Scattering of H10-mode wave by narrow conducting plate inside rectangular waveguide

Asymptotic relations are derived for scattering of an H(10)-mode wave by a thin (relative to skin depth) and narrow rectangular plate in a cross section of an infinitely long rectangular single-mode waveguide, this plate being oriented with its narrow sides parallel to the narrower waveguide walls. Such a plate does not appreciably perturb the incident field. The corresponding integral equation is solved for the jump of tangential magnetic field components at such an inhomogeneity, whereupon the shunting impedance in the two-port equivalent network is calculated. For an impedance film, the scalar potential cannot be defined and the problem is solved by the Galerkin method. For a small barrier far from the waveguide walls, with both length and width much smaller than the wavelength, the problem is solved in the dipole approximation, assuming that an incident field slowly varies over the barrier volume. The dependence of the shunting reactance on the wavelength and of the modulus of the shunting impedance on the surface impedance of the plate agrees numerically within 10% with results based on the exact solution.