A millimeter-wave substrate integrated waveguide filtering antenna loaded with C-shaped slot

This work proposes a substrate integrated waveguide (SIW) stacked filtering antenna for 5 G millimeter-wave applications, featuring broadband operation and high selectivity. The antenna integrates a dual-layer structure: a SIW cavity with an etched rectangular slot and symmetric C-shaped Defected Ground Structure (DGS) in the feeding layer, and four truncated-corner patches as radiators. Due to the perturbation of the rectangular slot, two resonant modes are generated in the SIW resonant cavity, and a radiation null is introduced to improve the out-of-band suppression. The slot couples with the upper 2 × 2 patch array, generating a third resonant mode and broadening the bandwidth. The energy radiated by the 2 × 2 patches superimposes in phase, significantly enhancing the gain. Furthermore, the DGS suppresses unwanted interference modes in the SIW, introduces a radiated null point that results in a filtering response, and provides additional resonant modes to further extend the bandwidth. To validate the design, the prototype of the antenna is fabricated and measured, and the measured results show that the proposed antenna has a −10 dB impedance bandwidth of 16.91% (24.13 ~ 28.59 GHz), a stable practical boresight gain of 4.5 to 6.2 dBi in the operating band, and >15 dB out-of-band rejection.