Showing papers on "Sine wave published in 1992"

A new impedance spectrometer for the investigation of electrochemical systems

Abstract: The development of a computer‐controlled electrochemical impedance spectrometer, based on a Fourier transform algorithm is described. Together with a fast potentiostat the system can be used in the frequency range 1 mHz to 100 kHz. The perturbation signal is a superposition of sine waves with properly chosen frequencies. The overall measurement time is limited only by the lowest frequency in the spectrum and by the data transfer to the computer, thus, time‐resolved impedance spectra measurements can be performed. The principle of operation and technical details are presented and discussed.

The application of network objective functions for actively minimizing the impact of voltage harmonics in power systems

Abstract: The impact of voltage harmonics on a power system can be minimized by using active filters to inject distortion-canceling currents. However, a network objective function must be specified before the optimum filter injection currents can be determined. The authors illustrate the application of a distortion-minimizing procedure with each of the following four network correction strategies, total harmonic voltage distortion, telephone influence factor, motor load-loss function, and single-bus sine wave correction. It is also pointed out that, as with any active device, care must be taken when sitting and controlling an APLC (active power line conditioner) to ensure maximum improvement in network distortion. If a network approach is not used, a poorly located APLC could have an overall negative impact. >

Reaction sensing torque actuator

Abstract: A reaction torque actuator has a sensor operatively coupled between a motor housing and an outer housing. A pair of bearings support the motor within the outer housing in a spaced, concentric relationship. The bearings allow a mutual angular displacement of the housing about the axis of rotation of the output shaft of the motor, but they isolate the sensor from the axial and radial moments. A resolver surrounds the shaft at its output end to produce a signal that accurately measures the angular position of the shaft. A controller regulates power to the motor windings as a function of signals from the resolver and the sensor and torque commands. In a preferred form for use in robotics where very accurate force control is desired, the motor: is a brushless D.C. motor, the sensor is of the strain gauge type, and the controller uses high quality amplifiers, sine wave commutation, cable shielding, and filtering to limit the noise generated by electronic switching.

Pseudorandom signals to estimate apparent transfer and coherence functions of nonlinear systems: applications to respiratory mechanics

Abstract: For pseudorandom (PRN) input stimuli, general expressions are derived for the apparent transfer (Z) and coherence ( gamma /sup 2/) functions of nonlinear systems that can be represented by a Volterra series. To avoid the problems that are shown here to be associated with harmonic distortions and to minimize the influence of crosstalk, a family of pseudorandom signals which are especially suited for the estimation of Z and gamma /sup 2/ in mechanical measurement of physiological systems at low frequencies is proposed. The components in the signals cannot be reproduced as linear combinations of two or more frequency components of the input. In a second-order system, this completely eliminates the bias, while in higher order but not strongly nonlinear systems, the interactions among the components are reduced to such a level that the response can be considered as if it were measured with independent sine waves of an equivalent amplitude. It is also shown that the values of gamma /sup 2/ are not appropriate for assessing linearity of the system. The theory is supported by simulation results and experimental examples. >

Analysis of nonlinearities in the flicker ERG.

Abstract: The electroretinogram (ERG) response to steadily flickering fields shows significant nonlinear components. These nonlinear components have been used to investigate the ERG. We find the following. (1) The fundamental retinal response can be recorded at frequencies greater than 100 Hz and the second and higher harmonic responses have measurable response frequencies as high as 200 Hz. Both the fundamental response component and the second harmonic response component have multiple local maxima as a function of frequency. (2) Measurement of the response of the retina to the sum of two sine waves indicates that there is an early low-pass temporal filter in the retina. This early filter has a cutoff frequency between 40 and 50 Hz. (3) The high frequency nonlinearity is not a compressive nonlinearity.

Photoplethysmographics using phase-division multiplexing

Abstract: First and second carrier signals, distinguishable by phase, are respectively applied to infrared and red energy emitters. A detector receives the sum of the energy after modulation at the infrared and red wavelengths. The signal received by the detector is then demultiplexed into its original first and second components, thereby allowing determining of both the infrared and red modulation components. The first and second carrier signals may comprise time-varying periodic signals with identical frequency and frequency spectra, such as a pair of sine waves which are indistinguishable except by phase and amplitude. A 90° phase difference is preferred, but any phase other than 0 or an integer multiple of 180° is workable. A carrier frequency which avoids excessive interference from ambient light is preferred.

Apparatus and method for phase resolved fluorescence lifetimes of independent and varying amplitude pulses

Abstract: A flow cytometer measures phase fluorescence lifetimes by the phase shift of a reference signal and an emission from a particle or cell in a flow chamber (17). An acoustic optic modulator (13) modulates laser light with a sinusoidal wave of a predetermined frequency to excite particles or cells. Detectors respond to emissions of individual particles or cells in the form of an output signal pulse at the predetermined frequency. The output signal pulse is divided into equal pulses with each at the modulation frequency, the same amplitude and fidelity and amplitude. One part of the divided pulse is stripped of its envelope to pass the width thereof and out of band components are rejected. A variable amplifier passes a portion of the pulse above a preset level. A delay line sets a central part of the signal at a predetermined point in time. A circuit limits the attenuated one part. A double balance mixer multiplies and the relates the limited signal with a reference signal to determine the phase shift. The next step attenuates the signal to a preset level so it can be limited, then filtered to remove harmonics above the modulation frequency and an envelope below. A double balance mixer multiplies the limited signal with a reference signal and produces a multiple signal and determining the relative phase shift of the emissions.

Newton algorithms for conditional and unconditional maximum likelihood estimation of the parameters of exponential signals in noise

Abstract: The authors present polynomial-based Newton algorithms for maximum likelihood estimation (MLE) of the parameters of multiple exponential signals in noise. This formulation can be used in the estimation, for example, of the directions of arrival of multiple noise-corrupted narrowband plane waves using uniform linear arrays and the frequencies of multiple noise-corrupted complex sine waves. The algorithms offer rapid convergence and exhibit the computation efficiency associated with the polynomial approach. Compact, closed-form expressions are presented for the gradients and Hessians. Various model assumptions concerning the statistics of the underlying signals are considered. Numerical simulations are presented to demonstrate the algorithms' performance. >

Automatic tuning apparatus for PID controllers

Abstract: An autotuning procedure for a PID-type controller employs a low frequency sine wave as an exciting input and models the controlled system as a second order linear system. The system is tuned to a desired damping ratio by following an overdamped trajectory, in closed loop gain and phase lag space, to the target closed loop gain and phase lag values on a locus of a desired damping ratio as based on that modeling system.

Code reading systems

Abstract: Bar code reading systems having enhanced detection capabilities are disclosed. The systems are particularly useful for invisible bar codes. The bar code is irradiated with radiation that is sine wave or square wave modulated at one or more frequencies. A detector is sensitive to a frequency related to the modulation frequencies, preferable to a sum or a difference of at least two modulating frequencies, produced by intermodulation of the modulating frequencies. Such intermodulation can result from the non-linear fluorescing characteristics of dyes incorporated into the bar code markings. The modulation can also be sinusoid or square wave at a single frequency. Detection of coded information on sheets containing whiteners or other dyes capable of fluorescing in response to the radiation utilized by the code reader is improved by employing radiation absorbing components in the code markings.

Modulation transfer function measurement technique for small-pixel detectors

Abstract: A modulation transfer function (MTF) measurement technique suitable for large-format, small-pixel detector characterization has been investigated. A volume interference grating is used as a test image instead of the bar or sine wave target images normally used. This technique permits a high-contrast, large-area, sinusoidal intensity distribution to illuminate the device being tested, avoiding the need to deconvolve raw data with imaging system characteristics. A high-confidence MTF result at spatial frequencies near 200 cycles/mm is obtained. We present results at several visible light wavelengths with a 6.8-micron-pixel CCD. Pixel response functions are derived from the MTF results.

A PWM strategy for reducing torque-ripple in inverter-fed induction motor

Abstract: A new PWM strategy suitable for an inverter-fed induction motor is described. The output waveforms in the proposed PWM inverter are investigated both theoretically and experimentally. Although the output waveform is a nonsinusoidal waveform, the induction motor driven by the proposed modulating signal produces approximately constant torque. A modulating signal for the three-phase PWM inverter is obtained by superposing a rectangular wave on the specific trapezoidal wave whose flat portion is 120 degrees. By using the proposed modulating signal, the amplitude of the fundamental component is increased by about 17 percent more than that of a conventional sine wave inverter. The new system reduces the torque ripple as well as achieving the effective utilization of the DC supply voltage for the inverter. >

Component wave delineation of ECG by filtering in the Fourier domain

Abstract: A complete solution to the fundamental problem of delineation of an ECG signal into its component waves by filtering the discrete Fourier transform of the signal is presented. The set of samples in a component wave is transformed into a complex sequence with a distinct frequency band. The filter characteristics are determined from the time signal itself. Multiplication of the transformed signal with a complex sinusoidal function allows the use of a bank of low-pass filters for the delineation of all component waves. Data from about 300 beats have been analysed and the results are highly satisfactory both qualitatively and quantitatively.

Electric control apparatus for brushless motor

Abstract: A control apparatus for controlling an output torque of a brushless electric motor based on a torque command signal received from a torque command signal generator. The control apparatus includes magnetic pole position sensors for producing position signals indicative of a rotational position of a rotor of the motor. A counter outputs an address signal based on the position signals. A sine wave memory, which stores plural sine waves, outputs a sine wave signal based on the address signal. Then the amplitude of the sine wave signal is linearly controlled based on the torque command signal, and stator current is applied to stator windings of the motor based on the linearly controlled sine wave signal.

Method and apparatus for providing tailored excitation as in Fourier transform mass spectrometry

Abstract: Tailored excitation of ions in a mass spectrometer is obtained by using an excitation signal which comprises at least one signal having the form of a sinc function modulated sine wave. The sinc modulated sine wave has a magnitude function in the frequency domain in the form of a rectangular function centered at the frequency of the sine wave and having a width determined by the width of the sinc function. Plural sinc modulated sine wave signals can be applied to the ion trap of the spectrometer, with the various signals having different sine wave frequencies, to provide a tailored excitation spectrum without the need for extended computation.

Reduction of aliasing ambiguities through phase relations

Abstract: A method for digital determination of a single frequency from a sine wave sampled at less than the Nyquist rate is discussed. The method makes use of phase shift information to eliminate the aliasing ambiguity. Multiple sampled data are required to eliminate ambiguity completely. Computer modeling using simulated data corrupted by uncorrelated Gaussian noise was used to verify the approach. The results demonstrate that the frequency of an input sine wave can be correctly identified. This approach can be applied to electronic warfare (EW) receivers to increase their input bandwidth. >

Periodic solutions of the intermediate long-wave equation: a nonlinear superposition principle

Abstract: Periodic stationary-wave solutions of the intermediate long-wave (ILW) equation are derived using the bilinear transformation method, and a new expression for the dispersion relation is obtained. The class of physically important real-valued solutions is identified. These solutions may be represented as an infinite superposition of solitary-wave profiles, a property shared by the related Korteweg-de Vries (KdV) and Benjamin-Ono (BO) equation. This nonlinear superposition principle, which has been the subject of various interpretations in the literature, is discussed. The ILW periodic solution approximates to a sinusoidal wave and a solitary wave in the limits of small and large amplitudes, respectively. For intermediate amplitudes the solution can be well approximated by either a sine wave or solitary wave. In the shallow-water (KdV) limit the ILW periodic solution leads to the familiar cnoidal wave, whereas the deep-water (BO) limit yields Benjamin's periodic wave. A previously unknown expression for the cnoidal-wave dispersion relation in terms of theta functions is obtained.

Method for driving three phase stepping motor

Abstract: As a method for energizing a three-phase stepping motor of Y-connection, driving current values are set to be values resembling sine wave input approximation, thus making it possible to effect driving at small vibration. Energizing of the three-phase stepping motor is performed by a two-three phase driving scheme which calls for alternately effecting a two-phase excitation of the coils in the motor and a three-phase excitation of the coils in the motor. The driving current flowing through each of the coils approximates a sine wave having normalized values defined by ± 1, ± 0.87, ± 0.5 and 0.

Electronic alarm for avoiding collision with animals in a non-destructive manner

Abstract: An electronic alarm is disclosed for use in a moving vehicle which generates ultrasonic sound for preventing animals from moving into the path of the vehicle. The device includes a simplified driver circuit for generating electrical impulses in the form of square waves having constant peak-to-peak voltages. The driver generates the square waves with periodic, sequentially increasing wave frequencies followed by sequentially decreasing wave frequencies. A coupling transformer converts the square waves into electrical sine wave voltages having high peak-to-peak voltages to cause a piezo-electric transducer to emit intense, ultrasonic sounds of periodically increasing frequencies followed by periodically decreasing frequencies simulating the warble effect of a siren without excessive heating and premature failure of the transducer. The ultrasonic warble effect confuses the animal to prevent inadvertent movement by the animal into the oncoming vehicle's path without injury to the animal.

Source of quantized samples for synthesizing sine waves

Abstract: Convergent and extrapolated samples are provided for synthesizing sine waves. In a first embodiment, memory having the sine function, sin(x), mapped therein provides convergent samples. Memory size is reduced in a second embodiment by summing the outputs of two memories to produce convergent samples, one memory having an auxiliary function, f(x), mapped therein and a second having the sine function less the auxiliary function, sin(x)-f(x), mapped therein. A sine wave quadrant is conceptually divided into a plurality of uniform phase sectors demarked by boundaries phases. Additional memory provides extrapolation value sets uniquely associated with the sectors. In a given sector, extrapolation samples are produced by serially adding values of the associated extrapolation set to the convergent samples selected in the sector. An auxiliary function is chosen to closely approximate the sine function at at least the sector boundary phases, the difference between it and the sine function never exceeding the dynamic range of the sin(x)-f(x) memory. Each extrapolation value set can define a ramp having a slope closely matching the sine function slope within the set's associated sector. The first embodiment's extrapolation sets are derived from the second terms of Taylor Series expansions of the sine function at sector boundary phases. The second embodiment's extrapolation sets can be likewise derived but are adjusted as needed to compensate for quantization errors introduced by truncating the f(x) samples and limiting there number, both done to reduce memory size.

Distribution of the sum of two sine waves and Gaussian noise

Abstract: The cumulative distribution of the envelope of the sum of two sine waves and narrowband Gaussian noise, the difference of the phases of the sine waves being uniformly distributed over (0, 2 pi ), is expressed as an integral that is evaluated by numerical quadrature. Approximation for the distribution valid in the limit of large signal-to-noise ratio are derived. The probability density function of the envelope is similarly treated. >

Voltammetry in static and flowing solutions with a large-amplitude sine wave potential

Abstract: Voltammetric detection is a potentially powerful method of detection for high performance liquid chromatography and flow injection analysis. A problem that needs a solution is its inferior detection limit compared to that obtained with amperometric detection. The shape of the potential waveform has been investigated in the search for methods of improving the detection limit of voltammetric detection. As a result, large amplitude sine wave potential perturbations have been found to give improved signal-to-noise ratios when compared to the values found for a corresponding triangle waveform (by a factor of from 1.1 to 5). This is principally due to the fact that the background current from a large amplitude triangle perturbation is spread over a wider frequency region. Signal processing techniques such as digital filtering have also been investigated. Digital bandpass filtering can be used to improve the signal to noise ratio by a factor of 2–13. Qualitative information (e.g., half-wave potential) is obtained through observing the phase angle at harmonics of the fundamental frequency.

Method for transducer transient suppression. I: Theory

Abstract: The problem of driving a transducer in such a way as to produce a tone burst of steady‐state sound radiation in the surrounding fluid medium is considered. The goal is to determine the driving voltage waveform to apply to a transducer to produce an acoustic pressure waveform in the fluid that is a segment of a steady‐state sine wave, beginning and ending at zero crossings of the sine, i.e., the usual turnon and turnoff transients are suppressed. The theoretical driving voltage waveform for a spherical transducer is shown to consist of a sum of a pedestal voltage, a ramp voltage, and a sinusoidal voltage that is phase shifted with respect to the sinusoid appearing in the fluid. Both theoretical and numerical calculations are given here. The following paper presents results of experimental measurements. The measurements were carried out on several spherical transducers (one of which was selected for presentation) and on an array of piezoelectric tubes. These experiments confirm the validity of the theory.

Time shift keying digital communications system

Abstract: A digital modulation technique is disclosed which is unique in that it does not utilize fixed time slots for varying the characteristics of an electromagnetic carrier signal, but actually uses variations of the time slots to transfer the digital information. The modulation is created by using direct digital synthesis techniques to produce a carrier waveform that closely approximates a sine wave carrier signal that can vary the time it takes for each peak to occur. The peaks of the carrier are tightly controlled to occur at exact discrete time slots that correspond to certain base band digital data. The time slot changes occur precisely at the sine wave peaks to minimize the bandwidth requirement and maximize the data rate.

Method and apparatus for optimum signal burst detection

Abstract: The present invention provides a time efficient and practical method for signal burst detection. The signal is first applied to a set of linear transformations and input to a one-bit analog to digital converter and stored. The stored signal is then correlated with stored replications of sinusoidal wave forms over the range of frequencies using either a random access memory (RAM) or EPROM chip. The maximum of the correlation outputs is then compared with a selected threshold to provide a decision for the existence or nonexistence of the signal. This information is used to signal the processor to proceed with the acquisition and processing of the signal to determine the frequency and phase.

Inhibitory sidebands in multiple angular frequency filters in the human visual system.

Abstract: The view of multiple spatial frequency channels to characterize spatial factors determining the processing of contrast and brightness information has been mostly based on studies using sine wave gratings. In a study of angular frequency filtering, we demonstrated the presence of multiple peaks reflecting inhibitory activity in the measurement of a 24-cycle angular frequency filter (Simas MLB & Dodwell PC (1990). Spatial Vision, 5: 59-74). We now report sensitivity functions for angular frequency filters at 2, 4, 9, 13, 16, and 47 cycles, and have included new data for 24 cycles using the same method and analogous equipment to allow comparisons with our previous study. The present findings consistently show inhibitory effects flanking the filter's specific test frequency and, in every case, much weaker or almost no inhibition occurs at the specific test frequency for the given angular frequency filter.

Stepper motor driver circuit

Abstract: A stepper motor driver circuit applies charging current to one phase of a two-phase stepper motor in a Sine wave configuration while simultaneously applying charging current to the opposing winding in a Cosine wave configuration to carefully control the position of the motor. To reduce memory storage requirements and therefore reduce size and cost, only quarter of the Sine and Cosine waveforms are stored in memory and with additional circuitry, reconstruction of the complete wave form is realized. Furthermore, the resulting circuitry provides the user with a Full Step position output thereby reducing the need for the controlling microprocessor to count micro-steps over long moves to monitor the motor position.

Exploitation of higher-order cyclostationarity for weak-signal detection and time-delay estimation

Abstract: The cumulant theory of cyclostationary time-series is applied to several types of problems that arise in the area of signal interception and to the problem of estimating the relative time-delay of a heavily corrupted signal received at two locations. The theory characterizes the additive sine waves present in the output of nonlinear transformations of such time-series. The detection and time-delay estimation problems posed are difficult to solve because the signal is weak, the noise and interference are nonstationary and non-Gaussian, and the signal does not exhibit second-order cyclostationarity. >

On the Fourier space decomposition of free shear flow measurements and mode degeneration in the pairing process

Abstract: A two‐dimensional shear layer perturbed by low level perturbation is studied experimentally. The driving signal is composed of two sine waves of fundamental and subharmonic modes of the most unstable natural frequency, with an adjustable phase angle. The flow is examined in a Fourier space and a phase measuring technique is employed to capture the disturbance field, including the subharmonic and its three higher harmonics. The flow field composed of the mean motion and the above‐mentioned modes is reassembled. By this quantitative method the crucial connection between the evolution of superposed instability waves, based on hydrodynamic stability theory, and the experimentally observed large‐scale orderly structures is made feasible. By considering the fundamental frequency field superimposed on the mean flow, two different Fourier mode structures, having two different phase speeds, are observed in the pairing region. This mode degeneration process is also observed in the fields of other higher harmonics o...