Efficient Microwave Heating of Arbitrary Loads in Multimode Cavities Employing Transformation Optics-Designed Dielectric Wedges

Variations in load shape, volume, and permittivity significantly impact microwave energy conversion efficiency within multimode heating cavities. This study introduces a wedge dielectric plate that enables asymmetric microwave propagation when being in contact with a load, thereby enhancing heating efficiency and robustness under load variations. First, based on the transformation optics theory, an asymmetric waveguide is established by the wedge dielectric plate. Experimental results show varying microwave transmission efficiencies in both forward and reverse directions. Second, a microwave multimode cavity with a dielectric substrate is designed. When the dielectric wedge, dielectric substrate, and load are in physical contact, an efficient microwave transmission path will be formed to enable directed propagation toward the load via surface waves. Simulation results show over 90% heating efficiency with loads of varying volumes, dielectric properties, and shapes. Finally, microwave heating experiments are conducted and compared with a domestic oven using different loads. The proposed method achieves approximately 40% higher temperature increase at 750 W. This method is advantageous due to its low manufacturing cost, high power, robustness, and versatility, making it highly suitable for industrial applications.