A Circularly Polarized Dielectric Discrete Lens Antenna With Wide Axial Ratio and Gain Bandwidths

Abstract

This letter presents a novel circularly polarized (CP) discrete lens antenna, which exhibits wide axial ratio and gain bandwidths. It consists of a transmitting surface (TS) and a linearly polarized feeding source. For the former, it is based on a dielectric unit cell (UC) which is composed of two parallel slabs. This UC is anisotropic in its cross-section and variable in its height, which provide two degrees of freedom to manipulate the phase difference and the phase shifts of two orthogonal electric field components, and thus the TS can seamlessly attain linear to circular polarization conversion and collimated beam. In the design of the TS, 3-bit phase quantization is adopted. Owing to the non-dispersive characteristic of the UCs, the proposed TS shows superior bandwidth performance over the existing studies. For the latter, it is a commercial wideband double-ridged horn antenna which matches with the TS in terms of bandwidth. As a proof of concept, a 9×9 prototype is fabricated by using 3-D printing technology. Experimental results show that the proposed antenna has a 3-dB axial ratio bandwidth (ARBW) of 44.2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> (8.8-13.8 GHz). The 1-dB and 3-dB gain bandwidths are 16.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> (11.7-13.8 GHz) and 40 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> (9.2-13.8 GHz), respectively.