Ultrawideband Flush-Mountable Dual-Polarized Vivaldi Antenna

A dual-polarized, flush-mounted, Vivaldi antenna directly integrated with all-metal cavity is introduced as an alternative to coax-fed quad-ridge (QR) horns. Eigen-mode analysis is used to demonstrate that the entire structure may resonate with degraded impact on its far-field when not properly integrated with the cavity. An approach based on shaping the side walls of the cavity is used to eliminate the occurrence of these resonances. The proposed dual-polarized resonant-free antenna has two orthogonal 2 × 1 arrays with two elements in the E-plane and one element in the H-plane and is fed using two 2-way power dividers that can be easily designed to maintain low amplitude and phase imbalances. The antenna is fabricated in a single piece and experimentally shows monotonic gain increase with low cross-polarization over 4:1 bandwidth. Symmetric far-field performance between orthogonal polarizations with gain better than 8 dBi and sidelobe levels lower than -20 dB from 2 to 8 GHz is demonstrated. VSWR <; 2, and port to port isolation greater than 35 dB is also measured over the same bandwidth.