Nonlinearly Modulated Scalar Metasurface with Circularly Polarized Butterfly-Shaped Beamforming

Abstract

This letter presents a nonlinear phase modulated (NPM), dual-beam, circularly polarized (CP) scalar impedance modulated (SIM) metasurface-based leaky-wave antenna (LWA) with butterfly-shaped beamforming, operates at f_r = 15.5 GHz. A comprehensive NPM technique is analytically presented to obtain proposed metasurface-based LWA. The proposed NPM function is numerically realized by its magnitude and phase response. Using NPM, a dual-beam linearly polarized (LP) surface impedance (Z_surf) is analytically mapped into CP impedance with simulated and measured data validation of proposed dual beam, CP LWA. An overall dimension of 15${{\lambda }_0} \times $ 7.5${{\lambda }_0}$ yields highly directive dual beam (i.e., {${{\theta }_n}$, ${{\varphi }_n}$} = {(−35$^\circ $, 0$^\circ $), (32$^\circ $, 0$^\circ $)}) with a maximum realized gain (g_max) of 21.52 dBic and half-power beamwidth of 4.2$^\circ $ each. A wideband axial ratio beamwidth of 1.8 GHz is obtained with an overall axial ratio of <1.2 dB.