Design and Experimental Validation of a Multiband Cross-Polarization Conversion (CPC) Metasurface for Radar Cross Section (RCS) Reduction

Radar cross-section (RCS) reduction is a fundamental requirement in modern stealth technology, playing a critical role in the low-observable performance of aerial and naval platforms. Among the various passive RCS reduction strategies, including radar-absorbing materials, absorptive coatings, and artificially engineered surfaces, metasurface-based cross-polarization conversion has emerged as a compelling approach owing to its structural simplicity and low profile. In this work, a single-layer cross-polarization conversion (CPC) metasurface developed on a cost-effective FR4 dielectric substrate (relative permittivity 4.4, loss tangent 0.02) is proposed for multiband RCS reduction. The designed structure achieves a polarization conversion ratio (PCR) exceeding 95% at three distinct operating frequencies of 7.8 GHz, 11.7 GHz, and 18 GHz, spanning the C-, X-, and Ku-bands, which directly translates into a monostatic RCS reduction exceeding 10 dBsm at the corresponding bands. The metasurface further demonstrates stable polarization conversion performance under oblique incidence up to 60 degrees, confirming its suitability for wide-angle illumination conditions encountered in practical deployment scenarios. Experimental validation conducted in an anechoic chamber confirms close agreement with full-wave electromagnetic simulations, substantiating the reliability of the fabricated prototype. The proposed design offers a lightweight, low-cost, and high-performance candidate for multiband stealth and low-observable platform applications.