Abstract A wideband filtering antenna design has been proposed in this paper. The proposed filtering antenna design is cavity-backed substrate integrated waveguide (SIW) based on a single layer slot antenna. Two E-shaped slots are engraved onto the ground face of the design to improve filtering selectivity and operational bandwidth. For achieving wideband response, a modified half-TE110 mode and a decreased radiation null are all produced by the E-shaped slots in the right-half cavity. The design is simple and compact, with only one substrate layer and a larger working bandwidth than its counterparts. The filtering antenna has a 13.1 % fractional bandwidth and works at a frequency of 28 GHz. The proposed prototype has been structured, tested, and the simulation and measurement results were analyzed.