Dual-polarized ku-band microstrip antenna array with metamaterial loading and protective superstrate for GB-SAR applications

This paper presents a high-performance 4 × 1 dual-polarized square-ring patch antenna array operating in the Ku-band for Ground-Based Synthetic Aperture Radar (GB-SAR) applications, with a compact size of 90 mm × 30 mm. The proposed design achieves compact integration by implementing dual-port polarization on a single substrate, enabling significant size reduction while effectively controlling mutual coupling and suppressing surface-wave propagation. To further enhance isolation and radiation performance, metamaterial unit cells (MTMLs) are introduced between adjacent elements to mitigate surface waves, while strategically positioned metallic vias improve port isolation. The antenna exhibits a wide impedance bandwidth from 16.3 to 18.5 GHz; however, the performance is specifically optimized within the 16.8-17 GHz band of interest for GB-SAR applications, where it achieves mutual coupling below - 12.5 dB, radiation efficiency exceeding 93%, and ECC values below 0.006. A two-layers dielectric superstrate are incorporated to improve radiation characteristics, resulting in a peak gain of 12 dBi, sidelobe suppression of - 16.8 dB, and a half-power beamwidth of 38.3°. These additional layers enhance gain and beam focusing while also serving as a protective shield against harsh automotive environmental conditions such as temperature variations, vibration, moisture, and mechanical stress. This protective layer ensures mechanical durability and stable RF performance without compromising radiation efficiency. The antenna array is fabricated and experimentally validated, with measured results showing strong agreement with simulations. The proposed configuration provides a compact, low-loss, high-efficiency, and environmentally effective solution suitable for advanced Ku-band radar applications.