A Modified Fast Far Field Approximation for Improving Speed and Accuracy in Electromagnetic Scattering Computationsa

The conventional fast far field approximation achieves its acceleration by dividing elements into groups and decomposing the conventional matrix-vector product into aggregation, translation, and disaggregation operations. However, conventional formulation of these operators neglects the distances between centroids of individual elements and their groups in the large argument approximation of the Hankel function, which compromises the accuracy of the technique. A method is described in this paper for retaining these quantities in the formulation, thereby increasing speed and accuracy relative to the conventional formulation. Results show that applying the correction factor to the problem of scattering from two dimensional conducting contours has the effect of decreasing peak error, RMS error, and computation time for all test cases