Anti-biased RF MEMS varactor topology for 20–25 dB linearity enhancement

A new topology for significantly improving the linearity of RF MEMS varactors is reported in this paper. A single MEMS varactor subject to a low frequency noise and/or modulating signal is the main structure under consideration. The key idea is to separate the single varactor into two varactors in parallel which are anti-biased. This leads to the opposing vibration of two beams under the influence of the low-frequency signal, which eventually leads to a nearly constant capacitance of the entire topology. The effectiveness of this method is demonstrated by both measured results from fabricated RF MEMS varactors and simulated results using a large-signal model of MEMS varactor in ADS. Both experimental and simulated results indicate an improvement of 20–25 dB compared to the conventional designs. This underlines the potential of the proposed topology in high-power RF MEMS circuits.