The concept of continuous-aperture multiple-input multiple-output (CAP-MIMO) technology has been proposed recently, which aims at achieving high spectrum efficiency by deploying extremely dense antennas or even continuous antennas in a given aperture. The fundamental question of CAP-MIMO is whether it can achieve much better performance than the traditional discrete MIMO system. In this paper, to model the CAP-MIMO, we use self-adjoint operators to depict the structural characteristics of the continuous random electromagnetic fields from physical laws. Then, we propose a non-asymptotic performance comparison scheme between continuous and discrete MIMO systems based on the analysis of mutual information. We show the consistency of the proposed scheme by proving that the mutual information between discretized transceivers converges to that between continuous transceivers. Numerical analysis verifies the theoretical results, and suggests that the mutual information obtained from the discrete MIMO with widely adopted half-wavelength spaced antennas almost achieves the mutual information obtained from CAP-MIMO.

翻译：近年来提出的连续孔径多输入多输出（CAP-MIMO）技术，旨在通过给定孔径内部署极密集甚至连续天线以实现高频谱效率。CAP-MIMO的核心问题在于其能否达到比传统离散MIMO系统更优的性能。本文为建立CAP-MIMO模型，利用自伴算子从物理定律出发刻画连续随机电磁场的结构特征，进而提出基于互信息分析的连续与离散MIMO系统非渐近性能比较方案。通过证明离散化收发装置间的互信息收敛至连续收发装置间的互信息，验证了所提方案的一致性。数值分析证实了理论结果，并表明采用广泛使用的半波间距天线的离散MIMO所获互信息与CAP-MIMO几乎持平。