Broadband Longitudinal Transducer Research Based On Mutiple-resonant Modals

As the core component of underwater sounds transmission,the performance improvement of underwater acoustic transducer is signality for the sonar system.Longitudinal transducer has been widely used in homing torpedoes and underwater acoustic countermeasure because of its simplicity,stability,good performance and easy mounting.This paper aims to study the mutiple-resonant broadband underwater transducer based on double-excited longitudinal transducer,to broaden the working bandwidth with less transmitting voltage response fluctuation range.Firstly,the anslysis of the resonant frequency and the electrical admittance of the double-excited transducer is provided based on the equivalent circuit method,the finite element method is also used to analyze and optimize the double-excited broadband transducer,and the effects of structure parameters variation on the performance of broadband transducer is researched.Then,a triple-excited broadband transducer is designed based on the double-excited transducer,and the finite element method is used to study the effects of structure parameters variation on the performance of broadband transducer.For the bandwidth of the designed transducer from 20kHz-50 kHz,the amplitude variation of the transmitting voltage response(TVR)does not exceed ±1.5dB and a minimum TVR of 136 dB is obtained.The double-excited and triple-excited broadband transducer samples are fabricated according to the design later.And the characteristics of impedance and TVR of the samples are measured in muffling pool.The results of the experiment show that,the amplitude variation of the transmitting voltage response(TVR)does not exceed ±3dB and a minimum TVR of 132 dB is obtained to the samples of the bandwidth from 21kHz-46 kHz.The study shows that,the experimental results agree well with the numercial results.The bandwidth of the double-excited and triple-excited broadband transducer improves greatly compared with the conventional longitudinal transducer.The triple-excited broadband transducer has advantages over the double-excited broadband transducer in optimization and TVR valley control.It can also be found that it's viable to design broadband longitudinal transducer based on mutiple-resonant modals,and it can be used in triple-excited broadband transducer design and development.