A Low-Profile Diplexing Filtenna Based on Quarter-Mode Substrate Integrated Waveguide

Abstract

In this letter, a low-profile diplexing filtenna based on a quarter-mode substrate integrated waveguide (QMSIW) is presented. A cross-shaped slot is etched on the top of the circular substrate integrated waveguide (SIW) cavity, dividing it into four parts, each of which can function independently as a QMSIW resonator. Four metallic perturbation vias are loaded in the cavity to tune the impedance matching. To suppress the cross-polarization generated by the introduction of the cross-shaped slot, four pairs of metallic suppression vias are loaded around the edges of the cross-shaped slot. Finally, a rectangular feeding cavity with a complementary split-ring resonator (CSRR) are utilized to excite the circular SIW cavity, achieving enhanced impedance bandwidth and filtering performance. To validate the design method, a prototype of the diplexing filtenna was fabricated and measured. The measured results are in good agreement with the simulated ones, showing that the diplexing filtenna exhibits fractional impedance bandwidths of 6.8% (3.84–4.11 GHz) and 6.6% (4.8–5.13 GHz) for lower and upper passbands, respectively. The realized gain curves experience good filtering with peak realized gains of 4.69 and 5.11 dBi at the boresight direction, respectively.