John Jelonnek (Senior Member, IEEE) received Dipl.-Ing. and Dr.-Ing. degrees in electrical engineering from Hamburg University of Technology (TUHH), Hamburg, Germany in 1991 and 2000, respectively. At TUHH, he developed rigorous self-consistent analyses for gyrotron oscillators, with particular focus on rigorous time-domain simulation at mismatched conditions and injection locking. From 1997 to 2011, he worked in several different positions in industry. Since 2011, he has been the Director of the Institute for Pulsed Power and Microwave Technology (IHM), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany. He is currently a Professor of high-power microwave technologies with KIT. He has carried out both research and development of high-power microwave sources, with particular focus on megawatt-class gyrotrons and applications of microwaves to energy efficient industrial processes using dielectric heating and microwave plasmas.