Microwave Diffraction Measurements in a Parallel-Plate Region

Abstract

Many infinite two-dimensional electromagnetic-scattering problems are strictly equivalent to the configuration obtained from the image principle by placing a finite-scattering obstacle between two parallel, infinite, and perfectly conducting planes and illuminating it with a plane or cylindrical incident wave confined to the parallel-plate region. An experimental approximation to this arrangement is described for use in the 3-centimeter wavelength region. Finite rectangular parallel metal plates support a transverse incident electromagnetic wave with the electric field oriented perpendicular to the plates. Absorbing wedges at the boundary of the region reduce reflections from this discontinuity. The electromagnetic field scattered from any particular obstacle may be investigated by means of a dipole probe introduced into the region through a moveable section of one of the plates. The success of this technique is demonstrated by comparing measurements of the total field scattered by infinite conducting wedges of included angle 0, 45, and 90 degrees with the known theoretical expressions, for perpendicular incidence. Agreement with theory is good. The effect of finite thickness of the diffracting screen (case of 0° wedge) in increasing the amplitude of the scattered wave is noted and compared to theoretical results derived for scattering from a thin conducting half-plane with a cylinder superimposed on the edge.