Bulk acoustic wave Barker code sequence and the application in ultrasonic NDT

A simple and convcnient method to gain bulk acoustic wave Barker code sequence is presented and the results of the correlation are givcn. The transducer response to a unit electric pulse is used as a unit code constituting the Barker code sequence of acoustic signal. The phase precision of the code sequence as well as the fairly ideal response function are guaranteed by the high accuraey of a DATA-2020 Arbitrary Waveform Synthesizer and a DATA-6000 Universal Wavcform Analyzer. Some deviations between the experiments and thcory are caused by the transient response and timc delay characteristics of the ultrasonic tansducer.

巴克码激励的超声气体流量测量研究

提出了一种用“编码激励＋相关测时”的超声气体流量测量方法。理论分析和数值仿真均表明，相同信噪比条件下，与传统的门限电平法及猝发脉冲激励相关法相比，巴克编码激励相关法的时延估计量方差具有更低的克拉美罗下界。采用标准表法标定实验，在200～1200m3／h范围内对比研究了巴克序列二进制相位调制激励相关和猝发脉冲激励相关的超声流量测量性能，前者测得流速的标准偏差和测量误差明显优于后者。