Compact wideband HMSIW bandpass filter with defected ground structure

A compact wideband bandpass filter based on the half mode substrate integrated waveguide (HMSIW) is presented in this paper. Two double-slit complementary split-ring resonators (DS-CSRRs) are etched on the bottom plane, which can improve the out-of-band rejection. The microstrip line is used to feed the HMSIW cavity and DS-CSRRs. A bandpass prototype with the center frequency of 7.6GHz is designed and fabricated. The measured fractional bandwidth is 53%. Good agreement is observed between simulation and measurement.