Optically Controlled Frequency Reconfigurable Antennas For Cognitive Radio Systems

With the rapid development of wireless communication technology,it brings convenience to people's lives,but also brings a thorny problem: radio frequency spectrum allocation of resources will be increasingly scarce.Cognitive radio system is considered to be a way to improve the efficiency of spectrum utilization.Its antenna consists of two parts,namely,ultra-wideband sensing antenna and narrowband reconstruction.The reconfigurable antennas will change to the spare frequency band,while the ultra-wideband antenna perceives an idle frequency band.In this thesis,we focus on the research of frequency reconfigurable antenna for cognitive radio system,and propose two novel optically controlled frequency reconfigurable antennas for cognitive radio system with high isolation.The main research contents of this paper:Firstly,in this paper those are introduced,such as the present situation,significance of radio frequency antenna reconfigurable for cognitive radio system and the related theory for antenna design including the basic principle of antenna radiation,the parameters of antenna,the principle of silicon,light's influence on silicon film's conduction properties,etc.Then,an optically controlled frequency reconfigurable antenna with two ports is presented for cognitive radio system.This antenna is composed of two parts,an ultrawideband antenna using dodecagon monopole covering 3.1-10.6GHz and a T shape reconfigurable narrow-band antenna.The narrow-band structure can operate three frequency bands of 7.0-8.6GHz,4.7-5.4GHz and 3.4-3.7GHz while the two switches using silicon film are in different states.Finally,another optically controlled frequency reconfigurable antenna with two ports is presented for cognitive radio system.The UWB sensing part can cover 2.7-12GHz;reconstruction part of narrowband can operate at 3.3-3.8GHz,4.9-5.5 GHz and 7.4-8.8 GHz at different time.The antenna is restructured by changing the matching between the ground and the reconstruction part.In this paper,the silicon photoconductive switches are adopted,which are easy to integrate with the antenna and the effect on antenna radiation is small.