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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Performance of a Y-Ba-Cu-O superconducting filter/GaAs low noise amplifier hybrid circuit

A superconducting 7.3 GHz two-pole microstrip bandpass filter and a GaAs low noise amplifier (LNA) were combined into an active circuit and characterized at liquid nitrogen temperatures. This superconducting/semiconducting circuit's performance was compared to a gold filter/GaAs LNA hybrid circuit. The superconducting filter/GaAs LNA hybrid circuit showed higher gain and lower noise figure than its gold counterpart.

Bhasin, K. B.↗
NASA NTRS1992

Electromagnetic characterization of conformal antennas

The ultimate objective of this project is to develop a new technique which permits an accurate simulation of microstrip patch antennas or arrays with various feed, superstrate and/or substrate configurations residing in a recessed cavity whose aperture is planar, cylindrical or otherwise conformed to the substructure. The technique combines the finite element and boundary integral methods to formulate a system suitable for solution via the conjugate gradient method in conjunction with the fast Fourier transform. The final code is intended to compute both scattering and radiation patterns of the structure with an affordable memory demand. With upgraded capabilities, the four included papers examined the radar cross section (RCS), input impedance, gain, and resonant frequency of several rectangular configurations using different loading and substrate/superstrate configurations.

Volakis, John L.↗
NASA NTRS1990

MSAT vehicular antennas with self scanning array elements

A new approach for designing low profile antennas for MSAT applications is presented. It is based on stacking two microstrip antennas that operate at two adjacent modes. The beam scanning is achieved by introducing a phase shift between the stacked elements and consequently a low cost self scan array element is developed. The concept is used to investigate two different antenna types: (1) a single element unit, with its phase shifter, that provides a moderate gain of about 7 dBic; and (2) a seven element array with a peak gain of about 14 dBic. Computed and measured data for each design are presented and discussed.

Shafai, L.↗
NASA NTRS1992

An optically controlled Ka-band phased array antenna

The design and development of a small, optically controlled phased array antenna suitable for communication satellite applications are discussed. A vertical integration architecture is used which minimizes the size of the array with its associated beamforming network (BFN). The antenna features a four-element linear microstrip array that uses aperture coupling of the antenna elements to the BFN; a modified Wilkinson power divider BFN; and 32 GHz, four-bit monolithic microwave integrated circuit (MMIC) phase shifters in customized quartz packages with corresponding optoelectronic interface circuits (OEIC's) for control signal reception.

Kunath, R. R.↗
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

Performance of a Y-Ba-Cu-O superconducting filter/GaAs low noise amplifier hybrid circuit

A superconducting 7.3 GHz two-pole microstrip bandpass filter and a GaAs low noise amplifier (LNA) were combined into a hybrid circuit and characterized at liquid nitrogen temperatures. This superconducting/seismology circuit's performance was compared to a gold filter/GaAs LNA hybrid circuit. The superconducting filter/GaAs LNA hybrid circuit showed higher gain and lower noise figure than its gold counterpart.

Bhasin, Kul B.↗
NASA NTRS1991

35 GHz integrated circuit rectifying antenna with 33 percent efficiency

A 35 GHz integrated circuit rectifying antenna (rectenna) has been developed using a microstrip dipole antenna and beam-lead mixer diode. Greater than 33 percent conversion efficiency has been achieved. The circuit should have applications in microwave/millimeter-wave power transmission and detection.

Yoo, T.-W.↗
NASA NTRS1992

Ka-band active MMIC subarray development

A 4 x 8 array consisting of two adjacent 4 x 4 MMIC subarray modules under development as part of a MMIC insertion program for the ACTS communication experiments is presented. The subarray features a high-density 'tile' configuration integrating 16 MMIC power amplifiers and 16 MMIC phase shifters. The radiating elements are cavity-backed, aperture coupled, linearly polarized microstrip patches arranged on a 4 x 4 square grid. Each module also incorporates a MMIC controller to set the phase shifts and to turn individual amplifiers 'on' or 'off'. The novel module construction technique is expected to establish a benchmark in Ka-band and higher-frequency array architectures. The hybrid integration approach used for the module can be replaced by multifunctional chips and multilayer distribution boards. The higher level of integration is to permit the dense grid spacing required for wide-angle scanning and reduced size, weight, and cost for the array.

Lee, Richard↗
NASA NTRS1992

Lumped-element models characterize DR coupling effects

An approach to the analysis of closely spaced resonances produced by a microstrip coupled dielectric resonator is presented. In particular, it is shown that the use of a lumped-element model significantly simplifies the analysis. An experimental verification demonstrates that the model predicts the adjacent complementary resonances to within 1.6 percent of the measured value.

Hearn, Chase P.↗
NASA NTRS1992

A vertically integrated Ka-band phased array antenna

The design, development, and experimental demonstration of a small phased array antenna suitable for applications on communications satellites are discussed. Each of the vertical layers was optimized for performance, and MMICs on custom carriers were characterized prior to insertion. A vertical integration architecture is used which minimizes the size of the array with its associated beamforming network (BFN). The antenna features a four-element linear microstrip array that uses aperture coupling of the antenna elements to the BFN; a modified Wilkinson power divider BFN; and 32 Ghz, 4-bit MMIC phase shifters on customized alumina carriers. Performance data are presented for all components, and far-field antenna radiation patterns are given.

Kunath, R. R.↗
NASA NTRS1992

Theoretical and experimental development of 10 and 35 GHz rectennas

A 35 GHz rectenna has been developed with 39 percent conversion efficiency. The rectenna uses a microstrip dipole antenna and a commercially available mixer diode. Over 60 percent conversion efficiency was demonstrated using this diode at 10 GHz. A theoretical analysis was derived to predict the performance of the rectenna. The analysis is a useful tool for device and circuit design. The theoretical and experimental results should have many applications in microwave power transmission and detection.

Yoo, Tae-Whan↗
NASA NTRS1992

Electrical-transport properties and microwave device performance of sputtered TlCaBaCuO superconducting thin films

The paper describes the processing and electrical transport measurements for achieving reproducible high-Tc and high-Jc sputtered TlCaBaCuO thin films on LaAlO3 substrates, for microelectronic applications. The microwave properties of TlCaBaCuO thin films were investigated by designing, fabricating, and characterizing microstrip ring resonators with a fundamental resonance frequency of 12 GHz on 10-mil-thick LaAlO3 substrates. Typical unloaded quality factors for a ring resonator with a superconducting ground plane of 0.3 micron-thickness and a gold ground plane of 1-micron-thickness were above 1500 at 65 K. Typical values of penetration depth at 0 K in the TlCaBaCuO thin films were between 7000 and 8000 A.

Subramanyam, G.↗
NASA NTRS1993

A class of hybrid finite element methods for electromagnetics: A review

Integral equation methods have generally been the workhorse for antenna and scattering computations. In the case of antennas, they continue to be the prominent computational approach, but for scattering applications the requirement for large-scale computations has turned researchers' attention to near neighbor methods such as the finite element method, which has low O(N) storage requirements and is readily adaptable in modeling complex geometrical features and material inhomogeneities. In this paper, we review three hybrid finite element methods for simulating composite scatterers, conformal microstrip antennas, and finite periodic arrays. Specifically, we discuss the finite element method and its application to electromagnetic problems when combined with the boundary integral, absorbing boundary conditions, and artificial absorbers for terminating the mesh. Particular attention is given to large-scale simulations, methods, and solvers for achieving low memory requirements and code performance on parallel computing architectures.

Volakis, J. L.↗
NASA NTRS1993

Microwave characterization of slotline on high resistivity silicon for antenna feed network

Conventional silicon wafers have low resistivity and consequently unacceptably high value of dielectric attenuation constant. Microwave circuits for phased array antenna systems fabricated on these wafers therefore have low efficiency. By choosing a silicon substrate with sufficiently high resistivity it is possible to make the dielectric attenuation constant of the interconnecting microwave transmission lines approach those of GaAs or InP. In order for this to be possible, the transmission lines must be characterized. In this presentation, the effective dielectric constant (epsilon sub eff) and attenuation constant (alpha) of a slotline on high resistivity (5000 to 10 000 ohm-cm) silicon wafer will be discussed. The epsilon sub eff and alpha are determined from the measured resonant frequencies and the corresponding insertion loss of a slotline ring resonator. The results for slotline will be compared with microstrip line and coplanar waveguide.

Simons, Rainee N.↗
NASA NTRS1993

Lumped elements characterize Q in dielectric resonators

It has been earlier observed (Podcameni et al., 1981) that, as the coupling factor between a microstrip-coupled dielectric resonator and the line becomes much larger than unity, the unloaded quality factor (Q) of the resonator decreases. In this paper it is shown that this effect can be explained using lumped-element models of the coupling line, when the dielectric resonator is either overcoupled or undercoupled to the line.

Hearn, Chase P.↗
NASA NTRS1993

Performance of TlCaBaCuO 30 GHz 64 element antenna array

A 64-element, 30-GHz microstrip antenna array with corporate feed network was designed and built on a 0.254-mm (10-mil) thick lanthanum aluminate substrate. One antenna pattern was fabricated from gold film, and a second pattern used TlCaBaCuO high-temperature superconductor. Both antennas used gold ground planes deposited on the reverse side of the substrate. Gain and radiation patterns were measured for both antennas at room temperature and at cryogenic temperatures. Observations agree well with simple models for loss and microwave beam width, with a gain on boresight of 20.3 dB and beam width of 15 deg for the superconducting antenna. The antenna loss is only 1.9 dB.

Lewis, L. L.↗
NASA NTRS1993

Novel miniaturised wideband baluns for MIC and MMIC applications

Very compact novel planar broadband baluns are described. Each balun consists of two Lange couplers. Less than 0.3 dB and 2.5 deg for the amplitude and phase balances, respectively, have been measured over the 1.0-2.2 GHz bandwidth for a microstrip balun. As compared with other reported baluns, these baluns are simpler, more compact, easier to design, and fabricated on only one side of the substrate. They are thus very attractive for microwave integrated and monolithic integrated circuit applications.

Nguyen, C.↗
NASA NTRS1994

Hermetic Packages For Millimeter-Wave Circuits

Advanced hermetic packages developed to house electronic circuits operating at frequencies from 1 to 100 gigahertz and beyond. Signals coupled into and out of packages electromagnetically. Provides circuit packages small, lightweight, rugged, and inexpensive in mass production. Packages embedded in planar microstrip and coplanar waveguide circuits, in waveguide-to-planar and planar-to-waveguide circuitry, in waveguide-to-waveguide circuitry, between radiating (antenna) elements, and between planar transmission lines and radiating elements. Other applications in automotive, communication, radar, remote sensing, and biomedical electronic systems foreseen.

Herman, Martin I.↗