RF MEMS Switchable Interdigital Bandpass Filter

By taking advantage of the MEMS contact type switches in tunable filters, a new method that allows both the adjustment of resonant frequency and the input/output and inter-resonator coupling is presented. A three-pole filter capable to switch to three different states is designed using this method. The measured center frequency for each state is 8, 9, and 10 GHz (25% tuning) with a constant bandwidth of around about 1 GHz. The measured insertion loss of the filter is better than 3.5 dB for all three states.