Nonlinearly Modulated Scalar Metasurface with Circularly Polarized Butterfly-Shaped Beamforming

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 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f_r</i> = 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 (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Z</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">surf</sub>) is analytically mapped into CP impedance with simulated and measured data validation of proposed dual beam, CP LWA. An overall dimension of 15<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${{\lambda }_0} \times $</tex-math></inline-formula> 7.5<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${{\lambda }_0}$</tex-math></inline-formula> yields highly directive dual beam (i.e., {<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${{\theta }_n}$</tex-math></inline-formula>, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${{\varphi }_n}$</tex-math></inline-formula>} = {(−35<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ $</tex-math></inline-formula>, 0<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ $</tex-math></inline-formula>), (32<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ $</tex-math></inline-formula>, 0<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ $</tex-math></inline-formula>)}) with a maximum realized gain (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub>) of 21.52 dBic and half-power beamwidth of 4.2<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ $</tex-math></inline-formula> each. A wideband axial ratio beamwidth of 1.8 GHz is obtained with an overall axial ratio of <1.2 dB.