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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Wideband Microstrip Antenna-Feeding Array

Special impedance-matching probes help reduce feed complexity. Lightweight array of microstrip antenna elements designed to transmit and illuminate reflector antenna with circularly polarized radiation at 1,545 to 1,550 MHz and to receive circularly polarized radiation at 1,646 to 1,660 MHz. Microstrip array is cluster of 7 subarrays containing total of 28 microstrip patches. Produces cicularly polarized beam with suitable edge taper to illuminate reflector antenna. Teardrop-shaped feed probe provides gradual change of field from coaxial transmission line into microstrip substrate. Intended to be part of larger overlapping-cluster array generating multiple contiguous beams.

Huang, John↗
NASA NTRS1995

Analysis of a microstrip reflectarray antenna for microspacecraft applications

A microstrip reflectarray is a flat reflector antenna that can be mounted conformally onto a spacecraft's outside structure without consuming a significant amount of spacecraft volume and mass. For large apertures (2 m or larger), the antenna's reflecting surface, being flat, can be more easily and reliably deployed than a curved parabolic reflector. This article presents the study results on a microstrip reflect-array with circular polarization. Its efficiency and bandwidth characteristics are analyzed. Numerous advantages of this antenna system are discussed. Three new concepts using this microstrip reflectarray are also proposed.

Huang, J.↗
NASA NTRS1992

Coplanar waveguide feed for microstrip patch antennas

A coplanar waveguide (CPW) loop is shown to be an effective low VSWR feed for microstrip antennas. The low VSWR transition between the CPW and the antenna is obtained without the use of a matching circuit, and it is relatively insensitive to the position of the antenna and the feed.

Smith, R. L.↗
NASA NTRS1992

Scattering from arbitrarily shaped microstrip patch antennas

The scattering properties of arbitrarily shaped microstrip patch antennas are examined. The electric field integral equation for a current element on a grounded dielectric slab is developed for a rectangular geometry based on Galerkin's technique with subdomain rooftop basis functions. A shape function is introduced that allows a rectangular grid approximation to the arbitrarily shaped patch. The incident field on the patch is expressed as a function of incidence angle theta(i), phi(i). The resulting system of equations is then solved for the unknown current modes on the patch, and the electromagnetic scattering is calculated for a given angle. Comparisons are made with other calculated results as well as with measurements.

Shively, David G.↗
NASA NTRS2008

VHF Wide-Band, Dual-Polarization Microstrip-Patch Antenna

The figure depicts selected aspects of a very-high-frequency (VHF) microstrip patch antenna designed and built to satisfy requirements specific to an airborne synthetic-aperture radar system for measuring the thickness of sea ice. One of the requirements is that the antenna be capable of functioning over the relatively wide frequency band of 127 to 172 MHz corresponding to a fractional bandwidth of about 30 percent relative to a nominal mid-band frequency of 149.5 MHz. Another requirement is that the antenna be capable of functioning in either or both of two orthogonal linear polarizations. In addition, the antenna is required to be as compact and lightweight as possible. In a basic design according to generally accepted microstrip-patch-antenna engineering practice, one would ordinarily use a relatively thick dielectric substrate and multiple feed probes to obtain the desired combination of wide-band and dual-polarization capabilities. However, the combination of a thick substrate and multiple feeds would give rise to higher-order electromagnetic nodes, thereby undesirably contributing to cross polarization and to reduction of the isolation between feed probes. To counter these adverse effects while satisfying the requirements stated above, the design of this antenna incorporates several improvements over the basic design.

Huang, John↗
NASA NTRS1978

Design of microstrip disk antenna arrays

The radio frequency characteristics and design parameters for microstrip disk antenna elements and planar arrays are presented. Two C-band model arrays (an 8 element linear and an 8 by 8 planar) were designed, fabricated, and tested to demonstrate the technique of using microstrip elements for array applications. These arrays were designed with a cosine amplitude distribution.

Bailey, M. C.↗
NASA NTRS1994

Parallel/Series-Fed Microstrip Array Antenna

Characteristics include low cross-polarization and high efficiency. Microstrip array antenna fabricated on two rectangular dielectric substrates. Produces fan-shaped beam polarized parallel to its short axis. Mounted conformally on outside surface of aircraft for use in synthetic-aperture radar. Other antennas of similar design mounted on roofs or sides of buildings, ships, or land vehicles for use in radar or communications.

Huang, John↗
NASA NTRS1993

Analysis of microstrip patch antennas with nonzero surface resistance

The scattering properties of a microstrip patch antenna with nonzero surface impedance are examined. The electric field integral equation for a current element on a grounded dielectric slab is developed for a rectangular geometry by using Galerkin's technique with subdomain piecewise linear basis functions. The integral equation includes a resistive boundary condition on the surface of the patch. The incident field on the patch is expressed as a function of incidence angle. The resulting system of equations is then solved for the unknown current modes on the patch, and the radar cross section is calculated for a given scattering angle. Theoretical results in the form of radar cross section as a function of frequency are compared with results measured at the NASA Langley Research Center.

Shively, David G.↗
NASA NTRS1999

Design of a Foldable Low-loss Microstrip Array Antenna

The design and analysis of a series-fed, foldable microstrip array antenna for radiometer applications is presented. The array antenna is composed of two equal sub arrays. Each sub array consists of a series of patches connected together through segments of microstrip lines. The sub arrays are fed 180 degree out of phase to ensure a symmetric radiation pattern. The design approach, is accomplished using the IE3D code that utilizes the method of moments. All experimental and simulated data are presented and discussed.

Christodoulou, C. G.↗
NASA NTRS2005

Aperture-coupled thin-membrane microstrip array antenna for beam scanning application

A microstrip array using aperture-slot-coupling technique with very thin membranes has been developed at the L-band frequency for beam scanning application. This technology-demonstration array with 4 x 2 elements achieved a relatively wide bandwidth of 100 MHz (8%) and +/-45(deg) beam scan. Very narrow coupling slots were used with each having an aspect ratio of 160 (conventional slot aspect ratio is between 10 to 30) for coupling through very thin membrane (0.05mm thickness). This thin-membrane aperture-coupling technique allows the array antenna elements to be more easily integrated with transmit/receive amplifier (T/R) and phase shifter modules. This paper addresses only the radiator portion of the array. The array and active components will be presented in a separate pape.

array antenna↗
NASA NTRS1991

Analysis of a slot loaded microstrip disk antenna for circular polarisation

A method is presented to analyze a circular microstrip disk antenna loaded with a narrow, inclined slot at its center and fed by a coaxial probe. Making use of the exact dyadic Green's functions for a grounded dielectric slab due to electric and magnetic currents, Richmond's reaction integral equation in conjunction with the method of moments (Galerkin), a generalized h-parameter equivalent network for the loaded patch is obtained. An expression for the input impedance of a slot loaded microstrip patch is obtained from the equivalent parameters. The theoretical results are compared with the experiment.

Rao, Y. R.↗
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 NTRS1998

Design of a low-loss series-fed microstrip array antenna

The design and analysis of a series-fed, low-loss, inverted microstrip array antenna, operating at 1.413 GHz is presented. The array antenna is composed of two sub arrays. Each sub array consists of an equal number of microstrip patches all connected together through a series microstrip line. The first element of each sub array is coaxially fed but 180 degree out of phase. This approach ensures a symmetric radiation pattern. The design approach, is accomplished using the IE3D code that utilizes the method of moments. All experimental and simulated data are presented and discussed.

Mahbub, M. R.↗
NASA NTRS1992

Mutual coupling between rectangular microstrip patch antennas

The paper presents a comprehensive study of the mutual coupling between two rectangular microstrip patch antennas. The cavity model is employed to give numerical results for both mutual impedance and mutual coupling parameters for the E-plane, H-plane, diagonal, and perpendicular orientations. The effects of substrate thickness, substrate permittivity, and feed positions are discussed.

Huynh, Tan↗
NASA NTRS1994

A 32 GHz microstrip array antenna for microspacecraft application

JPL/NASA is currently developing microspacecraft systems for future deep space applications. One of the frequency bands being investigated for microspacecraft is the Ka-band (32 GHz), which can be used with smaller equipment and provides a larger bandwidth. This article describes the successful development of a circularly polarized microstrip array with 28 dBic of gain at 32 GHz. This antenna, which is thin, flat, and small, can be surface-mounted onto the microspacecraft and, hence, takes very little volume and mass of the spacecraft. The challenges in developing this antenna are minimizing the microstrip antenna's insertion loss and maintaining a reasonable frequency bandwidth.

Huang, J.↗
NASA NTRS2005

Demonstration of an X-Band Multilayer Yagi-Like Microstrip Patch Antenna With High Directivity and Large Bandwidth

The feasibility of obtaining large bandwidth and high directivity from a multilayer Yagi-like microstrip patch antenna at 10 GHz is investigated. A measured 10-dB bandwidth of approximately 20 percent and directivity of approximately 11 dBi is demonstrated through the implementation of a vertically-stacked structure with three parasitic directors, above the driven patch, and a single reflector underneath the driven patch. Simulated and measured results are compared and show fairly close agreement. This antenna offers the advantages of large bandwidth, high directivity, and symmetrical broadside patterns, and could be applicable to satellite as well as terrestrial communications.

Nessel, James A.↗