New Fresnel Optical Antenna Design

Free space optical communication,generally using a laser as a carrier,is a wireless communication method for transmitting information in a free space.Compared with traditional radio frequency communication,wireless communication,free space optical communication has the advantages of good confidentiality,wide spectrum of use,low power consumption,small size,strong anti-electromagnetic interference,and relatively large transmission capacity.And it's a lot of attention.The Fresnel zone plate is also an important optical component because its structure is composed of transparent and opaque rings interleaved to avoid the problem of half-waveband occlusion in Fresnel diffraction,and under the structure,Compared with ordinary lens imaging,Fresnel can have far-reaching focal distances and can be easily folded.Therefore,Fresnel zone plates have been obtained in ranging,infrared,remote optical communication,and holographic technologies.Wide range of applications.The main purpose of this paper is to design a new type of Cassegrain antenna structure and optimize the Fresnel zone plate.Based on the structure of the traditional zone plate,the phase modulation part is added to make the zone plate possible.A hollow beam with adjustable light intensity and hollow radius can be generated.The phase modulation type Fresnel zone plate is attached to the antenna structure,so that the antenna structure avoids the problem of secondary mirror shielding and reduces transmission loss,thereby improving transmission.effectiveness.In the first chapter,it mainly introduces the research significance of space optical communication and the advantages compared with traditional communication,sorts out the development and trend of space optical communication in recent years,and introduces some recent researches on the related research of Explains the topic of this article and its significance.In the second chapter,we mainly introduce the theoretical knowledge used in the paper,including the characteristics of Gaussian beam and the change matrix theory of Gaussian beam propagation in free space,by passing the Fresnel after the beam passes through the zone plate.The Kirchhoff diffraction integral equations are theoretically explained;and the parameter design methods and points for antenna design are analyzed to convert the subsequent Gaussian beam into hollow vortex light,and provide content design,analysis,research and efficiency discussion through the antenna structure.Theoretical basis.In the third chapter,we mainly analyze the structure of the spiral zone structure zone plate and phase modulation spiral zone plate with phase modulation section.After analyzing the Gaussian beam after two kinds of zone plate The distribution of energy and the trend of change focus on the analysis of the influence of the phase modulation type zone plate and the parameters of the phase modulation on the light transmission.In the fourth chapter,mainly from the application of the two structures of the zone plate to the antenna structure,according to the already designed antenna structure,redesign the required zone plate structure,and attach the zone plate structure to the antenna main mirror.Through the simulation analysis of the new structure of the antenna transmission efficiency improvement.