Sensor Technology Based On Antenna And Design And Research Of Circularly Polarized Array Antenna

With the continuous development of antenna technology,related technologies have attracted much attention.And people began to explore the application of antenna in other fields.In recent years,more and more attention has been paid to the application of antenna in various Physical parameter measurement,so all kinds of sensors based on antenna came into being.This thesis is based on antenna technology,the antenna technology is applied to stress measurement,plasma electron density measurement,and 5G band broadband circularly polarized array antenna design.Based on the principle of antenna resonance,a stress sensor based on spring antenna and a plasma density sensor based on low temperature co-fired ceramic(LTCC)antenna are designed by using the relationship between the resonance frequency of antenna and the equivalent relative permittivity of medium.At the same time,a broadband circularly polarized array antenna for 5G band is designed by using array technology,slotting,adding surface EBG structure and parasitic branches,expanding the bandwidth of circularly polarized antenna and improving antenna gain.The main contents of this paper include:1.A stress sensor based on antenna is designed.Firstly,based on the principle of transmission line,the feasibility of applying the principle of transmission line to design the stress sensor based on the spring antenna is analyzed.The multi-layer dielectric antenna with air layer is used to realize the stress sensor.In this thesis,four springs are placed between the upper and lower layers of the sensor,and the pressure can be inversed by the relationship between the air layer thickness and the S₁₁parameters of the sensor.The influence of the thickness of air layer on the S₁₁parameters of the sensor is studied.At the same time,the change of the thickness of air layer will cause the expansion and contraction of the spring,which will lead to the change of the stress.Thus,the mathematical relationship between the resonant frequency and the stress of the sensor can be indirectly established,and the corresponding stress value can be obtained from the mathematical relationship.Finally,the simulation results,theoretical results and experimental results show that the relationship between the air layer thickness and the resonant frequency of the sensor is approximately linear,and the relationship between the spring expansion and the pressure is also linear.Therefore,it can be used to make stress sensor.2.A plasma density sensor based on LTCC antenna is designed.The sensor structure is divided into three layers.The top and bottom are LTCC dielectric plates,which can protect the internal structure of radiation patch and improve the equivalent permittivity of the sensor.The middle layer is the radiation structure of the sensor.Because the effective permittivity of the plasma will change under different plasma frequencies,the resonant frequency of the sensor will change with the plasma density.The antenna designed in this paper is wrapped in plasma to make it a plasma density sensor.The plasma density to be measured can be equivalent to a medium.However,the plasma density will change with the plasma frequency,which is equivalent to measuring a medium whose constant dielectric constant changes constantly.Meanwhile,the resonant frequency of the sensor will also change with the plasma density.When the plasma frequency changes from 0.3 GHz to 7 GHz,the step value is 0.1 GHz,the resonant frequency of the corresponding sensor changes from 4.076 GHz to 5.213 GHz,and the measurement accuracy is more than 90%.The main work of this thesis is the theoretical research and numerical analysis of the design of plasma density sensor.3.A 2×2 microstrip circularly polarized array antenna is designed,which adopts the sequential rotation phase feeding technology,improves the working bandwidth and gain of circularly polarized array antenna by slotting,loading parasitic structure and electromagnetic band gap(EBG)structure,and optimizes the antenna pattern.Firstly,the circularly polarized impedance bandwidth and axial ratio bandwidth of a single patch are analyzed.Secondly,the impedance bandwidth and axial ratio bandwidth are increased by adding the sequential rotation phase feeding technology,then the axial ratio bandwidth of the array is effectively improved by optimizing the slotting and parasitic structure loading.Finally,the peak gain is improved by adding the EBG structure and parasitic branch technology,and the antenna gain is more stable The gain increases 3 d Bi C bandwidth.The impedance bandwidth of the array antenna is 3.3 GHz-7.0 GHz(74%),the 3 d B axial ratio bandwidth is 3.5 GHz-6.4 GHz(58%),the gain peak value is 10.2 d Bi C,and the 3 d Bi C gain bandwidth is 4.2 GHz-5.9 GHz(34%).The array antenna is fabricated and tested,and the error is analyzed.The array antenna works in 5G band.If it can be applied in practice,it will have the advantages of 5G communication,such as wide bandwidth,fast speed and good stability.