Performance optimization of multi-stage MEMS W-band dielectric-block phase-shifters

This paper reports on the RF performance optimization of multi-stage distributed MEMS devices. The return loss (RL) is optimized, without substantially compromising in overall insertion loss (IL), for a 7-stage MEMS dielectric-block phase shifter by adjusting geometrical parameters of the distributed network, for the nominal frequency of 75 GHz as well as for performance within a 500 MHz and a 1 GHz bandwidth. Different optimization strategies have been investigated by simulations and by measuring fabricated devices. The best optimization concept was found for exponentially increasing distances between the stages, which takes into account the proper actuation sequence for all possible phase-shift combinations. As compared to a non-optimized device previously published, the design offering the best compromise between RL and IL results in a significant average RL improvement of 11.8 dB (simulated) and 6.98 dB (measured), while compromising the average IL by only 0.75 dB (simulated) and 0.92 dB (measured).