Design of a Degradation-Free Ultrawideband Dual-Polarized Antenna for Radars and Communication Systems

An ultrawideband (UWB) quad-ridged horn antenna (QRHA) with dual-polarization is proposed for radar and communication systems. The antenna features an open-boundary horn design with a wide impedance bandwidth covering 1-20 GHz. Unlike conventional ridged horn antennas that suffer from pattern degradation anywhere between $8-16 \text{GHz}$, the proposed antenna is carefully designed to avoid any such degradation in the desired band. Constructed entirely of metal, the antenna has a compact size of $\mathbf{2 6 0} \times \mathbf{3 0 0} \mathbf{m m}^{\mathbf{2}}$. Its internal exponential profile ensures excellent matching characteristics, while the matching aperture and shaped outer walls provide low cross-polarization, a critical parameter for radar calibration. The novel semispherical back-cavity design in the feeding section not only helps in improving the bandwidth of the antenna but also eliminates the undesired pattern degradation inside the band, thus addressing a common drawback of such antennas, without compromising other important parameters such as VSWR, bandwidth, gain, and cross-polarization.