THE PROPERTIES OF A RECTANGULAR WAVEGUIDE WITH A DISSIPATIVE SLAB AT THE CENTER

Abstract

Abstract : An exact solution is developed for the fields in a rectangular waveguide with a dielectric slab at the center. The surfaces of the slab are assumed to be parallel with the sidewalls of the waveguide, and the field is that of a TE mode with the electric vector parallel with the slab surfaces. The thickness of the slab is arbitrary, but the height of the slab is taken equal to that of the waveguide with the remaining space assumed to be free space. Although the equations are transcendental, it is possible to solve them to determine the guide wavelength and the guide attenuation constant if the slab parameters (dielectric constant, permeability, electric loss tangent and magnetic loss tangent and thickness) are known. Thus, the expressions are useful in the design of waveguide attenuators and phase shifters. The equations can be solved more readily for the parameters of the slab after the guide wavelength and attenuation constant have been measured, thus forming the basis of a promising technique for measuring dielectric constants, permeabilities, and loss tangents. Simplified equations are derived for nonmagnetic slabs which are very thin in comparison with the wavelength and the waveguide width, and a set of curves are included to facilitate dielectric measurements and the design of waveguide attenuators and phase shifters.