Implementation of ground plane membranes to realize a bandwidth and frequency tunable filter

A bandwidth and frequency tunable planar filter that uses dual behavior resonators is presented in this paper. The resonator topology is based on two stepped-impedance stubs as bandstop structures. Their impedance ratio as an n^th-order dual behavior resonator filter was considered to enable tuning of the transmission zero frequencies. Experimental validation was investigated in a microstrip filter employing MEM membranes to achieve a reconfigurable ground plane. Actuation of ground-plane membranes controls stub to ground plane spacing, and, thus impedance ratio, enabling filter tunability. Experiments led to variations of 15.1% for the low-frequency transmission zero, and 7.5% for the high-frequency zero.