Reconfigurable bandpass filter based on net-type stepped-impedance resonator

A novel reconfigurable bandpass filter based on a net-type stepped-impedance resonator (SIR) is investigated. This work aims to demonstrate a new approach to implement the reconfigurable centre frequency of the bandpass filter. The approach controls the ratio of the two characteristic impedances of a quarter-wavelength microstrip SIR with pin diodes. The proposed filter is designed to be reconfigured in the three centre frequencies: 720 MHz, 900 MHz, 1 GHz. A comparison between measured and simulated results shows good agreement.