Broadband Electrical Impedance Matching of Transmitter Transducer for Acoustic Logging While Drilling Tool

An electrical impedance-matching network (EIMN) is proposed to achieve a broad transmitter transducer bandwidth for the acoustic logging while drilling tool. The series–parallel inductor–capacitor–inductor (
${L}_{s}{C}_{p}{L}_{p}$
) network is used as the EIMN, and the simplified structure is found to be helpful for actual instrument installation. In contrast to conventional computer-aided methods for designing EIMNs, this study calculates the impedance-matching network parameters based on circuit equations and design indicators. First, the equivalent model of the transducer is identified through a nonlinear regression process. Then, the equivalent circuit of the transducer and the EIMN are combined, and the EIMN parameters are solved using circuit equations and design indicators. Simulations showed that the proposed impedance-matching network can effectively improve the active power and working bandwidth of the transducer. Further, the results of tests conducted on a sound field in an anechoic pool showed that after impedance matching, the electrical characteristics, that is, the active power of the transducer, is increased by 340%, and the frequency bandwidth is broadened by 1260%. The sound pressure radiated by the transducer was also increased by 307.56% in the required frequency band, and the sound power curve was similar to that of the electric power. In addition, the emission voltage response was highly consistent. The experimental results verify that the proposed impedance-matching network can significantly increase the output sound power of the transducer and can thus be a reference for instrument research and development.