随钻声波发射换能器宽频阻抗匹配设计及实验

Broadband impedance matching design and experiment for acoustic while drilling transducer

发射换能器是随钻声波测井仪器的核心部件,其工作带宽及辐射声波能量的强弱是仪器的关键技术指标。换能器是一个非线性容性负载,可以采用阻抗匹配的方式增强有功功率并拓宽工作频带。本文将换能器多模态等效电路与阻抗匹配网络结合,利用电路网格方程对元件参数进行求解。最终在消声水池进行声场测试,观测换能器有功功率、声场辐射声压、发射电压响应等电、声特性,综合评估阻抗匹配网络的效果,为后续的随钻仪器研发及实验测试提供帮助和指导。实验结果表明,本文所设计的阻抗匹配网络能够明显改善换能器的声波辐射性能,频带宽度拓宽3.3倍,有功功率提高1.7倍,声压增强1.8倍,发射电压响应提高5 dB,在12~16 kHz的频带内发射电压响应最高可达125 dB。

The transmitting transducer is the core component of the acoustic logging while drilling tool(ALWD).Its working bandwidth and the strength of the radiated acoustic energy are two key technical indicators of the instrument.The transducer is a non-linear capacitive load.The impedance matching can be used to enhance the active power and broaden the working frequency band.This article combines the multi-mode equivalent circuit of the transducer with the impedance matching network.And the circuit grid equation is utilized to obtain the component parameters.Finally,the sound field test is implemented in an anechoic pool,while observing the electrical and acoustic characteristics of the transducer terminal active power,sound field radiation sound pressure,and emission voltage response.The effect of the impedance matching network is evaluated comprehensively.It provides help and guidance for the follow-up ALWD instrument development and experimental testing.Experimental results show that the designed impedance matching network can significantly improve the acoustic radiation performance of the transducer.The frequency bandwidth is expanded by 3.3 times,the active power is increased by 1.7 times,the sound pressure is increased by 1.8 times,and the emission voltage response is increased by 5 dB.The transmit voltage response in the 12~16 kHz frequency band is up to 125 dB.