Common mode disturbance tolerant broadband differential SPDT switch for Ka-band radar

Abstract

The proposed broadband fully differential single-pole double-throw (SPDT) switch for Ka-band radar with high 1-dB power compression point (P_-1dB) and isolation is demonstrated using 0.13 µm SiGe BiCMOS technology. In contrast to traditional circuit, SPDT switch utilizes fully differential topology with virtual grounding, so it also offers cancellation to common mode disturbance. As a result, this SPDT switch will help in improving radar range due to its high P_-1dB, high range-resolution and accuracy due to its broad-bandwidth. Further, this paper also introduces the use of asymmetrical tapered inductor in SPDT switch to improve layout area of SPDT switch with normal spiral inductor. Measurement results of fabricated differential SPDT switch with conventional layout has demonstrated a minimum insertion loss of 2.9 dB and an isolation of -39 dB in 25 GHz to 40 GHz frequency-band, and input P_-1dB of 12.6 dBm at 34 GHz with 0.47 mm² area. EM simulation results of compact differential SPDT switch with symmetrically tapered inductor in layout has demonstrated minimum insertion loss of 1.8 dB and isolation of -39 dB in same frequency-band, input P_-1dB of 14.1 dBm at 34 GHz with 0.11 mm² area.