Showing papers on "Total harmonic distortion published in 1976"

A second harmonic analyzer for the detection of non-centrosymmetry

Abstract: The existence of optical second harmonic generation has been shown to be a highly reliable and sensitive physical test for the detection of crystalline non-centrosymmetry. A second harmonic analyzer has been constructed which can resolve space group ambiguities arising from Friedel's Law with a confidence level greater than 99%. The system has been optimized for use with powdered crystalline samples so as to obviate the need for large single crystals and thus facilitates rapid determination of crystalline non-centrosymmetry. The present analyzer can routinely detect second harmonic generation at levels 1/1000 of that generated in a quartz standard, this is about an order of magnitude increase over previously reported systems. Data are reported on several materials including dibenzyldisulfide, and [(C6H5)3P]3CuBF4. The detection of structural phase transitions with the second harmonic analyzer is reported for BaTiO3, colemanite and phenanthrene. Second harmonic generation in the `cubic' phase of BaTiO3 promises to be a powerful tool for determining the dynamics of the ferroelectric phase transition. It is the most direct method for establishing the existence or nonexistence of microscopic polar regions well above the Curie point in a nominally centrosymmetric phase.

Harmonic reduction in thyristor converters by harmonic current injection

Abstract: The paper describes analytical and experimental results for a new method of current harmonic reduction in thyristor converters. The principle of the method is to modify the current waveforms on the d.c. windings of the converter transformer by injecting harmonic currents at a particular frequency. In practice, third harmonic currents of the power frequency is most efficient. Experimental results carried out prove that the method is effective in reducing the alternating-current harmonics, and that it is applicable to any type of thyristor converters.

Adjustable speed A-C motor drive with smooth transition between operational modes and with reduced harmonic distortion

Abstract: Alternating voltage for energizing an adjustable speed a-c motor is derived from unipolarity input voltage by means of electric power inverting apparatus comprising at least one pair of alternately conducting controllable electric valves. The conducting states of these valves are periodically switched by control means responsive to frequency and amplitude command signals, whereby the frequency and the amplitude of the fundamental component of the alternating voltage are varied as functions of the respective command signals. The control means includes means for implementing a triangle interception mode of pulse width modulation (PWM) of the alternating voltage so long as the amplitude command signal does not exceed a predetermined reference value (which is less than 1.0 per unit) and the speed of the motor does not exceed a predetermined reference speed, and the control means additionally includes means for implementing a "transition" PWM mode of operation whenever the amplitude command signal exceeds its reference value or the motor speed exceeds said reference speed. As disclosed herein the transition PWM mode implementing means is a dual d-c level set scheme in which the lower level is varied as a function of the higher level so as to minimize selected harmonics of the alternating voltage and the higher level is varied as a function of the amplitude command signal thereby to vary the amplitude of the fundamental voltage component, and means is provided for smoothly transitioning to a square wave mode of operation as the amplitude command signal approaches 1.0 per unit.

Prediction of core losses for high flux densities and distorted flux waveforms

Abstract: This paper considers the problem of estimating the core losses in a thin magnetic steel lamination when the driving flux contains not only the fundamental, but also odd harmonic components. Two numerical methods of predicting the eddy current losses due to an arbitrary flux waveform are briefly described. The important case of 3rd harmonic distortion is specifically considered. The digital simulations are used to develop a very simple model that describes the eddy current and hysteresis losses under the assumed distortion conditions with good accuracy.

The differential pair as a triangle-sine wave converter

Abstract: The performance of a differential pair with emitter degeneration as a triangle-sine wave converter is analyzed. Equations describing the circuit operation are derived and solved both analytically and by computer. This allows selection of operating conditions for optimum performance such that total harmonic distortion as low as 0.2 percent has been measured.

A 500-stage CCD transversal filter for spectral analysis

Abstract: The operation and design of 500-stage charge-coupled device (CCD) transversal filters are described. The filters have been mask programmed for implementing two spectral analysis techniques: 1) bandpass filtering and 2) Fourier analysis using the chirp z transform (CZT) algorithm. The bandpass filter has a measured fractional 3 dB bandwidth of 0.0108 and 38 dB sidelobe rejection. The dynamic range is 75 dB with less than 45 dB total harmonic distortion. A sliding transform is defined which is useful for calculations of the power spectral density and is shown to be particularly advantageous in a CCD-CZT implementation. Using the sliding transform, a 500-point spectrum is calculated using CCD's with resolutions which can be varied from 1-200 Hz. The dynamic range of the power spectral output was measured to be 80 dB. A discussion is given of the performance limitation of a general CCD filter due to the inherent characteristics of the device. The results are evaluated for the 500-stage devices described above and indicate that sample rates from 25 Hz to 10 MHz are possible with a dynamic range approaching 100 dB while retaining high linearity.

A charge-transfer multiplying digital-to-analog converter

Abstract: A new charge-transfer multiplying digital-to-analog converter employs an array of binary-weighted MOS capacitors and MOS transistors as its only elements. It can be fabricated on the same chip and by the same process as most charge-coupled devices and bucket-brigade devices, and provides two- or four-quadrant multiplication. An experimental n-channel metal-gate MOS realization demonstrated accuracy to 7 bits plus sign, total harmonic distortion 60 dB below fundamental, 70 dB dynamic range, and 200 kHz bandwidth.

Line power distortion detector

Abstract: Apparatus for testing distortion of an AC power wave and providing an error signal if distortion of the type likely to cause DC output of a power supply receiving the AC power wave to fall below acceptable levels occurs.

A 500-stage CCD transversal-filter for spectral analysis

Abstract: The operation and design of 500-stage charge-coupled device (CCD) transversal filters are described. The filters have been mask programmed for implementing two spectral analysis techniques: 1) bandpass filtering and 2) Fourier analysis using the chirp z transform (CZT) algorithm. The bandpass filter has a measured fractional 3 dB bandwidth of 0.0108 and 38 dB sidelobe rejection. The dynamic range is 75 dB with less than 45 dB total harmonic distortion. A sliding transform is defined which is useful for calculations of the power spectral density and is shown to be particularly advantageous in a CCD-CZT implementation. Using the sliding transform, a 500-point spectrum is calculated using CCD's with resolutions which can be varied from 1-200 Hz. The dynamic range of the power spectral output was measured to be 80 dB. A discussion is given of the performance limitation of a general CCD filter due to the inherent characteristics of the device. The results are evaluated for the 500-stage devices described above and indicate that sample rates from 25 Hz to 10 MHz are possible with a dynamic range approaching 100 dB while retaining high linearity.

Method for Measuring Transient Intermodulation Distortion (TIM)

Abstract: A description of the square-sine intermodulation measuring method is given. The practical measuring procedure is described, and measurement results of commercial audio power amplifiers and integrated operational amplifiers are presented, in many cases showing appreciable transient intermodulation in units which have excellent total harmonic distortion and SMPTE intermodulation distortion specifications. The correlation of these measurements with results obtained using other methods, such as the CCIF-IM and the noise-transfer method, is treated, and the interdependence of these with the slew rate and the power bandwidth is discussed.

Variable frequency waveform synthesizer

Abstract: A variable frequency waveform synthesizer includes a programmable counter coupled to count cycles of a single reference clock signal and recycle at an intermediate frequency determined by a count number selected in response to frequency selection signals. Because of the need to select an integral count number, a count number that is exactly required for a desired frequency must be rounded off to the nearest integral number and the higher the number the lower the percent round off error. Thus, the percentage frequency error for a plurality of different waveforms that are synthesized as a sequence of discrete steps derived from a common reference clock signal is reduced by dividing the reference frequency to obtain an intermediate frequency signal and dividing each period of the intermediate frequency signal into a plurality of not necessarily equal steps to obtain a stepping signal commanding step changes in the synthesized waveform. The stepping signal is thus exactly periodic at the intermediate frequency and approximately periodic at the higher stepping frequency while the resulting synthesized waveform has a reduced percentage frequency error and only a small harmonic distortion.

Laser control circuit

Abstract: The operating current level of an injection laser is stabilized at a point of maximum linearity. A test signal modulates the laser current, and the operating current level of the laser is automatically adjusted until the harmonic distortion component in the output light at twice the test signal frequency is minimized.

Integrable, wideband, automatic volume control (a.v.c.) using Pythagoras's law for amplitude detection

Abstract: The design of an a.v.c. is a simple application of control theory. The main problem in realising an integrable wideband a.v.c. is the amplitude detector. An implementation of Pythagoras's law acts magnificently in a slow a.v.c. However, in a fast a.v.c., offset will cause some 2nd-harmonic distortion.

Linear charge-coupled device signal-processing techniques

Abstract: New methods for linear launching, weighting, and nondestructive charge sensing in charge-coupled devices (CCD's) are described. These methods employ electronic circuitry at the input and output nodes of the CCD, which linearize the signals, eliminate the nonlinear effect of depletion region capacitance and are also independent of device parameter variations such as electrode area, and absolute values of threshold voltage and oxide thickness. Results indicate a maximum nonlinear distortion of 2.4 percent which is equivalent to a second harmonic distortion level of -38 dB if all distortion present is assumed to be due to second harmonic distortion. Significantly better results are believed possible with circuit optimization. These methods are directly applicable to many CCD signal processing systems and are particularly aimed at CCD transversal filters.

Loudspeaker distortion

Abstract: Distortion in 3 types of loudspeakers is measured and compared. Horn, vented box, and total enclosure type speakers display increasing amounts of distortion in the given order. The most important type of distortion is modulation. Since this is usually several times the magnitude of harmonic distortion, and consists of frequencies which are not harmonically related to the input frequencies, modulation distortion is much more obnoxious than harmonic distortion. Modulating frequencies in the subsonic range were found to produce high modulation distortion in vented-box speakers. Reviewers of equipment who report 0.01% amplitude modulation distortion in amplifiers and ignore 10% or more amplitude and frequency modulation distortion in loudspeakers might well revise their prejudices.

Spiral traveling wave tube

Abstract: PURPOSE: To eliminate the transmission distortion caused by high harmonic waves by providing a circuit near the output circuit to block the high harmonic element against the signal frequency. COPYRIGHT: (C)1978,JPO&Japio

Supply charge isolation—A simple surface potential equilibration charge-injection technique for charge-coupled devices

Abstract: A simple high-linearity charge-injection technique for charge-coupled devices (CCD's) is described, analyzed, and practical results presented. The technique is of the potential equilibration type and utilizes the formation of a potential barrier and charge-storage site under one CCD electrode adjacent to an input diode. This obviates the need for an input clock, as used in previously reported surface potential equilibration charge-injection techniques, by isolating a fixed quantity of "supply charge" from the input diode and the CCD transfer electrodes. The analog signal is applied to the succeeding CCD electrode and depending upon its amplitude some, or all, of the supply charge is transferred to under this electrode, and by subsequent CCD action through the register. A theoretical analysis of the technique predicts that nonlinearity vanishes as the effects of the depletion region capacitance are eliminated. In practice, however, a small nonlinear effect, being mainly attributed to charge "slopping," does occur, causing a reduction in the useful dynamic range of the device for a particular level of linearity. Experiments have indicated that a useful dynamic range of 47.5 dB is attainable with all harmonic components at least 45 dB below the fundamental with a total harmonic distortion of less than 1.2 percent. Variations in threshold voltages between different input stages does not effect the quantity of charge injected (within certain operating limits), but does result in small variations of the maximum useful dynamic range of the devices. The technique is particularly suited to two-phase CCD's because it allows linear charge injection, charge transfer, and reset sensing to be accomplished using only one clock.

A dual differential charge-coupled analog delay device

Abstract: A dual differential charge-coupled analog device providing signal delays of 24 and 48 elements has been designed for sampled data analog signal processing applications. The aim of this design was to eliminate some of the disadvantages that have been associated with previous charge-coupled devices (CCD's). These include clock pickup, thermally generated dc offsets, and complex external control and amplification circuitry. The device has an input strobing circuit and an on-chip output amplifier. With a clock frequency of 8 kHz and a 400-mV rms input signal, the total harmonic distortion was below 0.2 percent and the signal-to-noise ratio was better than 70 dB with a 4-kHz bandwidth. The device gain was 6 dB and a gain variation of 0.2 dB was observed over a temperature range of 0 to 55°C.

Linear charge-coupled device signal-processing techniques

Abstract: New methods for linear launching, weighting, and nondestructive charge sensing in charge-coupled devices (CCD's) are described. These methods employ electronic circuitry at the input and output nodes of the CCD, which linearize the signals, eliminate the nonlinear effect of depletion region capacitance and are also independent of device parameter variations such as electrode area, and absolute values of threshold voltage and oxide thickness. Results indicate a maximum nonlinear distortion of 2.4 percent which is equivalent to a second harmonic distortion level of-38 dB if all distortion present is assumed to be due to second harmonic distortion. Significantly better results are believed possible with circuit optimization. These methods are directly applicable to many CCD signal processing systems and are particularly aimed at CCD transversal filters.

Harmonic Bandpass Distortion of a Chebyshev Nonlinearity

Abstract: Harmonic distortion imparted to the sidebands of an amplitude-modulated carrier by a system described by a Chebyshev series is evaluated. Sideband distortion increases with modulation depth but decreases with low carrier level, when even-harmonic contributions disappear.

Linear Charge-Coupled Device Signal-Processing Techniques

Abstract: Abstrocr-New methods for linear launching, weighting, and nondestructive charge sensing in charge-coupled devices (CCD's) are described. These methods employ electronic circuitry at the input and output nodes of the CCD, which linearize the signals, eliminate the nonlinear effect of depletion region capacitance and are also independent of device parameter variations such as electrode area, and absolute values of threshold voltage and oxide thickness. Results indicate a nonlinear distortion of 2.4 percent which is equivalent to a second harmonic distortion level of -38 dB if all distortion present is assumed to be due to second harmonic distortion. Significantly better results are believed possible with circuit optimization. These methods are directly applicable to many CCD signal processing systems and are particularly aimed at CCD transversal filters.

A New Approach to Computing Distortion of an FM Single-Tone Modulated Signal Due to Ideal Filtering

Abstract: By factorizing a finite sum of harmonics, an expression is obtained for an FM demodulator output when the modulating signal is a simple sinusoid and the RF filter is an ideal bandpass filter. Using this result, harmonic distortions and the signal-to-distortion ratio are defined and computed; several curves are drawn to show the variation of these quantities in terms of the modulation index and the normalized bandwidth.

Automated Third-Order Distortion Measurements

Abstract: A technique is described for the determination of third-order distortion produced in "linear" amplifiers by analyzing their complex transfer characteristic. A minicomputer is used for both control of the test equipment and analysis of the data.