Design of Decoupling and Matching Network in Near‐Field Wireless MIMO Using Dipole Antennas for Millimeter‐Wave Applications

Near‐field wireless MIMO (NFWMIMO) links are a promising solution for chip‐to‐chip and board‐level communication at millimeter‐wave frequencies. However, their performance is severely limited by strong mutual coupling and impedance mismatch due to subwavelength antenna spacing. This study presents a circuit‐theoretic framework and a practical design methodology for decoupling and matching networks (DMNs) applied to dense NFWMIMO dipole arrays operating at 30 GHz. Mutual coupling is analyzed using impedance and scattering parameter formulations, along with multiport network theory. LC‐based DMNs are designed for both 2 × 2 and 4 × 4 dipole arrays over the 24–36‐GHz band using full‐wave simulations in Altair Feko and network synthesis in Optenni Lab. The results demonstrate a substantial reduction in mutual coupling, with isolation improvements exceeding 30 dB for dominant coupling paths in the 2 × 2 configuration and notable suppression observed in selected paths of the 4 × 4 array. A trade‐off in impedance matching is observed in higher‐order arrays due to increased coupling complexity. Key MIMO performance metrics, including ECC, diversity gain (DG), and total active reflection coefficient (TARC), show improved behavior after applying the DMN. A fabricated prototype validates the antenna performance, showing reasonable agreement between simulated and measured results. The proposed approach provides a practical solution for enhancing NFWMIMO system performance in compact millimeter‐wave environments.