Coupling-Induced Capacity Analysis of Holographic MIMO Communication System

In recent years, the multiple-input-multiple-output (MIMO) technology has emerged as a focal point, due to the escalating demands for increased communication capacity. Holographic multiple-input-multiple-output (HMIMO), which aims to use dense antenna arrays to record and reconstruct the amplitude and phase of EM wavefronts, offers significant potential for the enhancement of the spectral efficiency. However, in HMIMO system, since the spacing between the array elements is significantly reduced (i.e., << λ/2), the mutual coupling between them is inevitable, which needs to be taken into consideration when evaluating the system performance. In this paper, the impact of mutual coupling on antenna radiation efficiency for both 1D linear antenna array and 2D surface array is investigated. Then, the capacity gain of a HMIMO system, taking into account the influence of coupling, is analyzed. Results show that, if the number of receive antenna elements is fixed, for a linear array, HMIMO communication systems cannot provide capacity gains. For a surface array, the capacity of HMIMO system is 2~3 bps/Hz lower than that of MIMO system.