A Reconfigurable Phase-Difference Coupler for Beamforming Network-Based Multibeam Antenna

This paper presents a reconfigurable phase difference coupler for multibeam antenna based on beam-forming network. The reconfigurable phase-difference characteristics are achieved by varying the capacitances of shorted capacitors, which are loaded at the intersections of series and parallel arms of a branch-line type coupler. To demonstrate the effectiveness of proposed coupler, a 2.4 GHz reconfigurable phase-difference coupler is designed and fabricated. Measurement and simulation data agree well, where the results indicate that the fabricated coupler can exhibit reconfigurable phase-difference characteristics. The output phase-differences vary from −155° to −25° when the capacitances change from 0.3 pF to 2.3 pF with the transmission and coupling coefficients lower than −4 dB and the reflection coefficient better than −10 dB.