High-order Probe Correction For Spherical Near Field Measurement

With the development of communication and electronic information technology,antenna plays an increasingly important role in wireless communication system.At the same time,the requirements of antenna measurement technology are more and more stringent,such as higher accuracy and larger bandwidth.On the one hand,spherical near-field measurement has been widely used in high-precision antenna measurement because it has no truncation error and can obtain the complete pattern of the antenna to be measured.On the other hand,the common probes for spherical near-field measurement are narrow-band antennas,such as the rectangular waveguide,the circular waveguide and the dipole.If broadband probes,such as horn antenna or log periodic antenna,are used for measurement,high-order probe compensation must be used in the corresponding near-field and far-field transform algorithm.The near-field of the probe is a summation of the spherical harmonics,and the components whose spherical harmonic coefficients are m =-1 or 1 are called low-order components,and the others are called high-order components.The narrow-band probes listed above have only low-order components,thus called low-order probes.And the two broadband probes are called high-order probes.The aim of this thesis is to develop a spherical near-to-far field transformation algorithms that can compensate high-order probes.The main work of this thesis is as follows:1.Introduces the spherical near-to-far field transformation algorithm without probe compensation.The specific algorithms of vector spherical wave function,forward spherical harmonic transform and reverse spherical harmonic transform are detailed.2.Studies the low order probe compensation algorithm.The spherical wave transmission equation and the method using the orthogonality of the rotation function to solve the spherical harmonic coefficient of the antenna under test are detailed.3.Uses the least square method for high-order probe compensation.First,the transmission equation is discretized according to the two scanning directions ? and ?,and converted into a large matrix equation.And then,the matrix is preconditioned by the least square method to obtain the good matrix equation.Then,all the spherical harmonic coefficients of the antenna to be measured are solved by an iterative algorithm.Finally,the accuracy of the algorithm is verified by the simulation models of the two antennas.4.Use fast Fourier transform/matrix inverse method for high-order probe compensation.First,perform fast Fourier transform on the transmission equation pair,and then expand the relevant expression into a Fourier series,and then obtain the spherical harmonic coefficients of the antenna to be tested through matrix inversion.The simulation model results show that the algorithm is accurate and effective of.This method requires multiple inversions of the matrix,but each matrix is relatively small,so the calculation is easy.