Research On The Wireless Passive Patch Reflective High Temperature Sensor

Temperature monitoring and testing in high temperature and harsh environments are pressingly desired in many fields such as industrial production,defense security,aerospace and so on.Such as the detection of the ring furnace temperature of the heated billet in a steel plant;measurement of downhole temperature during oil extraction;temperature control in combustion chambers of turbojet engines,etc.Similar to the acquisition of temperature parameters in these extremely harsh environments presents a great challenge to the traditional measurement methods.In view of the problem that the power and leads of traditional temperature sensors fail to work properly in high temperature environments,a wireless passive measurement method is proposed to achieve the temperature test in harsh environments at high temperature.In this paper,starting from the requirements of temperature testing in high temperature environment,by comparing and analyzing different principles and different types of wireless passive temperature sensors and their research status at home and abroad,a patch reflective temperature sensor is proposed and implemented in high temperature environment.The sensor is highly integrated with the patch antenna and realizes the integration of signal transmission and temperature measurement.It has the advantages of small size,low cost,high integration,and easy conformity with the carrier.The main research work in the paper is summarized as follows:(1)According to the principle of radiation and wireless measurement of the patch reflective sensor,a temperature extraction theoretical model of the electromagnetic wave frequency signal is established.The material properties(dielectric constant of substrate)and physical parameters of the sensor(patch size and substrate thickness)are fully considered to obtain a more accurate relationship between operating frequency and temperature,the theoretical calculation process is optimized,the accuracy of the theoretical calculation is improved,and the theoretical error is reduced,the model is more consistent with the actual results.(2)Based on the theoretical model of temperature sensor and wireless temperature measurement principle,the structure of wireless passive temperature sensor is designed.High-frequency structural simulation software is used to optimize the structural parameters of the sensor based on the theoretical values,and the optimal parameter values are obtained.The PCB material was used as a dielectric substrate,a physical verification device of wireless passive patch reflective was fabricated.The correctness of the wireless passive reflective temperature measurement principle and the feasibility of the program were proved through the temperature test,but also provided a low-cost wireless temperature measurement program.(3)According to the requirements of high-temperature thermal shock reliability of the sensor,the AIN ceramic-based wireless passive high-temperature sensor was fabricated by using a silver-palladium paste as a conductive material precursor and firing a thick film process.Metallographic microscope observation shows that the pattern edge of the AlN sensor is neat,the size change is small.A network analyzer was used to test its normal temperature operating characteristics,it was found that the operating frequency and the design frequency have differ little,confirming that the thick film process can be used for the preparation of the high temperature sensor.The high-temperature Al2O3-based broadband slot interrogation antenna of coplanar waveguide feed and patch loading was prepared.The effect of high temperature conditions on the operating bandwidth and gain of the interrogating antenna was investigated theoretically.It is found that even at 1050 ?,the interrogation antenna still has a good working bandwidth and gain,and can be applied to a high-temperature environment as a Tx/Rx component.Finally,a high-temperature test system was built based on a muffle furnace to achieve a high temperature measurement of 700 ?.(4)In order to further improve the high-temperature measurement capability,a high-temperature temperature sensor based on magnesium-aluminum spinel was explored to achieve the temperature test of 1000 ?.MgA12O4 spinel is an important welding material for sapphire structure and it has excellent high temperature resistance.A high-temperature sensor working in the microwave band is prepared on the MgAl2O4 spinel,not only achieving a higher measurement temperature,but also confirming the high-temperature measurement and microwave application ability of the magnesium aluminum spinel for the first time.It also offers the possibility of subsequent sapphire devices that are compatible with higher operating temperatures.During the testing process,both the sensor and the interrogation antenna are in a high-temperature closed and complex environment,simulating the actual application environment to the largest extent and realizing the in-situ temperature measurement.Compared with the open environment and local heating measurement method of the same type of sensor,the experimental results are more authentic and reliable.