Defocus Analysis And Optimal Design For Photonic Crystal Cassegrain Antenna System

At present, the communication form is microwave communication, no matter what is a satellite or terrestrial base station communication, they are based on microwave.However, the wavelength of microwave is too long, so the size of the antenna is also relatively large, bulky equipment, power consumption is correspondingly high.With communication increasingly demanding now, greatly increase the data capacity, but the microwave is difficult to satisfy the future requirements.In order to solve the problem of microwave communication capacity, many countries have turned to the light wave band in inter-satellite communications.Optical antenna is important device in space optical communication system. If the antenna have defocused by external impact, This space optical communication system will have a significant impact, even lead to space optical communication does not work properly. Due to a variety of disturbance in outer space, it is very easily lead to defocusing of the optical antenna system, Therefore it is necessary to research about defocuing antenna. This paper will study the defocusing effect on space optical communication systems in detail. Currently transmission efficiency of the optical antenna is so low in space optical communication, so it need to optimize the design for optical antenna, design better optical antenna and improve the quality of space optical communication.This paper studies the various defocusing properties of photonic crystals Cassegrain antenna, the various forms of defocusing are discussed in detail, the main contents are as follows:(1) Introduce alignment technology of semiconductor laser in the space optical communication, described the structure of a semiconductor laser and light-emitting mechanism and propagation property, Given the method of collimated Gaussian beam.(2) Described band gap properties photonic crystals, design a band gap for space optical communication channel frequency. It will be used to the surface of the Cassegrain antenna, to enhanced reflection of the antenna, preventing deformation of antenna. It is helpful to maintain the stability of the system structure.(3) It have studied about various defocusing characteristics in Photonic crystals Cassegrain optical antenna. Longitudinal and vertical defocusing of the primary mirrorand secondary mirror secondary mirror have researched and analyzed respectively.analysis the output of the beam waist and divergence angle of the laser beam in defocusing antenna. It have studied the defocusing effected on emission and transmission efficiency of the antenna.(4) Due to low compression ratio for photonic crystals Cassegrain optical antenna,so it optimized the structure parameters of photonic crystal Cassegrain optical antenna.The optimal structure will reduce greatly the emission beam divergence angle,increasing the distance of space optical communications.