影响超声波换能器回波频率的因素及控制方法

INFLUENCE FACTORS OF ULTRASONIC PIEZOELECTRIC TRANSDUCER ECHO WAVE FREQUENCY AND THE WAY OF CONTROLLING

在超声波换能器制造标准中规定超声波换能器的标称频率与其实际回波中心频率的误差不能超过±10%。在超声波换能器设计生产中,这是一个比较难以控制的指标。本文提出了用驻波理论设计出一个物理模型,将粘接后的保护膜与晶片看作一个整体,晶片中激发的超声波在这个整体中形成驻波。对给定频率的晶片可以用保护膜的厚度来控制探头的回波频率,减小保护膜的厚度,将提高探头回波中心频率,增加保护膜的厚度,将降低探头的回波中心频率。

Standard of making ultrasonicpiezoelectrictransducer stipulatesthat the error ofsymbol and truefrequency can'texceed ±10% . In theprocessof design and making ,thisfactorisdifficulttocontrol. This articlegivesa physicalmodle in view ofstandingwave theory. In thismodle , piezoelectriccrystaland protectivemembrane are connected as awhole . Shock wave in crystalforms standingwave inthe connected whole . When the crystalis given,wecan change the thicknessofprotectivemembrane tocontrolthe frequency of transducer. To increaseorreduce the thickness of protective membrane ,thefrequency of transducerwillriseor drop.