Tullio Rozzi is Professor of Electromagnetics and Head of the Department of Electronics and Control, University of Ancona, Italy, and Visiting Professor at Bath University, UK. In 1975 he was awarded the Microwave Prize by the IEEE Microwave Theory and Techniques Society. Professor Rozzi is author of the book Open electromagnetic waveguides (IEE 1997).Marco Farina is Assistant Professor at the Department of Electronics and Control, University of Ancona, Italy, and consulting engineer in electronics. His research topics are the analysis and synthesis of travelling wave amplifiers, FET design and electromagnetic modelling of planar devices.