Fabrication and characteristics of tunable band pass filter using MetalMumps technology

This paper presents a tunable RF MEMS filter based on the equivalent circuit of three-pole band-pass filter. The band-pass filter was manufactured on a standard low-resistivity substrate using MetalMumps fabrication process. To realize changeable frequencies and achieve high RF performance, the band-pass filter was adopted a suspended tunable capacitor, whose bottom plate was suspended 25μm from the inner surface of the etched silicon substrate. When voltage was applied across the top plate and bottom plate of the tunable capacitor, the central frequency of the tunable filter could be tuned. The measured results show that when the central frequency was changed from 600MHz to 900MHz, the tunable filter had the insertion loss about 4dB and the return loss a little more than 20dB.