A Novel Compact Reconfigurable Bandpass Filter Based on CMRC Structure

Abstract

Modern wireless communication system usually requires frequency agility. Although lots of research and investigations have been done in developing a reconfigurable filter, the reconfigurable function either bulks the size or causes reduction on the selectivity of filters. After compact microstrip resonant cell (CMRC) has been introduced, it is possible to achieve both a significant reduction in size and a better selectivity in performance. In this project, a new compact, reconfigurable and wide-band microstrip bandpass filter (BPF) based on a CMRC structure was built. The device consisted of a stepped impedance transformer with tapped line (SITTL), two T-shaped resonators, and four switching PIN diodes. The performances of SITTL and two resonators could be changed by switching PIN diodes into different states (on/off). By properly choosing the locations of PIN diodes and shapes of two resonators, both center frequency and transmission zeros were made reconfigurable. Based on both EM simulation and circuit simulation, the proposed filter were designed and fabricated on a substrate with a thickness of 1.57mm and a dielectric constant of 2.33. The experimental results are demonstrated and discussed.