Study On Conversion Accuracy In Antenna Spherical Near Field Measurement System

The development of communication technology has promoted the research work of antennas,and the measurement technology of antennas has been continuously improved.For example,satellite communication and the fifth generation(5G)mobile communication all need to use some complex large antennas,array antenna,etc.So the size of the antenna are getting bigger and bigger,and antenna's far-field measurement technology has not met the actual conditions,the near-field measurement technology that has emerged is more and more popular,and the antenna spherical near-field measurement technology is one of the ideal measurement methods in recent years.The main research of this thesis is carried out around the spherical near-field measurement technology.In addition,the research is based on the spherical wave theory in near field to far field(NF-FF)conversion.The accuracy of the near-far field transform algorithm in the spherical near-field measurement system is studied from the following three aspects by the mode expansion method:1.Combined with the theory of spherical near-field measurement,the paper analyzes the influence of probe's sampling position error on the converted far field in spherical near-field measurement.Then we simulate different degrees of near field's position error data,and obtain the simulated far field through the conversion algorithm.Compared with the ideal results for High Frequency Structure Simulator(HESS),as the position error increases,the influence on the converted far field is greater.2.Then,aiming at the radial error caused by the probe in spherical near-field measurement,the Taylor series algorithm of correction position error is proposed in this thesis.Combined with the theoretical basis of Taylor series,the radial position error of the probe is simulated.The far field obtained by conversion algorithm from the position error data and the simulated far field obtained by calibration are respectively compared with the ideal far field,it is found that the difference between the converted far field after Taylor series correction and the ideal far field is small,indicating the effectiveness of the Taylor series correction method.3.Finally,the thesis proposes to use the two-dimensional(2D)interpolation algorithm to interpolate the sampled data,which can improve the conversion precision.As the sampling interval increases,the difference between the conversion result and the ideal situation is larger,and the interpolation operation can be appropriately used between the sampling points.The near field information is restored,and the simulation results show that the converted far field obtained by the interpolation operation is closer to the ideal far field,which verifies the validity and correctness of the two-dimensional interpolation algorithm in antenna spherical near field measurement.