Multilayer Slot-Coupled Bandpass Filter Based on Integrated Substrate Gap Waveguide

This paper presents a multilayer slot-coupled bandpass filter based on integrated substrate gap waveguide (ISGW). The bandpass filter consists of two ISGW unit structures that are placed back-to-back. Source-load coupling is achieved by etching double rectangular slots on the common ground of the two ISGW unit structures that can achieve better filtering performance in addition to introduction of out-of-band transmission zeros. Simulation results show that a passband of the filter from 26.6 to 28 GHz, insertion loss of lower than 0.7 dB, and return loss of better than 20 dB. Two transmission zeros on both sides of the passband improve the frequency selectivity.