Advanced antenna analysis and design by tailored Eigenmode decompositions

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Software tools for the electromagnetic analysis and design of antennas typically utilize full-wave methods that solve Maxwell’s equations numerically. They allow for accurate modelling of even complex problems and enable numerical modelling being a fundamental part in design and analysis electromagnetic systems. While the entire electromagnetic field or current density are the universal solution to the problem, they offer sometimes less intuitive insight into the underlying physical behavior of the antenna. Modal decompositions of the entire current density, such as the so-called Characteristic Modes (CM) are designed to illuminate the electromagnetic behavior a little further by allowing to identify Eigenmodes of the structure that are most relevant for radiation. Meanwhile, Characteristic Mode analysis is included in some commercial software tools on a basic level allowing the educated user to benefit from this advanced insight. Within the last 10 years application of CM for the analysis and design of antennas has shown a rapid and continuous growth resulting in innovative antenna designs. However, Characteristic Modes is a specific modal decomposition focussing on the radiation properties of a structure. Parameters that rely on the stored energy, e.g. antenna impedance, are less accessible by this Eigenvalue problem. Recently, research started looking at different modal decompositions in order to design tailored Eigenvalue problems that address better other aspects of antennas. Although all Eigenvalue problems of the current density are based on the common impedance matrix of the underlying problem, each modal decomposition stands for its own and is associated with different Eigenmodes derived from the specific Eigenvalue problem. Consequently, mathematical relations between the different decompositions have to be derived in order to combine them to calculate meaningful parameters for a certain antenna. The overall objective of the project is to explore various modal decompositions of the impedance operator that highlight different antenna aspects and combine them purposefully for holistic antenna analysis and design. In order to achieve this overall goal a structured catalogue of modal decompositions will be generated first. The catalogue shall enable to identify similarities and differences of modal decompositions on the application level, formal level and interpretation level. Based thereon, a mathematical framework of modal decompositions based on the impedance operator will be developed that enables to purposefully design modal decomposition and convert between them. Computational and numerical aspects of modal decompositions and their conversion and correlation will be dealt with next. This shall allow for mixed modal analysis of a certain antenna problem and intuitive design and tuning of antennas with respect to target parameters.