A compact triple‐mode bandpass filter with wide‐stopband using half‐mode substrate integrated waveguide cavity loaded with slots

In this article, a new compact triple‐mode filter with wide stopband is proposed on half‐mode substrate integrated waveguide (HMSIW) with loaded slots. The loaded slots not only make the TE201 mode shift toward the TE101 mode, but also introduce an extra resonant mode to achieve a compact triple‐mode filter. In addition, the wide stopband is realized because the TE202 mode keeps nearly unchanged as the TE201 mode decreases to a much lower frequency by virtue of loaded slots. The working principle and design method are given in this context. All these triple resonant modes can be controlled as required. To verify the design concept, a prototype with only 0.23λg2 area is designed and the upper stopband can be extended to 1.87f0 with rejection level of 25 dB.