Substrate integrated waveguide elliptic filter with high mode

In this paper, a single-layer substrate integrated waveguide (SIW) elliptic filter is proposed. High mode is used to implement negative coupling, which is combined with positive coupling to generate the required finite transmission zeros at real frequencies. The filter is fabricated on a substrate with the standard PCB process, which takes the advantage of low cost and high selectivity. Simulated and experimental results of a four-pole elliptic filter are presented.