COMPACT RECONFIGURABLE HMSIW BANDPASS FILTER LOADED BY CSRR

A reconfigurable half-mode substrate integrated wave-guide (HMSIW) bandpass filter (BPF) loaded by complementary split ring resonator (CSRR) is investigated. The proposed HMSIW-CSRR structure allows the implementation of a forward-wave passband propagating below the characteristic cutoff frequency of the waveguide. By changing the effective capacitance to ground of the CSRR, frequency tuning of the resonator is observed without other external circuit. The proposed filter 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 reconfigurable filter, tuned between 3.6 GHz and 4.5 GHz with insertion loss less than 3.6 dB and return loss better than 17 dB, is fabricated based on the standard printed circuit board process. The measured results are in good agreement with the simulation.