Quaternion-APES Algorithm for Polarization-Space Adaptive Beamforming

In order to obtain a stable beam pattern and further improve the performance of adaptive beamforming for polarization sensitive array, a Quaternion-Amplitude and Phase Estimation (Q-APES) algorithm is presented for polarization-space adaptive filtering in the paper. First, the quaternion signal model is given and the inherent orthogonal structure of the two component signal output of each sensor has been kept well by using the quaternion signal model. It is obvious that the quaternion signal model is more suitable for two component vector sensor array signal processing than the conventional long vector signal model which is based on the complex number. Second, the conventional APES algorithm for spatial domain filtering has been expanded to the polarization-space adaptive beamforming. The proposed Q-APES algorithm is derived theoretically and the quaternion optimal weight vector is obtained following. Finally, computer simulation results are shown to verify the correctness of the proposed algorithm. The results indicate that Q-APES algorithm can achieve a better filtering performance than the existing Q-MVDR algorithm under the circumstances of strong desired signal power or low sampling snapshot numbers. Moreover, Q-APES algorithm can also perform well even if the incident interference signals are fully correlated with the desired signal.