Research On Near-field Microwave Scanning Microscope

Modern industrial technology is becoming more and more demanding on microscopy,but traditional microscopes are no longer able to meet the microscopic requirements of some specific fields,such as no contact,no damage,sub-surface detection,etc.,based on microwave characteristics,these can Become the advantage of near-field microwave scanning microscope.Near-field microwave scanning microscopy emission energy is low,the probe time without contact with the sample,can be no damage to the detection of samples.At the same time as the microwave can pass through the dielectric material,near-field microwave microscope can detect the characteristics of the internal sample.At the same time using the calibration algorithm,near-field microscopy can also be used to quantitatively measure the sample.Based on these irreplaceable advantages of near-field microwave scanning microscopy,it is of great significance to study the development of near-field microwave scanning microscopy.In this paper,based on the study of near-field microwave scanning microscope,the simulation software is used to explore the relationship between the measurement parameters such as the reflection coefficient S11 and the resonant frequency and so on.At the same time,based on the reasonable design,The microscope has made some improvements.Firstly,the working principle of near-field microscopy is analyzed,and the concept of near-field,the difference between near-field and far-field,the distribution of electromagnetic field in near-field are explored.Some important structures in the development of near-field microwave microscopy are mainly the structure of perforated probe and non-porous probe and their respective advantages.Based on the lumped parameter model and the transmission line model,the working principle of the near-field microwave microscope is analyzed.When the characteristics of the sample changes,the impedance will change,and thus affect the reflection coefficient,resonant frequency,etc.,changes in the characteristics of these samples,including dielectric constant,conductivity,loss tangent angle changes.In this paper,a near-field microwave microscope probe is designed based on the capacitive loading coaxial resonator.Through theoretical calculation,the length of the probe and the length of the inner and outer diameter are obtained.And the parameters such as the position of the coupling ring and the length of the inner and outer diameter are optimized by analyzing the characteristics of the capacitor loaded coaxial resonator and the near field microwave microscope.Based on the theory,the spatial resolution of the near-field microwave microscope is analyzed in detail,and the deviation of the resonant frequency,the amplitude and phase of the reflection coefficient are compared.The detection ability of the sub-surface sample is analyzed The relationship between the dielectric constant of the sample and the resonant frequency of the probe was analyzed.