Bounds on the distributed circular polarization purity of ring sources for broadside mode circular patch antennas

This paper investigates the distributed cross polarization ratio (CPR), which is relevant for scanning arrays and distributed sources such as those found in mobile communications. The maximum and average (over angle) CPRs are computed over different angular intervals, which represent either the scan sector of an array, or the target directions for the distributed gain of a fixed antenna. The results show that the best polarization purity is achieved with an optimum ring source radius of about lambda/4, which corresponds to an optimum value of the substrate relative permittivity in a circular patch antenna