Design of X-band 4×4 Butler Matrix for Microstrip Patch Antenna Array

This paper presents the design of planar 4times4 Butler matrix in X-band at center frequency of 8.3 GHz for satellite application. The Butler matrix is used as a beam-forming network to feed circularly polarized 4-element linear array to produce four steerable beams. The direction of these beam patterns are plusmn15deg and plusmn40deg with effective coverage over 120deg. The network is designed to work over the frequency range from 8.25 GHz to 8.35 GHz. The phase errors and couplings are within 8deg and -6.2plusmn0.5 dB respectively