Wideband Hybrid Couplers and Their Applications to Multi-beam Antenna Feed Networks

This paper presents a dual-layer 180 degrees hybrid coupler design with a wide operating bandwidth. The design can achieve a high isolation level between the sum and difference ports across a 30% bandwidth. The power division can be made equal or unequal between two ports by controlling the impedance of the shunted stubs and connected transmission lines. Based on the proposed hybrid couplers, the configurations of two multi-beam antenna feed networks, which can produce 6 and 12 beams, are synthesized. It is demonstrated that such multi-beam antenna feed networks can be built using only180 degrees hybrid couplers and phase shifters, and the proposed coupler design is an excellent candidate for building such networks with a wide bandwidth.