Antibiased Electrostatic RF MEMS Varactors and Tunable Filters

This paper presents a new approach for substantially enhancing the linearity and reducing the effects of bias noise for electrostatic RF microelectromechanical systems (MEMS) devices. The proposed method relies on applying bias voltages with opposite polarities to cancel the dynamic vibration of the MEMS structures. In this paper, the method has been applied to a shunt RF MEMS varactor and a MEMS tunable evanescent-mode tunable filter. In the first case, the shunt MEMS varactor is split into two identical parts that are biased with opposite voltages. This results in almost complete cancelation of the odd-order modulation components, leading to 20-28-dB linearity enhancement depending on the noise and the design. Analytical results, a computer-aided design model and measurements validate the proposed approach. In the tunable filter case, opposite bias voltages are applied on the tuners of its resonators. Simulated and measured results are also presented in this case. Measurements show a sideband reduction as high as 13 dB. In both cases, the effectiveness of the proposed method in the presence of fabrication uncertainties are also considered.