Adaptive space-time beamforming technique for passive radar system with ultra low signal to interference ratio

In recent years, the passive radar, using the noncooperative illuminators of opportunity, has attracted increasing attention. We discuss beamforming technique with application to the passive radar system. For realization issue, adaptive beamforming technique can be used to detect and estimate the signal-of-interest at the output of a sensor array by means of the adaptive spatial filter to suppress interference. Specially, the adaptive beamformer based on constrained least mean squares algorithm has been derived which is capable of adjusting an array of sensors in real time to detect the signal-of-interest and eliminate interference. We will exploit the space-time processing algorithm for the passive radar system, in order to increase the degrees of freedom without limiting the system output SINR. For more efficient and practical implementation, the proposed space-time beamformer can be realized by the recursively adaptive algorithm with multiple constraints. Finally, the proposed space-time beamformer can be operated in multiple linear constraint mode to combat the angle mismatch problem. From simulation result, it is shown that the multiple constraint space-time beamformer provides better OSINR performance with resistance to strong interferences.