The paper presents the results of a comprehensive study of the characteristics of a microstrip MIMO antenna system intended for application in fifth-generation communication equipment operating within the n79 frequency band (4.4–5.0 GHz). The purpose of the research was to develop a compact 1×2 antenna array on a single dielectric substrate and to evaluate its electrodynamic properties, taking into account factors capable of influencing matching and radiation parameters under real operating conditions. The proposed design incorporates two radiating elements, four excitation ports, and a modified ground plane, which provides enhanced functional stability and improved operational characteristics. Numerical modelling demonstrated that the developed antenna system ensures stable standing-wave ratio values, high antenna gain, and consistent radiation patterns across the entire operating frequency band. Particular attention was devoted to assessing the influence of external environmental effects, especially the formation of a thin water film on the radiating surface. The study revealed that the presence of moisture results in an SWR increase of more than 0.5, a decrease in antenna efficiency, and degradation of radiation characteristics at higher frequencies, highlighting the necessity of employing protective structural solutions when operating under humidity-prone conditions. Additionally, the feasibility of replacing copper with an ideal conductor in electromagnetic simulations was examined. The difference in SWR between the realistic and idealized models did not exceed 0.006, confirming that such a simplification may be applied during early design stages without significant loss of accuracy. An experimental prototype of the antenna was fabricated and tested under laboratory conditions. The obtained measurements demonstrated a high degree of agreement with the modelling results, validating the proposed mathematical model and confirming the practical applicability of the developed MIMO antenna system in next-generation communication infrastructures
A reconfigurable antenna is an antenna with parameters that can be varied according to the requirements of a particular situation. Under variable parameters we can understand the operating frequency range, radiation pattern, polarization, as well as various combinations of these parameters. In this paper, we propose the design of a reconfigurable microstrip antenna with tunable frequency and polarization, and investigate its radiation pattern and polarisation properties. The antenna has compact dimensions and can be used in wireless communication systems operating in the 2–7 GHz range. 5 pin diodes are included into the antenna design to change the resonant frequency and polarization of the antenna by turning the diodes on and off. The simulation of the proposed antenna was performed in the FEKO program and the main parameters of the antenna were obtained. The analysis of the simulation results showed that for the lower part of the studied frequency range (2.05, 2.45 and 3.7 GHz), the polarization is linear. When operating in the higher sub-range (5.4, 5.6 and 5.75 GHz), the antenna is circularly polarized, and the direction of the polarisation vector rotation depends on the connection of the diodes. This ability to switch polarization to orthogonal at the same frequency allows to perform efficient signal reception in the conditions of multipath propagation.
