Comparative Study of Square and Hexagonal Plate MEMS Variable Capacitors

Tunable filters are playing a vital role in RF MEMS circuits and its important element to vary the frequency is varicaps. Varicaps which are designed using conventional methods commonly encountered into problems namely low Q-factor and pull-in effect. In this paper, two different modified parallel plate RF MEMS variable capacitors have been designed, simulated and their performance is analysed with 6 GHz self resonance frequency, 250 Q- factor and 2:1 tuning range, to overcome the above mentioned problems. Also, we have presented S-Parameter analysis and Q-factor analysis for these improved versions of MEMS capacitors. These tunable capacitors have been designed using Poly MUMPS to produce freestanding structures with excellent structural quality and with lateral feature sizes as small as micron.