This study proposes a compact four-port multiple-input multiple-output (MIMO) antenna system to operate within a frequency range of 3.2-5.75 GHz to serve in 5G new radio (NR) sub-6 GHz n77/n78/n79 and 5 GHz WLAN with good impedance matching. To increase the isolation between the MIMO antenna elements with low complexity and cost, the antenna elements are orthogonally oriented to each other with distance spacing of 0.3λ˳ between elements, including electromagnetic bandgap (EBG) structure, defected ground structure (DGS), capacitive elements (CE), and neutralization line (NL). The simulation results show that the measured mutual coupling between the array elements is improved from −20 to −45 dB. The envelope correlation coefficient is enhanced. In addition, the diversity gain, mean effective gain, and total active reflection coefficient are improved simultaneously. The suggested structure has been designed on CST Microwave Studio 2019. The antennas' overall dimensions for all methods are the same as they approach 46 mm × 46 mm × 1.6 mm. The measured gain of the proposed designs ranges from 6 to 9 dBi, and the radiation efficiency approaches 90%. The antennas are fabricated and tested, where better experimental results are noticed compared to the simulation results. Our antennas are designed over FR-4 substrate with a noticeable cost reduction. Each antenna element has a dimension of 15 mm × 23 mm × 1.6 mm. An "EL" slot into the radiating element and two identical stubs coupled to the partial ground are used to improve the impedance matching and radiation characteristics across the bands of interest. The isolation decreases by 22 dB using the EBG method, reaching the value of −65 dB. Meanwhile, the isolation decreases by 19 dB using the DGS method, reaching −60 dB. Due to gaps between adjacent unit cells and the capacitance generated from the dielectric gap between the top metallic patch and ground plane, the EBG method gives the best results. However, in the CE method, capacitances resulting from the four transmission lines in the bottom side of the antennas (parasitic elements) decrease the isolation by 15 dB, reaching −40 dB. NL method makes the isolation to reach the value of −55 dB. Accordingly, the proposed antenna arrays support 5G NR sub-6 GHz n77/n78/n79 and 5 GHz WLAN, where n77 (3.3-4.2 GHz), n78 (3.3-3.80 GHz), and n79 (4.4-5.0 GHz) require a wideband coverage that extends from 3.3 GHz to at least 5.0 GHz.

In this paper, a compact two-port MIMO antenna array system is described. The antenna array spans the range from 27 to 40 GHz, whereas the impedance of the antenna element is matched at 50 Ω. The gain of the antenna element is between 5.5 and 8.5 dBi, and its radiation efficiency is between 65 and 90%. With high impedance matching for 5G MMW (Millimeter Wave), particularly at 28 GHz and 38 GHz, the 2-port antenna array operates in the frequency range of 27–40 GHz. The suggested MIMO array operates effectively with a gain of approximately 10 dBi and a radiation efficiency of approximately 95%. The antenna array's overall dimensions are a length of 55.27 mm, a width of 27.635 mm, and a depth of 1.6 mm with partial ground. A FR-4 substrate is used in the antenna's fabrication, greatly reducing the cost. In the antenna array, a decoupling surface is used between the antennas, with orthogonality being maintained between the ports to reduce mutual coupling. The results of the modelling show a reduction in the measured mutual coupling between array ports of less than − 35 dB. An envelope correlation coefficient (ECC) of less than 1 × 10–4 is preferable. Additionally, the channel loss capacity is less than 0.3 bits/s/Hz, the mean effective gain is approximately − 6 dB, and the total active reflection coefficient is upgraded to be less than − 30 dB. Moreover, a diversity gain of approximately 10 dB is achieved. The proposed construction was created using CST Microwave Studio 2019. When the antennas are constructed and tested, the experimental outcomes surpass those of the simulation. Each antenna element is 27.635 mm long, 27.635 mm wide, and 1.6 mm thick. Slots in the radiating circular patch antenna element could be used to improve the radiation characteristics across the intended bands. The parametric study specifies that the distance between the antenna elements should be 0.5 λ, where λ is the operational wavelength.

In most of the crowded cities and with the vast increase of capacity‐hungry applications, operators tend to use capacity enhancement techniques such as MIMO, OFDMA etc. Authors’ problem is completely different. In several rural areas, the needed capacity is very low and the single base station has a standard capacitance which is considered over sufficient with respect to the required spectrum in these rural areas. The solution to make the best use of such resources is to design a two‐sector antenna with a single feed. The proposed antenna covers two areas simultaneously. Thus, the spectrum capability is distributed over two sectors that share the available frequency resources. If the total area is small enough, then the base station power will be saved to the half as well as the number of antennas also reduced to the half. Otherwise, the concept of frequency reuse can be applied with minimum base stations. Authors’ antenna is designed over FR‐4 substrate with a noticeable reduction in the cost. A very good agreement between the simulated and measured results is noticed.