Multi-region reduced field testing (RFT) for matrix thinning

The reduced field testing (RFT) has some distinct advantages when compared with other matrix thinning techniques. An explicit sparse matrix is obtained, and is amenable in principle to either iterative or direct solution. The fill-up time of the matrix is cut to at most one third of the full matrix, because no comparison with a threshold is necessary. The choice of basis functions is done independently, enabling the incorporation of this method to any existing Moment Method code as retrofit. In accordance with the reduced testing of the far field approach, this method is primarily suited for modeling the far field behavior of scatters.