Effect of mutual coupling on the performance of GPS AJ antennas

In this paper, we discuss the effects of mutual coupling on the performance of GPS anti-jam (AJ) antennas. The physical size of the antenna is decreased while keeping the number of antenna elements fixed. It is shown that for a given distribution of antenna elements, the mutual coupling hardly degrades the nulling performance of an antenna array. For CW interfering signals, in general, the performance with mutual coupling is similar to the performance in the absence of mutual coupling. In the presence of wide-band (WB) interfering signals, as expected, the performance of the adaptive antenna degrades. The degradation with mutual coupling is somewhat larger than when the mutual coupling is excluded in the performance evaluation. However, as we have demonstrated earlier, one can easily recover the lost performance by using space-time adaptive processing (STAP). Again for STAP based adaptive antennas, the performance in the presence of wideband interfering signals is hardly inhibited due to mutual coupling between antenna elements. In this paper, we also discuss the physics behind this unexpected behavior.