High-power and low-loss SPDT switch design using gate-optimized GaN on SiC HEMTs for S-band 5G T/R modules

Radio frequency (RF) switches are one the fundamental components of modern communication systems. They enable the routing of high-frequency signals into different transmission paths. Therefore, they play a crucial role in transceiver (T/R) modules. Especially, 5G technology creates a demand for compact switches with high power handling, high isolation, and low insertion loss. GaN on SiC high electron mobility transistor (HEMT) technology stands out with its exceptional electrical and thermal characteristics among other semiconductor technologies. However, switch performance is limited by selected topology and transistor capability. Notably, the T-gate dimensions of the HEMTs directly affect the small-signal and large-signal performance of the switch. This study focuses on designing a single-pole double-throw (SPDT) monolithic microwave integrated circuit (MMIC) switch using gate-optimized HEMT in AlGaN/GaN on SiC technology. The foot length of the gate is varied from 200 nm to 250 nm, and the head length is varied from 500 nm to 750 nm in the T-gate structure to optimize the RF performance. An asymmetric SPDT switch using transistor with 500 nm head length and 250 nm foot length is designed to demonstrate transistor performance. The switch achieved an insertion loss of better than 0.85 dB throughout the 3.2–3.8 GHz bandwidth. The low-noise path can handle 25 W power level, while the high-power path can withstand up to 50 W of RF power at 1 dB compression level. The isolation performance is about 25 dB, while the return loss of the switch is better than 12 dB. The switch occupies a chip area of 2 x 2.2 mm2.