Compact diplexer with high isolation based on mixed‐mode triangular substrate integrated waveguide cavities

Abstract

AbstractA novel compact diplexer based on mixed‐mode isosceles right triangular (IRT) substrate integrated waveguide (SIW) cavities is presented. A dual‐mode IRT SIW junction cavity is direct‐coupled with two single‐mode IRT SIW cavities for lower and upper channels, respectively. The diplexer has two third‐order filtering channels, centred at 16 and 18.3 GHz with 400 and 422 MHz bandwidths. The in‐band measured return and insertion losses are 19 dB/1.3 dB in the lower band and 17 dB/1.36 dB in the upper band. Due to the orthogonality of TE102 and TE201 modes in dual‐mode IRT SIW cavity, high isolation (>45 dB) between two channels is obtained. Besides, the proposed diplexer based on the triangular SIW cavity also has advantages of low cost and easy integration with other planar circuits.