A Novel Dual-Band SIW Filter with High Selectivity

A novel dual-band substrate integrated waveguide (SIW) filter with multiple transmission zeros and good out-of-band rejection performance is presented in this paper. For this purpose, an orthogonal input/output (I/O) feeding structure directly connected to the substrate integrated waveguide (SIW) cavity is designed to split the resonant frequencies of the degenerate pair of mode. The filter can be modeled with a multi-path circuit formed by three modes (TE101, TE201 and TE102 modes) and weak cross coupling between I/O ports, thereby producing three transmission zeros which make the dual-band high selectivity. The offset of the input/output ports shifts the second transmission zero to a lower frequency from the upper passband. Several filter prototypes are designed and fabricated for demonstration, and the measured results validate the new structure for high selectivity applications.