Radiative Near Field Characteristic Analysis And "Null" Beamforming Of Transmitting Array Antenna

Platforms such as sail and altitude flight rely mainly on wireless communication to connect with other communication apparatus.Array antennas are widely used on these platforms.This makes the other electronic devices on the platform may be in the radiative near field of these array antennas.In this case,the radiation characteristics are different from radiation characteristics of the far field.Therefore,this article analyzes the characteristic of radiative near field and implements radiative near-field beamforming of the transmitting antenna.And to study the radiation near-field we must know relation between radiative near field and the distance from the antenna,so the near and far field boundary is discussed in this article.By studying the theory related to field division of ideal dipole,convex optimization and beamforming,this paper focuses on the analysis and study of the following aspects:(1)The critical distance of the antenna field is analyzed,and the use condition of the Rayleigh distance as the critical distance formula is discussed.The antenna field is defined in all kinds of books about antenna,the critical distance conditions of far and near fields and the critical distance conditions of radiative near field and reactive near field are given,but the conditions of using the Rayleigh distance as the critical distance between far and near fields are very vague.Therefore,the conditions of using the Rayleigh distance as the critical distance between far and near fields are discussed according to two characteristics of far field,and the condition D>>? becomes more specific.(2)The characteristics of array antenna radiative near field are quantitatively analyzed.Various types of antenna books have a description of changes of the array antenna field,but they did not quantitatively analyze the characteristics of array antenna radiative near field.So this paper simulates the 21-elements uniform linear array antennas,and collects the zero-depth value of the normalized beam pattern at different distances in the radiative near field,and analyzes its variation law.(3)In this paper,we use the full-wave simulation which is closer to the practical application to study the null beamforming of the uniform linear array.Since the full-wave simulation takes into account the mutual coupling factor,it is necessary to consider the effect of mutual coupling in the beamforming algorithm.The simulation method is used to simulate the uniform linear array in a certain direction,and a deep null is obtained in the zero direction.In this paper,we discuss the conditions of Rayleigh distance as the critical distance of the near-field,and people can apply the radiative near field characteristics of antennas more accurately.The beamforming is analyzed by the method of full-wave simulation,and the beam characteristics are closer to the radiation characteristics of the transmitting array antenna in the practical application.The deep zero is obtained in the zero direction,which reduces the interference to the surrounding electronic equipment.These study can provide some reference for future research.The related research results of this paper can provide theoretical and practical support for the electromagnetic compatibility problem of array antenna radiative near field.