Research And Design Of Ka Band Optical Zoom Reflector Antenna

Placing communication satellites into highly elliptical orbits rather than the geostationary orbit(GEO)has many advantages for countries at high latitudes.When the satellites traveling in highly elliptical orbits,the coverage area of satellite antennas varies in different positions.To guarantee the transmission quality and better regional coverage,the Half-Power Beamwidth(HPBW)should be varied dynamically,which is also called "zoom".Therefore,"zoom technology" could meet the need for satellite engineering,and it has a very wide application foreground.Aiming at this requirement,this thesis presents the research and design of Ka band optical zoom reflector antennas.Firstly,based on the research status of the zoom antenna,we have classified the zoom antennas according to their types.This thesis also offers a brief analysis of the key technologies involved,and compare the advantages and disadvantages of different technologies.It is found that there is few researchers designing antennas by optical zoom principle.Howard Luh proposed the design of dual reflector zoom antenna,but he did not present the design procedure in detail.Therefore,we introduce the idea of optical zoom into the design and research of the zoom reflector antenna.Second,we summarize the basic theory of reflector antenna and the basic principle of optical zoom.Specifically,we introduce the geometric characteristics of spherical antenna and parabolic antenna,the analysis method of reflector antenna,the paraxial imaging characteristic of sphere and the basic principle of dual lens zoom system,which could provide a theoretical basis for later analysis and design.Next,on the basis of summarizing and absorbing relevant research results home and aboard,we have designed the coaxial and off-axis dual reflector optical zoom antennas.Then,the antenna design methods are summarized,and the selection basis of parameters is analyzed in detail.After that,the simulation model was established by using GRASP software,and the electrical characteristics of the two antennas were compared and analyzed.Finally,based on the principle of optical zoom system,this thesis presents a novel design of coaxial and off-axis three-reflector optical zoom antennas.This structure could avoid moving the feed or the main reflector in the zoom process,which is the disadvantage of the dual reflector zoom antenna.We specifically introduce the design ideas and design steps of the two antennas,and summarize the selection basis of parameters.Similarly,we analyze the performance of the antennas by using GRASP software,and the advantages and disadvantages between the dual reflector and the three-reflector antenna are compared.In addition,we use MATLAB GUI module to design the user interface for calculating the zoom parameters and dynamically displaying the zoom track.