Compact Square Substrate Integrated Waveguide Filtering Power Divider With Wideband Isolation.

In this letter, a new compact filtering power divider (FPD) on the square substrate integrated waveguide (SIW) with wideband isolation is proposed. As the isolation network is embedded in a square SIW cavity, good in-band isolation, compact structure, and low insertion loss can be simultaneously attained. The proposed FPD consists of the coplanar waveguide feeding line of Port 1, the capacitor, a resistor, and the square SIW cavity. TE101, TE201, and slot-line modes can realize third-order filtering response. Center frequency ($f_{0}$) and bandwidth of the filtering response can be independently adjusted. In order to achieve out-of-band isolation, Port 2/3 is placed in the specific position to suppress the high-order modes according to the electric-field distributions of these modes. Finally, a prototype with in-band return loss of 20 dB across 5.59–6.4 GHz is designed at 5.99 GHz. The bandwidths of isolation higher than 21 dB and upper stopband attenuation higher than 20 dB are extended to $2.79f_{0}$ and $2.83f_{0}$ , respectively. [ABSTRACT FROM AUTHOR]