Showing papers on "Sine wave published in 1991"

A 150-MHz Direct Digital Frequency Synthesizer In 1.25/spl mu/m CMOS With -90dBc Spurious Performance

Abstract: A monolithic CMOS direct digital frequency synthesizer (DDFS) is presented which simultaneously achieves high spectral purity and wide bandwidth. Phase noise of the output sine wave is equivalent to or better than that of the 150-MHz reference clock. The synthesizer covers a bandwidth from DC to 75 MHz in steps of 0.035 Hz with a switching speed of 6.7 ns and a tuning latency of 13 clock cycles. An efficient look-up table method for calculating the sine function reduces ROM storage requirements by a factor of 128:1. All circuit designs are fully static and are tolerant to transistor threshold shifts caused by radiation or process variations. The DDFS was fabricated in a 1.25- mu m radiation-hardened double-level metal bulk P-well CMOS process which is tolerant to over 10/sup 6/ rd(Si) of total dose radiation. The die size is 195 mil*195 mil with a device count of 35,000 transistors. Power dissipation is 950 mW at a clock rate of 100 MHz. >

Source location in thin plates using cross-correlation

Abstract: In this paper an alternative method to first threshold crossing for acoustic emission (AE) source location is presented. For wave propagation in dispersive media, the accuracy of source location can be improved by locating corresponding phase points on the transducer outputs to determine the difference in arrival times. The phase point location was done by cross‐correlating the transducer outputs with a single frequency cosine wave modulated by a Gaussian pulse. Experiments were performed using a lead break as the AE source on the surface of an aluminum plate. Due to the plate geometry and source orientation, the wave produced was highly dispersive. Although this wave was unsuitable for first threshold crossing techniques, the time differences needed for triangulation could be determined using the cross‐correlation technique.

Application of a fast tool servo for diamond turning of nonrotationally symmetric surfaces

Abstract: The fabrication of nonrotationally symmetric surfaces by diamond turning requires tool actuation at a bandwidth significantly higher than the rotational frequency of the surfaces. This requirement cannot be met by standard slide drives due to their large mass and consequent low natural frequency. This articles describes the development of a laboratory-scale diamond-turning machine with piezoelectric-driven fast tool servo. The capability of this apparatus will be demonstrated for high-speed features such as sine wave, square wave, and ramp-shaped surfaces. Also described is the implementation of this fast tool servo on a commercial diamond-turning machine. Several nonrotationally symmetric surfaces have been machined, and their images are included.

Photoplethysmographics using component-amplitude division multiplexing

Abstract: A plurality of carrier signals, distinguishable by amplitudes of signal components (e.g., frequency components), are respectively applied to a plurality of energy emitters (e.g., infrared and red light emitters). A detector receives the sum of the energy after modulation at each emitter wavelength, e.g. by blood tissue of a patient. An output of the detector is then demultiplexed, whereby a component of modulation at each emitter wavelength may be determined. The carrier signals may comprise time-varying periodic signals with identical frequency and frequency components, such as mixtures of identical sets of pure sine waves. When the number of signal components exceeds the number of emitter wavelengths, sufficient information is provided during demultiplexing to detect and correct errors introduced by ambient light sources and other interference.

Active Control of Rotating Stall in a Low Speed Axial Compressor

Abstract: The onset of rotating stall has been delayed in a low speed, single-stage, axial research compressor using active feedback control. Control was implemented using a circumferential array of hot wires to sense rotating waves of axial velocity upstream of the compressor. Circumferentially travelling waves were then generated with appropriate phase and amplitude by “wiggling” inlet guide vanes driven by individual actuators. The control scheme considered the wave pattern in terms of the individual spatial Fourier components. A simple proportional control law was implemented for each harmonic. Control of the first spatial harmonic yielded an 11% decrease in the stalling mass flow, while control of the first and second harmonics together reduced the stalling mass flow by 20%. The control system was also used to measure die sine wave response of the compressor, which behaved as would be expected for a second order system.Copyright © 1991 by ASME

Switched mode power supply for single-phase boost commercial AC users in the range of 1 kw to 10 kw

Abstract: A DC to AC power converter is disclosed which is connectable to a DC source, and including a first and second pair of switches which converts the DC source directly to AC by alternately switching between each of the first pair of switches at high frequency modulation, and between second pairs of switches alternately switching at each of the half cycles of the low frequency fundamental output voltage, for producing a positive pulse train and a negative pulse train A transformer boosts the source voltage to the desired high voltage of the output of the converter circuit A filter is connectable to an AC load and having a plurality of damping modes for extracting fundamental frequency from the output of the transformer, and having a control responsive to a signal for switching between damping modes A sine wave oscillator generates a sine wave at the fundamental frequency Feedback circuits maintain the AC output at the fundamental frequency

Ultra-wideband beamforming in sparse arrays

Abstract: Transient radiated fields caused by impulsively excited apertures and aperture response caused by incident impulsive waves has been the subject of considerable research in acoustics. This research is also of importance to wideband radar. Medical ultrasound steered phased arrays use transmitted pulses consisting of from one to three cycles of a damped sinusoid, which is similar to certain ultra-wideband radar systems. Related studies applied to wide-band radar transmitting a single cycle of a sine wave indicate that it may be possible to construct a steered phased array radar with ultra high resolution using very sparse array apertures. In narrowband phased arrays, grating lobe considerations require that the array elements be placed close together. In contrast, very sparse, utra high resolution wide band arrays may be constructed without incurring grating lobe problems.

Laser beam scanner with low cost ditherer mechanism

Abstract: Two resonant cantilever beams oscillate in a sinusoidal pattern. Mirrors disposed on the oscillating ends of the cantilever beams are used to multiplex two scanning and collecting light beams. The cantilever beam parameters and mirror configuration are selected so that the scanning light beam is on the first mirror during the linear portion of its scan. As the first cantilever beam oscillates out of the linear portion of the sine wave, the deflection of the first mirror is just great enough to allow the scanning beam to strike the second mirror during the linear portion of the second mirror's scan. The process is repeated twice each cycle. The collection lens is large enough to receive the full aperture of both mirrors at all times. Multiplexing of scanning diodes is also accomplished by a controller circuit which alternately enables diodes disposed on the ends of respective first and second cantilever beams during the linear portion of each sine wave oscillation.

Power factor correction techniques used for fluorescent lamp ballasts

Abstract: Various power factor correction techniques used in fluorescent lamp ballast are described. The basic circuit used to control the lamp voltage and current is the current-fed sine wave inverter. Numerous different passive power factor correction circuits were designed, built, and tested. A continuous duty boost converter was designed, built, and tested to make the comparisons. In all cases the wattage line power draw was greater than 300 W. The analytical methodology used to define power factor corrections was reevaluated. A newer version was derived, and a more accurate form of power factor derivation is presented which takes into account distortions of the AC line voltage. An attempt is made to explain the need for low-source impedance to make the correct measurements. >

Electronic fluorescent ballast using a power factor correction technique for loads greater than 300 watts

Abstract: The authors describe various power factor schemes used to correct the power factor in electronic ballast or other types of power supplies. This system provides an acceptable sine wave voltage and current to the laps. When the input DC voltage to the power inverter is varied the arc current is also varied, and thus a dimming system is possible. The power inverter used for the fluorescent lamp load is a current-fed sine wave inverter while the unique power factor correction and dimming is accomplished with a boost approach. Keeping the invertor the same, several historical passive techniques were designed, built, and tested. The results are given for a matrix of low, normal, and high line voltages of a 4 lamp load greater than 300 W. >

Impulse compression using soliton effects in a monolithic GaAs circuit

Abstract: A monolithic GaAs impulse compressor circuit which utilizes soliton wave propagation effects in nonlinear transmission lines has been fabricated. The circuits compress a 20 dBm, 8 GHz sinusoid to a train of 3.9 V peak to peak, 5.5 ps full width at half maximum impulses.

Sine-Wave Amplitude Coding at Low Data Rates

Abstract: An analysis/synthesis system based on the sinusoidal speech model has been developed [1] In that system, the sine-wave amplitudes and frequencies are located by searching for the peaks of the magnitude of the short-time Fourier transform (STFT) of the input speech The phases are computed from the real and imaginary parts of the STFT at the measured frequencies The frequencies on successive frames are matched, used in a cubic phase interpolator and applied to a sine-wave generator Each sine wave is amplitude-modulated by the linear interpolation of the matched sine-wave amplitudes At a 10 ms frame rate, this system produces speech that is perceptually indistinguishable from the original [1] Since it is not possible to code all of the sine-wave parameters at low data rates, a system has been developed that codes the sine-wave frequencies by fitting a harmonic set of sine waves to the input waveform using a modified mean-squared error criterion [2], and codes the phase information implicitly using a voicing adaptive transition frequency to provide for a mixed voiced/unvoiced phase excitation model [3] Provided a postfilter is used at the synthesizer to attenuate the noise in the formant nulls, the speech synthesized by this system is of quite high quality having achieved a DAM score of 630 in the uncoded mode Since the fundamental frequency can be coded using ≈ 7 bits and the voicing measure can be coded using ≈ 3 bits, then the possibility exists for good speech quality at low data rates provided the sine-wave amplitudes can be coded efficiently In this paper the zero-phase, harmonic analysis/synthesis system and the post-filter design methodology will be described and then the various techniques that have been examined for coding the sine-wave amplitudes will be discussed

PSD computations using Welch's method. [Power Spectral Density (PSD)]

Abstract: This report describes Welch's method for computing Power Spectral Densities (PSDs). We first describe the bandpass filter method which uses filtering, squaring, and averaging operations to estimate a PSD. Second, we delineate the relationship of Welch's method to the bandpass filter method. Third, the frequency domain signal-to-noise ratio for a sine wave in white noise is derived. This derivation includes the computation of the noise floor due to quantization noise. The signal-to-noise ratio and noise flood depend on the FFT length and window. Fourth, the variance the Welch's PSD is discussed via chi-square random variables and degrees of freedom. This report contains many examples, figures and tables to illustrate the concepts. 26 refs.

Sine-wave phase coding at low data rates

Abstract: In the context of a sinusoidal representation for speech waveforms, it is shown that synthetic speech of high quality can be obtained using a parametric model for the sine-wave phases, hence obviating the need to code the phases at low data rates. It was found that if a synthetic linear phase term was computed based on the time of occurrence of an artificially generated sequence of pitch pulses, then high-quality voiced speech reconstruction was possible. For unvoiced speech, the modeling study showed that the sine-wave phases were essentially uniformly distributed random variables. >

Fitting dynamic models to the Geosat sea level observations in the tropical Pacific Ocean. I - A free wave model

Abstract: Free, equatorially trapped sinusoidal wave solutions to a linear model on an equatorial beta plane are used to fit the Geosat altimetric sea level observations in the tropical Pacific Ocean. The Kalman filter technique is used to estimate the wave amplitude and phase from the data. The estimation is performed at each time step by combining the model forecast with the observation in an optimal fashion utilizing the respective error covariances. The model error covariance is determined such that the performance of the model forecast is optimized. It is found that the dominant observed features can be described qualitatively by basin-scale Kelvin waves and the first meridional-mode Rossby waves. Quantitatively, however, only 23 percent of the signal variance can be accounted for by this simple model.

Asymptotic Cramer-Rao bounds for estimation of the parameters of damped sine waves in noise

Abstract: The problem of estimating the parameters of a signal composed of several damped sine waves in noise has applications, for example, in transient signal analysis. Explicit, closed-form expressions are derived for the Cramer-Rao bound of this problem in the case of low damping, low spectral interference between the signal components, and a sufficiently large number of samples. Among several conclusions which are drawn from the expressions, it is found that the estimation problem is much more sensitive to errors in the damping factor and frequency than to errors in amplitude and phase. >

Detection of damped sine waves in a magnestostrictive displacement transducer using pretrigger and detection thresholds of opposite polarity

Abstract: A damped sine wave detector for detecting the response of a magnetostrictive displacement transducer. A pretrigger comparator compares the signal to a predetermined negative threshold. A signal comparator compares the input signal to a predetermined positive threshold. The pretrigger comparator turns on a pretrigger flip-flop and starts a delay timer when the input signal falls below the predetermined negative threshold. The pretrigger flip-flop supplies the data input of a signal flip-flop. The signal flip-flop is clocked by the signal comparator when the input signal is above the predetermined positive threshold. The signal flip-flop turns on if clocked and the pretrigger flip-flop is on. The detector includes two timers for resetting the flip-flops. An inhibit timer resets both flip-flops upon expiration of an inhibit time longer than the maximum expected duration of the damped sine wave signal. A delay timer resets only the pretrigger flip-flop after a delay time greater than the maximum expected interval between when the damped sine wave falls below the predetermined negative threshold and when the damped sine wave rises above the predetermined positive threshold. Thus the circuit is less sensitive to noise.

Apparatus producing trapezoidal waveforms from a pair of magnetic sensors for detecting the rotating angle of an object

Abstract: A magnetic field generating member is attached to a rotable object the angle of which is to be detected. The apparatus includes first and second magnetic sensors located in the magnetic field generated by the magnetic field generating member, first and second detectors for generating first and second sine wave singles responsive to outputs of the first and second magnetic sensors, first and second limiters for limiting the first and second sine wave signals; and, a synthesizing circuit for synthesizing outputs of the first and second limiter to thereby obtain a synthesized output.

On the use of a compressive receiver for signal detection

Abstract: The performance of a compressive receiver is compared to that of a wideband radiometer in order to determine if there is any significant loss in detection performance that accompanies the added feature of frequency estimation in the compressive receiver. The waveforms to be detected are either sine waves or phase-shift keyed signals, where the latter waveforms can represent either narrow-band binary phase-shift keyed (PSK) signals or direct sequence spread spectrum waveforms. It is shown that the compressive receiver outperforms the radiometer in detecting the presence of a sine wave. The compressive receiver is also shown to exhibit superior performance when the input contains a binary PSK signal and the system is operating under the conditions of low input signal-to-noise power ratio and low probability of false alarm. >

Pulse width-modulation control device for invertor devices

Abstract: A pulse width-modulation control device includes a superposed signal creating circuit for superposing a sine wave signal having a predetermined frequency upon a triangular wave signal as a carrier signal, having a frequency higher than the predetermined frequency to form a superposed signal. A pulse width modulating circuit compares the superposed signal with a predetermined threshold level to form a pulse width modulated signal. A pulse width limiting circuit limits the pulse width of the pulse width modulated signal when the pulse width modulated signal has a pulse width lying outside a predetermined range, and supplies a pulse signal having a pulse width thus limited to a switching device.

Progression of states numerically controlled oscillator

Abstract: A numerically controlled oscillator includes a number of N-bit adders that perform parallel addition of a frequency setting word to an accumulated output. A first adder adds the frequency setting word to the accumulated output. A second adder adds a multiple of the frequency setting word to the accumulated output. Additional adders may be included to add other multiples of the frequency setting word to the accumulated output. The sum output of the adder in which the highest multiple of the frequency setting word is added is saved as the new accumulated output. The outputs of all the adders are saved and are mutliplexed out in sequence at a predetermined clock rate as a series of input values to a sine lookup table in a ROM. The outputs from the ROM form the digitized samples of a sine wave at the predetermined clock rate. The frequency setting word is applied to the adders at a reduced clock rate that is lower than the predetermined clock rate so that the adders operate at the reduced clock rate. Thus, the digitized samples of the sine wave are output at the predetermined clock rate that is greater than the clock rate at which the adders are required to operate.

Output peak current correction for PWM invertors

Abstract: A pulse width modulation type invertor device for an AC power unit. In one form of the invention, a waveform detecting circuit detects an waveform of an output alternating current in an output circuit of the invertor device, and a correcting circuit forms a feedback signal indicative of portions of the waveform of the output alternating current which are outside a predetermined range of amplitude, and compares the feedback signal with a sine wave reference signal to amplify a difference between the feedback signal and the sine wave reference signal. A pulse width modulating circuit is responsive to an output from the correcting circuit for forming a pulse width modulated signal. In another form of the invention, a correcting circuit superposes a pair of signals which are indicative of electric current detected via a pair of current-detecting resistances interposed in a pair of electric current passages in a bridge invertor of the invertor device and reverse in phase to each other to form a signal indicative of a waveform of output current, forms a feedback signal indicative of portions of the signal indicative of the waveform of the output current which are outside a predetermined range of amplitude, and corrects a sine wave reference signal based on the feedback signal.

Controller for electric automobile

Abstract: PURPOSE:To provide a controller for controlling power by delivering a signal having predetermined frequency to a power element in which electromagnetic noise is suppressed over a wide range, from normal traveling to high rotation load, and the power element is protected against overheating by varying the predetermined frequency according to the temperature of the power element. CONSTITUTION:An inverter 5 is provided with a thermister 13 for detecting the temperature of a power element and a carrier signal generator 9 determines a carrier frequency based on the temperature of the power element and generates a triangular carrier signal. The carrier frequency is set at a value higher than audible range, i.e., 20kHz, for a temperature lower than 70 deg.C, for example, and the carrier frequency is varied according to a linear function between 20kHz and 3kHz for the temperature in the range of 70-90 deg.C in order to avoid occurrence of noise due to abrupt variation of frequency thus lowering switching loss of the power element and preventing overheat thereof. A three- phases sine wave generator 11 then determines an inverter output voltage and a PWM signal generator outputs a gate signal for controlling the power of a motor 3.

Object displacement detection

Abstract: This invention relates to signal processing for enhancing detection resolving power on the basis of a periodic signal obtained in a displacement detecting device such as an encoder or a laser length measuring machine, and on the basis of input sine wave and cosine wave signals which are the references, a sine wave signal and a cosine wave signal of a frequency integer times as high as the frequency of the reference signals are produced by calculation by the use of adders, multipliers, etc.

Accurate measurement of signals close to the noise floor on a spectrum analyzer

Abstract: Because most spectrum analyzers are calibrated to read the true power of a sinusoidal signal, a correction factor is necessary to read the true power of a nonsinusoidal signal, such as noise. Consequently, when noise and a sine wave are both present, a correction factor that is a function of the signal-to-noise ratio is necessary to find the true signal power. For some spectrum analyzers the correction factor for pure noise is incorporated into the software, but the correction factor for signal-plus-noise is generally ignored. The authors derive this correction factor, which is significant where the signal-to-noise ratio is near unity. >

Analysis and comparison of real-time sine-wave generation for PWM circuits

Abstract: Four methods for hardware and software generation in real time of sine waves suitable for PWM circuits are presented. The sine waves are derived from a truncated modified cosine Taylor series, wt( pi -wt) function, a digitally filtered trapezoid, and a second-order differential equation. Triplen injection is incorporated by the addition of a defined magnitude triangular waveform of three times the fundamental frequency. Each sine wave generating technique is implemented, as applicable, in a programmable logic cell array and/or in microprocessor-based software. In each case, the output spectra and total harmonic distortion are compared with computer-simulated results. >