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Lokerson, D. C.

Publications and source records attributed to Lokerson, D. C..

17 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

NASA's flight-technological development program - A 650 Mbps laser communications testbed

A 650 Mbps laser communications testbed under construction for the development of flight qualifiable hardware suitable for near-term operation on geosynchronous-to-geosynchronous crosslink missions is presented. The program's primary purpose is to develop and optimize laser communications unique subsystems. Requirements for the testbed experiments are to optimize the acquisition processes, to fully simulate the long range (up to 21,000 km) and the fine tracking characteristics of two narrow-beam laser communications terminals, and to fully test communications performance which will include average and burst bit error rates, effects of laser diode coalignment, degradation due to internal and external stray light, and the impact of drifts in the optical components.

Hayden, W. L.↗
NASA NTRS1987

Parallel Analog-to-Digital Image Processor

Proposed integrated-circuit network of many identical units convert analog outputs of imaging arrays of x-ray or infrared detectors to digital outputs. Converter located near imaging detectors, within cryogenic detector package. Because converter output digital, lends itself well to multiplexing and to postprocessing for correction of gain and offset errors peculiar to each picture element and its sampling and conversion circuits. Analog-to-digital image processor is massively parallel system for processing data from array of photodetectors. System built as compact integrated circuit located near local plane. Buffer amplifier for each picture element has different offset.

Lokerson, D. C.↗
NASA NTRS1986

Evaluation of a Si:Ga direct readout array

Preliminary results from the Hughes 58 x 62 gallium-doped silicon infrared array are presented. The device functioned predictably and repeatedly at the low temperatures for the Space Infrared Telescope Facility (SIRTF). Power dissipation was reduced to acceptable levels while still maintaining the device speed. The infrared response was excellent and the degree of anomalous effects was compatible to conventional photoconductors.

Lamb, G. M.↗
NASA NTRS1980

A Fourier transform with speed improvements for microprocessor applications

A fast Fourier transform algorithm for the RCA 1802microprocessor was developed for spacecraft instrument applications. The computations were tailored for the restrictions an eight bit machine imposes. The algorithm incorporates some aspects of Walsh function sequency to improve operational speed. This method uses a register to add a value proportional to the period of the band being processed before each computation is to be considered. If the result overflows into the DF register, the data sample is used in computation; otherwise computation is skipped. This operation is repeated for each of the 64 data samples. This technique is used for both sine and cosine portions of the computation. The processing uses eight bit data, but because of the many computations that can increase the size of the coefficient, floating point form is used. A method to reduce the alias problem in the lower bands is also described.

Lokerson, D. C.↗
NASA NTRS1977

Speech analyzer

A speech signal is analyzed by applying the signal to formant filters which derive first, second and third signals respectively representing the frequency of the speech waveform in the first, second and third formants. A first pulse train having approximately a pulse rate representing the average frequency of the first formant is derived; second and third pulse trains having pulse rates respectively representing zero crossings of the second and third formants are derived. The first formant pulse train is derived by establishing N signal level bands, where N is an integer at least equal to two. Adjacent ones of the signal bands have common boundaries, each of which is a predetermined percentage of the peak level of a complete cycle of the speech waveform.

Lokerson, D. C.↗
NASA NTRS1975

Techniques for decoding speech phonemes and sounds: A concept

Techniques studied involve conversion of speech sounds into machine-compatible pulse trains. (1) Voltage-level quantizer produces number of output pulses proportional to amplitude characteristics of vowel-type phoneme waveforms. (2) Pulses produced by quantizer of first speech formants are compared with pulses produced by second formants.

Lokerson, D. C.↗
NASA NTRS1975

X-Y alphanumeric character generator for oscilloscopes

A method and apparatus is disclosed by which any general purpose external trigger laboratory oscilloscope can be utilized to display alphanumeric characters. Each character to be displayed is composed of a plurality of segments appearing at various segment positions in various segment rows to define a conventional matrix. In between character segments to be displayed, or when no display is desired, the trace is effectively blanked by a vertical clamping voltage so as to position the oscilloscope trace in an off-screen position. The clamping technique of the invention, i.e., biasing the oscilloscope trace to an off-screen position when no character segment is to be displayed; it eliminates the necessity of providing Z-axis modulation to effect blanking.

Lokerson, D. C.↗
NASA NTRS1969

Linear voltage-to-frequency converter

Voltage-to-frequency converter, with ultra-high input impedance and linear response, is used in analog to digital data conversion systems. Voltage-to-current converter, using MOSFET devices and a multivibrator, has ultra-linear voltage-to-frequency characteristics. It replaces voltage sensitive magnetic-core oscillators.

Lokerson, D. C.↗