The problem with (2) is that often it is difficult to obtain a good estimate S0. Now assume Si>>Ui and substitute into (2) instead of S0 Xk-just one trace. Remembering that Xk=Uk+Sk we get:
Here Uk/Sk is a complex constant. The contribution of the interfering source to each trace has been reduced by the absolute value of this constant (which is <<1 under our assumption), but the phase shift between channels is preserved. To summarize, the magnitude of the interfering source was reduced significantly without adding major artifacts, and location of the weaker source is now more feasible.