An electrostatic tunable RF MEMS capacitor with improved quality factor

摘要

A new micromachined varactor for the RF applications is proposed. Electrostatic actuation is chosen for the varactor because of the simplicity of the fabrication and low power consumption. The varactor is composed of two sets of actuation plates. The flip-flop structure of the varactor makes is possible to increase or decrease the capacitance, which results in a higher tuning range. One of the other advantages of this flipflop structure is the elimination of the pull-in effect. The proposed varactor has the tuning range of 139% and quality factor of 40 at the frequency of 1GHz. The operating voltage for the varactor is 2v which is in the range of CMOS circuits. The narrow beams of the MEMS varactor which introduce large series resistance are eliminated by dividing the bottom plate of the capacitor into two plates, which in turn causes the varactor to show better quality factor.