High-Isolation, Low Cross-Polarization, Dual-Polarization, Hybrid Feed Microstrip Patch Array Antenna for MPAR Application

This paper presents a high-isolation, low cross-polarization dual-polarized patch antenna for multifunction phased array radar applications. Its hybrid feed design has been implemented, and the vertical and horizontal polarizations are excited by a balanced-probe feed and a slot-coupled feed, respectively. Simulations and measurements have demonstrated an input isolation of 45 and 43 dB between the horizontal and vertical ports, respectively. For further improvement in the cross-polarization level, the image feed method is also implemented, and a 2 x 2-element array made up of designed elements with image configuration has been fabricated. The simulated and measured S-parameter and radiation patterns of the horizontal and vertical polarizations of the designed 2 x 2-element array are presented and the measured cross-polarization level of less than -37 dB is achieved. To examine the performance of the designed element in an array, a 3x3-element array of designed 2 x 2-element subarray is fabricated and tested. In the 6 x 6-element measurements, -35.4 and -36 dB cross-polarization levels for horizontal and vertical polarizations are achieved, respectively. Also, using the measured embedded element patterns, the cross-polarization level lower than -36 dB for scan angles up to 45 degrees is achieved.