A 24–40 GHz Differential SPDT Switch With an NMOS and PMOS Alternating Structure and Leakage-Canceling Capacitors

A 24–40 GHz CMOS differential SPDT switch that covers multiple frequency bands of millimeter-wave 5G communication is presented. The switch has a differential structure in which NMOS and PMOS are alternately connected, and leakage-canceling capacitors are cross-connected the two outputs of the switch. The differential structure allows it to have parasitic ground inductance robust characteristics. The opposite ON/OFF characteristics of NMOS and PMOS allow the gates of off-state NMOS/PMOS transistors to have lower/higher voltages than their source and drain without using DC block capacitors, improving both the power handling capability and the insertion loss. In the proposed SPDT structure, the resistors for source and drain biasing are eliminated, which resolves the trade-off between the ON/OFF time and the insertion loss. In addition, cross-connected capacitors in the differential structure are readily used as a leakage canceller, offering a high level of isolation at all frequency bands. The switch is implemented in a 65-nm RF CMOS process with a core area of only 0.016 mm2. Owing to the simple alternating structure, insertion losses lower than 1.6 dB and IP1dB higher than 24 dBm are achieved from 24 to 40 GHz. In addition, the isolation is improved by around 15 dB due to the proposed leakage-canceling capacitors. The measured isolation is higher than 30 dB from DC to 50 GHz.