High Frequency Output Research Articles

Electronic method and apparatus for modifying musical sound

A continuously varying electrical signal representing an original musical sound is divided at a selected mid-frequency of about 800 Hertz to provide upper and lower frequency signal bands which are then frequency-modulated with separate modulation signals that differ in frequency or amplitude or both, in order to produce a vibrato or tremulant effect and thereby enrich the harmonic content of the musical sound. In order to inject the vibrato or tremulant into each signal band, the modulation process utilizes a pulse sampling and delay circuit which minimizes clock pulse noise by selecting only the central part of each delayed pulse, and which also senses the original amplitude envelope of the unmodulated wave in order to augment the envelope that is recreated from the delayed pulses after they are recovered. The resulting modulated signals are recombined, producing a cross-modulation which adds further harmonic components, and the composite signal is again divided at a frequency of about 200 Hertz into high and low frequency output signals which are supplied to respective high and low frequency stationary loudspeakers.

NEW AND FUTURE DEVELOPMENTS IN SEISMIC EXPLORATION

Present research in reflection seismic prospecting is proceeding with three major goals.Intensive work is being done on the problem of obtaining useful reflections beneath complex near-surface materials. Such near-surface materials distort both the down-going and reflected wavefronts to an extent that deep reflections either cannot be distinguished or are so distorted as to conceal their true shapes. Current research seeks methods for obtaining enough information about near-surface irregularities to construct a model upon which to base a wavefront correction.The second major goal is to improve the resolution of the seismic reflection process. Resolution is lost because high frequencies are often weak in seismic sources and are severely attenuated by the earth, by receiver arrays, and by most processing steps. Seismic bandwidth can be increased by improving the high frequency output of the seismic source to compensate for attentuation in the earth, by reducing the size of receiver arrays, and by drastically reducing the inaccuracies of conventional processing algorithms.The third line of investigation seeks to increase the amount of information extracted from the seismic signal. The first step in this direction was the bright-spot technique, in which qualitative information on seismic reflection amplitudes was used to identify hydrocarbon deposits. Interval velocity estimation was a natural result of moving from a qualitative to a quantitative analysis of amplitudes. In theory, with a combination of P and S wave reflection data, virtually all elastic properties of subsurface rocks could be extracted from the data.In the more distant future, computers could handle complex interpretation tasks and make drilling decisions.The principal barrier to rapid implementation of virtually all of the new techniques is inadequate computer power. Despite the explosive growth of the power of computers, mainframe manufacturers have been unable to satisfy the even more rapidly increasing demands of geophysicists. Innovative processing techniques and specialized computer equipment will be essential to continuing rapid progress in geophysical exploration.

Current Response Simulation in Six-Phase and Twelve-Phase Cycloconverters

Cycloconverters are aptly used for the power supply of variable speed synchronous motors. However, output current offset and phase deviation increase in higher output frequency operation, and ripple current causes torque pulsation of the synchronous motor. A compensating method to improve current response performance is proposed and a digital simulation procedure in order to analyze the output current response of a cycloconverter is discussed. First, the six-phase noncirculating-type cycloconverter is discussed. Next the six-phase cycloconverter simulation was applied to the 12-phase cycloconverter. The simulated waveforms were compared with the experimental results in motor operation or regenerative operation. It was clarified that offset and phase deviation became zero using the compensating circuit. Additionally the average torque pulsation, the output current distortion factor, and the ripple torque versus the output-input frequency ratio were calculated by simulation in the cycloconverter-fed synchronous motor.

Single longitudinal mode operation of high pressure pulsed CO 2 lasers

A new method of obtaining high power single frequency output is described, where pulses are built up from the single mode radiation in the cavity of a hybrid laser having both low pressure continuous and high pressure continuous and high pressure pulsed gain sections.

X-ray Measurements near High-Power Klystrons

The intensity and quality of the x-radiation outside the lead shielding around ultrahigh-frequency and S-band klystrons were measured as a function of high voltage, pulse frequency, and microwave power output by use of ionization chambers. Independent 20 percent increases in each variable gave, respectively, 8-, 1.2-, and 1.5-fold increases in the intensity, and 36, 1, and 4 percent increases in the mean energy of the x-rays.

Stabilization and Modulation of Laser Oscillators by Internal Time-Varying Perturbation

The paper reviews the application of internal timevarying perturbation to the problem of laser mode control and stabilization. The spectral characteristics and time domain behavior obtained by means of phase type and loss type perturbations are considered. Two techniques which allow the attainment of high single frequency output powers from normally multimode lasers are described. A method for the absolute frequency stabilization of an FM laser is considered, and a brief discussion of an efficient method of internal modulation, termed coupling modulation, is given.

Stabilization and modulation of laser oscillators by internal time-varying perturbation

The paper reviews the application of internal time-varying perturbation to the problem of laser mode control and stabilization. The spectral characteristics and time domain behavior obtained by means of phase type and loss type perturbations are considered. Two techniques which allow the attainment of high single frequency output powers from normally multimode lasers are described. A method for the absolute frequency stabilization of an FM laser is considered, and a brief discussion of an efficient method of internal modulation, termed coupling modulation, is given.

Modulators, frequency changers and detectors using rectifiers with frequency-dependent characteristics

In the calculation of the performance of modulators, frequency changers, and detectors it is found difficult to allow for any frequency dependence of the resistance characteristic of the rectifier, although when copper-oxide rectifiers are used, such dependence is very severe. An approximate method of allowing for such an effect is described in the paper, and it can be applied easily to the analysis of circuits where the terminating impedances are finite only at a finite number of modulation-product frequencies and zero at all other such frequencies. In particular, the case where either the input or the output frequency is low, the carrier frequency is high and only one sideband is accepted is considered in some detail, and the results are illustrated by numerical examples based on copper-oxide modulators working at frequencies up to 6 Mc/s. It is also shown how the conversion insertion-loss can be stabilized against temperature variation by a suitable choice of terminating resistance. The working and results are the same for shunt, series and ring modulators, for conditions of low input frequency with high output frequency and vice versa.

Conversion of a Motor Generator into a Low Noise Power Amplifier

The noise output of motor-generator sets is so large as to impair their use in precision control work. This paper describes a method for reducing this noise by incorporating a motor generator in an electronic feed-back circuit. The method is based on the use of a high frequency output channel in parallel with the generator to permit cancellation of the higher harmonics of the noise. Design, construction, and performance of an amplifier based on a ½-kw M-G set are described. The noise output of this unit is ⅕ percent of the normal noise of the generator.

A Large Radius Stylus for the Reproduction of Lateral Cut Phonograph Records

This paper shows that novel and unexpected benefits are obtained by use of a stylus of sufficiently large tip radius to contact only the upper portions of the side walls of a laterally cut phonograph record groove. The benefits are: (a) an increase in high frequency output; (b) a decrease in acoustic radiation from the surface of the record; (c) an increase in record life; (d) an increase in stylus life; (e) a decrease in picked up scratch frown both new and worn records; (f) a decrease in stylus point pressure required for proper tracking. A stylus tip which will give this performance for the case of standard commercial records has a radius on the order of 4.2 mils or nearly double the radius of 2.3 mils heretofore thought most desirable. This device is in commercial use in conjunction with the Crosley radio-phonograph combinations and is the subject of U. S. patent 2,251,204. In commercial use the large radius stylus is combined with a special spring mounting and drives a crystal cartridge. The spring mounted stylus was developed in conjunction with Mr. Frank Goldsmith and the additional benefits obtained thereby are explained in the preceding paper. (The presentation of this paper will be accompanied by demonstrations of the benefits obtained with the large radius stylus utilizing both sound reproduction and oscillographic illustration.)