One and Two-Bit MEMS Distributed W-Band Phase Shifters

A wideband distributed microstrip phase shifter has been developed for W-band operation. The design is based on the distributed MEMS transmission line (DMTL) loaded with high capacitance-ratio varactors. The varactors are fabricated using a series combination of MEMS bridges and fixed-value capacitive microstrip stubs. A high-capacitance ratio varactor (1.5 to 2.5) results in a large loading on the microstrip line and therefore a large phase shift. The distributed phase shifter design on a 150 ¿m quartz substrate results in a reflection coefficient less than ¿15 dB and 260°/dB of insertion loss at 90 GHz. This design can be cascaded to result in a 2-bit, 0/90/180/270° phase shifter with 1-1.5 dB of insertion loss.