A DMS SIW Filtering Crossover with Wide Spurious-free Frequency Band

A compact wide stopband substrate integrated waveguide filtering (SIW) crossover is proposed. The TE ${ }_{102}$ mode in a half-mode SIW (HMSIW) cavity are well suppressed due to the application of the centered coupling windows. The additional parasitic frequency points are suppressed by defected microstrip structure, which results in the proposed filtering crossover with stopband suppression greater than ${- 2 0} \mathrm{dB}$ up to $\mathrm{1. 9 6} f_{0}$. And the stopband extends to 40 GHz at a rejection level better than 12 dB. A prototype operating at 8 GHz is fabricated and measured. The measured results and simulated results are in great agreement.