Design of X-Band MEMS Microstrip Shunt Switches

This paper presents the design and performance of X-band MEMS switches built in microstrip technology. The switches result in an insertion loss of less than 0.1 dB and a small isolation bandwidth, less than 10%, and are limited by the radial stubs band-widths. The isolation value is also not dependent on the down-state capacitance of the switch. The isolation bandwidth (less than -20 dB isolation) is improved to 8-13 GHz with the use of a π-network and two MEMS switches. The up-state insertion loss of the π switch is less than 0.25 dB. The paper demonstrates that the performance of microstrip switch circuits without via-holes is dominated by the shorting (radial) stubs, and careful design must be done to result in an acceptable bandwidth of operation.