Miloslav Capek received his Ph.D. degree in 2014, and was appointed Associate Professor in 2017, all from the Czech Technical University in Prague, Czech Republic. Miloslav is a senior member of the IEEE, a former EurAAP delegate (Region 8, 2015-2020), and an Associate Editor of IET Microwaves, Antennas & Propagation. He has been a grant holder and member of a research team for several national and international projects, including projects funded by the Czech Science Foundation, the Technology Agency of the Czech Republic, and European Cooperation in Science and Technology (COST ASSIST, COST VISTA). He leads the development of the AToM (Antenna Toolbox for MATLAB) package and serves as a vice-chair of the EurAAP “Software and Modeling” working group. He is the author or co-author of over 150 journal and conference papers. He received the IEEE Antennas and Propagation Edward E. Altshuler Prize Paper Award in 2023. His current research interests include the areas of electromagnetic theory, electrically small antennas, numerical techniques, and optimization. For more detailed information, see capek.elmag.org.

Upper Bounds on Antenna Gain and Its Reachability

Antenna gain, as a product of radiation efficiency and antenna directivity, is a crucial design parameter with its role even more pronounced in modern and future high-frequency applications, including automotive radars and 6G. As such, the question of its upper bound will be thoroughly addressed in this talk. Starting with the classical works of Uzkov, Bouwkamp, and Harrington and moving forward to recent advanced computational schemes based on modal theory and quadratic programming, it will be demonstrated that the upper bound for antenna gain of a fixed polarization has some unique numerical properties, making it possible to express the solution semi-analytically. The interplay between the electrical size of an antenna, material losses, and bandwidth will be discussed in detail, indicating that all these effects are closely interconnected. The difference between high-directivity (super-directivity) and high-gain (super-gain) will be demonstrated, and the optimal current densities for various antenna design regions will be shown. Considering the excitation of an antenna, i.e., possible mismatch, realized gain is another metric to be optimized. Ways to establish realized gain for multiport antennas and arrays and to identify available degrees of freedom for effective antenna design, in addition to their simultaneous optimization, will be discussed. The talk will conclude with a discussion of open problems and future challenges.