Low Insertion-Loss High Power X-Band SPDT Transmit/Receive Switches in 250 nm GaN HEMT

We present three X-band transmit/receive (T/R) switches utilizing single-pole double-throw (SPDT) structures in 250 nm GaN HEMT technology. The first T/R switch was designed to achieve low insertion loss by constructing the SPDT structure with a series λ/4 transmission line (T-line) and meticulously selected two HEMT switches in parallel for each transmit and receive path. Based on the proposed low-loss architecture, the second T/R switch integrated 2^nd and 3^rd harmonic rejection notches to suppress harmonic distortions effectively. The third T/R switch was implemented to operate with a positive control voltage, achieved by employing a positive bias voltage at the source of the HEMT with AC coupling capacitors at the drain and source of the normally-on HEMT. Measurements demonstrated that the fabricated three T/R switches achieved insertion losses of 0.44, 0.54, and 0.66 dB, corresponding IP_0.2dB of 44, 44, and 43 dBm, respectively. With a compact die size of 5.4 mm², the three T/R switches exhibited excellent RF performance, surpassing the recently reported novel X-band SPDT switches in 250 nm GaN HEMT.