Low-Profile Diplexing Filtenna Using Shielded SIW Cavities for Closely Spaced Frequency Channels

A compact, diplexing filtenna (DF) with second order filtering response for closely spaced frequency channels is presented in this work. The design is based on shielded half-mode substrate integrated waveguide (SD-HMSIW) and shielded quarter-mode substrate integrated waveguide (SD-QMSIW) cav-ities. A slot loaded SD-HMSIW cavity is used as the common radiating cavity for both frequency channels and SD-QMSIW cavities are utilized to introduce the filtering response. A proto-type of the proposed design is fabricated and measured to validate the concept. The fabricated prototype demonstrates peak gains of 6.2 dBi and 5.1 dBi at center frequencies of 5.35 GHz and 5.7 GHz with a fractional bandwidth (FBW) of 2.2% and 2.3%, respectively. The prototype achieves an inter-channel isolation better than 31 dB. This method delivers a considerable reduction in size compared to conventional cavity solutions.