Showing papers on "Total harmonic distortion published in 1970"

The effect of harmonic distortion in the use of vibratory surface sources

Abstract: Harmonic distortion apparently arising from nonlinear processes, especially coupling of the vibrator to the ground, has often been observed in land seismic operations utilizing a frequency‐modulated mechanical vibrator as a surface source. The effect of harmonic distortion is to add a long oscillatory tail to the correlogram of a single sweep for the case in which the sweep frequency decreases with time. For up‐sweeps the distortion effect appears as a forerunner. It is shown analytically that for kth harmonic distortion, the zero‐to‐peak amplitude of the distortion tail (or forerunner) relative to the autocorrelation peak when the seismogram is crosscorrelated with, the undistorted outgoing signal is given approximately by √1/(k−1)TW times the amplitude ratio of harmonic to fundamental. W is the frequency range of the fundamental sweep and T is its length. Some examples computed by crosscorrelating a fundamental sweep (generated artificially) with its harmonic components are shown to demonstrate the effe...

Multiple bridge differential voltage static inverter

Abstract: This invention relates to a static inverter circuit utilizing a combination of two or more bridge type inverter circuits interconnected by means of movable tap interphase transformers for developing a stepwise inverter output waveform with little harmonic distortion. Through selective positioning of the taps and proper sequential actuation of the power switch elements comprising the bridge circuits, a stepwise sinewave inverter output waveform can be generated.

Analysis of frequency modulation of junction lasers by ultrasonic waves

Abstract: An analysis of the interaction of ultrasonic waves with the junction-laser modes is performed, using first-order perturbation theory. It demonstrates that in the presence of sound waves, each laser mode is frequency-modulated with negligible harmonic distortion or mode mixing. It is also shown that bandwidths of several GHz, with high-modulation index are possible.

Harmonic DC Line Voltages Arising from HVDC Power Conversion

Abstract: Steady-state firing-angle control errors and ac voltage distortion lead to the production of abnormal voltage harmonics at the dc terminals of HVDC converters; these are in addition to the usually considered "normal" harmonics. This paper describes the analysis and a digital computer program by which the normal and abnormal harmonics can be calculated for both 6- and 12-pulse converter operation. Examples of computed values are presented.

The PAR Meter: Characteristics of a New Voiceband Rating System

Abstract: The peak-to-average ratio (PAR) meter provides a single number measure of the quality of circuits used for transmitting voiceband data signals. A PAR system consists of a generator and a receiver connected to opposite ends of a transmission network to be tested. The generator transmits a precise repetitive pulse through the system, and each pulse is dispersed by the distortions that it encounters. Then, the receiver responds to the pulse envelope peak and to the pulse envelope full-wave average and indicates the ratio on a zero suppressed scale. New equipment to obtain this measure has been designed to avoid ambiguities when used on systems with nonlinear distortion or phase intercept distortion. The PAR concept is reviewed, and the techniques used in this second-generation equipment to overcome these ambiguities and the affects of various distortions on the new meter's response are described. Also, PAR signal spectrum objectives and the measurement sensitivity to circuit parameters are listed.

The standardization of monaural phase

Abstract: This paper redefines and examines the problem of monaural phase distortion in audio systems Both technical and psychoacoustical aspects of the problem are considered The redefinition of phase distortion is based upon adopting the acoustical signal at the input of the system as the standard reference The sources of phase distortion in audio systems are examined with reference to this standard A review of early and recent psychoacoustic experiments concludes that monaural phase effects can significantly affect the quality of a perceived sound A signal detection model is used to determine a conservative equivalency between frequency dependent phase distortion and amplitude distortion It is suggested that a system which maintains a 3 dB tolerance in frequency response should also maintain a 17° tolerance in phase shift A recent experiment is shown to confirm the conclusion drawn from this model Absolute phase (polarity error) is evaluated with reference to amplitude distortion in light of recent experiments It is concluded that at high sound pressure levels absolute phase error is more detectable than 115 percent intermodulation distortion A set of standards for various types of audio equipment is defined, which if implemented would eliminate absolute phase error in audio systems Finally, the importance of these findings with reference to realism of reproduced sound is commented upon

Asynchronous motor traction drive simulation using Simulink dynamic systems analysis package

Abstract: This paper describes the modelling of an asynchronous motor traction drive system using the Simulink dynamic systems analysis package. Structured simulation of such a complex system has, in the past, been difficult if not impossible. The system consists of a PWM rectifier which converts the ac overhead supply to a dc bus voltage of 1500 V. This is fed to the variable voltage, variable frequency (VWF) inverters which supply the traction motors. The PWM rectifier displays unity power factor operation with minimal harmonic distortion of the supply current waveform. The rectifier may operate in a regenerative mode, thus allowing energy savings. The most significant results of the simulation are highlighted and presented.

Low harmonic distortion fsk oscillator

Abstract: An FSK oscillator which generates extremely low second and third harmonics without the use of either passive or active filters if provided. The triangular-wave output from a frequency shift modulated triangular-wave generator is combined with a fully limited portion of the same wave to produce a stable output signal having a waveform which closely approximates that of a sinusoid.

FM Distortion Caused by Head-to-Tape Spacing

Abstract: Although it is well-known that frequency-modulated waves are distorted by systems with non-uniform frequency response, this distortion is difficult to calculate for most systems. The nature of the head-totape spacing transfer function allows the development of a closed form solution for FM distortion. Three methods of processing the voltage off the playback head are considered. Integrating the voltage results in amplitude-frequency distortion, but no harmonic distortion. Taking the voltage either directly off the head or differentiating it give both amplitude-frequency distortion and harmonic distortion. Experiments have verified the theoretical results.

Improvements in or relating to a Harmonic Distortion Analyser

Abstract: 1,182,329. Measuring harmonic distortion. TESLA, NARODNI PODNIK. Nov.30, 1967 [Jan.20, 1967], No.54611/67. Heading G1U. In a system for automatically measuring a selected harmonic resulting from the passage of a signal through a system 11, which may be a loudspeaker whose non linearity is to be determined together with a microphone in a non echoic chamber, the signal is derived by beating together at 3 a continuously variable frequency signal f 1 from a variable frequency oscillator 1 with a fixed frequency signal f 0 and passing the resultant through a low pass filter 4. The output from this is applied as the input to the system 11. The output of the variable frequency oscillator 1 is also passed via a frequency multiplier 5 to a ring modulator 6 where it is mixed with the output fp from an auxiliary oscillator 7. The output from the modulator is passed via a band pass filter 8 to a further ring modulator 9, where it is mixed with the output from the system 11 under test. The nth harmonic in this output, where n is the factor introduced in the multiplier 5, beats with the signal from the filter 8 to provide a constant frequency output fn, whose amplitude indicates the content of the nth harmonic in the output from the system 11. This is displayed on a recorder 12, whose movement is coupled to the sweep of the source 1 of the signal f 1 , to provide an output showing the variation in the amplitude of this harmonic with respect to the input frequency. The analysing system may be used to determine inter-modulation products in a loudspeaker by exciting it with two gliding tones of constant frequency difference and suitably shifting the frequency of the auxiliary oscillator 7.