【作者】 王建玲；

【导师】 周东祥； 傅邱云；

【作者基本信息】 华中科技大学 ， 微电子学与固体电子学， 2009， 博士

【摘要】 无源无线声表面波传感器被认为是最有希望取代有源的无线传感器，然而到目前为止，通过改变布局图的方法，或者采用不同声表面波形式的方法对拓展其应用范围的作用都是有限的。声表面波的物理特性决定了被测量直接施加到其传播路径上是最好的，然而有些被测量不适宜直接施加，限制了其测量领域。利用阻抗传感器做为声表面波器件的负载，使被测量施加到阻抗传感器上，通过负载的改变来影响声表面波器件的响应，成为扩展声表面波无源无线传感范围的新途径。因此，本文围绕着基于声表面波谐振器（简称SAWR）的无源无线阻抗负载型传感器开展研究，具有重大的理论意义和现实的应用价值。论文首先对无源无线声表面波传感器的研究和发展状况进行了综合评述。然后采用自内到外的思路和样条插值相结合的方法提取了SAWR的分立元件等效电路参数。获得的结果是，在主谐振峰，串、并联谐振频率的相对误差都为零，串联谐振点电导的误差0．135％；二阶谐振频率的最大误差为2．88ppm，谐振电导误差3．67％。包括谐振点在内共2MHz的考查频率范围内，测量与计算特性曲线一致性明显。在SAWR提取参数的基础上，确定以最佳匹配的匹配网络为研究对象。按照着眼于整体匹配导纳特性的思路，先用双电抗元件将SAWR在谐振点频率附近匹配成等效RLC串联谐振电路，再串联阻抗传感器来获得稳定的低失配匹配网络。研究首先表明，阻抗传感器出现在X₃所在的位置对于获得稳定的低失配是必要的。然后，该匹配网络对应电容值0．6～7．5pF的变化范围可以获得270KHz的中心频率变化量，每点所对应的最小驻波比都在1．015以下，该特性在双SAWR结构中得以保持。试验获得驻波比的平均值小于1．2。T-CLC型低失配网络要求电容传感器具有初始电容小相对变化量大的特点。本文在周边固支的双振动膜模型基础上，采用中心岛型电极结构，通过控制电极／振动膜半径比值m的方法来实现该要求。研究表明，当固定两振动膜的中心位移与初始间距的比值，m增加则电容比按指数规律下降。当m=0．37，获得的电容比为10．将获得的电容-压力数据带入前述低失配网络，得到具有良好线性度的中心频率-压力关系曲线。最后，将发射和接收天线的二端口网络模型引入无源无线SAWR传感单元，构建了可以考察天线间距影响的完整模型。基于该模型，讨论了其影响机制，并提出将天线自阻抗与传输线特性阻抗相匹配，可以获得最小的间距变化对中心频率的影响。试验结果表明，当采用单SAWR结构，对应约20cm的间距变化范围，获得低至-1．75ppm／cm的中心频率-间距灵敏度。更多还原

【Abstract】 Passive Wireless SAW Sensors（PWSS）are considered the most promisingcandidates in place of active wireless sensors so far.However,changing the layout plan,orusing different SAWs forms seems not to make any further progress for the expansion ofthe application scope.The SAW’s physical properties determine that it is the best methodto apply the physical to the transmission path of the SAW.But some are not suitable fordirect measurement,which restrict the application area of PWSSs.Taking conventionalimpedance sensors as the loads of SAW devices,the new sensors which are named thePassive Wireless SAW Impedance-loaded Sensors（PWSIS）can be constructed.It is a newway to expand the sensing scope of PWSSs.Therefore,the PWSISs based SAW resonator（SAWR）needs to be extensively investigated and thereof the theoretical and applicationvalues are significant.In this paper,the current status of PWSSs and research progresses are reviewed in thepreface.Then,combining the from-inside-out idea and the spline interpolation method,theparameters of lumped-element equivalent circuit are extracted.The obtained results are asfollowing:the relative errors of series and parallel resonant frequencies of the mainresonance peaks are zero,and the relative error of series resonant conductance is 0.135%;the maximum relative error of the second-order resonant frequency is 2.88ppm,and that ofthe resonant conductance is 3.67%.In the 2 MHz frequency range around resonant peaks,the results of measurement and calculation have well consistency.On the base of extraction parameters,the best-matched matching network is taken asthe study objective.Focus on the overall admittance characteristics,the steps to obtainstable low-mismatched matching network include matching the SAWR to equivalentseries RLC branch with two reactive components and connecting the impedance sensor.The study shows that it is necessary for the impedance sensor to take the location of X₃ as it’s.For a capacitance range from 0.6 to 7.5 pF,the matching network can change thecenter frequency about 270 KHz,and the SWRs are all below 1.015.The characteristicsare maintained in the structure of dual-SAWR.The average value of measured SWR isbelow 1.2.The T-CLC low-mismatched matching network requires that the initial capacitance ofthe impedance sensor is small and the relative change is large.In this paper,on the base ofthe clamped-double-membrane model,using the center-island electrode structure,andcontrolling the electrode / diaphragm radius ratio m can meet previous requirements.Study shows that the capacitance ratio will decline with the increasing of m when the ratioof displacements of the two vibrating membrane and the initial distance is fixed.Whenm=0.37,the capacitance ratio is 10.Taking the obtained data of capacitance-pressure intothe previous low-mismatched matching network,the relation curve of center frequency-pressure has good linearity.Finally,the two-port network model of transmitting and receiving antennas isintroduced into the PWSIS unit,and the complete model which can examine the effects ofantenna distance on the center frequency is constructed.Based on the model,the influencemechanism is discussed,and a measure to weaken the impact is put forward.It ismatching the self-impedance of antenna to the characteristic impedance of transmissionline.The experimental results show that the sensitivity of center frequency-antennadistance is-1.75 ppm/cm.The results are obtained on the single-SAWR construct and adistance range about 20 cm.更多还原