Optimal Design Of Microwave Microfluidic Planar Resonant Sensor Based On Defected Ground Structure

Microwave planar resonant sensors are widely used for the identification and classification of dielectric materials due to their low cost and high sensitivity.In addition,the non-contact and realtime sensing characteristics of the sensor also meet the needs of sensing the complex permittivity of electrolyte solutions.This thesis aims to explore the performance potential of microwave microfluidic sensors based on defected ground structure and proposed several sensor improvement schemes based on defected ground structure.In the third chapter,the resonant structure for microfluidic sensing through a single defected ground structure is mainly introduced.The equivalent inductance generated by the increased reflux current of regional etching and the equivalent capacitance formed by the narrow channel with potential difference form a resonant circuit.A simplified circuit model analysis and transmission coefficient derivation were conducted on the dual port microstrip line,and a sensor based on DGSIDC structure was ultimately proposed.This structure eliminates the influence of side capacitance on sensitivity by isolating the resonant region.The complex dielectric constant of the sample was obtained by fitting the real part of the dielectric constant using relative frequency deviation,and combining the real part value and quality factor to fit the relationship function with dielectric loss.In the fourth chapter,in order to meet the challenge of high loss liquid sample,we try to use defected ground structure to improve the response amplitude of the sensor.Through the equivalent circuit analysis of process structure,a sensor based on DGS-IDC-DSRR structure was proposed.The sensor determines the notch depth through the introduction of the defected ground structure on the ground plane.Due to the existence of rectangle etching at the bottom,the flexibility of sensor design was improved,and the dual split ring structure was realized to further enhance the notch amplitude.The interdigital structure was used to increase the sensing area and sensitivity.The frequency response and sensitivity of the structure were verified by simulation,and the test was carried out after the physical processing.Using the obtained results,a mathematical model for the detection of unknown liquid samples was established,and the complex permittivity was extracted.The obtained values were in good agreement with the reference data.In the fifth chapter,considering the demand for high sensitivity scenarios,the feasibility of using defected ground structure to achieve ultra-high sensitivity microfluidic sensors was analyzed.A mode-split sensor was proposed by introducing a defected ground structure and metal through holes.The two metal strips in the ground plane defects are connected to the microstrip line through the metal through hole to realize the frequency division structure.Compared with the plane mode-split sensing structure,its performance is greatly improved in sensitivity,detection range and notch depth.The ethanol water mixed solution was used for experimental verification,and the ultra-high sensitivity was obtained.The results show that the sensitivity of dual mode measurement can be increased by43% compared with single mode measurement,which provides a useful reference for realizing high sensitivity and high resolution sensing applications.In summary,this thesis attempts to optimize the design of sensors based on defected ground structures.The study primarily focuses on improving sensor sensitivity and peak attenuation by introducing defected ground structures and made some beneficial progress.