The new 3-D proposed structure has a stop band at 2.45 GHz. This stop band is the operating frequency for common microwave heating devices. The structure is periodic. The infrared emissions are passed through a large enough opening inside the microwave cavity in order to allow the temperature of the object inside to be read by the thermopile installed outside the chamber. Using the FE Eigen analysis it was possible to design the unit cell of the structure in order to locate the stop bands. After locating the stop bands the structure was analyzed deterministically using an FE solver, then three unit cells was fabricated. Through the three unit cells fabrication and measurements satisfactory results have been achieved when the proposed structure was tested in a commercial microwave acid digestion system.