Performance Parameter Improvement Technique in Multiband CPW‐MIMO Antenna Using Metasurface‐Inspired Radiation Backplane.

ABSTRACT This article introduces a metasurface‐integrated CPW‐fed dual‐band 2 × 2 MIMO antenna designed for sub‐6 GHz 5G and Wi‐Fi 6E applications. The proposed 4 × 4 metasurface‐inspired radiating structure enhances antenna performance and exhibits dual‐polarization across two frequency bands. The slot‐cutting technique is used to achieve the targeted frequency bands, thereby improving impedance matching at the resonant frequencies. The entire antenna occupies a compact size of only 40 × 40 × 1.6 mm 3 (0.33 λ 1 × 0.33 λ 1 × 0.013 λ 1), where λ 1 is the wavelength at the lowest cutoff frequency of the first operating band. The low‐cost FR4 substrate (relative permittivity = 4.4, loss tangent = 0.02) is used in the antenna design, which resonates at 3.5 GHz for the sub‐6 GHz NR 5G band and at 7.5 GHz for Wi‐Fi 6E. Initially, diversity techniques ensure an average isolation of at least −20 dB across the bands. When the metasurface backplane is integrated, mutual coupling is significantly reduced. The mutual coupling is improved by 35 dB, reaching −55 dB in the first band. In the second band, mutual coupling is enhanced by 20 dB, reaching −48 dB. Along with the reduction in mutual coupling, the gain increases by 2.1 and 3 dB at the first and second resonant frequencies, respectively, achieving peak gains of 5 and 8.3 dBi. Additionally, the radiation efficiency improves by 34% and 40% at the respective bands. The simulated results are validated through measurements, demonstrating a diversity gain (DG) of 9.98 dB or higher, an envelope correlation coefficient (ECC) of 0.02 or lower, and excellent MIMO performance such as channel capacity loss (CCL) and the total active reflection coefficient (TARC), with CCL values below 0.4 bits/s/Hz and TARC under 10 dB in both the frequency bands. This antenna is suitable for use in portable devices supporting sub‐6 GHz 5G and Wi‐Fi 6E applications.