Study On The Nearfield Antenna Substrate Properties And Application

With the development of Radio Frequency Identification(RFID)technology,a secure communication technology that operates only for short distances(<10 cm)has emerged,namely Near Field Communication(NFC)technology.The NFC system only works on the near field radiation area of the antenna,and the signal transmission is completed by magnetic coupling of the near field area of the antenna.The antenna substrate which is studied in this dissertation is applied to this type of antenna working in the near-field region,which is called near-field antenna.With the popularization and application of near field communication technology,the near field communication system is gradually integrated into electronic devices such as smart phones,smart watches,stereos,and routers.In the electronic devices,the metal environment with a large number of circuit boards and batteries will greatly offset the magnetic field signals generated by the near-field antenna.Therefore,the near-field antenna integrated in the electronic device must use a magnetic antenna substrate to shield the metal environment from interference.Then this dissertation starts from the material properties of the near-field antenna substrate,studies the influence of the main parameters of the substrate on the near-field antenna.And combines the working principle of the near-field antenna to design the near-field antenna simulation and measurement method,and further proposes a design method to achieve the miniaturization and low-cost of the near-field antenna.According to the development trend of smart devices,a design method of near-field antenna under metal casing is proposed.Therefore,the main research contents and innovations of this dissertation include the following aspects:1.Study the influence of main parameters of magnetic substrate on impedance characteristics of near-field antennaBased on the failure principle of near-field antenna,to determine the influence of substrate thickness and electromagnetic parameters on the impedance performance of near-field antenna.Combined with the magnetic spectrum law of magnetic materials,the reasonable magnetic parameter range of the substrate is determined,so that the impedance characteristics of the near-field antenna are well-documented.In engineering applications,the permeability stability of substrate has a greater impact on the near field communication function of the device.In this dissertation,the bulk stability test method of the substrate is proposed by studying the regularity of substrate electromagnetic parameters.2.Research on simulation and test method for near-field antennaThe near-field antenna is different from the antenna in the typical sense,and the near-field antenna is not judged by radiation pattern and antenna efficiency.Therefore,the evaluation criteria for the near-field antenna design and the actual test method of the antenna are not perfect.In view of this situation,this dissertation improves the near-field antenna simulation test method based on the working principle of near-field antenna and provides a verification method for near-field antenna design and test.3.Research on miniaturization and low-cost design method of near-field antennaDue to the large area and the need to cooperate with the magnetic substrate to use,the near-field antenna has a high cost of the near-field antenna.Therefore,the research of miniaturization and low-cost of the near-field antenna have been the focus in this field.In terms of miniaturization,this dissertation proposes a design method for unilateral radiation of near-field antennas,which realizes that the area of the near-field antenna is greatly reduced in a single dimension.So that the antenna area is reduced by more than 60%and the antenna has good communication performance.In terms of low cost,this dissertation proposes a distributed substrate design method of near-field antenna.When the antenna area is constant,the antenna substrate area is greatly reduced,thereby reducing the antenna cost and improving the performance of the near-field antenna through the antenna structure design.4.Near field antenna design method in metal shell equipmentThe use of a metal shell increases the life and aesthetics of the device,but presents a challenge to the near field antenna design in the device.In this dissertation,a design method of the common clearance near-field antenna is proposed to realize the integration of the near-field communication system of the metal shell equipment through the analysis of the structure of the metal shell mobile phone.