An inflatable Microstrip Reflectarray concept for Ka-band applications

Abstract

An Inflatable Ka-Band Microstrip Reflectarray system for use in spacecraft application has been identified as an enabling technology for the challenging requirements of deep-space communication. To meet the challenge of such application, the National Aeronautics & Space Administration (NASA) has embarked in an effort to develop lightweight, large aperture radar and communication antenna. JPL and ILC Dover, Inc. have successfully developed a 3-meter inflatable Ka-band Microstrip Reflectarray prototype. The general concept of this Reflectarray consists of an inflatable rigidizable support structure bridged by rigid composite structures, an inflatable rigidizable feed support, a RF reflective membrane assembly, and membrane tensioning and adjustment hardware. The feasibility and efficacy of this concept were demonstrated by fabricating and testing of a full size model. The stringent requirements of flatness, 0.5 mm RMS and 0.8 mm peak, were met with significant margin. The membrane flatness was measured 0.118 mm RMS with a maximum deviation of ±0.3 mm. Additionally, RF tests performed at the indoor compact range of Composite Optics Incorporated (COI) in San Diego, California demonstrated excellent radiation characteristics, including good main-beam shape, excellent sidelobe level, and low cross- pol radiation. A detailed description of the mechanical and structural features of the 3m inflatable Reflectarray and discussion of some of the RF characteristics and results obtained during the testing of the antenna at the indoor compact range are presented in this paper. In addition, comments on continuing structural and RF design work and configuration studies are presented.