Jiarun Hu

We provide an electromagnetics (EM)-complete wireless system modeling framework for line-of-sight (LoS) communications, integrating Active Element Pattern (AEP)-based Infinitesimal Dipole Modeling (IDM) with dyadic Green’s function (GF) representation of EM wave propagation in practical generic MIMO links with arbitrary mutual coupling between the transceiver’s antenna elements. This novel AEP-IDM-GF methodology addresses three fundamental limitations of standardized models: (i) full-wave characterization of mutual coupling, (ii) incorporation of dyadic GFs beyond conventional spherical wave propagation physics, and (iii) polarization-complete channel representation. Among the main contributions of this work is the first complete derivation and decomposition of the MIMO channel matrix in terms of currents and free-space Green’s functions: we establish a rigorous integral representation that fully accounts for EM mutual coupling and introduce a novel decomposition of the channel matrix into isolated and mutual-coupling-induced components, which provides a foundational tool for quantitatively analyzing the effects of wave propagation and coupling effect. An efficient specialized implementation based on the IDM is also presented and compared with conventional full-wave EM solvers. The framework achieves sub-1◦ phase coherence and 0.1 dBm near-field (NF) power response fidelity relative to full-wave EM simulations, while maintaining computational efficiency with speedups of up to 42.9× compared to full-wave method of moments (MoM) simulations. This combination of accuracy and efficiency exposes inherent limitations in 3GPP models that significantly overestimate capacity in high-SNR regimes and underestimate performance in strong coupling configurations and low-SNR regimes. Numerical analysis of selected examples comprised of dense MIMO configurations demonstrates that mutual coupling interacts with full-wave spatial correlation to redistribute energy across eigenmodes: while spatial correlation leads to extreme concentration in dominant modes, mutual coupling of specific array configuration mitigates this concentration and improves energy spread to moderate-order modes, thereby increasing effective degrees of freedom (eDoF) and enhancing multiplexing capability, though with constraints on absolute multiplexing gain at high SNR due to fundamental spatial correlation limits.

We provide an electromagnetics (EM)-complete wireless system modeling framework for line-of-sight (LoS) communications, integrating Active Element Pattern (AEP)-based Infinitesimal Dipole Modeling (IDM) with dyadic Green's function (GF) representation of EM wave propagation in practical generic MIMO links with arbitrary mutual coupling between the transceiver's antenna elements. This novel AEP-IDM-GF methodology addresses three fundamental limitations of standardized models: (i) full-wave characterization of mutual coupling, (ii) incorporation of dyadic GFs beyond conventional spherical wave propagation physics, and (iii) polarization-complete channel representation. Among the main contributions of this work is the first complete derivation of the MIMO channel matrix in terms of currents and free-space Green's functions, independent of any specific numerical method, by employing an integral representation approach while fully taking into acount EM mutual coupling. An efficient specialized implementation based on the IDM is also presented and compared with conventional full-wave EM solvers. The framework achieves sub-1◦phase coherence and 0.1 dBm near-field (NF) power response fidelity relative to full-wave EM simulations, while maintaining computational efficiency with speedups of up to 42.9× compared to full-wave method of moments (MoM) simulations. This combination of accuracy and efficiency exposes inherent limitations in 3GPP models that significantly overestimate capacity in high-SNR regimes and underestimate performance in strong coupling configurations and low-SNR regimes. Numerical analysis of selected examples comprised of dense MIMO configurations demonstrates that mutual coupling enhances dominant eigenmodes while suppressing higher-order modes, thereby increasing effective degrees of freedom (eDoF) through EM energy concentration with the cost of constraining the theoretical multiplexing gain in high-SNR regimes.