Based on the equivalent formula of channel capacity of MIMO system, the optimal value is evaluated among the number of antennas, antenna spacing, angle spread and channel capacity, and impact of antenna correlation on MIMO channel capacity caused by the three space factors studied. Simulated results reveal that, increase of transmitting or receiving antennas can both significantly enlarge the channel capacity of MIMO systems, the latter of which shows better effect. But excessive increase of antennas will reduce the antenna spacing and increase the correlation between antennas and as a result the channel capacity will be reduced. Therefore, maximal number of antennas should be used in MIMO design while keeping antenna spacing and angle spread so as to ensure the optimal value of channel capacity.%基于多天线系统的容量等效公式，从空间因素着手，计算多天线系统中天线数量、天线间距、角度扩展与信道容量之间的最优值，并通过数值模拟验证，分析3个空间因素产生的天线相关性对多天线系统信道容量的影响。结果显示，增加发射天线数或者接收天线数都能显著地增加系统的信道容量，其中增加接收天线数比增加发射天线数效果更好。但是在有限的空间一味增加天线数量又会减小天线间距，从而增加天线之间的相关性，进而降低信道容量。因此，在设计多天线工程时，可在一定天线间距和角度扩展情况下，尽可能地增加天线数量，以达到信道容量的最优值。
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