Comparative Design of 28 GHz SPDT Switches with GaAs Passive pHEMTs and Diodes

This paper presents and compares four designs of single-pole double-throw (SPDT) switches at 28 GHz with diodes or passive pHEMTs in the 0.15 µm GaAs process. Both the λ/4 shunt and series-shunt topologies are adopted. The equivalent circuit models show that pHEMTs have larger parasitic OFF-state capacitances but with simple design of biasing network and easy cancellation of parasitic effect. Series capacitors and parallel inductors are applied in these switches to compensate parasitic effects. In the 5G millimeter-wave band, the series-shunt type SPDT switch with pHEMTs shows comparable isolation performance to other designs, with the insertion loss of 1.5 dB and the smallest area of 0.10 mm2, which is demonstrated by the good agreement between the simulated and measured results.