| In wireless communication system,antennas play the role of "bridge",they can both radiate and receive electromagnetic waves,thus achieving the purpose of transmitting information.According to the different current distribution,antennas can be roughly divided into two types:standing wave antennas and traveling wave antennas.Travelling wave antenna has a wide operating frequency band and leaky wave antenna(LWA)is one of travelling wave antennas.The biggest characteristic of LWA is that the main beam direction of its radiation pattern can change regularly with the change of frequency,which has the function of beam scanning.It is widely used in the fields where beam scanning is needed,such as microwave imaging,high resolution radar,etc.It can also be used in wireless communication system in closed scene.Beam scanning rate is one of the most important indexes of LWA.Beam scanning rate refers to the angle of beam scanning per unit relative bandwidth of LWA.The low scanning rate means that the LWA requires a large operating bandwidth to scan a wide range of angle,which puts a lot of pressure on the front-end RF circuit of the electronic device.In order to solve the above problems,the scanning rate of LWA is studied deeply in this paper.The main work of this paper is as follows:1.The working mechanism of LWA is analyzed and introduced.In general,the relationship between the phase constant of guided wave and frequency is nonlinear.The theoretical basis of frequency based beam scanning of LWA is described.2.A millimeter wave periodic LWA with high scanning rate and wide scanning angle is proposed.The antenna is a millimeter-wave LWA based on substrate integrated waveguide(SIW)structure.The main innovation of the antenna is the clever combination of split-ring resonator(SRR)and rectangular slot,so as to improve the group delay on both sides of the unit and achieve a high scanning rate.The measured results show that the proposed antenna can work in the band of 32GHz～36GHz,the scanning angle is-56°～+48°,the scanning rate of the relative bandwidth can reach 8.84°/%,and the gain is roughly between 7d Bi and 11 d Bi,which has excellent performance.3.A quasi-uniform LWA with high scanning rate based on composite right/left handed transmission line(CRLH-TL)is proposed.The main innovation is deeply studying the unit equivalent circuit of CRLH-TL,the necessary conditions for achieving high scanning rate are obtained through formula derivation,and then the antenna is designed.The experimental results show that the designed antenna can scan continuously from-31° to +41° in the frequency band from 9.11 GHz to 9.51 GHz,and its relative bandwidth scanning rate can reach 16.76°/%,and the gain is approximately between 6d Bi and 8d Bi.To sum up,this paper mainly explores the beam scanning rate of LWA,and designs two kinds of LWA with high scanning rate.Simulation and laboratory prove that the LWA has good radiation performance,which lays a foundation for the application of frequency scanning antenna based on leaky wave system in wireless communication. |
