Design of X-band SPDT in a GaAs pHEMT Process

A single-pole double-throw switch (SPDT) working in X-band is presented in this paper. The switch effectively improves isolation in interested band by concatenating an RC parallel structure at the source of the shunt switch transistor. In addition, the switch is designed with a high-low pass structure, which can effectively suppress the out-of-band signal in the on-state of the switch. The circuit was processed by 0.5 um GaAs process. The post simulation results show that in X band, the switch insertion loss is 0.95dB, the isolation is greater than 33dB, the input/ output return loss is greater than 13.5dB, and the P1dB is 20dbm. The chip area is 920um * 875um, which can be applied to the front of radar T/R module.