Ultra-high-isolation BiCMOS switch for extremely wideband microwave and millimeter-wave systems

A new RF switch architecture with ultra-high isolation and possible gain is proposed, analyzed and demonstrated using 0.18-μm BiCMOS technology. The new RF switch architecture achieves an ultra-high isolation through implementation of a new RF leaking cancellation technique, in which the RF leaking signal is suppressed by combining with its replica using a balun. Its isolation is substantially higher than that produced by a conventional switch topology. The newly designed 0.18-μm BiCMOS RF switch exhibits an ultra-broadband performance from 10 to 38 GHz with -2.6-dB loss to 0.4-dB gain, isolation from 40 to about 70 dB, and input return loss from 8 to 20 dB under small signal conditions. Within 35.5-38.5 GHz, its isolation reaches extremely high values, with the highest isolation around 70 dB at 36 GHz. Measured insertion loss and isolation under large-signal conditions at 35 GHz show around 1-2 dB and 51.5 dB, respectively. The RF switch consumes a dc current of only 8 mA from a 1.8 V source. The extremely high isolation achievable by the new RF switch demonstrates the possibility of pushing RF system performance limited by switch isolation to a next level.