A 28-GHz Butler Matrix Based Switched Beam-Forming Network with Phase Inverting Switch for Dual-Port Excitation in 28-nm CMOS

This paper demonstrates a 28-GHz 4 x 4 Butler matrix based switched beam-forming network with phase inverting switch for dual-port excitation in 28-nm CMOS. The beam-forming network consists of a SPDT reconfigurable switch network (RSN), two SPDT phase inverting switch networks (PSNs) and a Butler matrix. By using the SPDT RSN and SPDT PSNs, the proposed beam-forming network provides dual-port excitation modes without three crossovers and 180 degrees delay lines which are required for a SP4T RSN. The total insertion loss of beam-forming network is around 8.7 dB at 28 GHz, excluding the power division loss of the Butler matrix. From the array factors based on the measured S-parameters, the proposed beam-forming network can generate 7 beams, +/- 14.9 degrees, +/- 48.5 degrees in single-port excitation modes, and 0 degrees, +/- 28.6 degrees in dual-port excitation modes.