Theoretical Analysis And Design Of Compact Uwb-mimo Antennas

It’s necessary and imperative to overcome the bottlenecks of traditional wireless communication technology, such as narrow bandwidth and low channel capacity, so that the wireless communication will become high-capacity and high speed. Fortunately,some promising technologies have been proposed, including Ultra-Wide Band(UWB)communication and Multi-Input Multi-Output(MIMO) technology. Both of them have their own advantages and shortcomings, there are already a good deal of researches,combing the merits of UWB and MIMO technology, to further improve the channel capacity and the data transmission rate of wireless communication systems.Antennas have been paid a lot of attentions, as they are important elements of wireless communication systems. It’s impossible to design a high-performance wireless communication system without high-performance antennas. Although lots of UWB-MIMO antennas with good performance have been proposed, there still lacks of theories that can help designing such antennas efficiently. Based on this background,exploratory research on the theoretical analysis and efficient design methods of the UWB-MIMO antennas have been carried out in this thesis, and some valuable investigation have been provided.Firstly, the near-field pattern theory and the characteristic mode theory(or called eigenmode theory) are applied to analyze the factors that impact the mutual coupling of antenna elements. And then a compact UWB-MIMO antenna with high isolation is designed based on the characteristic mode theory and the ground antenna theory.Furthermore, a fast method for designing compact UWB-MIMO antennas is proposed.Two ways for accelerating the computing of eigenmode is presented at the same time.The thesis is organized as followed:Chapters 1 introduces the common ways for designing UWB-MIMO antennas and the applications of the antenna pattern and the characteristic mode theory in the analysis and design of UWB antennas. The design and applications of the Ground Antenna theory are also introduced.Chapters 2 and 3 describe the theories of radiation field of antennas, the characteristic mode theory and some mathematic concepts related.In the fourth chapter, the near-field pattern is applied to analyze the mutualcoupling between the elements of UWB-MIMO antennas.Chapters 5 is mainly on the fast computation of eigenmodes of wideband antennas,including parall computing and a new fast wideband mode tracking method(WCMTM).In Chapter 6, the eigenmodes of an UWB antenna and a series of two-element UWB-MIMO antennas are analyzed with the characteristic mode theory firstly. And appropriate arrangements for the antenna elements to decrease the mutual coupling of UWB-MIMO antennas are proposed.A compact UWB-MIMO antenna is designed in Chapter 7, based on the theory of characteristic mode and the ground antenna.Conclusions are made in the last chapter, the significances of the thesis and issues for further research are also indicated.