Performance of a configurable microstrip filter using triple mode resonator and RF-MEMS switches

This paper presents a configurable bandpass filter using commercial RF MEMS switches in a compact triple-mode resonator. Before designing the filter, the effect of using the RF-MEMS switch on the resonant frequency of a simple hairpin resonator is studied. The insertion loss of the switch is measured. A three-pole Chebyshev bandpass filter with a fractional bandwidth of 20% at a center frequency of 0.95 GHz is designed and fabricated. With a biasing voltage of 25 V, the center frequency of the filter can be switched to 0.70 GHz. The fractional bandwidth of the filter changes from 20% to 10%. This filter exhibits low harmonic response in the stopband.