Wireless Passive Surface Acoustic Wave Temperature Sensor And Its Measuring System

At present,the surface acoustic wave(SAW)industry is developing rapidly,and a large number of surface acoustic wave(SAW)companies are developing from leaps and bounds to strong competitors in many industries,and they are developing into leaders in the field of acoustics.Surface acoustic wave sensors play an irreplaceable role in many fields such as military systems,civilian consumer products,and commercial equipment.Using surface acoustic wave temperature sensors to monitor changes in temperature parameters can improve efficiency and ensure the safe operation of the system.Therefore,the study of SAW sensors and their measurement systems is of great significance to the acquisition of environmental parameters.Firstly,according to the principle of SAW temperature measurement,this paper analyzes the signal characteristics of the surface acoustic wave resonator and the equivalent circuit model of the SAW sensor at different frequencies.The equivalent circuit model includes single-port and dual-port surface acoustic wave sensors.A resonant surface acoustic wave temperature sensor was designed,and the relevant parameters of the sensor were obtained by finite element simulation,and the temperature sensor was fabricated by MEMS technology.Secondly,this article designs the overall scheme of the wireless passive temperature measurement system,and introduces in detail the design,production and testing of hardware circuits and software programs.The system includes a micro control unit,a transmitting and receiving unit.The micro-control unit composed of the main control board and the host computer controls the transmitting and receiving links.The transmitting link includes an excitation signal source,a modulation switch,a filter,and a power amplifier to realize the transmission of the inquiry signal.The receiving link includes low noise amplifiers,band-pass filters,operational amplifiers,and analog-to-digital converters.The Welch algorithm is used for frequency estimation,and the influence of noise on the echo signal is reduced by means of segmentation,compensation,and averaging.In order to improve the sampling rate of the measurement system,the multi-channel sampling method is used to alternately sample the measured signal in parallel.In addition,a correction method is proposed for the time mismatch problem in the time-alternating analog-to-digital converter(TIADC).The calculated difference between the sampled data and the reference channel data is used to judge the monotonicity of the signal,and then use the improved Taylor expansion method to compensate for the mismatch error.Using MATLAB to simulate the 200MS/S multi-channel parallel alternate sampling prototype,which verified the feasibility of the algorithm.Finally,the performance of the module and the measurement system was tested and the temperature rise experiment platform was built.The temperature rise experiment was carried out to explore the relationship between the resonance frequency and temperature.The test results show that the measurement results are reliable under the condition of the sensor performance and within the range of the resonance frequency change..When the transmitting power of the system is 22.5 dBm,wireless testing can be realized within a distance of 50 cm,and the measured sample standard deviation is 0.0829 kHz.