Localization Of PIM Sources Based On Subwavelength Structure Super-resolution Imaging

Ultra-high rate,ultra-large capacity and ultra-low delay are the characteristics of 5G mobile communication era.The base station antenna plays a key role in the mobile communication system as a device for transmitting and receiving electromagnetic waves,which is an important guarantee for the communication system with excellent performance.However,after the multichannel high-power signal passes through the nonlinear RF components of the base station antenna system,it is easy to generate interference signals of different frequencies,which radiate outward through the antenna in the form of electromagnetic waves,that is,Radiated Passive Intermodulation(R-PIM).R-PIM falling into the working frequency band of receiver leads to the waste of spectrum resources and the reduction of channel capacity,which is an important factor restricting the development of mobile communication technology.Therefore,accurate positioning of R-PIM source in base station antenna is an urgent problem to be solved.Electromagnetic imaging positioning can image the detection area according to the electromagnetic field in the component under test and locate multiple R-PIM sources at the same time,greatly improving the positioning efficiency.However,due to the diffraction limit,traditional electromagnetic imaging positioning cannot effectively distinguish and accurately locate multiple R-PIM sources with sub-wavelength spacing.To this end,this thesis proposes a subwavelength structured super resolution imaging localization method based on induced charge from the point of view of charge particle motion to achieve super-resolution imaging and accurate positioning of multiple R-PIM sources with subwavelength spacing in base station antennas.The specific research contents are as follows:Firstly,a subwavelength structure super-resolution imaging localization method based on inductive charge is proposed to solve the problem of simultaneous and accurate localization of multiple R-PIM sources at sub-wavelength spacing.The basic principle of super-resolution imaging localization of subwavelength structures is explained from the interaction between positively and negatively charged particles.Under the action of the electric field radiated by the R-PIM source,the free electrons in the subwavelength structure are forced to move,resulting in the accumulation of induced charge on the end face of the structure.The amount of induced charge decays rapidly with the distance between the R-PIM source and the end face of the subwavelength structure unit,and finally the electric field intensity is the strongest at the location of the R-PIM source on imaging surface and the field intensity around the source decreases rapidly,so as to achieve the super-resolution imaging and accurate positioning of the R-PIM source.Then,the R-PIM sources localization model based on the super-resolution imaging of subwavelength structure is established.The distance between the source and the front end of the subwavelength structure,the distance between the imaging plane and the back end of the subwavelength structure,and the influence of the parameters of the subwavelength structure on the transmission imaging resolution and positioning accuracy are analyzed.The results show that super-resolution imaging of the R-PIM sources can be achieved when the R-PIM sources and the imaging surface are at subwavelength spacing from the end face of the subwavelength structure,and accurate positioning can be achieved when the R-PIM source is facing the subwavelength structure unit.The subwavelength structure period is too large for the positioning deviation problem,and the structure parameters need to be determined according to the actual positioning accuracy requirements.Finally,the experimental platform of super-resolution imaging localization based on subwavelength structure is built.The experimental results verify the correctness and effectiveness of the super-resolution imaging positioning principle based on the induced charge subwavelength structure.Finally,the super-resolution imaging positioning of multiple R-PIM sources can be realized with the resolution up to 0.11λ and the positioning accuracy up to 1mm.