Antennas in Cognitive Radio Systems for 5G Networks: Challenges and Review
In CR systems, signal processing is moved as far as possible to the digital part. This makes from the physical interface one of the most challenging parts of the architecture. In this chapter, different CR architectures are described from antenna point of view. Key components of the front-end RF are identified with the associated antenna design challenges. Then, a state of the art of the most recent antenna systems proposed for CR is presented. It will be shown that strong constraints make antennas subject to several physical limitations. Metamaterials have proved to be helpful for overcoming these limitations. Finally, we present one of our recent antenna designs which is inspired from metamaterials and a good candidate for spectrum sensing operations.