High-performance 19 GHz-band GaAs FET switches using LOXI (Layered-Oxide-Isolation)-MESFETs

19 GHz-band GaAs MESFET switch ICs have been demonstrated, intended for use in high-speed wireless LAN systems. The FET channel is fabricated on a SiO/sub 2/ insulator in order to reduce parasitic FET drain-source capacitance (Cds) which acts as off-state capacitance (Coff) in switches. The LOXI (Layered-Oxide-Isolation)-MESFET has enough DC and RF performance for use as an active device. On-state FET resistance (Ron) remains the same as that of conventional MESFETs white Coff is reduced. This allows the use of larger gate-width switch FETs, which yield low insertion loss. The measured simple SPST (single-pole, single-throw) switch has low insertion loss of 0.5 dB and high isolation of 23 dB at 19 GHz. The measured simple SPDT (single-pole, double throw) switch also has good characteristics, 0.8 dB insertion loss and 17 dB isolation at 19 GHz.