A novel class of half-mode SIW filters with extracted poles

This paper proposes a novel class of single-sided extracted-pole filters in half-mode substrate integrated waveguide (SIW) technology. The design approach is based on the extracted-pole synthesis of a fully canonical low-pass prototype capable of a number of zeros equal to the number of poles, where one reflection zero at infinity is left. This topology allows for filters where the pass-band and the stop-band are relatively close. In the proposed filters, the extracted poles are obtained by using microstrip open stubs. The use of microstrip stubs is possible thanks to the geometry of the half-mode SIW, where the stubs can be easily connected to the open side. To validate the proposed class of filters, a filter with two extracted poles and a filter with four extracted poles were designed, measured, and compared to a classical microstrip filter with similar topology.