Low-Loss 5.15–5.70-GHz RF MEMS Switchable Filter for Wireless LAN Applications

Low-loss 3.6-GHz fixed and 5.15-5.70-GHz RF microelectromechanical systems switchable filters were designed and fabricated on quartz substrates. Detailed design equations for the capacitively loaded coupled open-loop lambda/2 resonators are given and the realization of the tunable filter using these equations is discussed. The use of capacitively loaded coupled open-loop lambda/2 resonators made it possible to realize the fixed and switchable filters with unloaded Q of around 150 resulting in a -1.4-dB insertion loss. The measured -1-dB bandwidth for the 3.6-GHz fixed and 5.15-5.70-GHz switchable filters were 4% and 5%, respectively. To our knowledge, this represents the lowest loss planar tunable filter to-date in the 4-6-GHz frequency range