OFF-AXIS DIFFRACTION BY PERFECTLY CONDUCTING CAPACITIVE GRIDS - MODALFORMULATION AND VERIFICATION

We consider the diffraction of plane electromagnetic waves incident at an arbitrary angle on a capacitive grid of perfectly conducting cylin ders of arbitrary length. We comment on the formulation of modes withi n the grid region, concentrating on the case of transverse magnetic po larization, for which the generalization from on-axis to off-axis mode s is not straightforward. We solve the diffraction problem by a mode-m atching method, and give analytic expressions for the inner products b etween plane waves and modes, and normalization factors for modes. We give numerical results of the diffraction formulation, and comment on tests for its accuracy.