Showing papers on "Sine wave published in 1990"

Pitch estimation and voicing detection based on a sinusoidal speech model

Abstract: A technique for estimating the pitch of a speech waveform is developed. It fits a harmonic set of sine waves to the input data using a mean-squared-error (MSE) criterion. By exploiting a sinusoidal model for the input speech waveform, a pitch estimation criterion is derived that is inherently unambiguous, uses pitch-adaptive resolution, uses small-signal suppression to provide enhanced discrimination, and uses amplitude compression to eliminate the effects of pitch-formant interaction. The normalized minimum mean squared error proves to be a powerful discriminant for estimating the likelihood that a given frame of speech is voiced. >

Multiple frequency bio-impedance measurement system

Abstract: The multiple frequency impedance measurement system of the present invention permits noninvasive examination of living tissue at any one of a plurality of frequencies. Precise frequency control is provided by a phase locked loop (PLL) circuit which is adjustable among at least a plurality of frequencies by locking the loop to the output signal generated by a voltage controlled oscillator (VCO) divided by a selectable divisor. By selecting the divisor of the output signal of the VCO, the frequency is changed and, due to the use of a PLL circuit, each selected frequency is stably maintained. Electrodes connecting the circuit to tissue to be monitored are driven by a high-Q filter and buffer amplifier which convert the square wave output from a voltage controlled clipper circuit to a sine wave signal. The clipper circuit receives the output signal from the VCO and is part of a feedback loop which maintains a constant examination current for the system. By monitoring the examination current via a precision resistor, a current reference signal is generated and used in the feedback loop to maintain the current at a substantially constant but selectable level. The reference signal is also used to drive a resistance synchronous detector and a reactance synchronous detector to derive resistance and reactance signals, respectively, which are representative of the resistance and reactance of the tissue at the selected measuring frequency. The resistance and reactance signals are displayed via a shared digital display which is switched between the two signals.

An approach to co-channel talker interference suppression using a sinusoidal model for speech

Abstract: The technique fits a sinusoidal model to additive vocal speech segments so that the least-mean-squared error between the model and the summed waveforms is obtained. Enhancement is achieved by synthesizing a waveform from the sine waves attributed to the desired speaker. Least-squares estimation is applied to obtain sine-wave amplitudes and phases of both talkers, based on either a priori sine-wave frequencies or a priori fundamental frequency contours. When the frequencies of the two waveforms are closely spaced, the performance is significantly improved by exploring the time evolution of the sinusoidal parameters across multiple analysis frames. The least-squared-error approach is also extended, under restricted conditions, to estimate fundamental frequency contours of both speakers from the summed waveforms. The results obtained, although limited in their scope, provide evidence that the sinusoidal analysis/synthesis model with effective parameter estimation techniques offers a promising approach to the problem of cochannel talker-interference suppression over a range of conditions. >

High speed data communication system using phase shift key coding

Abstract: An improved binary data communication system employs an improved VPSK encoding procedure wherein each input data bit has a bit period of M clock periods, and the data bit polarity changes are phase shift key coded with waveform widths of M/M, M+1/M, and M+2/M bit periods wherein M is an even integer greater than 3. Each of the data bits (except the last one in an encoding cycle) is encoded in an encoding signal which switches back and forth between "1" and "0" polarities and has assigned widths representing whether or not the polarity of the data bit is changed from that of the previous data bit, and whether it is the last (M-1th) polarity change in the encoding cycle. At the receiving end, a complementary procedure is used to decode the encoded signal. For transmission, the encoded signal is filtered for higher order harmonics and integrated in order to provide a sine wave output shifted 90 degrees in phase. Upon reception, the received signal is differentiated and a zero crossover detector is used to regenerate the encoded signal for decoding. The improved encoding technique can achieve Nyquist efficiencies of 10, 12.6, and 15.3 bits/Hz-bandwidth, or higher, for M equal to 6, 8, and 10 modulation levels, respectively. The encoded signal spectrum fits typically within about 1/6 of the bandwidth of the baseband NRZ signal. The encoded signal is particularly useful for transmission at high data rates in telephone, RF modulated carriers, and other transmission systems.

Regulated AC power system energized by variable speed prime mover

Abstract: A three phase alternator is driven by a variable speed prime mover, and its rectified output is pulse width modulated by a gate controlled H-bridge power switch circuit. Predetermined pairs of power switches are gated on and off according to programmed duration and timing instructions contained in a read only memory. In a first embodiment, a sine wave output is produced by successive pulse trains. The first pulse train has alternating positive and negative constant amplitude pulses, with the widths of positive pulses varying sinusoidally and the widths of negative pulses being constant. The second pulse train has alternating positive and negative pulses of constant amplitude, with the pulse widths of the negative pulse components varying sinusoidally, and the pulse widths of the positive components being constant. The components of the first and second pulse trains have an energy distribution which corresponds to one cycle of a sine wave having a fixed frequency. The pulse width modulated waveform is filtered to produce a smooth, low distortion sine wave output waveform. In a second embodiment, the on and off states, and the duration and timing of the on and off states, are controlled to produce a pseudo sine output power wave having an RMS value of 120 VAC at 60 Hz.

Noise reduction using a soft-decision sine-wave vector quantizer

Abstract: Noise reduction is performed in the context of a high-quality harmonic zero-phase sine-wave analysis/synthesis system which is characterized by sine-wave amplitudes, a voicing probability, and a fundamental frequency. Least-squared error estimation of a harmonic sine-wave representation leads to a soft decision template estimate consisting of sine-wave amplitudes and a voicing probability. The least-squares solution is modified to use template-matching with nearest neighbors. The reconstruction is improved by using the modified least-squares solution only in spectral regions with low signal-to-noise ratio. The results, although preliminary, provide evidence that harmonic zero-phase sine-wave analysis/synthesis, combined with effective estimation of sine-wave amplitudes and probability of voicing, offers a promising approach to noise reduction. >

Switched multi-tapped transformer power conversion method and apparatus

Abstract: A switched multi-tapped transformer-based power conversion circuit is disclosed. A polarity alternator comprising dual switch devices controlled by a microprocessor selectively periodically impresses across a transformer's center-tapped primary winding a voltage from a battery to produce a modified square waveform. Each of the taps of the transformer's secondary winding synchronously selectively switched by the microprocessor to a common wired-OR junction where the discrete voltage levels combine to produce a stepped approximation of a stored sine waveform. The switching circuits for each of the taps comprises dual back-to-back series-connected FET switches with diodes shunting each FET's source and drain. The microprocessor periodically senses the voltage across the primary winding, calculates the voltage across the secondary winding based upon the predetermined turns ratio of the tap that is switched to the common junction and compares the calculated output voltage with a normalized memory-based sine wave representation, thereby to determine when to switch to another tap. The converter, which operates concurrently as an inverter and a charger, responds in real time to changing DC source and AC load conditions. A similar converter having a full-wave rectifier on the primary winding side of the transformer is connectable to an AC source and provides for the charging of a connected DC load.

Adjustable ac power supply equipment for air-conditioner system

Abstract: In an adjustable a.c. power supply for an air-conditioner system, comprising a first frequency converter for driving a compressor motor of a first air-conditioner, a second frequency converter for driving a compressor motor of a second air-conditioner, and a common a.c. power supply for delivering a.c. power to both frequency converters, a rectifier included in at least one frequency converter is constructed as a controllable rectifier and subjected to phase-control so that a synthetic higher harmonic current of the two frequency converters as viewed from the a.c. power supply is reduced. By conducting phase-control of plural controllable rectifiers in a manner that, e.g., one rectifier has a phase-control angle of zero degrees and the other rectifier has a phase-control angle of 30 degrees, load current from the a.c. power supply is permitted to have a waveform closer to a sine wave, i.e., a waveform in which higher harmonic components are further reduced.

Two-frequency impedance plethysmograph: real and imaginary parts.

Abstract: A four-channel impedance plethysmograph has been designed. Impedance signals are obtained at two frequencies by measuring both real and imaginary parts. Particular attention has been paid to the sine wave generation circuits that provide system versatility. The required phase-sensitive demodulation is achieved by means of analogue multiplexers. Results show that there are significant variations in the thoracic equivalent capacitance related to respiration and that there is an increased sensitivity to cardiac activity at low frequencies.

The implementation of a digital sine wave oscillator using the TMS320C25: distortion reduction and applications

Abstract: The implementation of a digital sine wave oscillator using the TMS320C25 digital signal processor (DSP) is described. The system is implemented with the Dalanco Spry model 25 DSP board, and a software system is designed whereby an IBM PC host computer provides control of the waveform generator functions and parameters. Waveforms are generated using the lookup-table (LUT) method. The methods of direct LUT and linear interpolation of missing samples are implemented and compared with a method that uses a trigonometric identity to reduce the harmonic distortion of the sine wave by effectively increasing the table length of the direct LUT method. The results of an experiment performed in the digital domain are presented without consideration of the problem of analog reconstruction. The oscillator can produce a sine wave without the nonuniform sampling distortion associated with fractional addressing, over the range of 7.2 Hz to 58.8 kHz, with a resolution of 7.2 Hz using 384 data words. The trigonometric identity method uses less data memory than other methods for the same distortion levels. Waveforms for the sum of two sine waves, a frequency swept sine wave, amplitude modulation (AM), and frequency modulation (FM) signals are shown as applications of the waveform generator. >

Digital spectra of non-uniformly sampled signals: theories and applications. IV. Measuring clock/aperture jitter of an A/D system

Abstract: Theories and applications of a digital spectrum analysis technique for a class of nonuniformly sampled signals are described. A method based on asynchronous spectral averaging is presented to measure the standard deviation of a clock/aperture jitter of an A/D (analog/digital) system. A sine wave with frequency f/sub 0/ is used as the input test signal to an A/D system. Spectral averaging is performed on many asynchronously acquired data records with length N. The jitter standard deviation is calculated from the measured signal-to-noise (S/N) floor ratio. The expression which relates the S/N to the standard deviation, sigma /sub r/, of the jitter, r, is derived in closed form. Graphs showing good agreement between the theoretical equation and the simulation results are presented. >

A high-speed direct frequency synthesizer

Abstract: A UHF direct frequency synthesizer, which is primarily intended for radar and electronic warfare applications, is described. The device generates square-, sine-, and triangle-wave outputs, true and complement, in-phase and quadrature, over the range 1 Hz to 500 MHz. It is a fully integrated design, including two digital-to-analog converters (DACs), each of which has a faster operating specification than any DAC currently available. The circuit is composed of a number of structured circuit blocks, each of which can be tested independently on the chip. This approach has benefits both during device evaluation and as an aid to minimizing production test times. The chip is implemented in a 1 mu m silicon bipolar process. >

AC amplifier with automatic DC compensation

Abstract: An AC power amplifier (50) with a pair of push-pull transistors (Q1, Q2) driving opposite sides (36, 38) of the primary winding of an output transformer (T1) controlled by a pair of variable duty cycle, pulse width modulated width trains (A, B) generated on the output of a pulse width modulator (26) controlled, in turn, through means of a wave shaping feedback system to cause the AC output at the secondary winding (20) to track the output of a precision reference sine wave oscillator (12) and through means of another feedback system for automatic DC compensation including a pair of CMOS analog switches respectively driven by the two pulse width modulated pulse trains (A on 28, B on 30) to produce a pair of feedback signals. A junction (58) couples the pair of feedback signals to form a composite feedback signal and an error amplifier (14) also used in the wave shaping feedback system, responds to the composite feedback signal to balance the duty cycles of the pair of drive signals to reduce the introduction of DC to the output transformer (T1).

Method and apparatus for controlling induction motor for compressor

Abstract: DC power is supplied to an induction motor for a compressor by switching ON/OFF in response to a modulated voltage waveform obtained from modulating waves which are used for generating AC power for energizing an induction motor and a carrier wave according to PWM theory. The compressor has a compressing element rotated by the induction motor, and the modulating wave is corrected according to a rotational angle of the compressing element. A sine wave having the same frequency as the modulating wave is added to the modulating wave, and a phase of the sine wave is controlled so that a maximum value of the sine wave corresponds to the compression stage of the compressing element. Thus, a rotation speed of the compressing element is constant in a suction stage and a compression stage.

A New Approach to Frequency Analysis with Amplified Harmonics

Abstract: SUMMARY For stationary time series having a mixed spectrum, we introduce a new method for estimating the discrete frequencies based on amplification of the sine waves in the time series and on minimization of least squares regressions on amplified waves. Under the assumption that the continuous part of the spectrum arises from a stationary autoregressive moving average process, we show that the estimators for the discrete frequencies obtained with this method are strongly consistent: more precisely, as the serial length n tends to infinity, their bias almost surely converges to zero with the rate n - 3/2 (log n)5, 6 > 2. We also establish a central limit theorem which shows that these estimators have exactly the same asymptotic variance as that given by Whittle's method, which is known to yield the most accurate frequency estimates. However, the new technique has two advantages over Whittle's method. First, it yields an algorithm that is both robust against improper starting estimates and computationally efficient. Secondly, it gives rise to a simple tool based on its amplified harmonics for identifying the number of sine waves in a time series. A simulation study is also reported that gives statistical results on the properties of the new method on simulated series as well as comparative results with Whittle's method.

Progress on signal-selective direction finding

Abstract: The recently discovered Cyclic MUSIC algorithm for narrowband signal-selective direction finding using antenna arrays circumvents many drawbacks of conventional techniques by exploiting known spectral correlation properties (namely known cycle frequencies such as the baud rate or carrier frequency) of the desired signals to reject undesired signals, interference, and noise. Two recent advances in the capabilities of Cyclic MUSIC are described. The first enables Cyclic MUSIC to simultaneously estimate the directions of arrival of signals having different cycle frequencies instead of having to sequentially process each separate frequency in a list of cycle frequencies (either known a priori or measured). The second advance reduces the sensitivity of Cyclic MUSIC to error in the knowledge of the cycle frequency of interest by estimating the frequency of a quadratically-regenerated sine wave and then using that estimate as the cycle frequency parameter in the computation of the cyclic autocorrelation matrix, which is then processed to estimate the directions of arrival. >

Digital isolation monitor for an electrical power system

Abstract: A digital isolation monitor comprises a digital processing signal processor P1 designed to synthesize a sine wave in real time by a table, and to send the digital values of this sine wave to a digital-to-analog converter of an input channel to generate a low-frequency AC reference signal with a very low, stable phase distortion factor. An acquisition channel is fitted with a switching unit operating in conjunction with a dual measurement circuit to send an injected voltage signal and a leakage current signal to a low-pass analog filter in series with a sample-and-hold circuit and an analog-to-digital converter. The processor P1 then performs synchronous demodulation and transmits the data to a microcontroller P2.

Simulations of piezoelectric Lamb wave delay lines using a finite element method

Abstract: The method of piezoelectric finite elements was applied to the simulation of piezoelectric Lamb-wave delay lines with and without acoustical absorbers. In this finite-element analysis, free as well as electrically driven vibrations were computed. The shapes of the symmetric Lamb modes were determined by the solution of eigenproblems, and the transient mechanical build-up process was studied for a switched electrical sine wave excitation. The transfer function, the group delay time, and the impedance matrix of devices of different designs are calculated. The good agreement between simulation and experimental results indicates the suitability of the finite-element method for optimizing acoustic delay-line devices. >

MOS triangle-to-sine wave convertor based on subthreshold operation

Abstract: A novel MOS triangle-to-sine wave convertor (TSC) is proposed. The novel circuit is based on the exponential characteristics of MOS devices operated in the subthreshold region. The circuit with a total harmonic distortion of 0.21% and bandwidth of 100 kHz has been demonstrated by PSPICE simulation and experiments.

Effects of sine wave combinations on the development of precognitive mode in pursuit tracking.

Abstract: A pursuit tracking task was carried out to investigate the effects of combinations of sine waves on the development of precognitive mode, which is defined as open-loop mode with little feedback. Subjects were asked to track the targets, which contained two or three sine waves as components, and then to reproduce the target motion after the target had been removed. Frequency characteristics of tracking revealed the superiority of the faster component over the slower components in terms of both amplitude ratio and tracking lag. Subjects' reproduction after removing the target demonstrated that in general, subjects could learn and memorize also the slower component motion, which had yielded inferior performance during the tracking period. These results are discussed in terms of a model based on successive organization of perception.

Control system for electric power supply

Abstract: An upper limit value is set up which is larger by a prescribed value than a current value of an ideal sine wave, a lower limit value is set up which is smaller by a prescribed value than the current value of the ideal sine wave. Plural semiconductor switches are actuated according to a clock pulse of specified frequency supplied from a clock pulse generator so that a boosting mode is maintained until an alternate input current increases to reach the upper limit setting value during the boosting mode and a transfer mode is maintained until the alternate input current decreases to reach the lower limit setting value during the transfer mode, thus the semiconductor switches are actuated according to the frequency of the clock pulse at the time of this transfer mode.

Synthesis of discrete time-varying null filters for frequency-varying signals using the time-warping technique

Abstract: A synthesis of two second-order discrete time-varying filters (DTVF), capable of suppressing a sine signal with arbitrary frequency variation, is presented. These structures are obtained by using the time-warping concept. A noise analysis is carried out for these two DTVFs and their performance is compared. It is shown that for the particular application considered, the rule of time-dependence of the DTVF (the synchronization) may be effectively obtained by using a phase-locked loop (PLL) system. As an example, the DTVF-PLL system is used for synchronous phase estimation of a sine wave corrupted by closely spaced FM interference. Simulation results are provided to substantiate the analysis and demonstrate the efficiency of the proposed time-varying system. The main feature of the TLM method is its formulation and programming simplicity. The method also generates a large amount of information; not only is the impulse response of a structure obtained, yielding in turn its response to any excitation, but the characteristics of the dominant and higher order modes are also accessible in the frequency domain through the Fourier transform. >

New algorithm for frequency estimation from short coherent pulses of a sinusoidal signal

Abstract: It is well known that the problem of estimating the frequency from a train of short coherent pulses in additive Gaussian noise calls for efficient methods to deal with the ambiguities at the multiples of the pulse repetition frequency. As a very sensitive method a χ2 test procedure has been used. By simulation it has been demonstrated that under realistic signal-to-noise and limited-bandwidth conditions only a few staggered pulses are necessary to resolve the ambiguities and to achieve a highly reliable estimate. The method is described and numerical data on the estimation accuracy are given.

A three-phase sine wave inverter system using multiple phase-shifted single-phase resonant inverters

Abstract: Two novel systems for synthesizing three-phase sine waves with a combination of two units, using multiple phase-shifted single-phase resonant inverters, are proposed. The first system has the advantages of both a high-frequency resonant inverter and a high-frequency AC link. The second system has the advantage of a high-frequency resonant inverter. The structure and operating principles of both proposed systems are described and their features are compared with those of a conventional 12-step inverter. The simulated and experimental results show that the proposed systems have excellent characteristics and give high-quality output waveforms. >

Variable frequency sine wave carrier signal generator

Abstract: A system and method for generating a variable frequency sine wave carrier signal operates in response to a start signal and a rate signal. The system includes a first counter which drives a second counter via an EPROM; the second counter is clocked by the output of an oscillator. The output of the second counter is converted by filtering to the desired sine wave signal.

Analysis of a serial symbol timing recovery technique employing Exclusive-OR circuit

Abstract: An analysis is presented of the performance of a serial symbol timing recovery (STR) circuit which employs an Exclusive-OR circuit for conventional coherent digital modulated communication systems. The output of the timing circuit is a nearly sinusoidal wave whose zero crossings indicate the appropriate sampling instants for extraction of the data. Assuming that the data pulses entering the timing path are even symmetric, exact analytical expressions for the mean and mean-squared values of the timing wave and for the RMS phase jitter are derived as a function of various system parameters such as channel band limiting, postfiltering, delay element, and power spectral density of noise. Numerical results, also checked by computer simulations, show that considerable improvement can be obtained in jitter performance, in addition to the advantages over other STR techniques of lower cost and simpler hardware implementation. >

Ultrasonic Waves in Free Space

Abstract: Ultrasonic testing of materials utilises mechanical waves in contrast, for instance, to X-ray techniques which use electromagnetic waves. Any mechanical wave is composed of oscillations of discrete particles of material. The motion carried out by a small mass attached to a spring as shown in Fig. 1.1 if pulled down once and released, is called an oscillation. Left to itself, the mass oscillates about the equilibrium position. The nature of this oscillation is of particular importance inasmuch as it is sinusoidal, the path recorded as a function of time being a sine curve. It is obtained only if the driving force, in this case supplied by the spring, increases proportionately to the displacement. It is then also referred to as an elastic oscillation. Furthermore, one can imagine the body to consist of individual particles kept in position by elastic forces. Very much simplified, the model of an elastic body can be visualised as shown in Fig. 1.2, but three-dimensionally. Provided such a body is not stressed by compression or tension beyond its elastic limit, it behaves like this spring model. In it, the particles can perform elastic oscillations. How then does a wave arise from an oscillation?

Method and apparatus for improved tire uniformity

Abstract: An improved of processing a tire on a uniformity machine comprising the steps of sensing the radial force variations in a tire and generating a composite waveform corresponding to the sensed force variations, converting the composite waveform into a special function waveform selected from the class of waveforms which includes filtered partial square waves, partial sine waves and full sine waves, selecting either from a table or adaptively one of the special function waveforms and grinding of the tire in response to the selected special function waveform.

Reverse phase angle control of A.C. power loads

Abstract: AC power loads such as from transformers, motors, high in-rush heaters, air conditioners, etc., are controlled by the use of bipolar transistors, FET transistors, gate turn-off SCRs and IGBT to turn on the load at zero-cross over and to turn off the load at any point in the sine wave which produces the desired amount of power. This reduces RFI and virtually eliminates di/dt at turn on since both voltage and current start at the same zero cross-over, and hence will improve the power factor. Both analogue and digital logic systems can also be utilized to produce this type of phase control, and a wide variety of possibilities are available such as serial and parallel input, the use of full wave bridge control, etc.