Four-Element Adaptive Array Evaluation for United States Navy Airborne Applications

This paper provides background on the design methodology of an adaptive GPS antenna system and the testing methodology used to evaluate such a system. The challenge in evaluating multi-element active antenna arrays is that conventional antenna characteristics such as element phase, gain, or sidelobe levels do not easily translate into system level performance measures such as dynamic response time, pattern null width and null depth. The GPS Antenna System (GAS-1N) Foreign Comparative Testing (FCT) program evaluated a four-element, fourchannel adaptive antenna system for U.S. Navy airborne applications by using various measures of performance based on the stage of testing. Testing methodologies included anechoic chamber, F/A-18 full-scale model on an outdoor range, modeling and simulation techniques, and dynamic flight testing on a C-12J and F/A-18C. Additionally, side-by-side comparisons were made during flight testing using Fixed Radiation Pattern Antenna (FRPA), GAS-1N (4-element), and GAS-1 (7-element) antenna systems.