COMPACT RECONFIGURABLE HMSIW BANDPASS FILTER LOADED BY CSRR

A reconflgurable half-mode substrate integrated waveg- uide (HMSIW) bandpass fllter (BPF) loaded by complementary split- ring resonator (CSRR) is investigated. The proposed HMSIW-CSRR structure allows the implementation of a forward-wave passband prop- agating below the characteristic cutofi frequency of the waveguide. By changing the efiective capacitance to ground of the CSRR, frequency tuning of the resonator is observed without other external circuit. The proposed fllter exhibits improved selectivity due to the employment of the pseudo-S defected structure to generate transmission zero at the low stopband. To verify the presented design method, the predicted compact reconflgurable fllter, tuned between 3.6GHz and 4.5GHz with insertion loss less than 3.6dB and return loss better than 17dB, is fabricated based on the standard printed circuit board process. The measured results are in good agreement with the simulation.