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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

The electrical conductivities of the DSS-13 beam-waveguide antenna shroud material and other antenna reflector surface materials

A significant amount of noise temperature can potentially be generated by currently unknown dissipative losses in the beam waveguide (BWG) shroud. The amount of noise temperature contribution from this source is currently being studied. In conjunction with this study, electrical conductivity measurements were made on samples of the DSS-13 BWG shroud material at 8.420 GHz. The effective conductivities of unpainted and painted samples of the BWG shroud were measured to be 0.01 x 10(exp 7) and 0.0036 x 10(exp 7) mhos/m, respectively. This value may be compared with 5.66 x 10(exp 7) mhos/m for high conductivity copper.

Otoshi, T. Y.↗
NASA NTRS1992

Performance of a 12-GHz fiber-optic system for beam-waveguide antenna stability testing

A 12-GHz fiber-optic system is a critical part of a test configuration that was proposed for measuring the fractional frequency stability of the Deep Space Station (DSS)-13 beam-waveguide (BWG) antenna. This fiber-optic system is used to carry Ku-band (12-GHz) signals from a reference antenna to the DSS-13 BWG pedestal room. Tests performed only on the fiber-optic system portion of the overall test configuration showed that the 12-GHz fiber-optic system (installed at DSS-13) has a frequency stability of about 1.1 x 10(exp -16) for sampling time tau = 1000 sec for a nighttime run. This preliminary result establishes the lowest noise floor that can probably be achieved for the test configuration that will be used to measure the frequency stability of the DSS-13 BWG antenna.

Otoshi, T. Y.↗
NASA NTRS1992

Optimizing the G/T ratio of the DSS-13 34-meter beam-waveguide antenna

Calculations using Physical Optics computer software were done to optimize the gain-to-noise-temperature (G/T) ratio of Deep Space Station (DSS)-13, the Deep Space Network's (DSN's) 34-m beam-waveguide antenna, at X-band for operation with the ultra-low-noise amplifier maser system. A better G/T value was obtained by using a 24.2-dB far-field-gain smooth-wall dual-mode horn than by using the standard X-band 22.5-dB-gain corrugated horn.

Esquivel, M. S.↗
NASA NTRS1992

Coplanar waveguide feeds for phased array antennas

The design and performance of the following coplanar waveguide (CPW) microwave distribution networks for linear as well as circularly polarized microstrip patches and printed dipole arrays is presented: (1) CPW/microstrip line feed; (2) CPW/balanced stripline feed; (3) CPW/slotline feed; (4) grounded CPW (GCPW)/balanced coplanar stripline feed; and (5) CPW/slot coupled feed. Typical measured radiation patterns are presented, and their relative advantages and disadvantages are compared.

Simons, Rainee N.↗
NASA NTRS1992

Electromagnetic coupling between coplanar waveguide and microstrip antennas

Electromagnetic coupling between coplanar waveguides (CPW) and microstrip patch antennas has been investigated for two feed configurations: (1) direct aperture-coupled feeding of a patch antenna by a CPW feed, and (2) proximity-coupled feeding of a patch antenna by a microstrip line which is aperture-coupled to a CPW feed. Results indicate that both feeding approaches are feasible and yield high coupling efficiency.

Simons, Rainee N.↗
NASA NTRS1991

Analysis of EM penetration into and scattering by electrically large open waveguide cavities using Gaussian beam shooting

Gaussian beam (GB) representation methods are used to analyze the electromagnetic coupling into and the scattering by a large nonuniform cavity. The aperture field in the cavity is decomposed into beams using the Gabor expansion, and shooting techniques are then employed. The method is illustrated only for the two-dimensional (2-D) case. The GBs are tracked axially using the rules of beam optics which ignore any beam distortion upon reflection at the walls. The effects of beam distortion are not significant for relatively slowly varying waveguide cavities. The field scattered into the exterior by the termination within the cavity is found using a reciprocity integral formulation which requires a knowledge of the beam fields near the termination. Numerical results based on this GB approach are presented and compared with results based on an independent reference solution.

Burkholder, Robert J.↗
NASA NTRS1992

New Techniques for Exciting Linearly Tapered Slot Antennas with Coplanar Waveguide

Two new techniques for exciting a linearly tapered slot antenna (LTSA) with coplanar waveguide (CPW) are introduced. In the first approach, an air bridge is used to couple power from a CPW to an LTSA. In the second approach, power is electromagnetically coupled from a finite CPW (FCPW) to an LTSA. Measured results at 18 GHz show excellent return loss and radiation patterns.

Simons, R. N.↗
NASA NTRS1992

Coplanar waveguide aperture-coupled microstrip patch antenna

The performance characteristics of a coplanar waveguide (CPW) aperture-coupled microstrip patch antenna was investigated experimentally. A grounded CPW with a series gap in the center strip conductor was used to couple microwave power to the antenna through an aperture in the common ground plane. Results indicate good coupling efficiency and confirms the feasibility of this feeding technique.

Lee, Richard Q.↗
NASA NTRS1992

A low-noise 492 GHz SIS waveguide receiver

The design and performance are described of an SIS waveguide receiver which provides low noise performance from 375 to 510 GHz. At its design frequency of 492 GHz the receiver has a double-sideband noise temperature of about 172 K. By using embedded magnetic-field concentrators Josephson pair tunneling is effectively suppressed. Techniques for improving receiver performance are discussed.

Walker, C. K.↗
NASA NTRS1992

New coplanar waveguide feed network for 2 x 2 linearly tapered slot antenna subarray

A novel feed method is presently demonstrated for a 2 x 2 linearly tapered slot antenna (LTSA) on the basis of a coplanar-waveguide (CPW)-to-slotline transition and a coax-to-CPW in-phase, four-way power divider. The LTSA subarray exhibits excellent radiation patterns and return-loss characteristics at 18 GHz, and has symmetric beamwidth; its compactness renders it applicable as either a feed for a reflector antenna or as a building-block for large arrays.

Simons, Rainee N.↗
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

Conductor-backed coplanar waveguide resonators of YBa2Cu3O(7-delta) on LaAlO3

Conductor-backed coplanar waveguide (CBCPW) resonators operating at 10.8 GHz have been fabricated from laser ablated and off-axis magnetron sputtered YBa2Cu3O(7-delta) (YBCO) high-temperature superconducting (HTS) thin films on LaAlO3. These resonators were tested in the temperature range from 14 to 92 K. The unloaded quality factor at 77 K of the HTS CBCPW resonators was 3 to 4 times that of a similar gold resonator. To the authors' knowledge, these results represent the first reported measurements of HTS-based CBCPW resonators.

Miranda, Felix A.↗
NASA NTRS1993

Grounded Coplanar Waveguide Feeds Phased-Array Antenna

Prototype electronically steerable K-band end-fire antenna includes phased array of four printed-circuit linear dipole elements fed by grounded coplanar waveguide (GCPW). Distribution-and-phasing network of antenna fed through single entering antenna split equally by three GCPW T junctions onto four GCPW transmission lines.

Ponchak, G.E.↗
NASA NTRS1992

Atmospheric refraction correction for Ka-band blind pointing on the DSS-13 beam waveguide antenna

An analysis of the atmospheric refraction corrections at the DSS-13 34-m diameter beam waveguide (BWG) antenna for the period Jul. - Dec. 1990 is presented. The current Deep Space Network (DSN) atmospheric refraction model and its sensitivity with respect to sensor accuracy are reviewed. Refraction corrections based on actual atmospheric parameters are compared with the DSS-13 station default corrections for the six-month period. Average blind-pointing improvement during the worst month would have amounted to 5 mdeg at 10 deg elevation using actual surface weather values. This would have resulted in an average gain improvement of 1.1 dB.

Perez-Borroto, I. M.↗
NASA NTRS1992

DSS-13 beam waveguide antenna frequency stability

Measurements made on the frequency stability of the DSS-13 34-m diameter Beam Waveguide (BWG) antenna showed that at 46.5 and 37 deg elevation angles, the BWG antenna stability at 12.2 GHz was between 1.3 and 2.2 x 10(exp -15) for tau = 1024 sec and good weather conditions. These frequency stability values apply to the portion of the antenna that includes the main reflector, subreflector, tripod legs, and the six BWG mirrors. The test results reported are believed to be the first known successful measurements of the stability of the microwave optics portion of a large antenna to a level of 1 or 2 parts in 10(exp 15).

Otoshi, T. Y.↗
NASA NTRS1993

A technique for computation of noise temperature due to a beam waveguide shroud

Direct analytical computation of the noise temperature of real beam waveguide (BWG) systems, including all mirrors and the surrounding shroud, is an extremely complex problem and virtually impossible to achieve. Yet the DSN antennas are required to be ultra low-noise in order to be effective, and a reasonably accurate prediction is essential. This article presents a relatively simple technique to compute a real BWG system noise temperature by combining analytical techniques with data from experimental tests. Specific expressions and parameters for X-band (8.45-GHz) BWG noise computation are obtained for DSS 13 and DSS 24, now under construction. These expressions are also valid for various conditions of the BWG feed systems, including horn sizes and positions, and mirror sizes, curvatures, and positions. Parameters for S- and Ka-bands (2.3 and 32.0 GHz) have not been determined; however, those can be obtained following the same procedure as for X-band.

Veruttipong, W.↗