Ka-Band 4×4 Butler Matrix-Based Switched Beamformer Supporting Uniform EIRP Beams in Single-/Dual-Port Excitations

This paper presents a Ka-band 4×4 Butler matrix-based switched beamformer supporting uniform EIRP beams in single-/dual-port excitations. The switched beamformer is composed of a reconfigurable switched beamforming network based on a 4×4 Butler matrix which can generate total 7 beams, and bi-directional transmit-receive (TRX) channels with attenuators. The switched beamformer can support uniform EIRP beams in all possible modes by equalizing magnitudes at each antenna port in the dual-port excitation mode. Measured gain and OP1dB/element in TX mode are 30 dB and 13.6 dBm, respectively. In RX mode, measured electronic gain and IP1dB/element are 4 dB and --22 dBm, respectively, and the noise figure is below 7 dB at 27.8--31.5 GHz. To our knowledge, this is the first 4×1 switched beamformer addressing the issue of non-uniform magnitudes in the dual-port excitation mode.