A Sub-6 GHz Asymmetric GaAs SPDT Switch With High Tx-to-Rx Isolation and Low Insertion Loss

This letter introduces an asymmetric single-pole double-throw (SPDT) switch designed using the gallium arsenide pseudomorphic high-electron mobility transistor (GaAs pHEMT) process for sub-6 GHz applications, particularly in the n77 and n79 frequency bands, within the context of 5G. SPDT switches for 5G applications require high Tx-to-Rx isolation in Tx mode, low insertion loss to Rx path, high power handling capabilities, and a compact size. To achieve high Tx-to-Rx isolation in Tx mode, a series-shunt structure is used, while the transmit and receive paths are asymmetrically designed to minimize insertion loss. In addition, a stack configuration is used for the shunt arm to enhance power-handling performance, and the resonant inductor of the shunt-arm transistor is integrated to ensure a compact chip size. The proposed SPDT switch is fabricated using the GaAs pHEMT process and it operates in the sub-6 GHz frequency range, exhibiting an insertion loss of less than 0.53 dB in both TRx modes. In Tx mode, the isolation from transmit to receive is above 36.4 dB, and the input 1-dB compression point (IP1dB) at 4 GHz is 44.28 dBm (simulation), with measurements and verification conducted up to 40 dBm. Furthermore, the core area measures 0.84 ${\text{mm}}^{2}$ .