RF MEMS tunable filter: Design, simulation and fabrication process

This paper deals with a tunable bandpass filter topology which controls both the central frequency and bandwidth. This tunable filter results from the association of MEMS (microelectromechanical system) fixed-fixed beam, used as variable capacitors, with an original passive topology. The design proposed in this paper is the metallic bridge over a coplanar microstrip couple line suspended in both sides by two metallic posts. This MEMS filter is designed for operation at X-band satisfying the implementation requirements for radar and modern multi-band communication systems. The filter occupies a chip area of 12 times 3 mm² and achieved an insertion loss of only 0.5 dB and return loss of less than -15 dB throughout the operation band, thereby tuning the filter center frequency by 11% between 8.76 to 9.8 GHz. The S parameters and electromechanical displacement simulations are also presented.