Electromagnetically Realizable Super-Directive Hmimo Arrays for Near-Field 6G Communications

Super-directive holographic massive multiple-input multiple-output (HMIMO) antenna arrays are a key enabler for near-field beamforming, spatial focusing, and interference suppression in sixth-generation (6G) wireless systems. Although classical super-directive synthesis can, in principle, deliver extreme directivity, its physical realization is constrained by electromagnetic limits such as excessive reactive energy storage, bandwidth collapse, impedance mismatch, mutual coupling, and radiation-efficiency degradation. This paper presents an electromagnetic-aware design and validation framework for physically realizable near-field super-directive HMIMO arrays. The framework combines near-field array theory with fundamental bounds on directivity, quality factor (Q), sidelobe behavior, and realized gain, while explicitly enforcing practical constraints on excitation magnitudes, matching (S11), and efficiency. Full-wave electromagnetic simulations (CST Microwave Studio) are used to validate optimized planar HMIMO arrays across multiple aperture sizes. Results show that, when electromagnetic constraints are embedded in the design process, super-directive HMIMO arrays can generate highly focused near-field beams with stable impedance response and acceptable radiation efficiency, supporting practical 6G deployments in user-centric communications, integrated sensing and communication, localization, and wireless power transfer.