Research And Design On The Compact UWB MIMO Antennas

In order to meet the demand for large capacity, high rate, muti-function, reliability of wireless communication with the rapid development of electronic products, the UWB MIMO communication technology arises at the historic moment. As the main current technique in the short-distance communication field, UWB technology has many advantages, such as high transmission rate, low power consumption, low cost, perfect secrecy, high-precision and strong anti-jamming capability. In addition, the MIMO technology has space multipath characteristics using multiple antennas in the transmitter and receiver, which can obtain distinct multiplexing gain and diversity gain. It can greatly improve the system’s reliability and spectrum efficiency without increasing system bandwidth, which is an effective way to relieve the spectrum resources tense. Therefore, the thesis tries to combine UWB technology and MIMO technology. The MIMO technology can provide the UWB systems required reliability and adaptive ability. Then the UWB system would achieve long-distance and high-speed transmission.Now an important factor to restrict the development of ultra-wideband MIMO communication system is the design of commercial terminal antenna. Owing to integration of mobile terminal equipment, the antennas must be as miniaturized as possible. But the limited size would not only make bandwidth limited, but also produce coupling between antenna units. Therefore, the design of ultra-wideband MIMO antenna must consider the antenna’s miniaturization, broadband and low coupling between multiple antennas.This thesis firstly expounds the background and significance of ultra-broadband MIMO antenna. It summarizes the current research status of the ultra-wideband MIMO antenna. The principle of the antenna radiation and the performance parameters of the antenna are briefly introduced, the MIMO technology and related parameters of multiple antennas are also systematically summarized. It illustrates the basic design requirements for ultra-wideband MIMO antenna.Secondly, the thesis designed a two-port microstrip-fed ultra-wideband MIMO antenna with an stop band. Grooved through the floor and introduced a pair of L-shaped metal strip on the back of the antenna unit, the antenna unit can realize the UWB characteristics with an stop-band(5.1 to 5.9 GHz). The introduction of two I-shape decoupling strips can effectively improve isolation degree between antenna unit ports. Through test and analysis, it shows that the antenna’s measurement and simulation including S parameters, correlation coefficient, radiation pattern and gain have good agreement.Lastly, the thesis has also designed a compact four-port ultra-broadband MIMO antenna. The adjacent UWB antenna unit is vertically placed to improve the isolation between ports, primarily using the different polarization characteristics of the antenna units. The new isolation cross is loaded on the back of the antenna to further improve the isolation degree between the antenna unit ports. Through analysis, machining and test, it is founded that the performance including the S parameter, the correlation coefficient, pattern, and gain meet the design requirements, which shows that the broadband MIMO antenna is suitable for broadband MIMO system terminal equipment.