Compact or Wide-Stopband SIW Diplexers With High Intrinsic Isolations Based on Orthogonal Dual Modes

This brief proposes two miniaturized substrate integrated waveguide (SIW) diplexers with wide stopband and high isolation based on orthogonal dual-mode technique. With the orthogonal dual-mode SIW junction-resonators to eliminate the traditional T-junctions, significant circuit miniaturization and the inter-channel isolations can be achieved for SIW diplexers. Additionally, the fractional bandwidth (FBW) diagrams are utilized to identify the feasible FBWs in both passbands effortlessly. To verify the developed method, two types of SIW diplexers centered at 12 and 14 GHz are synthesized and fabricated utilizing a single layer printed circuit board technology. The performances of both diplexers are demonstrated by the measured and simulated results.