Tunable bandstop filter using equal-length two-section stubs and z-domain technique

This paper presents a tunable bandstop filter using the shunted two-section stubs and z domain technique. The proposed filter employs varactor shunt with two-section stubs to control the center frequency. In the measured results, the center frequency is tuned from 0.9 GHz to 1.3 GHz, and the ratios of the center frequencies of next higher order harmonics to fundamental frequencies are more than 5.