【作者】 谭六喜；

【导师】 刘胜； 张鸿海；

【作者基本信息】 华中科技大学 ， 精微制造工程， 2007， 博士

【摘要】 随着汽车拥有量的迅速增长和人们对汽车安全驾驶要求的提高,胎压监测系统逐渐成为汽车的必备配置。在研究目前国际市场上的轮胎压力监测系统优缺点以及国内外声表面波传感器研究状况的基础上,提出了基于声表面波传感技术的无源无线胎压监测系统。该系统不仅可以同时监测轮胎内部气体的压力和温度,还有无源、体积小、分辨率高等优点。本文对声表面波传感器的理论、设计、加工和封装进行了深入研究,并通过模拟试验对无源胎压监测方案进行了验证。论文首先进行声表面波传感器的理论研究。通过研究声表面波的传播特性以及声表面波传感器的工作原理,推导了声表面波速度变化的理论方程;研究了声表面波器件石英基片的特性;并依据石英基片的压力和温度的灵敏度系数、声表面波耦合系数和功率流等参数对传感器基片进行了优化选择。通过把叉指换能器的实际电场分布近似为纵、横场交替的一维场分布,分别建立了横场和纵场的等效电路模型,并在此基础上建立了叉指换能器的等效电路模型和反射器的等效电路模型;然后在叉指换能器和反射器等效电路模型的基础上建立了单端对声表面波谐振器的等效电路模型,为声表面波谐振器的内阻抗设计和网络匹配提供理论指导。然后进行了声表面波传感器的设计、加工和封装研究。在声表面波传感器理论研究的基础上,设计了可以测量轮胎压力和温度两个参数的双通道声表面波传感器,并用有限元法对传感器的谐振器进行了优化;分析了声表面波传感器的结构设计参数,包括谐振腔长度、叉指换能器、反射器的参数以及金属镀膜设计等;并依据传感器的等效阻抗特性模型设计了压力传感器芯片参数。研究了声表面波传感器的加工工艺流程,并依据相应的工艺加工了传感器芯片;设计了低应力的两层全石英封装结构,并用超声波设备制作了封装的石英盖板;通过对低温玻璃焊料和环氧胶的键合工艺研究,为传感器设计了不同键合形式的封装;并利用氦质谱仪和六轴微力测试平台分别对传感器进行了泄漏率检测实验和剪切强度实验。其次进行了测试电路、天线和匹配网络的研究。通过对传统测量电路系统构成的分析,设计了一次变频的系统构成方案;测量系统电路通过采用直接数字频率合成、提高系统隔离度和等幅自动增益控制放大等技术手段提高检测精度。通过对天线的特性指标和使用环境的研究,设计了变形的偶极子天线;通过分析声表面波传感器和天线的阻抗特性,设计了合理的匹配网络。最后设计了模拟试验对天线的通讯距离、增益等性能以及传感器的阻抗特性、回波信号和压力、温度响应等特性进行了测试。更多还原

【Abstract】 With the rapid growth of the car ownership and increasing demanding on automobile driving safety, Tire Pressure Monitoring System (TPMS) emerges as an essential requirement.Based on the survey of TPMS in the current domestic and international market and research on development of Surface Acoustic Wave (SAW) sensors, a new scheme of batteryless/wireless TPMS is proposed focusing on the technology of SAW sensors. This system could not only monitor the temperature and pressure in tires simultaneously, but also has the advantage of batteryless, small size and high resolution. Fundamental research has been done in this dissertation in terms of theoretics, design, manufacturing and packaging of SAW sensors, and simulating experiments have done to test the scheme of batteryless/wireless TPMS.First, research on theoretics of SAW sensors has been done. By researching on the propagation characteristic of surface acoustic wave and fundamental working principle of SAW sensor, the theoretical equation on velocity change of SAW is deducted. Moreover, characteristic of quartz substrate of SAW sensor is studied and optimum selection on SAW sensor substrate is carried out based on their pressure and temperature sensitive coefficients, effective SAW coupling coefficients and power flow angles.The real electric field of interdigital transducer (IDT) is approximately decomposed as longitudinal fields and horizontal fields. By modeling the longitudinal field circuit model and horizontal field circuit model,the equivalent circuit model of IDT and the reflectors are proposed. According to the equivalent circuit models of the IDT and reflector, the equivalent circuit models of SAW resonators are proposed. The equivalent circuit models of SAW resonators are instruction of SAW sensor’s impedance design and matching net of circuits.Second, research on design, manufacturing and packaging of SAW sensors has been done. A sensor with two IDT is designed for measurement of temperature and pressure based on research on theoretics of SAW sensors, and FEA method is used for optimum design for sensors’resonators. The SAW sensors are analyzed in details, including the length of resonating cavity, parameters of interdigital transducer and reflector, as well as the metal plating. Based on the analysis and the equivalent circuit models of SAW resonators, the parameters for SAW sensor are obtained.Process of SAW devices is studied and samples of SAW sensor are manufactured. A two-layer all quartz packaging that induces low stress is proposed for SAW sensors. Quartz caps used as the upper layer of the sensor are manufactured with ultrasonic devices. With study on glass frit of low melting point and epoxy glue, different bonding methods are applied in packaging for the sensor to form a hermetical bonding. Helium mass spectrograph is used to detect the leakage rate of the sensors’packaging, and six-axes micro-tester is used to measure the sensors packaging’s shear strength.Third, research on measuring circuit, antenna and matching net has been done. By analyzing the circuit of traditional measurement system, scheme of circuit with one mixer is proposed. In order to improve the precision of system, the system is designed with direct digital synthesize (DDS), high isolation RF switch and equivalent scope amplifier. By analyzing antenna characteristic index and the condition for its using, a transformative dipole antenna is designed. Matching net is design for system circuit by analyzing the impedance characteristic of SAW sensor and antenna.Last, simulating experiments are carried out to test the relation between distance and gain of antenna communication, the sensor characteristic of impedance, echo signal, and the response of temperature and pressure.更多还原