Study Of Bistatic Cylindrical Near-field Scattering Measurement Method

Near-field measurement technique is an important method in the research field of scattering characteristics of targets at home and abroad,which has a series of advantages such as high measurement precision,large information quantity obtained,short measurement distance and all-weather operation etc.In this paper,the near-field to far-field transformation formulas of bistatic cylindrical near-field scattering measurement method are obtained by near-field measurement theoretical analysis and the method is studied by computer simulation.The main work of this paper are as follows:Firstly,the infinitely long ideal conductor cylinder is used as the target to be measured in this paper.When the ideal plane wave is incident to the target,a known probe is used to scan on a cylinder in the near field region to obtain the scattered near-field data.Based on electromagnetic theory and combined with math method,the two-dimensional spread theory of cylindrical wave and the mathematical relationship between the scattered near-field and far-field RCS of targets is derived in detail.According to the theories derived,this method is computer simulated.We have some useful results and the results show that the method of calculating far-field bistatic RCS by near-field to far-field transformation is correct and valid.Secondly,after analyzing and discussing the results,the scattered near-field data are processed by the weighting method of cosine window function and then substitute it into the near-field to far-field transformation formulas.The calculation results show that truncation errors caused by finite scan cylinder can be effectively reduced and improved the measurement accuracy by this process method.Then,the parameters of cosine window function are optimized by Genetic Algorithm(GA)so that we obtained the best parameters and the best calculated results.Finally,the ideal conductor ball is used as the target to be measured.When the ideal plane wave is incident to the target,a known probe is used to scan on a cylinder in the near field region to obtain the scattered near-field data.the three-dimensional spread theory of cylindrical wave and the three-dimensional mathematical relationship between the scattered near-field and far-field RCS of targets is derived in detail.This method iscomputer simulated and the results show that the method is correct.Some analysis and discuss obout the results are also done at last.