Continuously Variable W-Band Phase Shifters Based On Mems-Actuated Conductive Fingers

This paper presents four continuously variable W-band phase shifters in terms of design, fabrication, and radiofrequency (RF) characterization. They are based on low-loss ridge waveguide resonators tuned by electrostatically actuated highly conductive rigid fingers with measured variable deflection between 0.3 degrees and 8.25 degrees (at a control voltage of 0-27.5 V). A transmission-type phase shifter based on a tunable highly coupled resonator has been manufactured and measured. It shows a maximum figure of merit (FOM) of 19.5 degrees/dB and a transmission phase variation of 70 degrees at 98.4 GHz. The FOM and the transmission phase shift are increased to 55 degrees/dB and 134 degrees, respectively, by the effective coupling of two tunable resonances at the same device with a single tuning element. The FOM can be further improved for a tunable reflective-type phase shifter, consisting of a transmission-type phase shifter in series with a passive resonator and a waveguide short. Such a reflective-type phase shifter has been built and tested. It shows a maximum FOM of 101 degrees/dB at 107.4 GHz. Here, the maximum phase shift varied between 0 degrees and 377 degrees for fingers deflections between 0.3 degrees and 8.25 degrees.