Showing papers on "Sine wave published in 1994"

The cumulant theory of cyclostationary time-series. I. Foundation

Abstract: The problem of characterizing the sine-wave components in the output of a polynomial nonlinear system with a cyclostationary random time-series input is investigated. The concept of a pure nth-order sine wave is introduced, and it is shown that pure nth-order sine-wave strengths in the output time-series are given by scaled Fourier coefficients of the polyperiodic temporal cumulant of the input time-series. The higher order moments and cumulants of narrowband spectral components of time-series are defined and then idealized to the case of infinitesimal bandwidth. Such spectral moments and cumulants are shown to be characterized by the Fourier transforms of the temporal moments and cumulants of the time-series. It is established that the temporal and spectral cumulants have certain mathematical and practical advantages over their moment counterparts. To put the contributions of the paper in perspective, a uniquely comprehensive historical survey that traces the development of the ideas of temporal and spectral cumulants from their inception is provided. >

Histogram measurement of ADC nonlinearities using sine waves

Abstract: This paper gives results concerning the measurement of differential and integral nonlinearity of ADC's using the histogram method with a sine wave input signal. We specify the amount of overdrive required as a function of the noise level and the desired accuracy and the number of samples required as a function of the desired accuracy, the desired confidence level, and the noise level. An analysis of the effect on the results of harmonic distortion of the applied signal is given. The error analysis assumes a mixture of coherent and random sampling rather than pure random sampling. >

Low-dimensional description of free-shear-flow coherent structures and their dynamical behaviour

Abstract: The snapshot form of the Karhunen-Loeve (K–L) expansion has been applied to twodimensional, two-component hot-wire data from the region of a weakly pertubed free shear layer that includes the first pairing process. Low-level external perturbation was provided by a loudspeaker driven by a computer-generated signal composed of two sine waves of equal amplitude at the frequencies of the naturally developing fundamental instability wave and its first subharmonic, separated by a controllable initial phase angle difference. It was found that a large fraction of the fluctuation energy is carried by the first few modes. A low-dimensional empirical eigenfunction space is obtained which describes the shear-flow coherent structures well. Galerkin projection of the Navier-Stokes equations onto this basis set of principal eigenfunction modes results in a low-order system of dynamical equations, and solution of this system of equations describes the dynamics of the coherent structures associated with eigenfunctions. Finally the simulation, as obtained from the system of dynamical equations, is shown to compare reasonably well with the experiments.

Vibration/noise control system

Abstract: A sine wave signal generated in synchronism with a pulse signal determining a frequency of vibrations and noises generated by a vibration/noise source is input to a W filter and a C filter. The C filter selects filter coefficients dependent on the rotational speed of an engine, and generates a transfer characteristic-dependent reference signal R dependent on a transfer characteristic of a vibration/noise-transmitting path, based on the filter coefficients. Alternatively, a divisional signal is prepared by dividing a repetition period of vibrations and noises by a predetermined number, and values of a sine wave generated in synchronism with occurrence of said divisional signal is delivered to a W filter, while the transfer characteristic-dependent reference signal is delivered from the C filter storing data of the transfer characteristic identified in advance to the W filter. Alternatively, a sine wave signal and a delayed sine wave signal delayed by a quarter of a repetition period of the sine wave relative to the sine wave, as well as phase and amplitude-related information of the transfer characteristic of the path are generated and delivered in synchronism with generation of the divisional signal. These sine wave signals and the transfer characteristic-dependent reference signal (phase and amplitude-related information) are used to actively control the vibrations and noises.

Wide band stepped frequency ground penetrating radar

Abstract: A wide band ground penetrating radar system (10) embodying a method wherein a series of radio frequency signals (60) is produced by a single radio frequency source (16) and provided to a transmit antenna (26) for transmission to a target (54) and reflection therefrom to a receive antenna (28). A phase modulator (18) modulates those portion of the radio frequency signals (62) to be transmitted and the reflected modulated signal (62) is combined in a mixer (34) with the original radio frequency signal (60) to produce a resultant signal (53) which is demodulated to produce a series of direct current voltage signals (66) the envelope of which forms a cosine wave shaped plot (68) which is processed by a Fast Fourier Transform unit 44 into frequency domain data (70) wherein the position of a preponderant frequency is indicative of distance to the target (54) and magnitude is indicative of the signature of the target (54).

Tracking analysis of an adaptive notch filter with constrained poles and zeros

Abstract: This paper analyzes the asymptotic tracking properties of an adaptive notch filter (ANF) with pole-zero constraints for the cancellation or retrieval of multiple time-varying sine waves in additive noise. The asymptotic mean square error (MSE) is analyzed using the methods of Ljung and Gunnarsson (1990) when the variations in the underlying frequencies are assumed to be sufficiently small. Closed-form expressions for the MSE are derived as functions of the tuning variables of the algorithm. The results give insight into the operational properties of the algorithm and are used in order to minimize the MSE with respect to the tuning variables. Computer simulations confirm the validity of the derived results. >

FM band multiple signal modulator

Abstract: Apparatus and a method for generating all of the assignable carrier frequencies in the FM broadcast band and for frequency modulating the generated carriers includes a generator of a train of pulses having a crystal-controlled repetition frequency and a specific pulse shape which together produce a spectrum of odd harmonics of the pulse repetition frequency whose separation in frequency is identical to that of the assignable carrier frequencies. This pulse train is then mixed with a 98.0 MHz sine wave to translate the spectrum to the FM band. Simultaneous modulation of all the carriers is achieved by frequency modulating the 98.0 MHz sine wave, whereby the same modulation is imparted simultaneously to all of the carriers.

A High Resolution Multibit Sigma-delta Modulator With Individual Level Averaging

Abstract: A second-order sigma-delta modulator with a 3-b internal quantizer employing the individual level averaging technique has been designed and implemented in a 1.2 μm CMOS technology. Testing results show no observable harmonic distortion components above the noise floor. Peak S/(N + D) ratio of 91 dB and dynamic range of 96 dB have been achieved at a clock rate of 2.56 MHz for a 20 KHz baseband. No tone is observed in the baseband as the amplitude of a 10 KHz input sine wave is reduced from −0.5 dB to −107 dB below the voltage reference. The active area of the prototype chip is 3.1 mm 2 and it dissipates 67.5 mW of power from a 5 V supply

Bounds on least-squares four-parameter sine-fit errors due to harmonic distortion and noise

Abstract: Least-squares sine-fit algorithms are used extensively in signal processing applications. The parameter estimates produced by such algorithms are subject to both random and systematic errors when the record of input samples consists of a fundamental sine wave corrupted by harmonic distortion or noise. The errors occur because, in general, such sine-fits will incorporate a portion of the harmonic distortion or noise into their estimate of the fundamental. Bounds are developed for these errors for least-squares four-parameter (amplitude, frequency, phase, and offset) sine-fit algorithms. The errors are functions of the number of periods in the record, the number of samples in the record, the harmonic order, and fundamental and harmonic amplitudes and phases. The bounds do not apply to cases in which harmonic components become aliased. >

High speed, low power direct digital synthesizer

Abstract: A method and apparatus suitable for generating programmable digital sine waves which involves converting the output of a direct digital synthesizer or numerically controlled digital oscillator to a higher frequency with a multiplier-less structure that takes advantage of the properties of trigonometric identifies for sine and cosine. Sine waves are generated digitally using a phase accumulator which is clocked at one fundamental frequency. The phase accumulator input provides a control word which determines the intermediate frequency of the direct digital synthesizer output. Taking advantage of the periodicity of the phase accumulator operation, the outputs of the accumulator are utilized to address a read only memory ROM lookup table which produces in-phase and quadrature samples of the sine wave at the intermediate frequency. The in-phase and quadrature samples are then complemented (i.e. negated) to produce an additional set of in-phase and quadrature samples which are 180° out of phase from the original samples. Switching between these four possible outputs at a higher fundamental clock frequency results in the translation of the intermediate frequency output to a higher frequency.

Feed forward amplifier

Abstract: In a feed forward amplifier (100), a main amplifier (125) is coupled between an input (102) at which an input signal is received and an output (173) at which an output signal is provided. The output signal is an amplification of the input signal. A sample of the output signal is compared (144) with a sample of the input signal to produce a difference signal indicative of distortions introduced by the main amplifier (125). An error amplifier (165) provides a distortion signal which is an amplification of the difference signal, and the distortion signal is combined (169) with the output signal to compensate for main amplifier distortions. A random frequency, constant amplitude sine wave pilot signal is combined (117) with the input signal, and a correlation power detector (194,195,202,212,213) is provided to determine the magnitude of the pilot signal in the output signal. The gain and phase of the difference signal is then adjusted (155) to minimize the magnitude of the pilot signal in the output signal. Additionally, a distortion signal power signal, which is indicative of the magnitude of the difference signal, is provided (151,158), and the gain and phase of the input signal is adjusted (112) to minimize the magnitude of the distortion signal power signal.

Method and apparatus for reduction of optical communication system impairments

Abstract: A method and apparatus for reducing noise in optical communication systems (21,24,26,27,28) is effected by modulating or dithering the laser (21) output frequency at a relatively low rate. The laser (21) may be dithered by applying a low frequency sine wave (from 22) either to the resistive heater in the phase control section or to the laser's active section directly. By dithering the laser at a low frequency and at a sufficiently high amplitude to cause large optical frequency excursions, the noise caused by multipath interference will decrease without substantially increasing negative dispersion effects.

A time-frequency distribution of Cohen's class with a compound kernel and its application to speech signal processing

Abstract: Time-frequency distributions belonging to Cohen's class have been discussed in deterministic nonstationary signal processing. The Wigner-Ville distribution is the first to be proposed among the class and is most widely studied and applied in the various fields. However, one of the main difficulties with the Wigner-Ville distribution is that it indicates spurious values in the intensity due to interference particularly prevalent for multicomponent signals. The authors propose a new type kernel function that is the product of the Choi-Williams kernel and the Margenau-Hill kernel. Specific types of signals: sinusoidal signals, chirp signals, and others are analyzed using the new distribution in comparison with the results by the Wigner-Ville and the Choi-Williams distributions. The present distribution does not indicate spurious intensity in the regions where the other two distributions do. In the authors' distribution, the spurious values are transferred to places where one would expect the signal's inherent intensity at least for a signal of pure sine waves. Thus correct values of the signal's intensity are slightly modulated due to cross talk. The three distributions are also compared numerically for these signals and for speech signals to show the advantages of the present distribution. >

Integral Equation Model for Wave Propagation with Bottom Frictions

Abstract: An integral equation method is developed to calculate wave propagation and runup in a two‐dimensional wave channel. First, the problem is formulated as a potential flow with nonlinear free‐surface boundary conditions. The effects of bottom friction are included in the model via a boundary‐layer approximation. Numerical solutions are obtained for the maximum runup heights of solitary waves and cnoidal waves on a constant slope. Numerical solutions are compared with available experimental data. A very good agreement is observed. The maximum runup height of a cnoidal wave is larger than that of an equivalent sinusoidal wave. However, the runup height of cnoidal wave is smaller than that of solitary wave with the same wave height. The runup height of cnoidal waves is not a monotonic function of the incident wavelength. Numerical solutions for the maximum runup heights confirm that the bottom frictional effects are important when the slope is less than 20°.

A high-speed wide dynamic range time-to-digital converter

Abstract: We describe a time‐to‐digital converter able to measure intervals as great as 100 ns with a resolution of 4 ps rms. It achieves this large dynamic range by simultaneously sampling four sinusoidal wave forms (sine and cosine waves at 200 and 6.25 MHz) derived from a single quartz oscillator. Twelve‐bit analog‐to‐digital conversion of the 200 MHz waves yields the high time resolution. Eight‐bit conversion of the 6.25 MHz samples removes the cycle ambiguity of the 200 MHz data. The digital words are pipelined in a fully parallel data flow architecture. A first‐in first‐out stage in the pipeline derandomizes the random event arrival times. A subsequent stage in the pipeline uses an arctangent function to convert the sine and cosine pairs into linearized measures of event time. These are subtracted to yield start–stop time interval sizes for individual photoevents. The minimum start–stop interval is 50 ns, set primarily by the cycle time. Because the same processing is employed for the start and stop events, a large class of potential error and drift phenomena are eliminated. The digitizer provides an accurate way to decode the outputs of delay line detectors, offering high event throughput and extremely good long‐term timing accuracy. As a side benefit, the pipeline data flow architecture permits simple breadboarding and low‐throughput testing of the system stages with the arctangent work implemented in a personal computer. This arrangement is also very convenient for logging diagnostic evaluation data. The same front‐end and data flow architecture is directly applicable to very high‐speed applications where the event processing is implemented in a digital signal processor.

Power factor correction circuit

Abstract: A compensation circuit in a boost-type preregulator of the type having a power factor control circuit operating in a critical conduction mode by providing a triangular modulation of current according to a sine wave envelope, the compensation circuit in the form of a charge pump circuit acting as a frequency-to-voltage converter and including a capacitor, diode and resistor network providing AC coupled current pulses from the output to the input of the power factor control circuit to reduce crossover distortion during the zero-crossing of input current drawn from a sine wave power source. A capacitor at the current envelope input of the power factor control circuit operates to time-average integrate the current pulses to provide a load-current-dependent bias or compensation signal to the power factor correction circuit regulating the critical conduction mode of operation. In another embodiment, the compensation circuit includes an amplifier connected to a current feedback resistor and to a fixed reference to provide the compensation signal.

Fundamental space-charge fields for applied alternating electric fields in photorefractive materials

Abstract: The fundamental component of the space-charge field in a photorefractive crystal is studied in the presence of an applied alternating electric field. A general equation for the amplitude of the fundamental space-charge field is derived, and a solution in integral form is given for the linear-modulation approximation. Exact and approximate analytical solutions are presented for the case in which the applied field varies in time as a square and a sine wave, respectively. The temporal variation of the amplitude of the space-charge field is investigated for both waveforms of the applied field, and the oscillation amplitude dependence on repetition frequency and interbeam angle is studied.

Pwm converter device

Abstract: PURPOSE: To eliminate the adverse effect of surge voltage on equipment connected to a same system by switching the reference signal of a current reference signal generator from the signal of a power supply phase detection circuit to the phase signal according to the operation by a microcomputer after detecting the loss of an input voltage. CONSTITUTION: When a power failure detection circuit 12 detects a power failure, the signal from a phase detection circuit 11 to a sinusoidal wave generator 4b is switched to a phase signal from a microcomputer 15 and a signal with the same phase as that of a power supply when no power failure occurs is given to the sinusoidal wave generator 4b. Then, an operation mode immediately before the power failure is judged according to the output of an operation mode detection circuit 14. In the case of power-running mode, a power converter 3 of a PWM converter is stopped. Then, after a specific amount of time passes, a stop command is outputted to an inverter device. When the operation mode immediately before power failure is in regeneration mode, the power converter 3 of the PWM converter is stopped after a specific amount of time and at the same time a stop command is outputted to the inverter device. COPYRIGHT: (C)1995,JPO

DSP-based digital control of a PWM inverter for sine wave tracking by optimal state feedback technique

Abstract: This paper proposes a fully digital control scheme for the closed-loop regulation of a single-phase PWM inverter used to synthesize a sinusoidal waveform even under large load variation. An accurate sampled-data model of the PWM inverter considering the sensor dynamics has been derived. The optimal state feedback gains of the proposed digital controller are determined by fitting a specified step response through the steepest descent method. The gating signals of the switching devices are computed at every sampling instant by instantaneous feedback of the inductor current and output voltage. The design procedure of the proposed digital controller and its software realization have been described in detail. Moreover, a DSP-based (TMS320C14) fully digitally controlled PWM inverter has been constructed to verify the proposed control scheme. The simulation and experimental results show that satisfactory results can still be obtained even at low sampling frequency. >

An analog memory integrated circuit for waveform sampling up to 900 MHz

Abstract: The design and implementation of a switched-capacitor memory suitable for capturing high-speed analog waveforms is described. Highlights of the presented circuit are a 900 MHz sampling frequency (generated on chip), input signal independent cell pedestals and sampling instances, and cell gains that are insensitive to component sizes. A two-channel version of the memory with 32 cells for each channel has been integrated in a 2-/spl mu/m complementary metal oxide semiconductor (CMOS) process with polysilicon-to-polysilicon capacitors. The measured rms cell response variation in a channel after cell pedestal subtraction is less than 0.3 mV across the full input signal range. The cell-to-cell gain matching is better than 0.01% rms, and the nonlinearity is less than 0.03% for a 2.5-V input range. The dynamic range of the memory exceeds 13 bits, and the peak signal-to-(noise+distortion) ratio for a 21.4 MHz sine wave sampled at 900 MHz is 59 dB. >

Theory and application of a capacitive sensor for safeguarding in industry

Abstract: A capacitive sensor for the safeguarding of automatically working machines in industry has been developed. It can be used as a complement to more expensive pressure sensitive mats, light curtains or fences. The sensor consists of two electrically conducting planes, insulated electrically from the ambient. The planes are placed opposite each other, one in the floor and one in the ceiling of for example a robot cell. One of the planes is used as the antenna of the transmitter and the other works as the antenna of the receiver. When conductive conditions in the space between the two planes are altered, e.g. a person enters, the signal from the receiver changes and indicates the presence of the person. By the use of a current/voltage-converter followed by a lock-in amplifier as receiver an excellent signal-to-noise ratio is achieved. A sine wave modulated by bandwidth limited white Gaussian noise is used as transmitting signal. This signal reduces the strength of the electric field per frequency unit, radiated by the sensor. The theory for the sensor and the sensor signal handling is presented and some practical experiments are described. The theory is well verified by the experimental results. >

FSK detector for determining an increasing time period between adjacent pulses of an FSK modulated square wave pulse train

Abstract: An FSK detector circuit and method which may be utilized for the demodulation of a digital data signal from a modulated sine wave carrier signal. A simple, low parts count FSK detector is disclosed which is readily implemented as an integrated circuit for the detection of a digital data signal in wireless applications without the use of an associated phase locked loop or other frequency detection circuitry.

Spectral properties of DDFS: computer simulations and experimental verifications

Abstract: In the present paper we shall discuss generation of spurious signals in direct digital frequency synthesizers (DDFS) with different output waves with the assistance of computer simulations. First, we shall deal with simple square wave and triangular wave outputs. However, our main attention will be paid to the systems generating sine signals since they exhibit the lowest level below one cannot get. The major sources of spurious signals are phase truncation, the limited length in sine look-up tables, the finite resolution of digital to analog convertors DAC, and intermodulation problems. The latter are not easy to appreciate. >

Method and apparatus for controlling spindle motor

Abstract: A brushless DC motor in which rotor magnetic poles were sine wave polarized is used. A rotational speed of the motor is detected by using one of Hall elements built in the DC motor. A control gain (A) to maintain the motor at a specified rotational speed is detected. Drive signals of three phases which were sine wave amplitude modulated on the basis of the detected rotational speed and the detected gain are supplied to the DC motor. A pulse amplitude control circuit which is used to activate the motor is used as a gain sensor. A gain which is used for the sine wave amplitude modulation is detected from a pulse amplitude modulation signal.

A direct digital frequency synthesizer using an IIR filter implemented with a DSP microprocessor

Abstract: Direct digital frequency synthesizers (DDFSss) are generally implemented by successively scanning trough a lookup table stored in a read-only memory (ROM) and converting the recalled sine samples to an analog waveform via a digital to analog converter (DAC). This paper describes a new implementation of a DDFS using a second order IIR resonator, whose impulse response is a sine wave; as this impulse response can be expressed in a second order recursive form, sample generation only requires few multiplications and additions. Therefore, the idea is to use a fast DSP microprocessor that can implement the recursive equation in "real-time". This technique guarantees a larger set of output frequencies, a high spectral purity and a very simple, compact, and reliable hardware design. >

Control of PWM voltage inverters in the pulse dropping region

Abstract: The overmodulation of pulse width modulated (PWM) inverters causes a nonlinearity in the feedforward channel. The type of modulator, sine wave, space vector, or third harmonic, establishes the characteristics of the transition region's nonlinearity. The characteristics for a number of modulation strategies are introduced. Test results from commercially available volts per hertz (V/F) drives reveal their inability to provide rated voltage even at rated input conditions. The adverse effects of the overmodulation region on current regulated AC inverters are demonstrated by experimental results. A compensated modulation technique (CMT), adaptable to continuous and discontinuous modulators, provides the exact inverse of the nonlinearity; thus it produces a smooth transition to six-step operation without inducing a voltage transient. Experimental results presented in the paper demonstrate the CMT's smooth transition to six-step and the improved performance of the CMT-PWM. Finally, a comparison of the CMT with the other known overmodulation strategy shows the CMT provides a simple technique with essentially identical harmonic characteristics. >

Circuit for estimating a peak or RMS value of a sinusoidal voltage waveform

Abstract: An estimating circuit for application in estimating or deriving the value V 2 rms or V 2 peak , of a line voltage VAC provides fast response time and a substantially ripple free value for these signals by the utilization of a controlled harmonic oscillator whose output precisely tracks the input voltage waveform. Two out of phase (by π/2) sine wave signals are derived (by 101,102) from the input sine wave (on 105), and these two out of phase signals are squared (in 115,117) and summed (in 119) to derive or estimate the desired square of the sine waveform signal at a fast response time while substantially excluding ripple of the estimated out of phase sine waves. An estimating circuit, described herein, comprises two integrator circuits (101,102) series connected into a substantially closed loop. The output of the second integrator (102) circuit is fed back to the input of the first integrator circuit (101). The output of each individual integrator circuit is a voltage sine wave separated in phase from the output of the other integrator by π/2 and in synchronism with the input substantially sine wave voltage VAC. The output of each of the integrator circuits is squared in an associated squaring circuit (115,117). Each output of one of the two squaring circuits is summed (in 119) with the output of the other squaring circuit to produce the desired value of V 2 peak or V 2 rms .

Absolute position detector and its error correcting method

Abstract: PURPOSE: To obtain an absolute position detector where a hardware for correction is eliminated by performing all error compensation with software by a high-speed arithmetic processor. CONSTITUTION: The title detector is provided with a sine wave/consine wave generation part 12 for generating one set or plural sets of sine waves/cosine waves in a period, an A/D conversion parts 5a and 5b for converting the input of sine waves/consine waves generated by the sine wave/consine wave generation part 12 to digital values, and an operation part 101 for correcting an error containing offset and amplitude/phase errors based on the digital values from the A/D conversion parts 5a and 5b. The operation part 101 obtains phase by operation before or halfway through error correction and also obtains phase from the digital quantity from the A/D conversion parts 5a and 5b. COPYRIGHT: (C)1995,JPO