Design Of Reconfigurable Terminal Antenna Based On Graphene And Varactor

With the development of mobile communication,the demand for information rate of terminal equipment has increased sharply.The number of antennas in the terminal equipment increased to adapt to the complex communication environment.And the trends of miniaturization and full screen lead to the reduction of the space left for antennas.Reconfigurable antenna can dynamically tune the frequency,direction pattern and polarization modes and reduce the number of antennas in the system,so it has become one of the hotspots in the field of antenna design.More and more researchers have explored the reconfigurable antenna,and a variety of new materials have emerged on the basis of the traditional adjustable components.Thus,the design of reconfigurable antenna is gradually not limited to the loading of single adjustable components.Graphene,as a new type of two-dimensional nanomaterial,has the advantages of tunable,thin thickness,good compatibility and flexible loading form.Besides,varactor has the characteristic of continuously tunable compared with other switching devices.In view of the current development of terminal antenna,this thesis researches the frequency,pattern and hybrid reconfigurable antennas and studies the design methods of reconfigurable antenna based on various adjustable components.The main contents are as follows:1.Aiming at the low radiation efficiency of most graphene-loaded antennas,an impedance regulation method of graphene-loaded branches is proposed.The input impedance of multistage cascaded,multistage parallel and composite impedance graphene loaded branches are explored which can solve the problem of antenna radiation efficiency loss under the graphene loading.2.Based on the impedance regulation theory of graphene-loaded branches,a frequency reconfigurable mobile phone antenna is designed.A composite impedance network is loaded on the middle of the LOOP antenna in parallel.The composite impedance network consists of 12 parallel graphene pads and 12 transverse graphene pads on T-shaped branches.Switching the resistance of graphene between 1000 Ohm and 10 Ohm can enable the antenna to operate at 1.84 GHz and 2.4GHz,respectively.Besides,the radiation efficiency of the antenna at low frequencies has increased by 2.1d B.The efficiency loss problem of antenna under graphene loading is solved preliminarily,which provides support for the application of graphene in reconfigurable antenna.3.A graphene-based pattern reconfigurable WIFI antenna is proposed.The antenna is based on a Vivaldi antenna and two dipole antennas,which is excited by a reconfigurable feeding network loaded with three graphene.The resistance of each graphene can be switched between 1000 Ohm and 10 Ohm,and the antenna that has 0° and ±90° three adjustable beams is realized.A WIFI antenna with agile frequency and direction pattern is proposed,which realizes frequency tuning of 2.15-2.4GHz by the loading of varactors on the horizontally polarized omnidirectional antenna.The radiation pattern is controlled by14 directors and 14 reflectors around the frequency reconfigurable antenna,so that the antenna can be switched between omnidirectional and directional radiation states.In the directional radiation state,the directional pattern scanning can be realized in a horizontal range of 360° with an angular resolution of 25.7° by adjusting the directors and reflectors,which increases the flexibility of frequency and pattern control of the traditional reconfigurable antenna.