A 12-18-GHz three-pole RF MEMS tunable filter

This paper presents a state-of-the-art RF microelectromechanical systems (MEMS) wide-band tunable filter designed for the 12-18-GHz frequency range. The coplanar-waveguide filter, fabricated on a glass substrate using loaded resonators with RF MEMS capacitive switches, results in a tuning range of 40% with very fine resolution, and return loss better than 10 dB for the whole tuning range. The relative bandwidth of the filter is 5.7/spl plusmn/0.4% over the tuning range and the size of the filter is 8 mm/spl times/4 mm. The insertion loss is 5.5 and 8.2 dB at 17.8 and 12.2 GHz, respectively, for a 2-k/spl Omega//sq bias line. The loss improves to 4.5 and 6.8 dB at 17.8 and 12.2 GHz, respectively, if the bias line resistance is increased to 20 k/spl Omega//sq. The measured IIP/sub 3/ level is >37 dBm for /spl Delta/f>200 kHz. To our knowledge, this is the widest band planar tunable filter to date.