| With the rapid development of microwave and radio frequency circuits,the characterization of permittivity of materials becomes more and more important.Among many detection methods,microwave detection has become an important detection method in material development and many sensing fields because of its advantages of high sensitivity,simple design and low processing cost.Due to the unique structure and electromagnetic characteristics of Substrate Integrated Waveguide(SIW),microwave sensors based on the structure of SIW have received much attention.Because the substrate of SIW can well meet the requirements of microwave sensors for high quality factor and planar design.Based on material perturbation theory,two miniaturized microwave sensors using SIW technology and split ring resonator were designed in this paper,which were respectively applied to the measurement of permittivity of solid materials and microfluidic detection.The relevant research can be divided into the following two parts:(1)A miniaturized microwave sensor based on SIW structure is designed,which is suitable for the characterization of permittivity of solid materials.The microwave sensor belongs to symmetrical double-port network and adopts metal-dielectric-metal structure.The design of microwave sensor miniaturization is completed by loading the elliptical opening ring.In addition,the influence of material magnetic loss on permittivity measurement is not only reduced,but also the relative frequency offset of microwave sensor is increased by optimizing the size of the region to be measured.The simulation and measurement results show that the relative frequency offset of the microwave sensor is up to 32.39%,the normalized sensitivity is 4.8%,and the measurement error of the permittivity is less than 3%,which further verifies the application value of the microwave sensor in the permittivity detection of solid materials.(2)A multifunctional microwave sensor for detecting microfluidic temperature and concentration is proposed.In order to meet the requirements of microfluidics detection,based on the design in the previous chapter,the symmetrical two-port network is changed into a single-port network,the SIW structure is replaced by the CSIW structure,the structure of the split ring resonator is changed,and the measured area is adjusted.By loading open rings on the surface of the CSIW structure,the miniaturization design of the multifunctional microwave sensor is completed.Compared with the microwave sensor before miniaturization,the electromagnetic field of the microwave sensor at this time is highly separated.And the electric field intensity of the area to be measured increases significantly.The frequency offset increases by 54%.The equivalent circuit model of microwave sensor is established.The effect of split ring resonator on its resonant frequency is analyzed,and the working principle of multifunctional microwave sensor is expounded.In order to reduce the influence of the volume of solution on the resonant frequency of microwave sensor,a special microfluidic channel is introduced.The multifunctional microwave sensor is simulated and tested.The test results show that the error of solution temperature is less than 3.4℃,and the concentration of glucose is less than 6mg/ml.The concentration error of ethanol is less than 2.8%.The experimental results verify the feasibility and reliability of the multifunctional microwave sensor for the detection of solution temperature and concentration.In conclusion,this paper mainly explores the structure of Split Ring Resonator and SIW.And successfully designed two types of miniaturized microwave sensors,which can be used for the measurement of permittivity of materials and the detection of solution temperature and concentration respectively.These designs have broad application prospects in microwave and radio frequency device design,food safety,biomedicine and other fields. |
