Performance comparison of two sets of constraints in multi-path environment

The performance of two sets of constraints for a robust adaptive beamformer in the multi-path environment is studied. By constraining the magnitude or real component of the array responses of the coherent signals to be greater than unity, the desired signal cancellation is avoided. It is shown that although in the single-path environment the two methods have almost the same performance, for the multi-path case, the method imposing extra constraint on the imaginary part of the array response has a better performance.