Substrate Integrated Waveguide Filter With Wide Stopband Up to (2k + 3) f₀

With the development of multistandard, multiband wireless/microwave circuits and systems, a wide stopband could be essential for a substrate integrated waveguide (SIW) filter to eliminate interference. However, the performance of the current wide-stopband SIW filters is not good enough, particularly the stopband extension. Here, based on a multilayer SIW filter without degrading its passband performance, we advance the slot element into a slot array as the intercoupling structure to significantly improve the stopband extension upper limit. It is achieved by splitting the conventional magnetic intercoupling slot element into a slot array with $2k$ parts and moving them away from the edge by about 0.5/( $2k$ + 1) of the edge’s length. For an SIW filter working in TE101 ( $f_{0}$ ), one can use Type-0, $\text {Type-1}, \ldots $ , and Type- $k$ slot arrays to eliminate all the spurious modes below ${\mathrm {TE}}_{(2k + 3)0(2k+3)}$ and extend the stopband to ( $2k$ + 3) $f_{0}$ . In this paper, we present three prototypes that respectively use 2–4 types of slot arrays. Without complex design or passband degradation, the measured results show that their stopbands are, respectively, extended up to $4.67f_{0}$ , $7.03f_{0}$ , and $9.31f_{0}$ , which are significantly better than those of their counterparts based on the slot element. The proposed technology should be efficient for developing high-performance wide-stopband SIW filters in wireless/microwave circuits and systems.