A V-band switched beam-forming network using absorptive SP4T switch integrated with 4×4 Butler matrix in 0.13-µm CMOS

An integrated switched beam forming network is demonstrated at V-band by integrating an absorptive single-pole four-throw (SP4T) switch together with a 4×4 Butler matrix using 0.13 μm CMOS process. The fabricated absorptive SP4T switch shows a measured insertion loss of 4.5 dB at 60 GHz and isolation higher than 31 dB from 57 to 63 GHz. The return losses of the deactivated output ports also maintain better than 14 dB due to the absorptive configuration. The entire insertion loss of the integrated beam former IC was around 7.5 dB at 60 GHz, among which 3 dB is attributed to Butler matrix. The overall phase error was within ±12%. The calculated array factor from the measured S-parameters shows that the beam-forming network generates four beams at ±14°, ±54°. To the best of our knowledge, this is the first demonstration of CMOS switched beam-forming network integrating an absorptive SP4T switch and Butler matrix at V-band.