A Millimeter-Wave Dual-Band Substrate Integrated Waveguide Filter with Complementary Split Ring Resonators

This paper presents a millimeter-wave dual-band bandpass filter based on a substrate integrated waveguide (SIW). The dual-band response is realized by embedding two pairs of complementary split-ring resonators (CSRRs) with different dimensions in the SIW cavity. Their geometry-dependent resonances introduce frequency-selective transmission zeros, reshaping the inherent high-pass response of the SIW into two passbands. The effects of the CSRR dimensions and loading sequence are investigated using several resonator configurations to clarify the formation and frequency control of the two bands. A prototype is fabricated using a wafer-level packaging process. The measured passbands are centered at 54.2 and 87.3 GHz, with insertion losses of 2.69 and 2.83 dB and fractional bandwidths of 21.8% and 13.3%, respectively. The measured results agree well with the simulations. The filter has a compact footprint of (0.63λg×0.29λg).