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A general formulation based on frame re-expansions of Gaussian beam fields in the course of Gaussian beam shooting algorithms will be outlined, and closed form expressions used for frame decomposition of incident beam fields and frame change will be given. The algorithm will be tested on a specific 3d problem chosen with a view toward ground-based Radar application in semi-urban environments. The range of validity of closed form expressions for frame re-expansion coefficients will be discussed, and the accuracy of Gaussian beam summations after such re-expansions will be compared to reference solutions in cases involving diffraction.

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In the context of ground based Radar or wireless communications, non line of sight situations occuring in suburban type built environments are particularly demanding regarding the accuracy of field simulations. This communication presents new developments of the frame-based Gaussian beam shooting method to address some of the diffraction problems encountered in the presence of buildings. The presentation is focused on the problem of back-scattering by the bottom and the top of a building, which is addressed through incident beam selection, image frame and frame redecomposition. Numerical results obtained with this algorithm are compared to results obtained with the Parabolic Equation and with reference results.

Frame-based Gaussian Beam Shooting is presented as an alternative to ray-based methods, when reliable and accessible knowledge of propagated electromagnetic fields is required at all points in built-up environments. This communication presents a general Gaussian Beam Shooting algorithm based on paraxial beam tracking complemented with the use of "image" frames and with frame redecomposition on reflecting surfaces, to account for the presence of ground and buildings. Numerical results obtained in the case of a "single wall" and of a "parallelipedic building" are compared to Parabolic Equation and FEKO software results.