A Switchable Bandpass Filter Employing RF MEMS Switches and Open-Ring Resonators

A switchable bandpass filter is presented in this paper, which is able to operate at two different frequencies. The “open-ring” resonators and cantilever microelectromechanical systems (MEMSs) switches are employed to form the switchable filter with a high rejection at out-of passband and a controlled dc bias of 26 V. A hybrid resonance circuit with both series circuit and parallel circuit are used as the equivalent circuit, which is used to accurately analyze the structure parameters. The MEMS switch capacitance, used for equivalent circuit and driving voltage estimation, is analyzed to achieve an exact predicted value by equivalent microstrip line model. The isolation of designed MEMS switch is greater than 40 dB with a wideband from 4 to 9 GHz, the filter is switched on and off to achieve the center frequency at ~7.81 and ~8.35 GHz separately. The filter is fabricated on high-resistancesilicon, and the measured results showed a good agreement with the simulated results. The filter performance shows a sharp rejection greater than 40dB at the frequency of (f
₀
±0.5 GHz), and the insertion loss is >-3.4 dB in the passband.