A reconstruction technique of the antenna pattern for correcting the polarization measurement bias is proposed in this paper. In the case of the prior knowledge of patterns at some scanning angles, the pattern at other beam position can be estimated by application of the minimum norm least-square solution. Once the pattern is reconstructed, the corresponding projection matrix could be obtained in the presence of the mutual coupling and edge effects in the polarimetric phased array antenna. Thereby, the correction matrix for the polarization scattering matrix is repaired. A microstrip patch array antenna is designed to demonstrate the validity of the proposed method, and the performance of bias correction is manifested using several polarimetric variables. Specifically, the bias of differential reflectivity (Z b DR), the bias of linear depolarization ratio (L b DR) and the phase difference are less than 0.14 dB, 46.85 dB, 3.31◦ in a wide scanning angle range, respectively.

Introduction

Phased array antenna (PAA) with agile electronic beam steering capability has been successfully utilized in the communication, military application and weather observation [1]–[۶], with respect to the mechanically scanning dish antenna. In addition, since the accurate multiparameter measurement ability of the polarimetry has matured for years, the polarimetric PAA (PPAA) with the dual-polarization capability will be indispensable in future targets or weather observation [7]. Currently, two main challenges that still trouble the PPAA technology are the requirements of wide angle scan and high accuracy for polarimetric measurements [8], [9]. Specifically, when the beam is scanned away from the antenna’s principal plane, the beam will broaden considerably, and the electric fields radiated from the horizontal (H) and vertical (V) polarization ports are not orthogonal to each other. The cross-polar components are produced, and this is where the polarization biases yield. Hence, the polarization isolation requirement should be met for alternate mode (where the polarization states are switched alternately on transmission) and hybrid mode (where both polarization states are transmitted and received simultaneously). And the polarization purity requirement is more stringent for the hybrid mode compared to the alternate mode of operation [10]. To solve the cross-polar problem, the projection matrix method was proposed in [3], and the method was examined with a pair of crossed dipoles. The biases can be removed through a multiplication operation to the measured scattering matrix.