Edge subdivision for fast diffraction calculations

A continuous-time edge-diffraction impulse response (IR) can be expressed as a line-integral along the diffracting edge. With such a formulation, the discrete-time IR is found by subdividing the edge into segments, and for each segment integrating over its length and distributing the result among the appropriate time samples. Two basic subdivision strategies have been considered previously: one in which the segments are aligned with samples of the impulse response (i.e. each segment contributes to exactly one sample), and a second in which the segments are of a fixed length, and thus may contribute to one or multiple samples. In this paper, a hybrid subdivision strategy is proposed in which a sample-aligned segment is used only for the first sample of the IR, and evenly sized segments which span many samples are used to process the remainder of the edge. It has been found that the use of this hybrid method can result in a significant decrease in processing time with a minimal reduction in the accuracy of the IR calculation, and thus may allow for rapid diffraction calculations in complex, multi-edge simulation environments.