Smoothness of A_k(t) on channels

In our previous model, we set A_k(t)s on the non-desired signal region, which is not constraint by (i) and (iii), have been to zero. However, zero-setting might cause a decrease in the quality of the segregated signal form our experience and some reports [Boll1979].

To consider the above disadvantage, we consider the constraint of smoothness on the frequency axis instead of zero-setting. This constraint is shown in Table 1 (ii-b). For any t, we set values, which are determined by using spline interpolation, into A_k(t)s when these are not satisfied in grouping constraints.