Measurements on a GPS Adaptive Antenna Array Mounted on a 1/8-Scale F-16 Aircraft

B. Rama Rao and Jonathan H. Williams

Abstract:	The performance of a conformally mounted, airborne GPS adaptive array can be affected by interactions between the array elements and the aircraft fuselage. This paper describes the design and measurements on a seven-element microstrip-patch antenna adaptive array mounted on the fuselage of 1/8-scale F-16 aircraft to evaluate such antenna - aircraft interactions and their effect on the performance of the array in nulling multiple wideband jammers. The array operates at 12.6 GHz over a 160 MHz bandwidth - which is 8 times the GPS L 1 frequency and bandwidth, respectively. Far-field antenna patterns for all seven elements have been measured across the scaled frequency band in a near-field antenna range. To obtain a better understanding of the influence of the airframe on the antenna pattern, the measured patterns for an isolated microstrip patch element have been compared to the antenna patterns computed from the OSU - NEWAIR code which uses Uniform Theory of Diffraction for analyzing the interaction of the antenna with the fuselage. There is good agreement between the measured and computed patterns. The data gathered from these scale model measurements is being used to test the effectiveness of Space Time Adaptive Nulling algorithms developed at MITRE in the presence of multiple wideband jammers located at various orientations relative to the aircraft. Measurements have also been made to demonstrate the nulling capabilities of this array in the presence of two narrow band jammers using a simple Direct Matrix Inversion algorithm. The measured adapted array pattern agrees well with theoretical predictions. The advantages of scale model testing for verifying the nulling performance of airborne adaptive arrays is explained.
Published in:	Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998) September 15 - 18, 1998 Nashville, TN
Pages:	241 - 250
Cite this article:	Rao, B. Rama, Williams, Jonathan H., "Measurements on a GPS Adaptive Antenna Array Mounted on a 1/8-Scale F-16 Aircraft," Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998), Nashville, TN, September 1998, pp. 241-250.
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