New frequency-dependent edge mode current density approximations for TM scattering from a conducting strip grating

Two new frequency-dependent strip-grating current densities are derived for TM mode incidence on a conducting strip grating. The current densities are assumed to be the product of a spatial function and a frequency function. One spatial function is the traditional frequency-independent edge mode current density. The other is found by the use of conformal mapping. The frequency function is derived by use of the radiation integral and the periodic Green´s function. The new resultant current densities are both exact for small strip widths. The conformally mapped solution is also valid for wide strips and is exact in the limit as the strip width equals the grating period. Although the solutions are not as accurate as the moment method at all frequencies, they produce computationally faster solutions and offer further insight into strip-grating behavior