An Integrated Tunable Band-Pass Filter Using MEMS Parallel-Plate Variable Capacitors Implemented with 0.35μm CMOS Technology

This paper presents an integrated tunable bandpass filter with RF MEMS varactors fabricated using the TSMC 0.35 μm CMOS process. A maskless post-processing technique is developed which enables the fabrication of RF MEMS parallel-plate capacitors with a high quality factor and a very compact size. A 2-pole coupled line tunable bandpass filter with a center frequency of 9.5 GHz and a 9% relative bandwidth is designed, fabricated and tested. A tuning range of 17% is achieved using integrated variable MEMS capacitors with a quality factor exceeding 20. The filter has an insertion loss of 5.66 dB and occupies a chip area of 1.2 × 2.1 mm².