Study Of Bistatic Cylindrical Near-Field Scattering Measurement Method Based On Plane Wave Synthesis Technique

In recent years,much research on planar near-field measurements are performed,while relatively few researches on cylindrical near-field measurements are performed.Compared with the planar near-field measurements,in this thesis,the truncation errors caused by finite scan plane can be greatly reduced by means of cylindrical near-field measurements.Bistatic cylindrical near-field scattering measurement based on plane wave synthesis technique is studied by means of the combination of theoretical analysis and computer simulation.The main work of this thesis are as follows: Firstly,in the study of two-dimensional problem,the formulas for plane wave synthesis based on the least square method with the circular array as a model derived,and the amplitude and phase distribution of the quasi-plane wave are calculated.Then the plane wave synthesis based on the least square is applied in bistatic cylindrical near-field scattering measurement.With an infinitely long ideal conductor cylinder as the target under test,computer simulation is performed and the results are compared with the near-field to far-field transformation results based on the cylindrical wave expansion method and results calculated theoretically.Secondly,the genetic algorithm is combined with the least square method to furtherly optimize.in the case that scan cylinder is finite.The cosine window function is utilized and optimized for the near-field to far-field transformation cylindrical wave expansion method.The calculation results show based on the truncation error caused by the finite scan cylinder can be effectively reduce by optimizing the excitation weights obtained by the plane wave synthesis based on least square method with genetic algorithm.At the same time,the calculation results are compared with the results obtained by processing the scattered near-field data with the weight of optimized cosine window function in traditional cylindrical near-field to far-field transformation.Finally,in the three-dimensional problem,by means of the theory of plane wave synthesis based on least square method,the electric dipoles arranged orthogonally in the cylinder scan surface are used as scan probes to synthesize quasi-plane waves and the application in bistatic cylindrical near-field scattering measurement is studied by theoretical analysis and computer simulation with the ideal conductor ball as the target under test.The scattered near-field data are obtained by theoretical calculation,and then the far-field bistatic RCS are obtained by cylindrical near-field transformation for plane wave synthesis based on least square method and traditional near-field to far-field transformation based on cylindrical wave expansion method respectively and compared with the theoretical far-field bistatic RCS.The calculation results show that the results obtained by the least square method are RCS pattern obtained by the least square method better than the results obtained the traditional cylindrical wave expansion method.The space and the theoretical space RCS pattern drawn for comparison,which confirms the advantages df the least square method.The results of computer simulation show that compared with the traditional near-field to far-field transformation method based on cylindrical wave expansion,the method presented in this thesis can obtain better accuracy in the case that the size of scan cylinder is finite.