Near-Field Test Method Of Array Antenna Based On Field Source Reconstruction

Array antennas are a key component in the implementation of multiple-input multipleoutput(MIMO)technology in 4G and 5G communications,and will play an important role in low-orbit satellite base stations for sixth-generation mobile communications technology(6G).Therefore,it is especially important to accurately measure the radiation performance of the array antennas,so that engineers can find out the problems of the array antennas based on the measurement results,and thus optimize them in time to avoid functional limitations after installation,which will cause more economic losses.The methods of measuring array antennas include direct far-field method and near-far field transformation method.The direct far-field method is to test the radiation pattern of the array antenna in a huge microwave anechoic chamber that meets the far-field test distance.However,the construction cost of a large-scale microwave anechoic chamber is very expensive.Although the near-far field conversion method can avoid the huge capital cost of building a large-scale anechoic chamber,Its The near-field sampling interval needs to satisfy Nyquist’s law.It takes several days to scan a sphere with a single-probe anechoic chamber.In addition,anechoic chamber calibration and near-far field conversion are also time-consuming operations,which seriously affect the test efficiency in the high-frequency field.In this paper,we propose a fast measurement method for array antenna near field based on field source reconstruction to address the above difficulties and do the following work.1.In this paper,the genetic algorithm is used to perform repeated iterations and inverse operations according to the electric field distribution,and the optimal number and position of the dipoles of the equivalent source are searched,so as to reconstruct various vector information of the equivalent source,and obtain the radiation pattern by calculation.This method only needs a sparse spherical near-field sampling interval,and the near-field sampling time is only tens of minutes,but the genetic algorithm usually takes more than 10 hours to reconstruct the equivalent source,and there is also the risk of computer crash due to insufficient running memory.2.According to the singular value decomposition theory,this paper proposes an equivalent model of a uniformly distributed dipole cube based on the maximum physical size of the antenna.The number and position of the dipoles are directly determined,so all the parameters of the equivalent source can be determined only by one inverse operation.Therefore,the reconstruction speed is increased by hundreds of times,which is about 10 minutes after experimental verification.3.The article uses the singular value truncation method to eliminate the invalid dipoles in the equivalent model of uniformly distributed dipole cubes to further optimize the number of dipoles in the equivalent source model and reduce the memory occupation of the computer.4.The directional map errors caused by near-field eccentricity are corrected using the proposed novel field source reconstruction method.Based on the above work and innovation,the antenna near-field test method based on the field source reconstruction theory is promoted to be applied to the actual array antenna measurement faster,providing a fast,accurate,low-cost and eccentricity-correcting measurement method for array antennas.