Showing papers on "Total harmonic distortion published in 1975"

New sinusoidal pulsewidth-modulated invertor

Abstract: Sinusoidal p.w.m. invertors depend intrinsically for their operation on quite complex modulation processes. An in-depth study of these modulation processes is presented and the sources of possible operational problems are identified. These problems are shown to be manifest in low-frequency harmonic distortion and the possible existence of subharmonics at noninteger frequency ratios, particularly at low-frequency ratios. These problems restrict the viable invertor-output frequency range. A new method of control is presented which overcomes these problems and allows the possibility of low-frequency-ratio operation, resulting in significantly wider invertor-output frequency ranges. An analytic comparison of both the existing and new methods of control is presented, using a 3-dimensional modulation-model approach. The results of this analysis provide the system designer with generalised frequency-spectra characteristics for any particular frequency ratio and modulation depth by direct inspection.

Linearity of electrical charge injection into charge-coupled devices

Abstract: This has been studied by measuring the generated higher harmonic components of a sinusoidal input. Results obtained with various injection methods and device geometries have been compared. Best results, with all harmonic components more than 40 dB below the fundamental, have been obtained for surface channel devices with a potential equilibration method in which the signal is applied to a second input gate, while the first input gate is held at a d.c. reference potential. It is concluded that this version of the potential equilibration method is readily adoptable for CCDs with any number of phases and that, if the active gate areas are suitably enlarged, harmonic distortions of less than -60 dB may be expected.

A low-distortion oscillator with fast amplitude stabilization

Abstract: An improved technique is proposed for stabilizing the output of a variable-frequency RC sine-wave oscillator. Very low harmonic distortion figures and fast amplitude settling are achieved together by sampling the peaks of the output waveform to produce a d.c. voltage having virtually no ripple content. A simplified analysis of the stabilization loop is included, and the effects of non-ideal sampling on distortion are considered.

Reduction of intermodulation distortion with harmonic injection for wideband traveling-wave tubes

Abstract: Large signal studies on octave bandwidth traveling-wave tubes show that significant improvements in tube linearity can be achieved with harmonic injection, in addition to efficiency enhancements and suppression of parasitic harmonic signals. In multisignal operation considerable reduction of the intermodulation distortion can be expected with this scheme. This requires that the injected harmonic signals be optimized in amplitude and phase with respect to the fundamental signals. In practice the harmonic signals can be generated with an octave bandwidth driver tube, and a harmonic conditioner can be designed to optimize the injection conditions. With two and four simultaneous signals improvements in intermodulation distortion by about 6 dB have been demonstrated at saturation with intermodulation levels of approximately 18 dB below the signals.

Linearity of high-power, high-radiance Ga x Al 1-x As:Ge double heterostructure LED's

Abstract: Distortion measurements on a series of Burrus type germanium-doped GaAlAs double-heterostructure LED's indicate that in the investigated doping range the overall shape of the total harmonic distortion (THD) versus dc bias curve is relatively insensitive to the amount of dopant present either in the active or second confining layers. The THD figures measured at 1 KHz with 100 mA dc bias and 36 mA peak-to-peak modulation currents were in the range of 42 to 44 dB down on the fundamental. The results of temperature measurements show that with increasing temperature the THD increases; at 100mA dc bias, the increase is linear with a slope of approximately 0.06 dB/°C.

High efficiency LF amplifier - switching amplifier designed as self-sustained oscillating control cct.

Abstract: The self-oscillating control circuit consists of an electronic switch and a linear division system. The electronic switch consists of cascade connected open differential amplifier, dead zone and two power switches. The dead zone consists of an n-p-n and a p-n-p transistor. The dead zone transistors' emitters are at frame potential, and their bases are controlled by the differential amplifier. A diode, or a Zener diode, is inserted between their emitters and frame. The division system consists of three first order delay lines. Even at high output the nonlinear harmonic distortion factor is reduced, theoretically to zero.

A Shortcoming of the Median Evoked Response

Abstract: A shortcoming of the Median Evoked Response is discussed and a means for dealing with it is suggested.

Nonlinear Distortion Analysis in the Frequency Demodulator Using Feedback

Abstract: A general method for the accurate analysis of the response of a frequency demodulator using feedback (FMFB) to an arbitrary frequency modulated (FM) signal is developed. This approach is employed to determine the FMFB outputs for two specific modulating signals, Gaussian noise, and a single sine wave. The proposed method is then applied to three different FMFB configurations differing in their low-pass filter structure. As a result, generalized curves enabling easy evaluation of the intermodulation (IM) distortion and the harmonic distortion are obtained. When designing the FMFB on the basis of these results, the influence of the relevant system parameters, such as IF filter bandwidth, feedback factor, position of the channel in the baseband, structure of the low-pass filter, etc., on the nonlinear properties of the FMFB can be controlled, simply and in a straightforward manner. The accuracy of the method has been verified in those rare cases for which solutions are already known.

A new amplitude stabilization of twin-T oscillators

Abstract: Amplitude control in twin-T oscillators operating at a fixed frequency is achieved by periodic resetting of the harmonic voltage across one bridge capacitor to the amplitude of a constant reference voltage. In the thus produced sinusoidal voltages having amplitude stability equal to the stability of the reference voltage, total harmonic distortion of 5 x 10-4 has been found at a frequency of 1 kHz. The same distortion is expected through the acoustic frequency region. The fast accommodation of the amplitude of the generated signal to the reference voltage gives the possibility of efficient amplitude modulation.