The rapid growth of 5G millimeter-wave (mmWave) networks demands compact, low-profile, and efficient performance of multiple input multiple output (MIMO) antennas capable of supporting high data rates, reduced latency, and polarization diversity. This work presents a compact and low-profile dual-sense circularly polarized (CP) quad-port MIMO antenna particularly designed for use in 5G mmWave technology. The proposed single antenna employs a symmetric feed network incorporating a folded and stepped impedance microstrip line, a via-less coplanar waveguide (CPW) -fed monopole extension with an F-shaped patch, and a modified ground structure (MGS). This configuration enables efficient excitation of orthogonal modes for dual-sense CP across two distinct frequency bands. The four MIMO radiators, implemented on a single-layer low-cost substrate and arranged orthogonally, achieve high isolation through a cross-shaped isolator. The overall antenna size is \ (1. 87 ₀ 1. 87 ₀ 0. 019 ₀\), where \ (₀\) representing the free-space wavelength corresponding to 28 GHz. Simulated dual-sense impedance bandwidths are 26. 08–28. 41 GHz and 29. 89–31. 06 GHz, with isolation levels better than 21. 5 dB and 18. 4 dB, respectively. The antenna produces left hand circular polarization (LHCP) in the lower frequency band and right hand circular polarization (RHCP) in the upper frequency band, with axial ratio bandwidths (ARBW) below 3 dB at 27. 53–28. 16 GHz and 30. 13–30. 81 GHz. At broadside, the antenna attains maximum gains of 5. 9 dBic at 28 GHz and 4. 0 dBic at 30. 7 GHz, while maintaining radiation efficiencies above 80% across the operating frequency bands. An equivalent circuit model (ECM) is developed to clarify the operating principles. Close correspondence is observed between the simulated and experimental outcomes. Diversity performance is significantly enhanced, with low envelope correlation coefficient (ECC), balanced mean effective gain (MEG), high diversity gain (DG), and low channel capacity loss (CCL), ensuring reliable and high-capacity mmWave 5G communication.
Hayat et al. (Sat,) studied this question.