Double-actuation extended tuning range RF MEMS Varactor

This paper presents the design and testing of a MEMS Varactor for microwave applications. The tunable capacitor consists of a movable bridge shunt-connected to a 50Ω coplanar line on HR-silicon substrate. The design is based on double actuation mechanism with a mechanical central bond that inhibits the pull-in and allows for theoretically infinite tuning ratio. The measurements show a total capacitance ratio of 5.7 with 2.6 continuous tuning ratio with a 0-50V operating voltage. The measured capacitance values are in the range 105fF-615fF with a resonant frequency above 30GHz for the downstate position. At the same frequency, the measured Q (quality factor) is about 30. Good RF and mechanical performance repeatability have been demonstrated by checking six different samples.