Quaternion-valued Widely Linear Adaptive Beamforming via Involution Augmentation

An adaptive beamformer based on quaternion-valued widely linear processing is proposed, in which the output is expressed in quaternions for each array element. Taking into account the array output vector and its three involutions simultaneously, a quaternion-valued augmented signal model is established to exploit the noncircular information of the desired signal. The involution augmented adaptive beamforming is finally fulfilled based on the quaternion-valued widely linear processing. Compared with the conventional quaternion beamformers, the proposed beamformer has an improved reception capability for noncircular signals. The aperture of the array is extended and hence the degree-of-freedom of interference suppression is increased via widely linear processing. Simulations results illustrate the performance of the proposed beamformer.