Efficient methods for transducing electromagnetic energy into heat are explained. These methods make use of planar technologies such as microstrip and stripline, along with special ceramic materials developed by Microbiotech S.L. The electromagnetic fundamentals of the presented methods are stated, and the simulated and measured results are presented for each model. The efficiency of the transducers is analysed and compared with the state-of-the-art, and finally the possibility of an array scheme for uniform heating purposes is pointed out.Introduction: Although the use of microwaves has been traditionally restricted to applications such as radio links, mobile and spatial communications systems, radar or radioastronomy, in the past half century some energetic applications for microwaves have arisen. Industrial heating, sterilisation, drying, cooking or material synthesis are only some of these applications [1,2]. Microwave processing of materials has been extensively used instead of traditional heating methods, thanks to its advantages. Nevertheless, the quality of results in these applications is conditioned by the field distribution achieved inside the microwave applicators. These applicators are usually multimodal cavities, and the interaction of the propagating modes and their numerous reflections foster a very irregular field distribution. In addition, these cavity-based techniques are usually mismatched techniques, in which a substantial part of the energy delivered to the applicator is reflected back to the source, lost in cavity walls or simply resonates, thereby reducing the efficiency of these methods [3].Several solutions have been used to make the heating more uniform, such as conveyor belts, magnetron arrays, moving platforms or mode stirrers, but these solutions introduce an additional mechanical complexity and usually do not solve the mismatching problem [3][4][5][6].This Letter presents two novel technologies able to transduce microwave energy into heat in such a way that it achieves a notable efficiency and a uniform nature. These technologies can act as small planar radiators that can then be arranged in an array configuration capable of heating in a uniform way.Although other electric energy transducers based on the Joule effect do exist, such as DC resistors or resistive paintings, they can raise their temperature just as fast as they lose it, due to their high thermal conductivity. These disruptive novel heat radiators are based on the dielectric heating of sheets of ceramic materials, and they present a nonreciprocal behaviour, being able to absorb microwave energy much faster than they tend to lose the generated heat. This is a key parameter for the use of these transducers as very efficient heating cells.
