The Study Of Metamaterial Dielectric Constant Sensor

Metamaterial is an artificial material with supernormal electromagnetic properties.The proposal and development of metamaterial have been controversial.Up to now,metamaterial have been proved to have many electromagnetic properties beyond conventional materials,such as negative refractive index.With these extraordinary physical properties,researchers have developed a large number of applications.Electromagnetic cloak,electromagnetic induced transparency,polarization converter and high performance antenna are well developed on the basis of the research of metamaterial.Because of the sensitivity of electromagnetic metamaterial,metamaterial sensors have been extensively studied.The types of sensors include refractive index sensors,displacement sensors and biological sensors,etc.In this paper,two kinds of permittivity sensors are fabricated on microwave substrates by using two-port and single-port devices respectively,and their sensing performance is validated by experiments.The sensing mechanism is analyzed and discussed by equivalent circuit and electric field energy density.The experimental results are consistent with those of CST Microwave Studio.The main work of this thesis is summarized as follows:(1)On the basis of dual-port microwave devices,a dielectric constant sensor is designed with a complementary rectangular ring.It works under 1 GHz.Six different concentrations of ethanol solutions are allocated and tested.The measured relative dielectric constant(real part)ranged from 20 to 78.5,and the sensitivity is 1.13MHz per relative dielectric constant.The experimental results show that the sensor has the characteristics of high sensitivity,high precision and fast response.And a small number of samples can also have good measurement results.The principle of the sensor are analyzed by using equivalent circuit.The simulation results are in good agreement with the experimental results.In measurement,a small number of samples and low working frequency make the sensor suitable for a variety of applications.The characteristics of high sensitivity and fast response meet the needs of biosensors and have considerable potential in personal condition monitoring.(2)A narrow band high Q antenna is designed by method of filtering antenna.The gas concentration is detected by the effect of the absorption of ethanol vapor by dielectric plate on the resonance of the sensor.The working frequency is 4.10 GHz,the Q factor is 128,the sensor sensitivity is 3.23 MHz/(mmol/L),the test range is 0-877 ppm.The experiment is carried out in the filter bottle,which avoids the leakage of volatile gas to a certain extent and reduces the impact of the corresponding gas leakage.The ethanol vapor at different concentrations is well measured,and the sensor is further analyzed by using the electric field energy density distribution of the equivalent circuit.Rapid response and recovery make the sensor have potential value in real-time monitoring of special environment.