An effective method on increasing the null depth of beam forming via virtual array transformation

When conventional virtual array transformation algorithm is used in adaptive beam forming, the nulls formed in the directions of interferers are relatively shallower, especially when hyper degrees of freedom coherent interferences incide on array sensors, the performance of virtual array will decrease, sometimes it can´t reach the index of output signal to interference and noise ratio(SINR) which the system demands. Aiming at this disadvantage, an improved method is proposed in this paper, it is based on subspace projection concept, the interference direction information is imported into transformation matrix, thus the interference components in sampling covariance matrix can be enhanced. With this approach, the nulls can be steadily formed, and the interferers can be suppressed fairly deeply, simultaneously a high output SINR is also ensured. The validity of this presented algorithm is verified by theoretical analysis and computer simulation.