Design Of Array Antennas For The Near-Field Applications By Introducing The Concept Of Inter-symbol Interference

Based on the various applications of near-field antennas in the fields of remote sensing,security inspection,and medical care,more and more people are working on the near-field antenna research recently.This paper mainly studies array antennas for near-field applications,combines the theory of inter-symbol interference in signal transmission,and establishes a new design specification of array antennas working in near-field communication systems.According to inter-symbol interference,one kind of X-band near-field focused sparse array antenna with fairish focusing performance made by slotted was designed.First,this thesis introduces the basic theory of antenna radiation field,the electromagnetic field area division of antennas,and the basic evaluation index of near-field antenna performance.In addition to the traditional indicators such as beam width,side-lobe level,return loss and gain,the near-field array antenna also specifically need to investigate inter-symbol interference characteristics and be establish the interference calculation method owing to the multipath effect.Second,this paper proposes a millimeter-band near-field wireless access system using a large planar array antenna,which can be used as a solution for implementing virtual cells for 5G.Based on the measured field strength,signal to noise ratio and bits error rate of near-field array antennas with different aperture size,the main characteristics of inter-symbol interference actually proved,and the theoretical expression of inter-symbol interference calculation was verified.The near-field wireless access system using near-field communication with large-aperture array antenna is highly susceptible to short delay due to its high carrier frequency and high communication rate.This thesis uses the method of simulation and numerical calculation and mainly analyzes the inter-symbol interference of the planar array antenna working in the near field from the aspects of parameters of communication system,antenna feed network,antenna aperture size,aperture area source distribution,array element arrangement,etc.The analysis results will provide the theoretical foundation for designing the planar array antenna in a millimeter-wave band Gigabit compact-range wireless access system in the future.Then,based on the concept of inter-symbol interference in the near field of the array antenna,a double-layer near-field focused slotted waveguide array antenna with four-corner feeding is modeled by HFSS simulation software.The antenna has low inter-symbol interference ratio,low side-lobe level and narrow focal spot,which can be used in imaging,medical,near field communication and other fields.During the design process,an unique external-inside quadrilateral feed method was proposed,whose feed delay compensates for some of the multipath effects in order to reduce inter-symbol interference ratio at the focal point.In addition,using the particle swarm algorithm in the design process to adopt a sparse arrangement method for the sake of reducing the structure and processing costs.Furthermore,sparse arrangement of slots is able to reduce the lateral side-lobe level of focus and improve the focusing performance.Finally,this paper analyzes and compares the S-parameters,the focusing performance,the in-bandwidth robustness and the inter-symbol interference within the 3 dB depth of focus of this near-field focusing array antenna.The combination of Matlab calculation and HFSS simulation validates the design theory and structure of the near-field focused array antenna in feasibility and reliability.