Design And Performance Of PDC Wireless Passive Temperature Sensors And Interrogation Antenna

Turbine engine combustion chamber is in high temperature,high pressure,high corrosion and other environments,so it is necessary to use temperature sensors to monitor its interior in real time.This kind of sensor not only needs to be able to be applied in the above harsh environment,but also needs to have the characteristics of wireless and small size.At present,the key of temperature measurement technology lies in the lack of new sensitive element dielectric materials and wireless sensing mechanism.In this paper,a wireless passive temperature sensor with a slotted antenna is proposed.The sensor uses PDC SiBCN ceramic as dielectric material,silver as metal conductor to form a resonant cavity,and slotted antenna as transmission line to realize wireless passive transmission of microwave signal.In this paper,through the design of PDC material,combined with CST simulation software,the structure of the sensor and the external interrogation antenna are designed and optimized,and the wireless passive temperature sensor and interrogation antenna with long transmission distance and high sensitivity are developed.In the material design of PDC,using psnb as precursor,low density PDC SiBCN and high density PDC SiBCN thermosensitive materials were prepared by powder compaction and liquid phase injection molding,and silver as conductor to form a resonant cavity sensor with slotted antenna.The sensitivity and transmission distance of two kinds of PDC SiBCN sensors were studied by using the high temperature test platform.It is found that the sensor with high density of PDC SiBCN ceramics has higher sensitivity and longer transmission distance.The dielectric constant of PDC SiBCN is about 2.587,which is deduced from the formula and compared with 2.57measured by coaxial line method.The dielectric properties of porous PDC SiBCN ceramics and dense PDC SiBCN ceramics were tested.It was found that the dielectric loss of porous PDC SiBCN ceramics was significantly greater than that of dense PDC SiBCN ceramics.The structure design of the sensor mainly includes the shape and size design of the sensor and the shape,position and size design of the slotted antenna.The results show that the resonant frequency of the sensor is affected by the shape and diameter of the slot antenna,and the resonant frequency of the rectangular block resonator is higher than that of the square resonator,and the resonant frequency of the circular block resonator is higher than that of the rectangular block resonator;The smaller the diameter is,the larger the resonance frequency is.When the shape and size of the sensor are fixed,the position and size of the slotted antenna will also affect the resonant frequency of the sensor.The size of the resonant frequency decreases with the increase of the length La of the slotted antenna and the position d from the center,and increases with the increase of the width W,Finally,through the parametric scanning of the shape of the resonator and the shape of the slotted antenna,the optimal sensor after optimization is selected for testing,and the sensor with higher sensitivity than before optimization is obtained.In the case of a certain shape and size,the shape of the slotted antenna is designed,and it is found that the|S₁₁|value of the cross slot antenna is the smallest.The test results also show that the sensor with the cross slot antenna as the slotted antenna has higher sensitivity.In order to further improve the transmission distance of the sensor,the structure of the external interrogation antenna is designed,and the size of the external interrogation antenna is optimized by using parametric modeling,and the external interrogation antenna with better performance is obtained.It is found that the designed CPW antenna and horn antenna can meet the design requirements,and the maximum transmission distance between CPW antenna and sensor can reach 57mm,while the maximum transmission distance between horn antenna and sensor can reach400mm.Setting the sensor as an array element and changing the number of array elements can further improve the transmission distance（500mm）and sensitivity of the sensor.In order to improve the stability of the material at high temperature,the pyrolytic temperature of the material is increased.The performance of the sensor using PDC SiBCN ceramics at different pyrolytic temperatures as the temperature sensitive medium is studied.It is concluded that increasing the pyrolytic temperature can reduce the resonant frequency and sensitivity of the PDC SiBCN wireless passive temperature sensor.The higher the pyrolytic temperature is,the smaller the resonant frequency and sensitivity of the sensor are.Through the phase analysis and dielectric properties test of PDC SiBCN ceramics at different pyrolysis temperatures,it is found that the pyrolysis temperature will increase the dielectric constant and loss of the sensor,and the dielectric constant and loss are related to the free carbon content in PDC SiBCN ceramics and its order degree.