An SSPP Leaky-Wave Antenna With Circular Polarization Based on the Anisotropic Holographic Technique

Based on the holographic technique, a design method for circular polarized spoof surface plasmon polariton (SSPP) leaky-wave antennas is presented. For the first time, anisotropic unit cells were employed to reach circular polarization in the SSPP leaky-wave antennas without using any parasitic element. Anisotropic unit cells consist of the modulated surface in a hollow metallic ellipse shape. Employing the particle swarm optimization (PSO) algorithm and a combination of the transformation optics’ equations, we extracted the corresponding dimensions of the anisotropic unit cells' surface impedance matrix. The required components of the surface impedance tensor were determined, and the hologram was realized by the hollow metallic ellipse rotation angles and the large and small diameters’ variations. The gain, radiation efficiency, axial ratio bandwidth, and sidelobe level (SLL) of the proposed antenna at the design frequency were about
${\text{11.3}}$
dBi,
${\text{86}}{\bm{\% }}$
,
${\text{40}}{\bm{\% }}$
, and
$ - {\text{10}}$
dB, respectively. Moreover, the maximum scanning angle of 30°, i.e., from
$( {{\bm{\theta }},{\bm{\varphi }}} ) = ( {5^\circ,90^\circ } )$
to
$( {{\bm{\theta }},{\bm{\varphi }}} ) = {\bm{\ }}( { - 25^\circ,90^\circ } )$
, was attained when the frequency varied from 16 to 24 GHz. The proposed antenna was fabricated, and its radiation characteristics were measured after simulations in MATLAB and CST Microwave Studio software.