Scattering from a double-strip grating: rigorous equivalent network formulation

An exact solution for the problem of transverse electric (TE) or transverse magnetic (TM) plane-wave scattering from a periodic, planar double-strip grating at a dielectric interface is described. The metal-strip grating is assumed to be perfectly conductive and infinite in length, with two different strips within a unit-cell. The formulation is based on a multimode equivalent network representation, and uses a rigorous solution for the relevant integral equation that extends the novel solution developed previously for the single-strip grating. Expressions for the elements of the multimode coupling matrices are given, together with a comparison of results for power transmitted through the grating, obtained by using the networks developed with the present method and a simple point-matching solution. Results are presented to illustrate the differences between single and double-strip gratings