Abstract:The active arrays can extend the virtual aperture greatly by transmitting orthogonal signals, and degrees of freedom are increased exponentially. In this paper, By transmitting orthogonal signals , virtual subarrays are designed, and the Virtual Subarrays Smoothing(VSS) algorithm is proposed for the coherent case. Virtual subarrays with identical sensors avoid the reduction of the array effective aperture, and make this approach estimate coherent returns at most. Simulation results show that the VSS algorithm is effective and need only a little sensors transmitting signals.