Compact Cross-coupled Quarter-mode SIW Bandpass Filters with Different Locations of Input and Output Ports

Cross-coupled quarter-mode substrate integrated waveguide (QMSIW) bandpass filters (BPFs) with different locations of input and output (IO) ports are presented based on a novel negative coupling structure, which is constructed by two coupled stepped-impedance spurlines (SISs). Open ends of two SISs are coupled to achieve the capacitive coupling. Two adjacent QMSIW cavities are arranged to share one equivalent electric wall. One or two finite transmission zeros (FTZs) can be produced with different locations of IO ports. By this characteristic, a quasi-elliptic QMSIW filter operating at 2.4 GHz is designed, fabricated and measured. Benefitting from the size-reduced QMSIW cavities with SISs, advantages of compact size and wide stopband are achieved.