Square-Shaped Circularly Polarized MIMO Dipole Antenna With Dual-Sense Characteristic for 5G Application

Abstract

A new approach of dual-sense circularly polarized (CP) MIMO dipole antenna design is presented in this study, which is suitable for Sub-6 GHz 5G applications, explicitly targeting the n78 frequency band (3.3–3.8 GHz). The proposed antenna comprises four printed dipole elements arranged orthogonally on a $105\times 105 \times 23$ mm3 substrate. Each balun-fed dipole pair is excited through a 3-dB branch-line coupler. This technique generates high purity in right-handed circular polarization (RHCP) and left-handed circular polarization (LHCP) modes. By simultaneously activating any two of the four ports of the MIMO antenna, the design accommodates multiple polarization configurations, offering advanced polarization diversity through RHCP-RHCP, LHCP-LHCP, RHCP-LHCP, and LHCP-RHCP modes. The proposed design achieves an impedance bandwidth of 3.08–4.03 GHz for RHCP and 3.12–4.06 GHz for LHCP, respectively, with CP performance in the entire operating frequency band. With peak gains of 7.15 dBic for RHCP and 6.80 dBic for LHCP, and axial ratio values below 1.32 dB across the operating band, the antenna exhibits exceptional performance. Furthermore, isolation levels exceed 23.8 dB for co-polarization ports and 30.1 dB for cross-polarization ports, ensuring minimal mutual coupling. The envelope correlation coefficient (ECC) is below 0.0021 for co-polarization ports and below 0.0007 for cross-polarization ports, confirming excellent MIMO performance. Simulated and measured results strongly agree, validating the design’s robustness and suitability for Sub-6 GHz 5G applications. Its compact structure, wide bandwidth, high gain, and superior CP purity make it an ideal candidate for next-generation wireless communication systems.

Keywords

• Circular polarization
• dipole
• dual-sense
• 5G
• MIMO