Ku-band RF MEMS tunable comb line band reject filter on coplanar transmission line

Abstract

A band reject filter with tuning capability is presented on a CPW transmission line on silicon substrate using comb line and RF MEMS variable capacitor, enabling compatibility with planar IC technology. A conventional CPW on a substrate consists of a central strip conductor with semi-infinite ground planes on either side. A comb line is etched on the signal line of the CPW and the MEMS bridge capacitor is put on the same line in shunt. Tunability of the filter is achieved by putting the MEMS bridge in either up or down state. The rejection at the centre frequency of stop bands are around −40.24dB for down state and −38.21dB for up state of the bridge. A low insertion loss, as low as −0.68dB, is obtained in the pass band. The proposed device structure is simulated using ANSOFT HFSS v13® for RF analysis and COVENTORWARE (2008)® for mechanical and electromechanical characterization, both static and transient analysis.