Research On Beam Steering Holographic Metasurface Leaky-wave Antenna Based On Liquid Crystal

In recent years,with the rapid development of satellite communication system,the demand for beam steering antenna is increasing.At the same time,beam steering antenna are required to be of a higher standard.Compared with the traditional mechanical beam steering antenna,the electronically controlled beam steering antenna has the advantages of fast scanning speed and high scanning accuracy,which has attracted many scholars' attention and research.The leaky wave antenna itself has the characteristics of beam scanning with frequency.By loading electrically modulated materials on the leaky wave antenna,the beam steering leaky wave antenna at fixed frequency can be designed to satisfy the demand of modern satellite communication system.In order to realize the beam steering leaky wave antenna at fixed frequency,this thesis studies the beam steering holographic metasurface leaky wave antenna based on liquid crystal as follows:Firstly,the beam control method based on holographic principle is studied.In order to modulate the beam of the antenna effectively,the beam control method based on holographic principle is studied on the basis of leaky wave antenna.The amplitude modulation beam control method and the binary modulation beam control method are proposed,and the advantages and disadvantages of the two modulation methods are compared and analyzed.Secondly,two kinds of metamaterial elements loaded with liquid crystal materials are designed.Firstly,the electromagnetic characteristics of the liquid crystal are introduced.And based on the electrical modulation characteristics of the liquid crystal materials,the liquid crystal material is introduced into the metamaterial antenna elements.The first antenna element is a rectangular slot,which fills the whole liquid crystal between the rectangular slot and the radiation element;the second antenna element is a complementary electric resonance(cELC),and the liquid crystal material is filled between the CELC slot and the metal ground.By applying an electric field to both ends of the liquid crystal,the two antenna elements can independently control the radiation energy.Thirdly,two kinds of one-dimensional liquid crystal holographic metasurface leaky wave antennas are designed.Firstly,the designed antenna elements are composed into an array,Based on the beam control method of holographic principle,the radiant energy distribution of each element on the antenna surface is designed according to the different beam direction,and the corresponding feed network is designed for each antenna.By changing the bias voltage at both ends of the liquid crystal material on each antenna element,both antennas both antennas can achieve the large Angle beam scanning characteristics.Fourthly,two kinds of two-dimensional holographic metasurface leaky wave antennas based on liquid crystal are designed.Firstly,the one-dimensional antenna array is extended to two-dimensional antenna array.Combined with the beam control method based on the two-dimensional holographic principle,the two-dimensional holographic metasurface leaky wave antenna based on liquid crystal can be scanned at any azimuth angle.On the basis of realizing the beam scanning of the antenna,the circular polarization holographic metasurface antenna is explored.By changing the holographic distribution formula and the structure of metamaterial antenna element,the circular polarization characteristic of the antenna is realized.