The scattering from three-dimensional cracks has been analyzed and measured. The crack geometry is a rectangular groove in a perfectly conducting surface. The groove forming the crack may he terminated with an open aperture creating a slit in the conducting surface or with an impedance boundary creating a trough. The scattered fields from a crack were analyzed with two types of scattering mechanisms, a component directly related to the scattered fields from a two-dimensional crack and a traveling wave component. scr'cc' condvc'or /

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Abstrmt-The electromagnetic backscattering from a finitelength rectangular trough in an infinite ground plane is examined. A physical basis formulation, as introduced by Richmond [l], is used to express the unknown currents in the trough aperture in terms of a forced wave resulting from the incident plane wave, and one or more pairs of oppositely directed traveling waves propagating along the trough. A Galerkin solution is employed to solve a very small system of equations to determine the weights of the postulated aperture currents, and then radiated to compute the radar cross section (RCS). These results are then compared with a measurement of a trough in a finite ground

The electromagnetic backscattering from a two‐dimensional ogive is examined, including a mechanism‐by‐mechanism account for the scattered field. The uniform theory of diffraction is used in conjunction with a simple creeping wave representation to yield a solution which provides an accurate and continuous backscattering result for a wide range of ogive geometry parameters. Although not a rigorous derivation of higher‐order diffraction coefficients, this solution provides insight into the relative contributions of the various creeping waves which are generated and propagate around the two‐dimensional ogive. Comparisons with moment method (MM) calculations are used to demonstrate the range of applicability of this high‐frequency asymptotic solution.

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