Engineering topics

Otoshi, Tom Y.

Publications and source records attributed to Otoshi, Tom Y..

10 records

NASA NTRS1996

Thin-Ribbon Tapered Couplers For Dielectric Waveguides

Thin-ribbon tapered couplers proposed for launching electro-magnetic waves into dielectric waveguides, which include optical fibers. Intended for use with ribbon dielectric waveguides designed for operation at millimeter or submillimeter wavelengths, made of high-relative-permittivity, low-loss materials and thicknesses comparable to or less than free-space design wavelengths. Coupling efficiencies exceeds those of older tapered couplers.

Otoshi, Tom Y.↗

NASA NTRS1994

A Method For Modeling Discontinuities In A Microwave Coaxial Transmission Line

A methodology for modeling discountinuities in a coaxial transmission line is presented. The method uses a none-linear least squares fit program to optimize the fit between a theoretical model and experimental data. When the method was applied for modeling discontinuites in a damaged S-band antenna cable, excellent agreement was obtained.

Galileo S-band antenna discontinuities↗

NASA NTRS1994

Simulation Diagnostics of Multiple Discontinuities in A Microwave Coaxial Transmission Line

Multiple discontinuities in microwave transmission lines can cause unusual reflection and transmission loss charactristics as functions of frequency. This article presents a methord for developing models that simulate return loss and insertion loss data measured over a broad band of frequencies.

Microwave↗

NASA NTRS1994

Equipment For Testing Beam-Waveguide Antennas

Two portable packages designed for use in determining such radiometric quantities as directivity, efficiency, noise temperature of paraboloidal-dish antenna 34 m in diameter and losses of signal power in parts of beam waveguide through which antenna coupled to receiving station. One package takes measurements at frequency of 8.45 GHz; other at 32 GHz.

Otoshi, Tom Y.↗

NASA NTRS1994

Measuring Frequency Instability Of A Large Antenna

Frequency instability of antenna under test determined from measurement of phase deviation between outputs of two antennas. Fiber-optic system used to minimize spurious component of frequency instability contributed by propagation of signal from reference antenna to Allan-variance-measuring instrument. Intended primarily to reveal contributions of wind and air-temperature effects on antenna and beam-waveguide structures to overall frequency instabilities of received signals. Technique simpler, less expensive, potentially capable of providing instability data in shorter measuring times, and more precise.

Otoshi, Tom Y.↗

NASA NTRS1992

Measurements of a deep space station fractional frequency stability to the 10 exp -15 level

This article presents techniques for measuring frequency stability of a deep space station that was configured with a new X-band transmitter subsystem to enable high-quality radio science data to be obtained for a Gravity Wave Experiment. The instrument and test procedures for performing frequency stability measurements in the field are described. Test results from measurements made on various transmit receive subsystems, as well as the overall transmit-receive end-to-end systems below the antenna feed horn are presented. The subsystem test data proved to be useful for assessing the frequency stabilities of various subsystems. This assessment design improvements needed to meet stringent frequency stability requirements for forthcoming gravity wave experiments.

Otoshi, Tom Y.↗

NASA NTRS1992

Dual-Passband Microwave Dichroic Plates

Perforated metal plate with dielectric-filled holes acts as dual-passband dichroic microwave plate. Use of dielectric enables use of smaller, more-closely-spaced holes, reducing undesired diffraction-grating lobes. Arrangement and sizes of holes, distances between them, and material and dimensions of dielectric plugs chosen to satisfy design requirements.

Otoshi, Tom Y.↗

NASA NTRS1992

Beam-waveguide antenna performance predictions with comparisons to experimental results

An overview of a NASA/JPL antenna project is presented, with specific focus on the methodology used to predict the microwave performance of a 34-m-diameter beam-waveguide (BWG) reflector antenna, designated DSS 13 (Deep Space Station 13). DSS 13 is the R&D facility serving the NASA/JPL Deep Space Network. Microwave performance predictions as well as a summary of test results for the antenna are given. The antenna has Cassegrain and centerline BWG operating modes at X-band (8.450-GHz) and Ka-band (32-GHz) frequencies. The performance predictions regarding antenna area efficiencies, corresponding beampeak gains, and for several (but not all) operating noise temperatures are found to agree reasonably well with the corresponding experimental results.

Bathker, Dan A.↗

NASA NTRS1992

Portable microwave test packages for beam-waveguide antenna performance evaluations

Portable microwave test packages used to evaluate a new 34-m-diameter beam-waveguide (BWG) antenna are described. The experimental methodology involved transporting test packages to different focal points of the BWG system and making noise temperature, antenna efficiency, and holography measurements. Comparisons of data measured at the different focal points enabled determinations of performance degradations caused by various mirrors in the BWG system. It is shown that, due to remarkable stabilities and accuracies of radiometric data obtained through the use of the microwave test packages, degradations caused by the BWG system were successfully determined.

Otoshi, Tom Y.↗

NASA NTRS1992

Efficiency measurement techniques for calibration of a prototype 34-meter-diameter beam-waveguide antenna at 8.45 and 32 GHz

Efficiency measurements at 8.45 and 32 GHz (X and Ka bands, respectively) were carried out on the new 34 m diameter beam waveguide antenna now in use at the NASA Goldstone Deep Space Communications Complex. The use of portable test packages enabled measurements at both the Cassegrain and beam waveguide focal points. Radio sources (quasars and Venus) were used as calibrators, and updated determinations of flux and source size correction were made during the period of the measurements. Gain and efficiency determinations as a function of elevation angle are presented, and the effects of the beam waveguide system and antenna structure are clearly seen. At the beam waveguide focus, an 8.45 GHz peak efficiency of 72.38 pct was measured; at 32 GHz, 44.89 pct was measured.

Slobin, Stephen D.↗