An asymptotic analysis of a leaky parallel-plate waveguide.

Abstract

An asymptotic analysis of a leaky parallel-plate waveguide is presented. The walls of the waveguide consist of bonded wire meshes which are modeled using a sheet impedance boundary condition. The fields are excited by magnetic line sources exterior to the waveguide. The wire meshes allow for coupling between the interior of the waveguide and the exterior region. In addition, each mesh can support a surface wave. We employ Fourier transform techniques to derive an integral representation for the magnetic field. We present various interpretations of the integral representation and evaluate the integral asymptotically using the method of steepest descents. The case of a pole near the saddle point is considered in detail. The integral is also evaluated numerically to determine the accuracy of the asymptotic results. The contributions to the radiation pattern of the structure from the surface-wave and leaky-wave poles, as well as the saddle point, are considered individually. The parameters of the structure are adjusted to exploit the contributions from the poles in the near far zone. The transient response of the structure to a double exponential pulse is also investigated. An alternative representation which is computationally efficient for computing the transient response in early time is derived. The use of the alternative representation for dense distributions of leaky-wave poles is also considered.