###### Abstract
Each pair functions at a certain resonant frequency. Each pair operates at a specific resonant frequency, two linearly polarized elements are assumed, which are each rotated by 90\({}^{\circ}\), thus offering a dual polarization operation mode. Four different random array types were contrasted in [18]. Specifically, the array factor's mean and variance calculations were derived. Hence, offering a partial statistical characterization that enabled highlighting certain key characteristics of random arrays and linking them to the elemental count and aperture of the array. In addition, additional weight was also placed on the experimental part because there was not a straightforward analytical tool that worked well enough, especially when considering the side-lobe level. For achievement purposes, Monte Carlo simulations were carried out in order to experimentally construct the side-lobe distribution as a function of the quantity of radiators and the typical distance between neighbouring radiators. The experimental results obtained showed that random arrays with the freedom to set restrictions on the minimal distance between adjacent components were achieving performance comparable to that of other techniques without such restrictions. However, the former were preferred as they can reduce the impacts of reciprocal coupling by reducing the likelihood that nearby radiators will be closer together than a predetermined minimum distance. In order to enhance the isolation among the radiating elements, several approaches are considered. These techniques include isolating structures insertion such as neutralization lines (NL), Defected Ground Structures (DGS), Electromagnetic Bandgap Structures (EBG) and Artificial Magnetic Conductors (AMC) [19; 20; 21]. An antenna for mobile terminals with a wideband printed dual-antenna is examined in [19]. The dual-antenna is printed on a printed circuit board and consists of two symmetric antenna elements and three neutralization lines (NLs). The mutual coupling is reduced throughout a broad frequency spectrum by the three NLs. S-parameters, surface current distributions, and a simplified equivalent model are used to assess the three NLs' functioning mechanisms and provide simple guidelines for optimizing them. With the insertion of isolating structures, a 6 dB enhance isolation was achieved. Similarly, in [20], a DGS was considered in order to implement effective isolation between units of a multi-input multi-output (MIMO) antenna. Specifically, a two-element antenna with coaxial feeding that operates at 5.8 GHz. The middle of the two elements created as a DGS had a zigzag groove placed into it to less mutual coupling between the parts. A scattering matrix, including the reflection coefficient S11 and transmission coefficient S21 between two element ports, was tested to confirm this design. The antenna's diversity gain, envelope correlation coefficient (ECC), current distribution, and radiation pattern were all simulated and tested at the same time. The results revealed that using a DGS reduced mutual coupling by 28.8 dB, and the ECC was less than 0.02. An innovative EBG design and a hair-pin-shaped DGS are used in combination in [21] to achieve excellent isolation between two-element MIMO antennas operating at 27.5-28.35 GHz. The suggested EBG provides a broad frequency band-gap between 26.2 and 32.03 GHz by being developed on layered dielectric substrates. In order to minimise surface wave coupling, a 2 \(\times\) 3 array of the EBG is placed between two electromagnetically coupled radiating patches. A SIW feeding network and cavities are selectively integrated into the proposed antenna for boosting the radiation output and decreasing feed losses. When contrasted to an unloaded MIMO antenna, EBG exhibits an average isolation improvement of 13.9 dB within the 5G spectrum. In [22], an eight element MIMO system is presented in which the isolation is increased up to 15 dB with insertion of isolating structure. Similarly in [23] a DGs technique is used to enhance isolation up to 21 dB.