Linear-to-Circular Polarization Converter With Wide Angular Stability and Near Unity Ellipticity—Application to Linearly Polarized Antenna Array

A transmission type linear-to-circular polarization converter is proposed using split-rings and metallic strip printed on the both sides of the dielectric substrate and is further utilized to obtain a circularly polarized (CP) antenna array with high gain. The size of the unit cell of the converter is
$0.394\times 0.374\times 0.15\,\,\lambda _{o}^{3} $
(
$\lambda _{o}$
is the free space wavelength with respect to 29.85 GHz). The axial ratio bandwidth (ARBW) and ellipticity (
${e}$
) of the polarization converter remain relatively stable under both the transverse electric (TE) and transverse magnetic (TM) polarization up to oblique incidence of 60° and 45°, respectively. The proposed converter exhibits a measured ARBW of 9.67% (29.50–32.50 GHz). Furthermore, the
${e}$
lies in the range of 0.94–0.98 in the operating band of the converter. The CP antenna array with an overall size of
$4.38\times 4.38\times 0.75\,\,\lambda _{o}^{3} $
is obtained by placing a 45° rotated
$15\times15$
array of converter’s cells broadside to
$4\times4$
linearly polarized (LP) patch antenna array and exhibits measured peak gain of 18.7 dBic. The proposed polarization converter and CP antenna array can find applications in the uplink Ka-band fixed-satellite services (29.5–30.0 GHz).