A CENTER TYPE ARSR/SSR INTEGRAL FEED ANTENNA

Abstract

The integral feed antenna of the SSR with a sharp cutoff pattern in elevation is studied here to improve the conventional SSR which is often bothered by target loss and false target. It employs the reflector of ARSR for common use as both frequencies are in the same frequency band. New SSR has two types; the offset feed type and the center feed type. The offset feed type, as our previous paper (ENRI Papers NO.41) has reported, is very effective in improving current SSR's problems as mentioned above. However, it has some defects such as beam skew and beam offset due to the SSR radiator's location, and it is not suitable for a monopulse application, which provides a higher accuracy in the aircraft azimuth estimation. Therefore a center feed type antenna was developed. This paper first describes detailed analyses on its radiation characteristis and a comparison with the offset feed type, and secondly discusses its merits and demerits based upon these analytical results and measured data. Finally, it is shown that the center feed type antenna meets the specification of the current SSR and is suitable for the monopulse application.