Analysis and Design of Multiple Element Antennas for Urban Communication

With the increasing interest in sophisticated algorithms and network configurations in order to increase the data rates demands of current and future communication systems, less attention is paid to the antenna in-system optimization. Yet, network providers and antenna engineers are still faced with the problem of addressing upcoming infrastructure needs, such as more cost efficient antenna solutions. To aid in this decision making process, the attention of this work is focused on the analysis and design of multiple element antennas (MEA) and their interaction with the propagation channel. Moreover, focus is given to the “Karlsruhe" propagation channel and how its information throughput, i.e. capacity, can be improved. With this in mind, an existing network model of the communication system is extended to include a modal description of both mobile and base station antennas in order to reduce computation time. Reduction of simulation time is proven to increase linearly with the number of antennas, when it exceeds the number of modes considered. On the basis of this model, an extensive capacity study of different antenna setups based on measured radiation patterns of commercial antennas is performed, with varying inter element spacing at both the base and mobile station. As result, a set of guidelines for optimum antenna placement and setup selection is given based on the capacity of equivalent isotropic normalized channels. This type of normalization, however, is not unique. Depending on the evaluation needs other norms might be used and comparison among different works results in a difficult task. To address this issue the adoption of an eigenvalue dispersion metric as a compact and information rich evaluation measure is proposed, with which the capacity for any normalization and SNR regime can be estimated. Finally, the communicational limits of linear arrays in different propagation scenarios are explored and a synthesis method for achieving maximum information throughput is derived. In this way it is proven that even better capacities to those achieved by the studied commercial antenna setups could be attained, not by increasing the number of antennas, but by adding subchannels to the existing ones. Hence, antenna driving networks capable of producing several array excitations are suggested as the next step toward better capacities in urban mobile communication systems.