A high power 2-18 GHz T/R switch

Abstract

A high-power 2-18-GHz T/R (transmit/receive) switch monolithic microwave IC (MMIC) has been developed for use in broadband T/R modules. This switch has a power handling of better than 35 dBm (3.2 W), 8-dB higher than any previously reported broadband switch. A combination of techniques was used to yield higher power handling while preserving low loss and high isolation. These circuit techniques include an asymmetrical design of the transmit and receive arms, the use of dual-gate FETs for handling large voltages, and the use of large FET peripheries for handling large currents. The use of dual-gate FETs in place of a stack of individual FETs reduces the device area, with a resulting reduction in parasitic series inductance through the FET and in shunt capacitance from the FET to ground. Power handling is somewhat lower for the dual-gate FET than for conventional stacked FETs, since RF voltage cannot be distributed as uniformly across the gates. Offstate capacitance is higher for a dual-gate FET than for a stacked FET, since the close proximity of the elements leads to additional parasitic capacitances.<>