Investigation on the interfering effect of feeding network on the performance of a beamforming antenna array

It is widely accepted that the unwanted radiation from some feeding networks could degrade the performance of the antenna array. However, this interfering effect was not seen to be characterized in the open literature. This paper investigated this effect by a comparative study on a microstrip 4 × 4 Butler matrix fed linear patch antenna array at 2 GHz. The designs and measurement of the Butler matrix and the array are presented.