Substrate Integrated Waveguide Filtering Crossover With High Isolation Insensitive to Bandwidth

A novel substrate integrated waveguide (SIW) filtering crossover with improved isolation insensitive to bandwidth is proposed. Four TE101 -mode SIW cavities and one square SIW cavity operating at two degenerate modes are used to realize the filtering crossover. The symmetrical coupling windows on each side of the square SIW cavity are used to obtain 180° phase difference between input and isolated ports, and then, high isolated level can be obtained, which becomes insensitive to the variation of filter bandwidth. Finally, an SIW filtering crossover sample operating at 20 GHz is designed and fabricated on the standard printed circuit board technology.