Schaltungstheoretische Methoden in der Kommunikationstheorie

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In this research project, the theoretical limits of multi-antenna communications which are imposed by physical law are investigated and solutions for optimum design within those limits are developed. Multiport theory provides a platform for the physically consistent derivation of various figures of merit of multi antenna communication systems. Yet the results obtained up till now using this theory are mostly based on rather idealistic assumptions – such as absence of heat loss –, not including important aspects – like the trade-off between bandwidth and other performance measures –, and rely on physical models which ignore important parts of engineering reality – such as the need for antenna support structures and other complicated obstacles within the vicinity of the antennas such as a human body. A part of this research project is therefore focused on overcoming issues due to over-idealization, and, thus, to arrive at sound models for which theoretical predictions are in good agreement with reality and from which the system parameters for optimum performance can be obtained from the theory. In this research project, the channel, as seen in the information theory and signal processing layer of abstraction, is not apriori given, but rather forms part of the design. In our approach, antennas, their arrangement in space, impedance matching networks, and lownoise amplifiers form part of the channel. By jointly designing these elements, the resulting information theoretic and signal processing channel with respect to some figure of merit, such as channel capacity will be analyzed and optimized. We also hope to gain deep insight into the physical limits of communications, especially their influence on the performance of matching networks.