Broadband Filtering Patch Antenna Based on Quad-Mode Resonance With High Out-of-Band Rejection Level

This letter proposes a broadband filtering patch antenna based on quad-mode resonance, exhibiting high out-of-band rejection level and enhanced selectivity. The antenna employs a stacked structure of the driven patch and parasitic patch to achieve dual-mode resonance within the band. By loading C-shaped slots and flag-shaped strips on the driven patch, two additional modes are also generated within the band, achieving quad-mode resonance and obtaining a broadband response. Meanwhile, the two loa