Research On MIMO Antenna Technology Based On Mode Decomposition

As the increasing of the requirement for mobile communication system capacity and reliability, multiple input multiple output(MIMO) technology has been widely studied as an effective measure to solve this problem in recent years. Antenna researchers are focus on research and develop high isolation and low correlation MIMO antenna suitable for mobile terminals. In recent years, some of the literatures have put forward some methods of improving isolation, but they are only effective in high frequency, single frequency and narrow band. In order to satisfy the demand for multiband and broadband, we introduced and improved the MIMO antenna design method based on mode decomposition in this thesis. Several MIMO antennas were designed based on this method. As a result, high isolation and low correlation were achieved in multiband and broadband. The main contribution of this thesis have the following aspects:1. First of all, analyzed the influence of the chassis on antenna bandwidth and pattern. In view of the importance of the chassis in antenna design, MIMO antenna design method based on chassis current mode decomposition has been proposed.2. Several MIMO antennas working at 2.5GHz has been designed based on mode decomposition, each of the antennas has obtained high port isolation which has proved the feasibility of this method. Then, analyzed the effect of space wave coupling and chassis current coupling on port isolation. As a result, chassis current coupling can reduce the isolation greatly, shows the rationality of the method proposed in this thesis.3. A MIMO antenna working at LTE band 13(746~787MHz) has been designed in this chapter. The isolation is higher than 30 dB, and the correlation is lower than 0.001. The results are much better than the literature has ever reported.4. First, three antennas have been designed which can cover six bands, seven bands and eight bands respectively. These antennas are suitable for mobile because of the design concept is clear, simple structure, low profile and good performance. Combine the six bands antenna and the seven bands antenna reasonably, a multiband and broadband MIMO antenna has been achieved. The isolation is higher than 23 dB in low band(GSM900), and higher than 18.5dB in high band(1710~2690MHz). The correlation is lower than 0.01 in the designed frequency bands. The results are much better than the literature has ever reported.