Showing papers on "Sine wave published in 1997"

Speech intelligibility as a function of the number of channels of stimulation for signal processors using sine-wave and noise-band outputs

Abstract: Vowels, consonants, and sentences were processed through software emulations of cochlear-implant signal processors with 2-9 output channels. The signals were then presented, as either the sum of sine waves at the center of the channels or as the sum of noise bands the width of the channels, to normal-hearing listeners for identification. The results indicate, as previous investigations have suggested, that high levels of speech understanding can be obtained using signal processors with a small number of channels. The number of channels needed for high levels of performance varied with the nature of the test material. For the most difficult material--vowels produced by men, women, and girls--no statistically significant differences in performance were observed when the number of channels was increased beyond 8. For the least difficult material--sentences--no statistically significant differences in performance were observed when the number of channels was increased beyond 5. The nature of the output signal, noise bands or sine waves, made only a small difference in performance. The mechanism mediating the high levels of speech recognition achieved with only few channels of stimulation may be the same one that mediates the recognition of signals produced by speakers with a high fundamental frequency, i.e., the levels of adjacent channels are used to determine the frequency of the input signal. The results of an experiment in which frequency information was altered but temporal information was not altered indicates that vowel recognition is based on information in the frequency domain even when the number of channels of stimulation is small.

Whisper, a resonance sounder and wave analyser: Performances and perspectives for the Cluster mission

Abstract: The WHISPER sounder on the Cluster spacecraft is primarily designed to provide an absolute measurement of the total plasma density within the range 0.2–80 cm-3. This is achieved by means of a resonance sounding technique which has already proved successful in the regions to be explored. The wave analysis function of the instrument is provided by FFT calculation. Compared with the swept frequency wave analysis of previous sounders, this technique has several new capabilities. In particular, when used for natural wave measurements (which cover here the 2–80 kHz range), it offers a flexible trade-off between time and frequency resolutions. In the basic nominal operational mode, the density is measured every 28 s, the frequency and time resolution for the wave measurements are about 600 Hz and 2.2 s, respectively. Better resolutions can be obtained, especially when the spacecraft telemetry is in burst mode. Special attention has been paid to the coordination of WHISPER operations with the wave instruments, as well as with the low-energy particle counters. When operated from the multi-spacecraft Cluster, the WHISPER instrument is expected to contribute in particular to the study of plasma waves in the electron foreshock and solar wind, to investigations about small-scale structures via density and high-frequency emission signatures, and to the analysis of the non-thermal continuum in the magnetosphere.

Electrosurgery apparatus waveform generator

Abstract: Waveform generator 2 supplies a 350 kHz square wave or sine wave output from a transformer 11 to an active hand-held electrosurgical electrode 5. Primary winding 15 of transformer 11 is connected to MOSFET switches 17,18 driven by a gate logic circuit 20, and to a modulating transistor 28 driven by the output of a sine wave generator 30 which includes a resonant LC circuit and transformer 32. The transistor 28 is connected to a 100 volt DC source 26 and provides full wave rectified sine wave voltage to transformer 11 when a sinusoidal output is required. When a square wave output is required, the transistor 28 is shunted by a manual switch 29 so that DC voltage is supplied to the centre tap 25 of primary winding 15.

Actuating circuit of piezoelectric transformer and actuating method thereof

Abstract: An actuating circuit of a piezoelectric transformer which is small in thickness and size and has a wide input voltage range is developed In the actuating circuit of the piezoelectric transformer, when a sine wave outputted from a AGC circuit is input to a delta-sigma modulator, the sine wave switches output driver and switches a second output driver through an invertor with a 1-bit quantized bit signal so as to generate a pulse signal having an amplitude of power supply voltage Vdd from the GND potential Actuating waves output from the output drivers and are applied to 1 piezoelectric transformer extracting resonance frequency of a piezoelectric transformer through a filtering effect provided with an input capacitance of the piezoelectric transformer and coil converting the 1-bit quantized bit signal into a sine wave Consequently, since the piezoelectric transformer can be operated with the sine wave, the piezoelectric transformer can be actuated efficiently

Inverse vertical seismic profiling using a measurement while drilling tool as a seismic source

Abstract: A reverse VSP system is provided and uses a frequency-controllable modulator of an MWD tool as a downhole seismic source. The modulator has a rotor and stator arranged to provide substantially sinusoidal outputs, and is controlled to provide a "Vibroseis"-type frequency sweep (preferably from 1 Hz to 50 Hz). With the bit of the MWD tool in contact with the bottom of the borehole, the force generated by the frequency-controllable modulator will generate measurable axial compressional (P-) waves. These waves which move through the formation are detected by an array of geophones on the formation surface, and a reference signal is obtained by a kelly-mounted accelerometer or strain gauge. The reference signal and signals obtained by the geophones are processed using known signal processing techniques. The disclosed downhole frequency-controllable seismic source provides many advantages including: good resolution due to the ability to output a sinusoidal wave at desired frequencies and the fact that the location of the source signal is well-defined (at the bit), the ability to image formations ahead of the bit, and the ability to conduct reverse VSP processing without adding downhole hardware equipment and without requiring trips out of the well.

Analysis of accumulated timing jitter in the time domain

Abstract: This paper deals with the effects of accumulated timing-jitter on the signal-to-noise ratio (SNR) of real sine waves. Such a problem was recently investigated by the author, using the discrete-Fourier method. However, the frequency-domain analysis has some limitations due to the fact that some of the accumulated timing-jitter noise power, found at the fundamental frequency component, would be added to the power of the input signal itself. Thus, in this paper, the analysis is performed in the time-domain and is restricted to the SNR measurement. An expression for the SNR in terms of timing-jitter distribution parameters, and the number of samples of the input signal, is developed. Computer simulations are presented, which showed excellent agreement with the developed expression. Also, a comparison between the results obtained from the time-domain analysis and the frequency-domain, is presented.

Pulse width modulator (PWM) system with low cost dead time distortion correction

Abstract: A pulse width modulator (PWM) system (100) detects several load current conditions to completely correct for the distortion caused by deadtime insertion when driving an inverter-fed inductive load, such as a three-phase AC motor. The system includes an inexpensive voltage sensor (140) which senses the output voltage at the end of each successive dead time interval in which neither a pullup transistor (51) nor a pulldown transistor (52) is driving. The system (100) includes a programmable PWM (125), two storage elements (131,132) such as D-type flip flops, and a memory-mapped register (133). The register stores the output of the flip-flops to indicate a near-zero load current condition. When it detects this condition, the system (100) changes the duty cycle of the PWM output signals to yield output voltages and currents which more closely approximate a sine wave. The system (100) is particularly useful as part of a low-cost microcontroller (120).

A synchronous-frame controller for a single-phase sine wave inverter

Abstract: A synchronous frame controller for a single-phase PWM inverter with an LC output filter is presented. These types of inverters are often used in uninterruptible power supplies (UPS) where a sinewave output voltage is to be maintained. The advantages of a synchronous frame regulator are well known in three-phase controllers where regulated AC variables (voltage, current, flux) are "-rotated" into a frame synchronous to the fundamental output frequency where they appear as DC vector quantities. Such a controller can regulate the steady-state errors of the corresponding DC quantities to zero. While the familiar dq transformation is not applicable in a single-phase system, a frame synchronous to the output fundamental can be formed by recognizing that the filter capacitor current and the filter capacitor voltage are identically 90/spl deg/ out of phase. Thus, orthogonal quantities much like dq components exist, and can be used to create a rotating frame where a composite reference vector can be summed with a similar measured vector. Simulations of a synchronous controller and a conventional state-feedback cascaded controller are presented and compared. Preliminary experimental results are also presented.

Adaptive algorithm for sinusoidal interference cancellation

Abstract: A simple method is presented for the adaptive cancelling of a sine wave signal of known frequency in a time series The system is characterised by the phase and amplitude parameters which are updated directly according to an LMS-style algorithm The convergence behaviours and variances of these parameters are analysed It is demonstrated that the proposed method can effectively remove the 50 Hz power line interference in the recording of electrocardiograms (ECG)

Radio transmitter apparatus and method

Abstract: An FM transmitter includes I and Q channels, each deriving a baseband sinusoidal wave having a frequency determined by speech and/or music broadcast information amplitude and nominally having the same maximum amplitude. Each wave drives a different balanced mixer, each responsive to orthogonally phased carrier waves. Outputs of the mixers are added to derive a frequency modulated output wave. The channels, mixers, and circuitry associated with them tend to introduce unwanted components in the output wave. Offset, peak amplitude, phase and relative delay of the added mixed outputs are such that the unwanted components are substantially eliminated from the output wave. The sinusoidal waves are derived by DACs responsive to signals derived by a digital processor having a memory storing amplitude vs. phase position values and slope vs. phase position values that are combined in response to samples of the broadcast information. The stored amplitudes and slopes control sinusoidal wave offset, peak amplitude and phase. The waves and delay times of the channels driving a power amplifier of the transmitter are calibrated on line according to certain embodiments.

Measurement of AC magnetic field distribution using magnetic resonance imaging

Abstract: Electric currents are applied to body in numerous applications in medicine such as electrical impedance tomography, cardiac defibrillation, electrocautery, and physiotherapy If the magnetic field within a region is measured, the currents generating these fields can be calculated using the curl operator In this study, magnetic fields generated within a phantom by currents passing through an external wire is measured using a magnetic resonance imaging (MRI) system A pulse sequence that is originally designed for mapping static magnetic field inhomogeneity is adapted AC current in the form of a burst sine wave is applied synchronously with the pulse sequence The frequency of the applied current is in the audio range with an amplitude of 175-mA rms It is shown that each voxel value of sequential images obtained by the proposed pulse sequence is modulated similar to a single-tone broadband frequency modulated (FM) waveform with the AC magnetic field strength determining the modulation index An algorithm is developed to calculate the AC magnetic field intensity at each voxel using the frequency spectrum of the voxel signal Experimental results show that the proposed algorithm can be used to calculate AC magnetic field distribution within a conducting sample that is placed in an MRI system

Control method for semi-active damper

Abstract: A semi-active control method for a controllable fluid damper (22) used in seat support (11). The present method filters a relative displacement signal (44) phase shifting the relative displacement sine wave by an angle from greater than 0° through an angle less than 90° to get a relative rate. The sign of the relative rate is compared to that of an absolute velocity curve obtained by integrating the absolute acceleration value obtained by an accelerometer (40) attached to the controlled seat (11). If the signs are the same, the output to the damper (22) is set to a minimum; if the signs are different, the value is set at the absolute velocity multiplied by an input gain. Endstop limits can be implemented with this control method.

Sinusoidal Voltammetry for the Analysis of Carbohydrates at Copper Electrodes

Abstract: A digital approach for the collection and analysis of electrochemical frequency domain spectra is presented for the oxidation of carbohydrates at a copper electrode using a continuous, large-amplitude sine wave as an excitation waveform. The background charging current response is a phase-shifted sine wave with the major frequency component concentrated at the fundamental frequency. A nonlinear faradaic response due to the oxidation of sugars produces significant signal intensities at the higher harmonics as well as the fundamental frequency. Examination of the frequency spectra of glucose and maltose leads to selective and sensitive detection of these sugars at a copper electrode. The selectivity of this measurement relies on the inherent difference in the frequency domain spectra (i.e., magnitude and phase of each harmonic) of sugars of different sizes. This frequency distribution is dramatically affected by temperature, indicating the effect of kinetics in the mechanism for the oxidation of sugars. The...

Active vibration reducing apparatus and method for identifying transfer function in active vibration reducing apparatus

Abstract: Described are a vibration actively reducing apparatus and a method for identifying a transfer function in the vibration actively reducing apparatus. An identification signal which is a quantization of at least one sinusoidal wave is supplied from a controller of the vibration actively reducing apparatus to a controlled vibration source in synchronization with a predetermined output sampling clock (SCo) to develop an identification vibration therefrom. The controller reads a residual vibration signal from a residual vibration detector of the actively reducing apparatus in synchronization with a predetermined input sampling clock (SCi). After read of the residual vibration signal as a time series data for each frequency, an FFT calculation is carried out for each time series data to extract a frequency component of the original sinusoidal wave. An inverse FFT calculation is, then, carried out for the result of the synthesis of each extracted frequency component to derive an impulse response as the transfer function.

Switch mode sine wave driver for polyphase brushless permanent magnet motor

Abstract: A switch mode sine wave driver circuit selectively sources and sinks driving currents to and from a dc brushless motor. A signal waveform monitoring circuit (58) puts out motor phase reference signals. A phase clock generator (102) provides a motor-synchronized clock signal. A phase counter (62) is clocked by the motor clock signal and is reset by the phase reference signals. A motor state decoder (116) generates state control signals based on the phase reference signals. A pulse width modulator circuit (84) responds to the output and generates phase pulses in order to rotate the motor.

Wireless modem jack

Abstract: A wireless power line carrier data communication device is provided. The device is specifically adapted to meet the requirements of high-speed modem data transmission, such as is typically required by digital computer networks and similar devices. The device employs an improved power line transmitter power output which reduces the effect of harmonic distortion and also employs a bit-stream sine wave generator with a digital to analog converter to producing a sine wave for the sub-audio carrier signal, which also reduces the effects of harmonic distortion. The device is specifically designed for data transfer over the AC power lines and is compatible with standard AC power signals as well as standard modem equipment and standard telephone connections.

Analysis of alignment data

Abstract: Alignment data is analyzed to determine machine condition information that is not necessarily related to alignment Alignment fixtures provide alignment data to an analyzer that finds a curve of a predetermined type, such as a sine curve, that best fits the data A confidence factor is calculated indicating the probability that the alignment data corresponds to misalignment The alignment data is further analyzed to determine a condition, other than misalignment, that contributed to the magnitudes of the alignment data Preferably, the analyzer is used to check for machine conditions such as looseness in the machine, rubs, and spall defects in a bearing Preferably, the condition analysis is based on both the confidence factors and curve parameters, such as phase, offset and amplitude of a sine curve In the condition analysis mode, the analyzer provides both manual and automatic routine for removing selected segments of data to produce trial data sets that are analyzed to determine machine conditions

Blood concentration by superposition of higher harmonics of ultrasound

Abstract: A method for concentrating cells in blood using an acoustic radiation force generated by superposition of the higher harmonics on fundamental ultrasound has been investigated. From the theoretical estimation, the efficiency of concentration of blood cells in a chamber based on a rectangular acoustic radiation force slope calculated by integration of the higher harmonics of ultrasound was 17% better than that based on a sine wave, while the peak pressure was reduced to 82% of that in the sine wave case. Concentration of blood cells was also performed experimentally using superposition of higher harmonics on a 500kHz sine wave. At a 1.2ml/min fluid flow rate, the blood cells were concentrated on the pressure node within 9s, with a cell distribution half-width of 348 μm (i.e., 76% of blood cells concentrated within 23% of the chamber width), which is 5% narrower than that of the sine wave. Though the experimental result was insufficient for the realization of the theoretical estimation because of the incomplete synthesis of the desired waveform, these results suggest the potential usefulness of this superposition method for improving the concentration efficiency with maintenance of the width of the potential slope and reduction of peak pressure.

Ion acoustic soliton excitation using a modulated high-frequency sinusoidal wave

Abstract: Experiments on the excitation of ion acoustic solitons using a fine mesh grid in a normal two component plasma are described. The excitation is novel in that a modulated high-frequency sinusoidal wave voltage signal is applied to the grid. The carrier frequency of the high-frequency sinusoidal wave is above the ion plasma frequency. An interpretation of the velocity modulation and bunching of free streaming ions that pass through the grid to which the signal is applied is given.

Switching power source

Abstract: PROBLEM TO BE SOLVED: To enable constant current-voltage drop overcorrent control by a simple circuit, by making a switching power source have a switching circuit, a resonance circuit, a transformer, an output rectifying and filtering circuit, and a circuit for protection from overcurrent. SOLUTION: A pseudo sine wave current corresponding to the resonance frequency of a resonance circuit 2 flows to the resonance circuit 2 and the primary winding 31 of a transformer 3 by the switching operation of a switching circuit 1. At this time, induced voltage is generated in the secondary winding 32. This induced voltage is converted into DC by an output rectifying and filtering circuit 4 connected to the secondary winding 32 of the transformer 3, and then, outputted. A control circuit 6 increases the operation frequency in the case that the output voltage is high so that the output voltage Vo outputted from the output rectifying and filter circuit 4 may be constant, and controls a switching circuit 1 so as to lower the operation frequency in the case that the output voltage is low. A circuit 5 for protection from an overcurrent detects the terminal voltage generated at a resonance inductor 22, and outputs it as an overcurrent detection signal S1. COPYRIGHT: (C)1998,JPO

Encoder interpolation circuit which corrects an interpolation angle between a received sine-wave encoder signal and a cosine-wave encoder signal

Abstract: An encoder interpolation circuit for obtaining interpolation data within one wave from two sine-wave encoder signals of different phases comprises interpolative computation means (2) for receiving two sine-wave encoder signals received and carrying out to interpolative computation within one wave, signal deviation detecting means (3) for detecting a deviation of the two sine-wave encoder signals, correction data forming means (4) for outputting correction data corresponding to the detected deviation and the output of the interpolative computation means, and corrective computation means (5) for obtaining the corrected interpolation data by carrying out corrective computation for the output of the interpolative computation means with the correction data and obtaining corrected interpolation data.

Geophysical exploration system using seismic vibrator source which provides a composite sweep

Abstract: A system for geophysical exploration uses a single source (30) which emits signals over multiple octaves. The source is driven by a composite sweep signal having two or more sweeps, one of which covers the lower octave (10) while the other sweeps cover the remainder of the bandwidth. The signals covering the lower portion are reduced in the case of a sweep which varies linearly with time in proportion to the square root of the ratio of the sweep rate of the signals covering the upper end to the sweep rate of the signals covering the lower end. The signals are transmitted simultaneously. Because of the composite sweep the same energy spectrum is transmistted as with a sine wave sweep which extends over the entire frequency band, while reducing the peak power and radiator displacement required at lower frequencies to maintain a flat spectrum. The size of the equipment can be reduced.

Absolute position detection method for stroke sensing cylinder

Abstract: An improved absolute position detection method is provided for a stroke sensing cylinder which includes a magnetic scale detecting step for obtaining a plurality of sine wave form voltages having different phases using a magnetic sensor unit in accordance with a driving operation of the cylinder. A wave form generation step is also provided for converting the sine wave form voltage obtained in the magnetic scale detection step into a square wave form and generating a triangle wave form having the same period as the thusly converted square wave form. A first absolute position value detection and stroke direction judging step is then provided for judging a first absolute position value and stroke direction of the cylinder using a pair of square and triangle wave forms generated in the wave form generation step. Lastly, a second absolute position value computation and storing step is provided for computing and storing a second absolute position value having a predetermined value based on the first absolute position value. The method of the present invention is directed to detecting a magnetic flux change of a magnetic scale using a plurality of magnetic sensors. The magnetic scale is disposed along the cylinder rod and includes at least one different magnetic scale processing period contained within a regularly protruded and recessed portion. Signal-processing is achieved using a microprocessor and a 1/N-dividing counter. The thusly signal-processed wave forms are counted and an absolute position and stroke direction is determined.

On the Use of a Sinusoidal Model for Speech Synthesis in Text-to-Speech

Abstract: We discuss the adequacy of a model that represents the speech signal as a sum of sine waves to the requirements of concatenative speech synthesis in text-to-speech (TTS). This model allows wide-range and high-quality prosodic modifications, and produces smooth transitions where the speech segments are joined. A preference test was carried out between speech synthesized using a pitch synchronous linear predictive coding (PS-LPC) synthesizer and the sinusoidal synthesizer.

Particle image velocimetry for the measurement of mean and acoustic particle velocities

Abstract: A novel method is outlined which allows measurement of the amplitude of oscillation of a sinusoidal sound field and the mean flow using particle image velocimetry. The method involves simplifying the interrogation area in such a way that the autocorrelation function contains four significant peaks. The accuracy is of the order of half pixel resolution, once a constant offset related to the non-continuous nature of the probability function of a sine wave is taken into account. This constant, which originates from the pixelation of the image, is shown to be 0.85 pixels.

AC-DC converter

Abstract: An AC-DC converter includes an adjusting unit 13 which operates to zero the difference between a DC output voltage instruction value and a DC output voltage detection value; and a modulator 16 which compares a carrier wave based on an output signal- of the adjusting unit 13 with a modulating wave to output drive pulses, a switching element 3 is turned on and off with the drive pulses to provide a Dc output voltage which is higher than a full-wave rectification voltage of an AC input voltage. In order to obtain the carrier wave, the AC-DC comprises further includes an AC input voltage polarity detector 7, a PLL circuit 11, and a multiplier 14 for multiplying the sine wave by an output signal of the adjusting unit 13.

Numerical study of MUSCL schemes for computational aeroacoustics

Abstract: Two upwind finite-volume schemes are studied for solving the solutions of 2D Euler equations. They are based on the MUSCL (monotonic upstream scheme for scalar conservation law) approach with the Roe approximate Riemann solver for the numerical flux evaluation. First, dissipation and dispersion relation and group velocity are carried out to analyze the capability of one of the proposed schemes for capturing physical waves. Then two schemes are greatly enhanced through a special treatment on the numerical dissipation to effectively handle aeroacoustic computations. The numerical results indicate that the numerical dissipation treatment allows that two schemes simulate continuous waves at fourth-order accuracy and captures discontinuous waves sharply as well as most of upwind schemes do. The tested problems include 1D group velocity analysis, propagation of discontinuous and sine waves, shock and sine wave interaction, and 2D traveling vortex in an uniform freestream. The numerical results show that the proposed dissipation treatment can reduce dispersion and dissipation errors of two upwind schemes for simulating the aeroacoustic problems. (Author)