AN/GPA-123 SUM AND DIFFERENCE ANTENNA GROUP
ROME AIR DEVELOPMENT CENTER GRIFFISS AFB NY
Pagination or Media Count:
Prior to this development Interrogation Side Lobe Suppression ISLS was accomplished with the use of two separate antennas a directional and an omnidirectional antenna. The same results, however, can be achieved through the use of a single directional antenna which can produce two distinct patterns. The sum and difference patterns are obtained by feeding the antenna in two halves by means of a hybrid junction. This system also has an additional benefit of effectively sharpening the beamwidth when interrogating ISLS equipped airborne transponders. A trade-off is necessary, however, in that the one antenna system is more complex and requires a greater degree of precision. Operational tests conducted indicate that the development effort was successful and ISLS is possible using this system. Requirements of the specification and design objectives were for the most part achieved.
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