Symmetric and Asymmetric GaN-on-Si SPDT Switches Reusing Loaded Effects for 5G Millimeter-Wave Front-End Modules

This article proposes a novel series of on-chip single-pole double-throw (SPDT) switches reusing the loaded effect of adjacent channels. For SPDT switches, crosstalk between the transmitter (TX) and receiver (RX) channels remains a big challenge, adversely affecting both bandwidth and impedance matching performance. Conventional approaches use quarter-wave impedance transformers to decouple the TX and RX channels but significantly increase both chip area and transmission loss. To solve this issue, a new switch topology is proposed, which effectively reuses the loaded effect through multiport coupling matrix methodology. A shunt resonator reusing the loaded effect of adjacent resonator is introduced first. By introducing a coupling to the GaN HEMT-based resonator, the <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small>-state channel of the SPDT switch turns to a multiorder coupled-resonator circuit. Baase on coupling matrix method, a flexible tuning of frequency and bandwidth can be realized by selecting appropriate coupling parameters. Low insertion loss of TX branch and high isolation to the RX branch can be simultaneously realized by selecting different circuit orders. In this way, the proposed switch supports both symmetric and asymmetric SPDT configurations, aiming at diverse requirements of front-end modules (FEMs). For demonstration, a 28-GHz symmetric SPDT switch using 100-nm GaN-on-Si process and a 28-GHz asymmetric SPDT switch using 150-nm GaN-on-Si process were fabricated. A particular low insertion loss of 0.8 dB is realized for the TX channel and high isolation beyond 28 GHz is obtained for the RX channel.