A method of decreasing cross-polarization in dual-polarized patch antennas

In this paper, we propose a method for decreasing cross-polarization in the tilt plane by optimizing the dielectric substrates of dual-polarized patch antennas. At the same time, we clarify the limit values for the cross-polarization level. First, we use a cavity model of the patch antenna to find cross-polarization dielectric characteristics in the tilt plane. We learn from this that the direction of cross-polarization increase or decrease in relation to the dielectric is reversed during horizontal polarized excitation and vertical polarized excitation. Therefore, if the cross-polarization level during horizontal polarized excitation and vertical polarized excitation is the same dielectric, the lowest cross-polarization level can be obtained in conditions where both horizontal polarization and vertical polarization are decreasing cross-polarization. Next, we investigate the case where parasitic elements are mounted on the patch antenna, and use the FDTD method and test to show that our method is valid. In addition, if the patch is positioned perpendicularly to the horizontal plane, we show that the optimum dielectric remains virtually unchanged in the tilt plane up to about 15 degrees from the horizontal plane. (c) 2007 Wiley Periodicals, Inc.