Study On UWB-MIMO Antennas

The UWB-MIMO wireless communication system is referred to as an Ultra-wideband(UWB) wireless communication system combined with the Multiple-Input Multiple-Output(MIMO) technique. The main merits of the UWB wireless communication systems operating from 3.1 GHz to 10.6 GHz are included high data rate, great capability to combat multipath fading, etc., and thus, by combining the UWB wireless communication system with the MIMO technique where the multipath problem is treated as a favorable factor and can improve the channel capability of a communication system without additional bandwidth consumption, a high data rate of 1Gb/s will be achieved in the UWB-MIMO wireless communication system. Meanwhile, the radiated power of the UWB wireless communication system is strictly limited by Federal Communications Commission(FCC) which leads to a short communication range of the UWB system, However, by adopting MIMO technique in the UWB wireless communication system, the communication range can be improved through beam forming, and moreover, with the low radiated power, the UWB-MIMO wireless communication system will have low energy consumption and is accorded with the green communication concepts which have arisen in the world in recent years. Additionally, the UWB wireless communication system can realize communication, localization, imaging under partition wall condition due to the high penetration capability of the UWB signal, these advantages cannot be achieved by IEEE 802.15.3c devices which are based on the application of millimeter wave at 60 GHz and also have very high data rate. Just because of such superior and special characteristics, the UWB-MIMO system has attracted wide attention of many scholastics at home and abroad in recent years. As the key device of the UWB-MIMO system, the UWB-MIMO antennas are receiving gradual attention.The UWB-MIMO antennas that are the key device of the UWB-MIMO wireless communication system which has great development potentiality are mainly concerned and studied in this dissertation; some new technique and methodology in designing such antennas have been studied. The major works and contributions of the dissertation are outlined as follows:A polarization diversity UWB-MIMO antenna is studied and designed in the first part of the dissertation. According to narrow operating bandwidth and large size dimension problem existing in the polarization diversity UWB-MIMO antenna with T shaped decoupling structure, a novel decoupling technique with the exponential curve is presented in this dissertation. A miniaturization polarization diversity UWB-MIMO antenna is successfully designed by adopting the exponential decoupling structure. The simulated and measured results proved the feasibility of the design proposal, and the proposed antenna has not only wide impedance bandwidth, but also miniaturized size and higher average peak gain.Some pattern diversity UWB-MIMO antennas are studied and designed in the second part of the dissertation. According to the problem of the complicated decoupling structure and great difficulty in designing the miniaturization pattern diversity UWB-MIMO antennas currently, a universal methodology based on “E-plane Cut” method for designing a pattern diversity UWB-MIMO antenna is presented in this dissertation, and the mechanisms of each step are also illustrated. The presented methodology is carried out from a symmetrical UWB planar monopole antenna as a pattern diversity UWB-MIMO antenna’s original modal. The pattern diversity antenna designed by the presented methodology has not only miniaturized size but also with simple decoupling structure which can simplify the design procedure and improve the design efficiency. For the purpose of proving the feasibility of the design methodology, the presented methodology is firstly applied to a circular disc monopole antenna and a pattern diversity antenna is successfully designed, constructed, and measured. The simulated and tested results verified the feasibility of the presented methodology. For the purpose of proving the universality of the presented methodology, another pattern diversity antenna is simulated by applying the presented methodology to a beveled rectangular UWB planar monopole antenna which has also a symmetrical structure. The simulated results indicate that the presented methodology has good universality and can be applied to a UWB planar monopole antenna with arbitrary symmetrical construction. Meanwhile, the pattern diversity UWB-MIMO antenna designed by the presented methodology can be miniaturized furthermore; the miniaturized one can still meet the requirement for UWB-MIMO application by optimizing the parameters of the antenna construction.Some band-notched pattern diversity UWB-MIMO antennas are studied and designed in the final part of the dissertation. According to the interference between the UWB-MIMO system and the existing narrow band wireless communication systems, a single band-notched and dual band-notched pattern diversity UWB-MIMO antenna are presented. By introducing two inverted L shaped slits in the antenna elements, a single band-notched pattern diversity UWB-MIMO antenna is successfully designed which can eliminate the interference with WLAN band. By introducing two complementary split ring resonators(CSRR) in the antenna elements, a dual-band notched pattern diversity UWB-MIMO antenna is successfully designed which can eliminate the interference with the C-band and WLAN band. The feasibility of the design proposal is verified by the simulated and tested results.