Low-Cost Measurement System and Filter for Reduction of Emc Interferences in Radio-Frequency Applications

Abstract

For drying building structures [1], dielectric heating using RF energy (in this case 13.56 MHz) is an efficient and fast alternative to conventional heating methods based on heat transfer from the surface to the interior of the masonry. Another innovative application of volumetric RF heating is the chemical-free pest control in wood-based materials [2]. For such applications where the RF systems often are not completely shielded, the propagation or coupling of the electromagnetic wave into wires that are placed inside the field cannot be neglected which represents a certain risk. Depending on the different electromagnetic coupling mechanisms, several interference signals can be generated. In order to protect electrical equipment in the surrounding, these interferences have to be significantly reduced by electrical filters. For this purpose, initially a cost-effective (at least in comparison to standard RF measurement systems) and more robust measuring concept was developed. With the help of this system, the common mode (I_CM) interference could be identified as the dominant part and the differential mode (I_DM) interference as a minor disturbance. Based on the experimental evaluation, a cost-effective filter for the respective disturbance was constructed and successfully tested.