### ASA 127th Meeting M.I.T. 1994 June 6-10

## 1aSA8. Edge effects in finite gratings of cylindrical scatterers.

**Douglas R. Denison
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Robert W. Scharstein
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*Elect. Eng. Dept., Univ. of Alabama, Tuscaloosa, AL 35487-0286
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Edge effects in finite arrays are studied via the analysis and
interpretation of one canonical geometry---a linear grating of thin circular
cylinders. The partial field scattered by each element in a finite array is
decomposed into three components: (1) the contribution of the infinite or
periodic array, (2) a component due to the presence of the left edge of the
array, and (3) a component due to the right edge of the array. The scattered
field due to either array edge is derived from a separate analysis of the
appropriate semi-infinite array and is interpreted in terms of a decaying wave
that is launched from the array end. This solution to the well-posed boundary
value problem is numerically verified via boundary condition satisfaction,
where the accuracy of the edge-wave decomposition persists for all tested
values of element spacing and plane wave incidence angles. [Work supported by
NSF.]