| Metamaterials with specific properties cannot be directly obtained in nature but only be synthesized by artificial composite materials.After the new material was verified by theories and experiments,the research on its application was gradually carried out.Subsequently,a large number of research applications based on metamaterials such as filters,couplers,sensors,antennas,and absorber have appeared.In recent years,with the development of the research and application of metamaterials,the basic unit structure of metamaterials such as SRRs has been found to significantly improve the sensitivity of sensing devices.In particular,it has a huge potential application prospect in non-contact biological detection,which is simpler and more sensitive than macroscopic material detection.Compared with traditional mechanical sensors and nanomaterial sensors,metamaterial sensors have significant application value in military science,medical monitoring,clinical experiment and diagnosis,environmental pollution detection,and biochemical engineering condition control.Therefore,the application of metamaterials to design high-sensitivity microwave sensors has received more and more attentions.We designed two kinds of metamaterial-inspired sensors based on CSSR and SRR,respectively,and resonant characteristics and sensing characteristics of the structure are analyzed through equivalent circuit theory.First,we use the CST microwave studio for model simulation and optimization,and then use the vector network analyzer coaxial feed for testing.The numerical simulation results are in consistent with the experimental results.The main work of this paper can be summarized as follows:(1)We proposed a complementary single-opening resonant ring(CSSRR)and a circular microstrip line to realize a non-contact rotation sensor.The experiment results are in good agreement with the simulation.The working principle of the sensor and the sensing characteristics under different angles are analyzed through the equivalent circuit model.The results of circuit simulation,performed by extracting the equivalent circuit parameters,are consistent with the experimental results.The compact sensor has sensitivities of 0.21,0.43 and 0.77 at angles of 30°,60° and 90°,respectively.This kind of sensing device has potential applications in the further integration of MEMS.(2)A gas-liquid sensor is based on Semicircular-split resonant ring(SRR)was designed with high sensitivity,and its induction curves for gas and liquid at room temperature was simulated.The design of this sensor is based on an improved spilt-resonant ring(SRR)coupled with a U-shaped microstrip line,which constitutes an LC resonant tank with a high quality factor(Q)and operating frequency close to 1.75 GHz.A capacitive gap is designed between the split-ring structures and the split-microstrip line to achieve high electric field strength.A small change in the concentration of gas or liquid in this area cause a slight change in the equivalent medium around the sensor,resulting in a substantial change of the resonant frequency.The molecular density and specificity of different gases and liquids can be determined by examining the change in resonance frequency and the Q factor of the transmission coefficient.The sensor is compact in structure,and can be well integrated in the design of microchip,and can also be applied to the design of a small electronic noses in the future. |
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