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 x 0.374 x 0.15 lambda(3)(o) (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 degrees, 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 x 4.38 x 0.75 lambda(3)(o) is obtained by placing a 45. rotated 15 x 15 array of converter's cells broadside to 4 x 4 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).