High Frequency Electromagnetic Propagation/Scattering Codes

Our overall objective is to develop a high frequency algorithm capable of simulating the full spectrum of electromagetic scattering and propagation problems including multiple reflections and diffraction phenomena such as diffraction on smooth surfaces,edge diffraction, and multiple diffraction effects. Our approach will utilize the wavefront evolution method which we intitiated during the phase Iand augmented it with the edge diffraction effects. The proposed method allows to accurately determine wavefront positions, boundaries, extensions to the shadow region,and junctions between the reflected, transmitted and diffracted wavefronts. The fieldsassociated with the wavefronts will be evaluated using an improved version of Uniform Theory of Diffraction. The planned algorithm will possess the following features:(a)Asymptotic frequency independent computational cost (b)Consistent (compatible withreciprocity) treatment of reflections to all orders combined with diffraction to a selected order. Reflection and diffraction processes may occur in an arbitrary order. Diffraction effects will include edge, corner, and smooth-surface diffraction,(c)Ability to handle realistic complex CAD geometries. We also propose to develop a time-domain version of the HF algorithm, which will include: a) Description of short pulses, both delta-function type, and those of finite width, dominated by high frequencycomponents(b) Full treatment of multiple reflections of pulses (c) Treatment of leading effects due to diffraction of pulses, in combination with reflections. Significant improvement over the cababilities of the existing high frequency algorithms whichare of interest to DoD and industry will be achieved. In particular, the improved capability to predict surface scattered fields in the shadow region will increase the accuracy of solving electromagnetic compatibility problems for antennas mounted onairborn vehicles.