Design And Research Of SIW Resonant Wireless Passive High Temperature/pressure Composite Sensor

Currently,major equipment or components in aerospace,industrial metallurgy,resource extraction and other fields are in high temperature,high pressure and other harsh environments.Real-time in-situ temperature and pressure monitoring of such components can ensure the safe operation of the equipment,based on which a measurement system for real-time temperature and pressure monitoring is proposed in this paper.The system is designed based on the microwave scattering principle and consists of two parts: a sensor and an interrogation antenna.The interrogation antenna emits electromagnetic waves to the sensor,which are coupled to the sensor interior through the slit antenna.A specific frequency resonates inside the sensor to form a standing wave,and the rest of the signal is reflected back to the interrogation antenna to obtain the resonant frequency of the sensor.When the ambient temperature or pressure changes,the dielectric constant of the sensor dielectric substrate material will change,making the resonant frequency change,so that the function of temperature,pressure and resonant frequency can be established to achieve the monitoring of environmental parameters.Sensors include temperature sensors and temperature-pressure composite sensors.The temperature sensor is designed based on the substrate integrated waveguide(SIW)and slit antenna theory,and is filled with ceramic media inside.On the basis of the temperature sensor,the temperature-pressure composite sensor is designed with simultaneous measurement of both temperature and pressure parameters.The sensor has two sensitive units,one of which can establish the resonant frequency as a function of temperature;the other unit is designed with a sealed cavity inside.When the external pressure changes,the upper and lower layers of the cavity will deform to the inside,and the resonant frequency of the sensor will be changed to achieve pressure measurement.The inquiry antenna adopts a coplanar waveguide structure with ceramic as the substrate,which can resist high temperature and high-pressure erosion.The sensor and antenna are prepared by laser cutting,punching,micro-hole injection,screen printing and high-temperature sintering processes,and a high-temperature pressure test rig is built for experimental testing.The test results show that the performance of the silicon carbide ceramic temperature sensor is better than that of the alumina ceramic temperature sensor;and the resonant frequency varies linearly within 25～500 ℃ and 500～1000 ℃,and the sensitivity is divided into 73.68 k Hz/℃ and 440 k Hz/℃.The temperature-sensitive unit of the high-temperature pressure composite sensor has a linear change in resonant frequency in the interval from 25 to 500 °C and 500 to 1000 °C,with a sensitivity of 63.216 k Hz/°C and 400 k Hz/°C.The temperature-pressure sensitive unit has a linear decrease in resonant frequency in the pressure interval from 0 to 700 kpa at room temperature,with a pressure sensitivity of171.429 k Hz/kpa.The pressure sensitivity was 228.571 k Hz/kpa at 800 °C in the pressure range of 0-700 kpa,and a quadratic polynomial fit and a nonlinear surface fit were performed to obtain the resonant frequency as a function of the environmental parameters to solve for temperature and pressure.The experimental tests proved that the sensor has excellent temperature and pressure monitoring capability.