A broadband model of the characteristic currents for rectangular plates

This paper presents an approximate model of the characteristic currents for rectangular plates. This model provides a broadband description of the characteristic current distributions, which could be used for the far-field or near-field cases. For narrow rectangular plates, a modified cosine function and sine function are adapted for the odd and even modes, respectively. As the narrow case is fundamentally a 1-D problem, the presented solution could be scaled for arbitrary combinations of plate length and operating frequency. For wide rectangular plates, each characteristic current is decomposed into four parts along the plate edges, which decay exponentially toward the opposite edges. Variance of the characteristic currents with plate dimension is observed and briefly discussed. The frequency-dependent but axis-independent mode coefficients are utilized and numerically evaluated to verify the proposed model. The modal solutions of two rectangular plates that are illuminated by a normally incident planar wave are given and compared with the full-wave solutions. The modal solutions composed of the lowest four terms provide an explicit description of the surface currents with reasonable accuracy. Axis dependence of the mode coefficients is briefly discussed, and the first-order expression contributes an improved accuracy when the mode number is larger than 1.