An extended UTD analysis for RCS computations involving higher order curved surfaces

An extended utd (eutd) solution is developed for the scattering and diffraction of high frequency em fields from higher order (polynomial and spline defined) curved surfaces. The new solution is computationally efficient and overcomes the difficulties of the classic go/gtd/utd solutions near ray caustics and caustic terminations. The approach for constructing the eutd solution is based on a spatial domain radiation integral representation for the scattered field which is then reduced using a uniform asymptotic procedure. Further heuristic modifications are also made and correct the go induced current assumption near the shadow boundaries. New uniform reflection, first order edge diffraction, and zero-curvature diffraction coefficients are then derived and involve higher order phase integrals as canonical functions. Numerical results involving third and fourth order polynomial strips are provided and compare favorably with reference moment method results. abs]Fr|RésuméUne théorie uniforme de la diffraction étendue (eutd) est développée pour la diffraction ď un champ électromagnétique à haute fréquence sur des surfaces de courbure complexe. La nouvelle résolution est intéressante du point de vue du temps de calcul et permet ď éviter les difficultés classiques des méthodes gtd/utd près de certaines caustiques. ľ approche prise pour la construction de ľ eutd est basée sur une représentation intégrate dans le domaine spatial du champ diffracté, réduite par une procédure asymptotique uniforme. Des modifications heuristiques sont faites qui corrigent le courant ď optique géométrique près de la frontière ď ombre. Des expressions uniformes sont alors déduites qui demandent le calcul ď intégrates de termes possédant une phase ď ordre élevé. Des résultats numériques sont donnés et comparés avec ceux obtenus par une méthode des moments.

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