Polarimetric phased array radar bias dependence on antenna shape obtained from computational electromagnetic modeling

Biases in polarimetric variables of weather radars depend on cross-polar antenna patterns and the polarimetric mode of operation. In the simultaneous transmission and reception of Horizontally and Vertically (SHV) polarized fields, the required cross-polar isolation is about two times (in dB) larger than in the alternate mode of transmission (AHV). The SHV mode is preferred on operational radars for other reasons. Herein we consider Polarimetric Phased Array Radars (PPAR) and the biases these cause. The ensuing complication is the dependence of the copolar and cross-polar patterns on beam pointing direction. We evaluate biases caused by PPAR antennas of three different shapes: square, cross, and circle.
To begin with, we use computational electromagnetic (CEM) simulation to determine embedded element patterns of the Advanced Technology Demonstrator (ATD) radar antenna. These patterns are then used to determine the embedded element pattern, model the three antennas via CEM, and obtain the radiation patterns. Finally, we evaluate polarimetric biases associated with the three topologies and compare the results. The sample comparisons are for the three topologies pointing to a few directions, in and out of the principal planes.