Research On Design Method Of Compact Field Feed System Based On Gaussian Beam Pattern Analysis

Quasi-optical technology is a popular research direction in the millimeter wave,submillimeter wave,and terahertz frequency bands.Quasi-optical systems have the advantages of wide operating bandwidth,low transmission loss,high power withstand,relatively low processing difficulty,and can be frequency multiplexed,polarization multiplexed,and are widely used in deep space exploration,radar guidance,terahertz imaging,and other fields.In recent years,according to the development trend of quasi optical systems at home and abroad,the research direction of quasi optical systems tends to be high-frequency and complex,so the requirements for design,simulation,and testing of quasi optical systems have also increased.The compact field antenna measurement technique is one of the important techniques for high-frequency antenna testing.It can generate quasi planar waves in a limited space to provide reception to the antenna under test,and is an effective method for testing large antennas in the quasi optical frequency band.The performance of the compact field system directly affects the test results,so it is very meaningful to study and design a high-performance compact field test system.This article will focus on the improvement of important indicators and structural optimization of the compression field system,and compare it with the simulation results of GRASP simulation software to verify the feasibility and accuracy of this method.The research content package of this article is mainly divided into the following two aspects:1.A fast design method for the compact field of low cross polarization three mirrors based on Gaussian beam pattern analysis is proposed.The Gaussian beam mode analysis algorithm will not consider the low cross polarization condition that the structural parameters of the compact range need to meet,and the Particle swarm optimization algorithm can quickly optimize the structural parameters in limited space.On the premise of the same static zone cross polarization performance,compared with the traditional modeling and simulation re optimization method,the computational efficiency is significantly improved,and it is universal and universal.The compact field structure can be flexibly designed according to the actual situation.2.In order to improve the utilization rate of the static zone in a single mirror compact field system,a feed design method based on pattern shaping is proposed.This method uses the Gaussian beam pattern decomposition theory to decompose the ideal feed pattern of a compact field system into a set of Gaussian beam patterns of different orders,and then designs this pattern based on the Gaussian beam pattern analysis method,making the output field in this mode fit into an ideal feed pattern.Finally,the synthesized pattern of Gaussian beam mode is compared with the ideal feed pattern,and the difference between the two central regions is less than±0.5dB.In GRASP software,the directional patterns of the two are respectively fed to the compact field of a single mirror.From the simulation results,it can be seen that the design method proposed in this paper can achieve a static zone amplitude jitter of less than 1 dB,aperture utilization ratio greater than 60%,and phase jitter of less than 7.5° for the primary mirror output field.