Novel RF MEMS Mechanically Tunable Dielectric Phase Shifter

This paper presents three variations of novel single-stage digital passive RF MEMS phase shifters. Relative phase shift is achieved by moving a micromachined lambda/2-long dielectric block by a MEMS actuator above a 3dimensional micromachined coplanar waveguide. The relative phase-shift of a single stage is determined by an artificially tailor-made dielectric constant of the block which is designed by a periodically etched pattern. The devices are fabricated and assembled by wafer-scale processes using bulk and surface micromachining. The measurement results show that already the first prototypes of the phase-shifter designs at the nominal frequency of 77 GHz have both in the up and in the down state a return loss better than -25 dB for 45 degrees and 300 phase shifter and better than -12 dB for 15 degrees phase-shifter with an insertion loss better than -0.9 dH at 5 GHz bandwidth. The phase shifters also perform well from 10-100 GHz with the return loss better than -10 dB, an insertion loss of less than -1.5 dB and a fairly linear phase-shift for the whole frequency range.