Hybrid-Structure Filters by Combining SIW and Microstrip Technologies

Abstract

Substrate integrated waveguide (SIW) and microstrip are the most widely used technologies that can could be easily integrated with other planar circuits, providing excellent platforms to implement various microwave filters. In this paper, the general filter design methodology by combing both the two technologies is presented. This hybrid approach shows some particular advantages such as wide stopband, compact size, moderate quality factor, independent coupling path for each SIW mode, and easily achievable cross coupling for SIW cavities without extra negative coupling structures. Four hybrid-structure filters, which present wide-stopband characteristics, flexible dual-mode responses, and quasi-elliptical dual-band function, are presented, reviewed and discussed.