Showing papers on "Total harmonic distortion published in 1973"

Use of charge-coupled devices for delaying analog signals

Abstract: The use of charge-coupled devices for delaying analog signals is discussed and demonstrated. Some of the relevant operational factors of the CCD, such as the effect of transfer inefficiency, maximum delay, signal-to-noise ratio and power dissipation are presented. These show that devices with delays in the range 10/SUP -1/-10/SUP -6/s operating at frequencies up to several megahertz and having wide dynamic ranges are possible. Measurements of device frequency response, harmonic distortion, and transfer noise for a 250-element 2-phase device are presented. The use of both a linear and an area CCD to delay Picturephone video signals is shown. In the latter case a device having a serial-parallel-serial organization and holding 13780 charge samples at any given time was operated with a delay of 16.7 ms.

Harmonic and power factor compensation means and method for power systems controlled by a non-linear device

Abstract: The fundamental frequency power factor is improved and a practical reduction in significant harmonic current is made in electrical power systems where the power to the load is controlled by a non-linear device, such as a saturable reactor, by using series inductive-capacitive filters to filter the significant harmonic current to act as a shunt for harmonic current in conjunction with a supply line inductive reactance. The resonant frequency of each filter is less than the frequency of the harmonic current and the impedance of each said inductivecapacitive filter is a net inductive reactance. The capacitive element of the filter provides a leading power factor component to compensate for the lagging power factor component imposed on the supply system by the non-linear control device.

Distortion Generated in Angle-Modulation Systems by Phased Arrays

Abstract: The case of linear, uniformly weighted phased arrays is examined via time and frequency domain analyses. Bounds that must be placed on array length, modulation frequency, modulation index s, and scan angle relationships if excessive distortion is to be avoided in wideband angle-modulated communication systems are established. Distortion is shown to consist of odd harmonic terms. It is also shown that, for one class of equivalent RF signals, phased arrays produce approximately three times as much distortion in frequency-modulation (FM) systems as in phase-modulation (PM) systems. Graphs of distortion plotted as functions of signal and array parameters show that, for practical array sizes, distortion is a monotonically increasing function of the product of L and sin ? where L is the length of the array expressed in modulation wavelengths ?m and ? is the scan angle. In PM systems, distortion also increases monotonically with the modulation index s. Plots of distortion versus L sin ? show that even relatively small arrays can produce intolerable distortion levels in wideband systems; e.g., an FM system having s = 3,L = 0.35?m, and ? = 60 degrees exhibits approximately 20 percent distortion.

Transmission line simulator

Abstract: A transmission line simulator which is capable of simulating a variety of transmission lines. In addition to simulating the specified characteristics of these transmission lines, the simulator is also capable of simulating a number of random transmission line effects which are especially important to digital data transmission. Among these transmission line effects that can be simulated are phase jitter, frequency shift, amplitude hit and/or drop out, harmonic distortion, phase hit, broad band and impulse noise. Each of these effects can be simulated along with simulating delay and attenuation of one of the transmission lines. The amplitude, frequency and timing of the random effects can be varied by an operator, or, if desired, omitted. As a portion of the simulator disclosed herein, a novel line simulator is employed for simulating specified characteristics which are attenuation and delay. It is made up of a number of operational amplifier filters whose filter characteristics can be electronically switched to simulate a variety of different characteristics such as the different line characteristics available from the common carriers.

Rotating capacitor square wave filter and applications thereof

Abstract: Filtering a zero median value square wave signal having predetermined transitions out of a composite signal including said square wave signal and other signals, including applying said composite signal to the input of a rotating capacitor square wave signal filter including a rotating capacitor C connected between terminals T1 and T2 and an electrically associated resistor R, and repetitively reversing the connection of the capacitor C to the terminals T1 and T2 in synchronism with the transitions of the square wave signal whereby, upon the RC time constant of the resistor R and the capacitor C being much greater than the period of the square wave signal, substantially only the square wave signal is across the output of the rotating capacitor square wave signal filter; and applications thereof.

Low distortion automatic phase control circuit

Abstract: A voltage controlled phase shifter is rendered substantially harmonic distortion free over a large dynamic input range by employing two oppositely poled, equally biased varactor diodes as the voltage controlled elements which adjust the phase shift. Control voltages which affect the bias of both diodes equally are used to adjust the phase shift without increasing distortion. A feedback stabilized phase shifter is rendered substantially frequency independent by employing a phase detector to control the phase shift of the voltage controlled phase shifter.

A Precision Stabilized Sine-Wave Source for AC Power Measurements

Abstract: The design of a stable sine-wave source for error determination of ac-measuring instruments is discussed. The electronic amplitude control circuit has been constructed using standard integrated circuits. The fluctuations of its rms output voltage, observed over the period of 1 h, are 1 · 10-6 peak-to-peak. Since the total harmonic distortion is less than 1 · 10-3, its contribution to the error of the rms value may be neglected.

A frequency synthesizer for 10/2π kHz

Abstract: A sinusoidal voltage source of frequency nominally 10/2π kHz (w = 104 rad/s) is derived from a 5-MHz standard. Digital counters are used to generate the required frequency, which differs from 10/2π kHz by less than 2 parts in 108, and is as stable as the standard. Using a crystal filter and low-distortion amplifiers, an output of 10 V rms with total harmonic distortion less than 1 part in 103 is obtained.

On transient distortion in hearing aids with volume compression

Abstract: The influence of harmonic distortion on the performance of ordinary hearing aids is discussed, as well as several kinds of possible distortions found in the transient state when compression is introduced. Transient response was determined for several hearing aids with compression that are available on the market. It is shown that each transient response is composed of two parts: the first part is determined by the frequency response of the whole transmission channel; the second one by the transient response of compression. The latter may cause overshoots, during which large distortions are found in some hearing aids. In others, a superposition of, or a modulation by, the damped low-frequency oscillation was observed at the output. Examples of such distortion are presented.

Method and device for automatic correction of harmonic distortion

Abstract: The distortions caused by each harmonic of the periodic signal delivered by a controlled system each undergo cyclic correction which consists in measuring the distortion factor of the emitted signal corresponding to the nth harmonic under consideration, in producing a periodic correcting signal having a frequency nF in synchronism with the control signal, in deriving the signal representing the amplitude of the distortion by reversing the direction of variation of the phase shift and of the amplitude of the correcting signal each time the derivative passes from the minus sign to the plus sign and by endowing the variations of the correcting signal both in phase and in amplitude with a velocity which varies linearly with the measured harmonic ratio, in superposing the correcting signal thus treated on the control signal at the input of the system.

A new concept for generating three-phase sine wave voltages with semiconductor power switches

Abstract: A rational method for using switching circuits to produce precision three-phase sine wave power from dc or ac power sources has been developed. A three-phase sine wave format is considered to be composed of voltage segments consisting of stepped waves and square waves generated by separate circuits and combined on a threephase line to produce voltage waveforms with a total harmonic content of 4% prior to filtering. The stepped portions of the wave, called X and Y functions, are generated by a tapped autotransformer and appropriate switches. Only about 20% of the power is generated in the form of steps. A simple circuit that generates a square wave voltage called the "center" function, handles more than 80% of the inverter power. The inverter has the following characteristics: high input power factor (typically 0.9 to 0.95); low output impedance; can energize nonlinear loads without significant change in total harmonic content; and easy to parallel because of low energy storage in the output filter. The inverter has an efficiency of 88-93% and weighs about 120 lb (breadboard). Power rating is 10 k W with 200% overload capacity and output frequency is 60 or 400 Hz.

Circuit for generating a stereo pilot signal

Abstract: A 38Khz square wave is divided by two in a flip-flop to produce a 19KHz square wave which is integrated and then shaped to provide a 19Khz substantially sine wave signal in phase with the 38 KHz square wave.

A video bandwidth communications system utilizing optical fiber transmission.

Abstract: A video bandwidth communications system utilizing optical fiber transmission was designed, constructed, and tested. An amplitude modulated gallium arsenide light emitting diode is driven by a transistor circuit. The output is detected by a wide bandwidth silicon detectorpreamplifier hybrid circuit. Properties such as bandwidth and harmonic distortion were measured for the individual system elements and the overall system. A closed circuit television signal was sent through the system and a sharp clear picture was observed on the monitor.

A Multipurpose Low Cost Distortion Factor Meter

Abstract: Though quite a number of distortion factor meters and harmonic wave analysers based on different established principles are commercially available, the author is tempted to construct one which measures harmonic distortion and many other variables quickly with reasonable accuracy and at low cost. The principle of fundamental suppression using a simple resonance bridge is used. The instrument is capable of measuring distortion with an accuracy of 2 per cent over the frequency range of 1–20 kHz in steps.