The core competency »Electromagnetic Fields« embraces several fields of scientific activity, all of which are important to ensure the proper functioning of modern radar and communication systems. These include cross-disciplinary research tasks such as the numeric modeling of electromagnetic fields, wave propagation in various media, the development of antennas and the corresponding components as well as HF measurement technology which are currently performed by approx. 25 employees in various departments. The scientific challenge lies in the implementation of differential (Maxwell's) equations for electromagnetic fields in numerical calculation methods which then form the basis for the subsequent development of efficient software using high performance computing (HPC). Depending on the complexity of the object and its size compared to the wavelength, various approaches, e.g. geometric optics, physical optics and ray-tracing, are used and combined with each other (hybrid methods). Fraunhofer FHR has been working on the development of special hybrid methods for the numerical calculation of electromagnetic fields for a number of years already. The newly developed software, such as FARAD, Cyl-Patch® and FEBI®, which are now registered trademarks, is used to design and analyze antennas and antenna arrays. Compared to other software that is commercially available for the HF area, it offers greater flexibility and is a unique selling point of the institute. Due to their precision and efficiency, the simulation tools also achieve very good results in international benchmarks (e.g. JINA Workshop EM2).