Signal Processing Technique to Increase Cross-Polar Isolation on Fully Digital Phased Array Radars

Abstract

A signal processing technique to improve cross-polar radiation pattern isolation for phased array radar systems is presented. The technique is based on “flipping” the polarization of certain array elements to transmit a scaled version of the original waveform in the orthogonal polarization, where the cross-polarization is observed. The number of flipped elements, their location in the array, and the scaling factor applied are output variables of the proposed technique, all of which depend on the intrinsic array performance and the steering angle. This technique is evaluated using two-dimensional, single-element measurements from a state-of-the-art, dual-polarization, stacked microstrip patch array antenna panel, designed by the Advanced Radar Research Center (ARRC) team at The University of Oklahoma. Preliminary results show that the proposed technique can provide an additional 20 dB in cross-polar isolation at broadside, at the cost of a 0.2 dB loss in co-polar pattern gain. The technique can be readily implemented in fully digital phased arrays to improve cross-polarization performance.