Radiation pattern prediction analysis of elliptically polarized cavity‐backed aperture antennas in a finite ground plane is carried out using a combination of the finite element method (FEM), method of moments (MoM), and geometrical theory of diffraction (GTD). The magnetic current on the cavity‐backed aperture in an infinite ground plane is calculated using the combined FEM‐MoM analysis. GTD is used to calculate the diffracted fields due to both soft and hard polarizations at the edges of the finite ground plane. The slope of the incident magnetic field at the diffraction points is derived and analytical expressions are presented. Numerical results for the radiation patterns of a cavity‐backed coaxial cavity and also a cavity‐backed circular spiral microstrip patch antenna excited by a coaxial probe in a finite rectangular ground plane are computed and compared with measured results.

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Abstmct-NASA Langley Research Center (LaRC) has pursued the development of tensioned membrane antenna technology for several years. For many applications, it is desirable to have space-based antennas which are very large. As the physical size increases, antennas constructed of conventional materials quickly become too bulky and heavy to be practical for space applications. For some of these applications, such as earth remote sensing, reducing electromagnetic losses in the antenna is also critical. For this reason, there is interest in finding new methods of fabricating large antennas which not only exhibit lighter weight than conventional antennas, but also meet stringent electromagnetic performance criteria.One configuration which has been investigated by NASA LaRC is a slotted waveguide array antenna constructed of a metallized thin membrane material. Several test articles have been built and tested to validate this configuration. This concept will lend itself to compact packaging for launch, and can be tensioned on an inflatable, rigidizable support structure, which would deploy once on orbit. One