Résumé:
To meet the high-speed demands required by next-generation wireless communications and the extensive expansion of mobile internet worldwide (5G networks and beyond), one solution involves increasing the number of antennas for both transmission and reception in wireless links. This technology is known as Multiple Input Multiple Output (MIMO) technique. Additionally, reconfigurable antenna technology, capable of dynamically adjusting the operating frequency characteristics, can be employed in conjunction with MIMO systems to further enhance the capacity and reliability of wireless communication networks.
This thesis focuses on the study and design of frequency reconfigurable multiantenna
for advanced wireless communications. After introducing Multiple Input, Multiple Output (MIMO) technology, a comprehensive state-of-the-art on frequency reconfigurable multi-antenna and various reconfiguration types is provided. Several prototypes with distinct operational mechanisms were developed and tested. The first prototype is a compact, two-element reconfigurable MIMO antenna with four different operating modes for 5G sub-6GHz and cognitive radio applications. The second prototype is a dual-band 2×2 MIMO antenna offering the necessary flexibility to switch from dual-band to single-band mode and vice-versa. The third prototype is a triple-band two-element antenna capable of operating in any combination of bands involving the three most commonly used wireless standards (WiFi, WiMAX, and WLAN). The fourth prototype is a 2-element SWB MIMO antenna operating between 3.2 - 50 GHz for millimeter-wave (MMW) 5G. The final prototype includes two filtering mechanisms integrated into each radiating element of the initial UWB MIMO antenna to reject the WLAN band (5.15 - 5.8 GHz) and the C INSAT band (6.3 - 7.3 GHz), respectively. The structures were designed and simulated using CST Microwave Studio, fabricated, and measured experimentally. The experimental results concur with those obtained by simulation and validate the different design approaches proposed in this thesis, whether with an integrated reconfigurable operating mode (cognitive radio) or a simple operating mode without a reconfiguration mechanism (5G and 5G sub- 6GHz).
