Analysis On Performance Of Spatial Fading Correlation Models For Compact MIMO Antenna Array

Multiple Input Multiple Output (MIMO) has been widely adopted in both the transmitting and receiving terminals of wireless communication system. The MIMO system can effectively overcome difficulties brought with the undesirable environment, so that it can acquire a larger channel capacity and provide better transmission quality compared with Single Input Single Output (SISO) system. Because of the limitation of transmitting and receiving set as well as the lack of scatters in the wireless transmitting environment, every unit of the antenna arrays cannot be independent from each other, there is a correlation between them which will affect the performance of the antenna system, and the affection is enlarging for the higher requirement of compact antenna arrays. So it is of great significance to analyze the influence of MIMO system brought by the spatial fading correlation (SFC). In this paper we focus on the variation of the SFC led by the different modeling of the antenna arrays, and further result in a difference of the channel capacity, then the performance of MIMO system based on different antenna arrays can be judged objectively. The main work of this paper detailed as follows.Firstly, we derive the exact function of spatial fading correlation in the case of three different azimuth of arrival (AOA) distributions which are uniform angular distribution, Gaussian angular distribution and Laplacian angular distribution applying uniform linear antenna (ULA) array as the model, in order to analyze the influence to the SFC under the azimuth parameters. We also derive the approximate function of SFC for reducing the amount of computation as well as improving analyzing efficiency. Results show that the SFC decrease if the distance of antennas increases, or the AOA decreases as well as the azimuth spread (AS) increases.Secondly, as the two-dimensional antenna array model only concerned about the mean azimuth of arrival and the azimuth spread, elevation angular parameters are introduced to create three-dimensional models of ULA, uniform circular array (UCA) and uniform rectangular array (URA). The SFC functions are derived under the condition of uniform angular AOA distribution, and it is obviously that each of SFC of the three models is quite different from the other two.Thirdly, in order to get full access to multi-dimensional polarization information of the signal, electromagnetic vector sensor (EVS) is introduced to build a antenna array model to replace the original scalar sensor array (SSA). We also derived the SFC functions under the conditions of the above three models, and compare the result with SSA through analogue simulation. It shows that the antenna array based on EVS performs better in terms of correlation suppression.Fourthly, by deriving the function of channel capacity of MIMO antenna system deployed with different antenna array models, the performance of each system can be shown visually according to the angular parameters.