Hybrid Spoof Surface Plasmon Polariton and Substrate Integrated Waveguide Broadband Bandpass Filter With Wide Out-of-Band Rejection

This letter presents a novel hybrid spoof surface plasmon polariton (SSPP) and substrate integrated waveguide (SIW) filter, which has the broadband bandpass and wide out-of-band rejection features. The lower and upper cutoff frequencies of the passband can be independently adjusted by changing the structural parameters of the SSPP and SIW units, respectively. The dispersion curves of the SSPP and SIW units are analyzed and the influences of some structural parameters are investigated. A hybrid SSPP-SIW filter is fabricated based on the proposed method, and the measured passband is at 7.3-11.2 GHz with a relative bandwidth of 44%. The upper stopband rejection level is lower than -40 dB from 11.8 to 19.8 GHz.