A review of diverse MIMO antennas design for Cognitive Radio applications

Cognitive Radio (CR) systems require antennas that exhibit adaptability, enabling the efficient utilization of available spectrum while ensuring optimal operational efficiency under dynamic real-time conditions. To fulfill these criteria, multiple input multiple output (MIMO) antennas must possess the capability for broad or multi-band frequency operation, integrate reconfigurability, maintain compact architectural designs, and achieve significant isolation between elements to mitigate mutual interference. This review critically assesses various classifications of MIMO antennas, including ultra-wideband (UWB) antennas, dual UWB antennas, filtenna, and reconfigurable antennas, and investigates methodologies for attaining spatial, polarization, and pattern diversity. Sophisticated optimization methodologies and simulation tools are applied to enhance antenna performance, with evaluations centered on crucial parameters such as return loss, gain, bandwidth, and diversity gain. Furthermore, the review addresses the challenges associated with the integration of MIMO antennas into CR platforms, encompassing interference management and the maintenance of consistently high performance levels. In projecting future advancements, emphasis is placed on the significance of smart materials, innovative fabrication techniques, and ML methodologies in the enhancement of next-generation CR applications. This review also highlights emerging research trajectories and potential avenues in the development of MIMO antennas for future wireless communication systems.