, sawtooth, square and pulse waves. The study has shown the relationship between the vibratory sensibility and the electric signal generated in a living body. The threshold curve for square waves is lower by 12·3dB than that for sine waves at about 30 Hz. We consider that the evaluation of vibratory sensibility should be performed by a physical measurement, which also relates to subjective evaluation It is necessary to find the new physical measurement. We have observed that subjective vibratory sensibility and potential variations take place linearly with the vibratory level.

Inverting arrangement employing compressed sine waves and class B amplifiers

Abstract: An inverter utilizes class B amplifiers to amplify a compressed sine wave signal. Increased efficiency of the inverter may be achieved by utilizing supplemental paths in the amplifier, to carry the load current with less dissipation, for at least a portion of the signal cycle. In addition, a filtering arrangement, including a transformer having a three leg core, may be utilized to provide a sine wave voltage between the output lines and a neutral point, as well as from line to line.

Sine wave reference waveform generator

Abstract: An operational amplifier is used to synthesize a sine wave from a plurality of phase displaced rectangular waveforms of magnitude selected for minimum distortion. The rectangular waveforms are applied to the inverting (summing) input terminal of the operational amplifier while the non-inverting input terminal is maintained at a direct voltage resulting in an output of the synthesized rectangular waveforms that is symmetrical about the voltage level of the non-inverting input terminal. Application of this waveform to a simple first order filter, such as an integrator provided by a feedback network on the same opamp, results in a smooth sine wave of high precision suitable for various applications such as in cycloconverters.

Sequence amplitude modulated inverters

Abstract: This Static Inverter produces a true stepped waveform from a direct current source, which is symmetrical from one half cycle to the next half cycle. Because of its low output impedance and OC half-wave circulating path for current, the Inverter will deliver rectified, non-linear loads and still operate normally (low distortion) and under extremely poor power factor loads. The method used to obtain this type of stepped waveform was originally developed in 1965. With the advent of integrated circuits, the complexity and cost of the design was considerably reduced. Production of the eight steps of the waveform previously required eight separate volt· age generating sources. Today, through the use of integrated circuits, two or three voltage sources can perform the necessary function of producing eight to twenty-six (or more) steps if desired in a half wave cycle period. Only a fraction of the power (7%) is switched at a high frequency rate as compared with a Pulse Width Modulated technique. The bulk of the power (70%) is generated at the output frequency. The method of inversion discussed here can generate a high quality, high power sine wave voltage that meets most of the desirable character· istics of a high-quality inverter including low output impedance.

Frequency modulation circuit

Abstract: A first operational amplifier, used as an active filter tuned to a predetermined carrier frequency, is connected in a loop circuit with a second operational amplifier, used as a saturable amplifier. A square wave is generated by the saturable amplifier and is passed by the filter to develop a sine wave at the filter output. This sine wave carrier is modulated in frequency by a modulating signal applied to the gate of a field-effecttransistor which is connected across the input of the filter.

Electronic signal multiplier for flowmeters

Abstract: A frequency multiplier for frequency variable electronic signals for use with a fluid flow measuring system. The generally sinusoidal output signal from a fluid flowmeter is converted to a square wave signal of the same frequency. The square wave signal is integrated to form a triangular wave signal variable in both amplitude and frequency with the frequency of the square wave signal. The peak-to-peak amplitude of the triangular wave signal is then adjusted to a predetermined value irrespective of input signal amplitude or frequency in an automatic gain control circuit, and the frequency of the triangular wave is thereafter doubled to the desired value by cascaded doubling stages. Each doubling stage includes a two-channel half-wave rectifier, means for shifting the bias of the rectified waves, and means for both inverting one of the bias shifted waves and for combining the inverted wave with the other bias shifted wave to center the combined wave about a zero volt axis. In an alternative embodiment, with the output signal from the flowmeter in the form of a series of constant amplitude, constant width, variable recurrence rate pulses, a reversible ramp generator is used to form a triangular wave signal having an amplitude and a frequency variable with the frequency of pulse recurrence. The peak-to-peak amplitude of this triangular wave is likewise adjusted to a predetermined constant value and the frequency multiplied in cascaded doubling stages as described above.

Subaudible remote control tone encoding system

Abstract: A paging system includes a transmitter for transmitting a carrier frequency signal modulated by subaudible tone signals in response to audible tone signals coupled to the transmitter from a remote point. An encoder at the remote point develops the audible tone signals which are coupled to the transmitter over standard telephone channels. At the transmitter, a circuit converts the audible tone signals to first square wave signals having the same frequency as the audible tone signals. A divider circuit divides the first square wave signals by a particular number to develop second square wave signals having the same frequency as the desired subaudible tone signals. The second square wave signals are coupled to a low pass filter which attenuates all frequencies above the subaudible tone signal frequencies and develops a sine wave having the desired subaudible tone frequency. A frequency selector circuit may also be employed and is coupled to the divider circuit. The frequency selector circuit is operative to select the second square wave signals having a frequency above a predetermined frequency and couple them to a first filter; and is further operative to select the second square wave signals having a frequency below a predetermined frequency and couple them to a second filter. The first and second filters have low pass attenuation characteristics and are operative to filter the square wave signals coupled thereto and develop the particular subaudible tone signals therefrom for modulating the transmitter RF carrier.

Apparatus for testing an amplifier

Abstract: A testing device for measuring phase shift and amplitude changes in an amplifier. A frequency synthesizer provides a sine wave through first and second channels with the amplifier being connected in the first channel. The outputs from the first and second channels are applied to a computer for analysis. The computer is programmed to calculate the phase angles for the waveforms. The difference in these phase angles is the phase shift of the amplifier under test, and this difference is presented in a readout device.

A Precision Stabilized Sine-Wave Source for AC Power Measurements

Abstract: The design of a stable sine-wave source for error determination of ac-measuring instruments is discussed. The electronic amplitude control circuit has been constructed using standard integrated circuits. The fluctuations of its rms output voltage, observed over the period of 1 h, are 1 · 10-6 peak-to-peak. Since the total harmonic distortion is less than 1 · 10-3, its contribution to the error of the rms value may be neglected.

Method and apparatus for determining tacan bearing

Abstract: This invention relates to a method and apparatus for extracting antenna modulation components by phase locking a locally generated sine wave at the desired frequency with the actual antenna modulation. A phase locked oscillator is triggered at predetermined reference points on the received Tacan signal. The output of the oscillator is phase shifted in the direction of coincidence with th received modulation envelope. A comparator compares the phase shifted signal and the envelope of the received signal and generates an error signal if coincidence does not exist. The error signal is fed back and multiplied betwen phase shifted signal; in one case after the phase shifted signal is limited and in another case after the phase shifted signal is further shifted by 90* and limited. In the first case the result of the multiplication is integrated and used to modify the amplitude of the phase shifted signal. In the second case, the result of the multiplication is integrated and controls the amount of the phase shift imparted on the locally generated signal to achieve coincidence.

Delay distortion measurement system

Abstract: A method of measuring frequency delay distortion of a communication channel comprising, generating at a sending end of said channel a plurality of sustained sine wave signals distributed throughout a frequency spectrum of said channel, modulating at a lower frequency each of said sine wave signals in repetitive progression for a preselected period of each, transmitting the modulated signals over said channel to its distant end, and at said distant end, locally generating a signal of frequency substantially that of said modulating frequency, detecting and filtering said modulated incoming signals, and measuring the difference in time between that at which each said detected and filtered signal goes to zero and that at which said locally generated signal goes to zero, for adjacent cycles timewise thereof respectively, the frequency of the locally generated signal being synchronized with the incoming modulating frequency upon receipt of one of said sine wave signals employed as a reference frequency, or alternatively, following receipt of all of said series of sine wave signals and a constant correction applied in accordance with the measured delay of the reference frequency.

Synthetic phasor generator

Abstract: A stepped approximation of a sine wave is generated by operational amplifiers, having feedback resistors of a given magnitude, which are connected through successive input resistors to a signal representing the magnitude of the desired synthetic sinusoid by means of an electronic multiplexing switch which is advanced by clocking signals spaced one sixteenth of the period of the desired synthetic sinusoid so as to cause 16 steps spanning discrete angular fractions of the period of said sinusoid, the input resistors having magnitudes related to the given magnitudes of said feedback resistors by the sine of the accumulated angle of said angular fractions, in relation to the successive clock signals.