A Novel Compact Butler Matrix Without Phase Shifter

A novel compact 4 × 4 Butler matrix using only microstrip couplers and a crossover is proposed in this letter. Compared with the conventional Butler matrix, the proposed one avoids the interconnecting mismatch loss and imbalanced amplitude introduced by the phase shifter. The measurements show accurate phase differences of 45±0.8° and -135±0.9° with an amplitude imbalance less than 0.4 dB. The 10 dB return loss bandwidth is 20.1%.