Mutual coupling between circular apertures on an infinite conducting ground plane and radiating into a finite width slab

The problem of electromagnetic coupling between two horns for the Microwave Reflectometer Ionization Sensor (MRIS) that will be used in NASA´s Aeroassist Flight Experiment (AFE) is considered. Laboratory measurements of mutual coupling between conical horns have shown a strong dependence on the finite dimensions of the shuttle tile over the apertures. Since both the dielectric tile and the plasma outside the tile reflect microwaves, a study should be done to isolate the two mechanisms so that the MRIS reentry flight data can be interpreted correctly. Once the coupling due to the tile itself is determined then the location of the critical electron number density layers can be determined. The geometrical theory of diffraction was used to modify the existing solution to mutual coupling between apertures with infinite dielectric sheets. Results from two cases with different tile thicknesses have indicated that the main contribution to mutual coupling is due to diffraction from the bottom and top (back and front) wedges.<>