Research On Dielectric Properties Measurement And Characterization Methods Based On Resonance Effect

Dielectric properties are the basic properties of materials in electromagnetic fields.In many fields such as medical imaging and medical diagnosis,the measurement and characterization of the dielectric properties of tiny liquid materials have important research and application values.In this thesis,the measurement and characterization of the dielectric properties of tiny liquid samples are the research objects,and a single-split ring micro-liquid dielectric properties measurement device at microwave frequency is proposed and designed,and the dielectric properties of an improved resonant cavity high-loss materials at millimeter wave frequency are proposed and designed.A measuring device and a single-polarization double-opening C-type array structure micro-sample dielectric characteristic characterization device at the terahertz frequency.At the same time,the method for characterizing the dielectric properties of thin film samples by the dual-polarization square array structure and the method for characterizing the dielectric properties of micro-liquid samples with a dielectric characterization device based on the terahertz thermoacoustic effect are studied.It lays a theoretical and experimental basis for the study of the measurement and characterization methods of the dielectric properties of tiny biological materials.The main research contents and innovations are as follows:1.A method for measuring the dielectric properties of tiny samples based on a planar resonance structure and corresponding measuring devices are proposed,in order to realize the measurement of the dielectric properties of micro-liquid samples at microwave frequencies.The device is composed of a double-ended three-section coupled microstrip line,a multi-inner ring opening resonant structure and a quartz capillary tube.Among them,the resonant structure is composed of a rectangular measurement area and an open resonant ring containing two inner metal rings,the rectangular measurement area can realize the enhancement of the electric field,which can better realize the interaction between the electric field and the liquid sample;the double inner metal ring structure can be effective improve the quality factor of the detection structure,thereby improving the detection sensitivity of the device.Experiments have found that the measurement method can achieve the measurement of the dielectric parameters of inositol solutions with a concentration as low as 10 mg/ml,indicating that the method and the corresponding measurement device can be used in the measurement of the dielectric properties of micro-liquid materials in the biological field.2.An improved resonant cavity perturbation method and corresponding measuring device for measuring the dielectric properties of cavity-type tiny liquid samples are proposed,in order to solve the problems of low Q factor,poor sensitivity and traditional resonant cavity perturbation method that cannot meet the measurement of dielectric properties of high-loss materials when the traditional dielectric parameter plane measurement device measures in the high frequency range.The device is composed of a WR-28 standard rectangular waveguide,a sheet coupling structure and a quartz capillary tube.By changing the position of the columnar sample in the cavity,it solves the problem that the strong absorption of the electric field by the high-loss sample causes the traditional perturbation formula to fail.Experiments have found that the device can be used to measure the dielectric properties of breast cancer cells with a volume fraction of 0.046 and a melanoma cell suspension with a volume fraction of0.041 at 30.352 GHz and 35.117 GHz.This indicates that the method and the corresponding device can be used.Used in the measurement of the dielectric properties of cancer cells in the high frequency range.3.A sample dielectric characterization device based on an array resonance structure is proposed and designed,in order to realize the characterization of the dielectric properties of tiny samples at terahertz frequencies.The device consists of a double-opening C-type array structure built on a quartz substrate and the corresponding clamping device is composed.The array structure is formed by periodic arrangement of double-opening C-type metamaterial unit structures with sharp ends.When a single-polarized terahertz wave is perpendicularly incident on the surface of the array structure,the electric field can be enhanced at the local position.Based on the above-mentioned device and THz-TDS technology,the dielectric properties of two amino acid samples were characterized at the frequency of 0.98 THz.Experiments have found that the measuring device can realize the characterization of the dielectric properties of inositol and L-leucine samples with a minimum error of 4%.It shows that the device could be used to characterize the dielectric properties of tiny samples at terahertz frequencies.4.A dual-polarization square array dielectric characterization method based on terahertz time-domain spectroscopy is proposed,in order to realize the characterization of the dielectric properties of tiny samples at dual frequency points at terahertz frequencies.The array structure exhibits two different resonance characteristics when dual-polarized(y-polarized and x-polarized)terahertz waves are incident vertically.The influence of different structural parameters on the resonance characteristics of the array structure is analyzed.By establishing the relationship between the dielectric characteristics of the test sample and the two frequency shifts,the dielectric characteristics of the lossless and lossy samples can be characterized.5.A method for characterizing the dielectric properties of tiny liquids based on the terahertz thermoacoustic effect is proposed,in order to solve the problem that the strong absorption of electromagnetic waves by water and other polar molecules at terahertz range,which leads to poor sensitivity of the dielectric characterization device.A simulation model of the system for characterizing the dielectric properties of liquid samples was established,and the influence of different electromagnetic parameters of the terahertz source on the amplitude of the acoustic wave signal was analyzed.This method has potential application value in the characterization of the dielectric properties of tiny polar molecule liquids.