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 mm 2 , the three T/R switches exhibited excellent RF performance, surpassing the recently reported novel X‐band SPDT switches in 250 nm GaN HEMT.