Research On The Propagation Properties And Regulation Technology Of Quasi-optical Beam

Quasi-optical technology uses bunching propagated electromagnetic wave to transmit the millimeter or sub-millimeter wave signal.Compared with other transmission lines,it has the advantages of lower loss,withstanding higher power,easier manufacture and operating in multi-beam,multi-polarization.In recent years,the quasi-optical technology has been widely researched and applied in many fields,such as radio astronomy system,radar system,deep space detection and so on.Quasi-optical Gaussian beam theory is the guided wave or transmission line theory of quasi-optical technology.It's fundamental and viatal of studying the propagation characteristics of quasi-optical Gaussian beam and its low loss regulation to promote the development of quasi optical technology.In radar systems,monopulse technology,as a precision angle measurement technology,has been widely used in all kinds of precision guided radar systems.In addition,the sum-difference network,as the core component of the monopulse antenna,determines the performance of the monopulse antenna to a great extent.As a result,it has a high research value.So far,the monopulse antenna at microwave or millimeter wave has been extensively studied,but the research results of monopulse antenna at sub-millimeter wave are very few.On the basis of the predecessors' work,I have studied and summarized the propagation characteristics of quasi-optical Gaussian beam through mirrors based on various face shapes.The mirror image method is introduced to deal with the problem about quasi-optical Gaussian beam reflected by a plane mirror.In addition,there is obvious error in deducing the transformation properties of quasi-optical Gaussian beam reflected by a parabolic mirror with the analytical formula.That means it is not satisfied with the requirements of designing quasi-optical system composed of parabolic mirrors.Therefore,a large number of simulations about the transformation properties of Gaussian beam reflected by a parabolic mirror in the Ka-band are carried out with CST.As a result,the analytical formula is revised with the help of the simulation results and also applicable for W-band.Based on the research of the propagation characteristics and control technology of the quasi-optical Gaussian beam,I optimized the sum-difference network at sub-millimeter waves using the full wave simulation software and FDTD analysis method.By adjusting the structure and the parameters of the sum-difference network,the output waveform is improved and the working bandwidth is increased.In addition,the feed network of quasi-optical monopulse antenna at sub-millimeter waves is researched,including feed horn,beam waveguide transformation structure and quasi-optical faraday rotator,which is in favor of the further research of monopulse antenna at sub-millimeter waves.