Compact Reconfigurable Dual-Band MMIC SPDT/SP4T Switches With On-Chip Coupled-Line Structure in GaN-on-SiC HEMT Technology

This paper presents the design and analysis of dual-band monolithic microwave integrated circuit (MMIC) switches, including a single pole double throw (SPDT) and a single pole four throw (SP4T). With a novel on-chip coupled-line (OCL) topology, the input signal can be switched into low- or high-band paths to create dual-band characteristics. By carefully selecting the electrical lengths of OCLs and device size for corresponding shunt-FETs, the operating frequencies for low- and high-bands can be determined. This brings about improved insertion loss (IL) and isolation (ISO) in a compact structure. With the proposed techniques, two switch prototypes have been designed and fabricated in a 0.25- $\mu $ m GaN-on-SiC process for high-power capability. The SPDT consists of a low-band path and a high-band path. It achieves an average IL/ISO of 1.0/32 dB with the best input 1-dB compression points (IP1dB) of 37.2 dBm at a low-band of DC-15 GHz; and an average IL/ISO of 2.0/28.5 dB with the best IP1dB of 32.8 dBm at a high-band of 20-40 GHz, respectively. The return loss is better than 11 dB for each port. The SP4T achieves a fully integrated dual-band transmit/receive (T/R) switch with doubled low-/high-band paths. It shows an average IL/ISO of 2.26/27.5 dB with the best IP1dB of 31.2 dBm at a low-band of 5-15 GHz; and an average IL/ISO of 2.7/26.5 dB with the best IP1dB of 30 dBm at a high-band of 20-30 GHz have been achieved, respectively. Better than 11.3 dB return loss is obtained for each port. The chip sizes are $1.8\times 0.9$ mm2 for the SPDT and $2.2\times 1.7$ mm2 for the SP4T.