Research And Design Of Antenna Sensor For Detecting Dielectric Property

Traditional sensors are difficult to meet the needs of modern detection technology due to their slow response,low precision,high energy consumption,poor adaptability to harsh environments and short lifespan.Antenna sensors integrate the function of antenna and sensor.By detecting the signal characteristics of the antenna,the changes of detected physical quantity can be indirectly obtained.Also,the antenna sensor has the advantages of simple fabrication,high sensitivity,fast detection and low energy consumption.So,it has broad application prospect.This thesis studies and designs two antenna sensors to detect dielectric correlation characteristics.The specific work is as follows:(1)A microstrip antenna sensor for measuring the dielectric constant of solid state media is designed.Its overall size is 80 mm×80 mm.It is composed of radiation patch etched slot,a substrate and a ground plane.The dielectric constant of the tested medium is obtained by measuring the resonant frequency of the antenna sensor.In addition,by etching the complementary resonant ring on the radiation patch,a strong local electric field is generated that the sensitivity of the sensor is improved.The simulation results show that when the relative dielectric constant of the sample increases from 2 to 10,the relative frequency offset percentage reaches 6.50-34.80.Compared with the conventional microstrip patch antenna sensor with the same resonant frequency,the sensitivity of the sensor is increased by 7.00-7.50 times.At the same time,the effects of sample size,thickness,and the imaginary part of the dielectric complex on sensitivity were explored.The experimental results show that the sensor has high sensitivity,and the relative error is within 8%.(2)A microstrip antenna sensor for detecting the dielectric defect is designed.Its overall size is 12.5 mm×60 mm.It is composed of microstrip transmission line,a substrate and a ground plane.By loading four different resonant units on both sides of the transmission line,four resonant frequencies with uniform distances are generated.The cracks are located and their properties are identified based on the changes of four resonant frequencies by measuring the transmission coefficient of the antenna sensor.The simulation results show that when the crack is located in different detection regions,it can be located by the migration of corresponding resonant frequencies.At the same time,the length,width,angel and position of the crack can be identified according to the transmission amplitude of the antenna sensor and the offset degree of the resonant frequency.The minimum crack size which can be identified is 1×10×0.15 mm under the100 MHz frequency offset standard.The experimental results are in good agreement with simulated ones which verifies the sensing performance of the sensor.