Multiport Antenna Systems for Space-Time Wireless Communications

Doktorsavhandling, 2013

Multiport antenna systems are indispensable part of modern wireless communication systems. Their crucial impact on the overall performance requires sufficient regard and dedication to a precise design and characterisation. This concern has been to a considerable extent addressed in the frame of the current thesis. The thesis starts by a brief review of the evolution on wireless communication systems. In particular, the role of multiport antennas in modern communication systems is highlighted. The multidisciplinary nature of multiport radiation terminals makes them the subject of many research groups worldwide, resulting in inconsistent nomenclature. Thus, a few words are dedicated to throwing light upon some important metrics in this discipline. The notion of richness threshold as a further crucial performance metric is introduced. The importance of the latter parameter is emphasised by virtue of some practical examples. We describe how an RF Butler network can be used to remarkably enhance the performance of spatial diversity systems. Subsequently, the advantage of a predictor antenna system in modern moving relays is underlined. We illustrate and quantify how the coupling removal can improve the prediction capability of this system. This can be most conveniently carried out through signal processing, amplifying the prediction reliability. To verify the foregoing achievement, some results associated with measurements in actual scenarios are presented. Moreover, a quick and inexpensive measurement of antennas in multipath environments is of foremost concern for antenna system designers. This issue is simply possible by reverberation chamber technologies. We briefly clarify how further analysis can be utilised to facilitate measurements in these chambers. At the end, we devote a short discussion to some state-of-the-art antenna designs which are suitable for the modern compact mobile terminals, manifesting certain rewarding features.