A near zero refractive indexed non-uniform metasurface for broadband RCS reduction of an antipodal Vivaldi antenna

This research reports the design of a polarization converter based non-uniform metasurface in which the unit cells have been arranged in such a manner that both co and cross polarized reflections are minimized which results in mitigation of radar cross-section (RCS). The propounded metasurface has been integrated with an antipodal Vivaldi antenna for facilitating it’s wideband RCS reduction from 14 to 36 GHz. Maximum monostatic RCS reduction across 84.6% frequency bandwidth is 30 dB for both x-polarized and y-polarized incident waves. Bistatic angular view of the antenna with metasurface is 70⁰ at 27 GHz. A high bistatic angular view ensures that the metasurface integrated antenna exhibits similar electromagnetic performance like reflection and radiation characteristics even when the incident or observation angle changes significantly. The specific property conveyed is angular stability, which refers to the ability of the structure to maintain its resonant frequency and electromagnetic characteristics (reflection/transmission/gain) when the incident angle varies. The antenna’s radiation and scattering characteristics remain nearly constant even when the direction of incoming or outgoing waves changes since the metasurface comprises periodic unit cells with sub-wavelength dimensions, which exhibit high angular stability. An equivalent circuit model has been proposed for the polarization converter-based unit cell which exhibits negative permittivity and zero refractive index. The radiation characteristics of the antenna are not affected adversely by the incorporation of the polarization converter based metasurface. Peak gain of the antenna is 9.3 dBi. Measured results of the fabricated non-uniform metasurface and Vivaldi antenna closely match the simulations.