Two novel structures for tunable MEMS capacitor with RF applications

Abstract

Two novel structures for high-Q MEMS tumble capacitors are presented. The proposed designs include full plate as well as the comb structured capacitors. They can be fabricated employing surface micromachining technology which is CMOS-compatible. The structures do not require the cantilever beams which introduce considerable series resistance to the capacitor and decrease the quality factor. Therefore, our proposed structures achieve better Q in a smaller die area. The simulated results for 1 pF full plate capacitor shows a tuning range of 42% and a Q of 47 at 1 GHz. However, with the same initial capacitance, but the comb structure, the tuning range is increased to 43% but the Q is decreased to 45 at 1 GHz. The simulated Pull-in voltage with no residual stress is 3.5 V for both capacitors. The S11 responses are reported for a frequency range from 1 up to 4 GHz.