Research Of MEMS Bionic Vector Hydrophone Based On Silicon

The application of vector hydrophone endows several advantages for detection of submarines: It can obtain both the sound pressure and particle velocity of sound field simultaneously, and effectively reduce received intensity of isotropic hindrance and so on. Therefore, all countries with noticeable navy force have drawn unprecedented attention on the vector hydrophone and many works have been done about it. Although great achievements have been made nowadays, there are still some limitations in following topics about design of vector hydrophones:(1) High sensitivity;(2) Ultra-low-frequency detection;(3) Miniaturization of vector hydrophone;(4) Self-noise control.Above problems require development of bionic technology of new sensor based on MEMS technology and bionic theory as well as piezoresistive principle and be finally solved in sonar design with the help of bionic microsystem integrated technology. In this paper, a piezoresistive bionic vector hydrophone based on MEMS had been proposed. It is desirable that the application of ingenious bionic structure and piezoresistive effect may improve the low-frequency sensitivity of vector hydrophone. It is desirable that the application of batch fabrication technology of MEMS may improve the miniaturization and consistency of vector hydrophone. It is desirable that the application of MEMS technology and assembly processing may effectively solve the bionic manufacture problem of complex structure. It is desirable that the low-frequency sensitivity and miniaturization as well as consistency of vector hydrophone may be benefit because of the above method the technology.In this paper, the bionic theory and piezoresistive principle of semiconductor material had been detailedly analyzed. And since the thesis concerns application of new principle of acoustic signal detection, the feasibility and correctness of the detection theory originate from the correctness of analysis of vibration sensing mechanism. Therefore the condition of vibration sensing of vector hydrophone had been analyzed from acoustic point of view, and the theoretical model be established from theory of vibration, the feasibility of application of new principle, new technology and new techniques .piezoresistive effect had also been discussed according to the design of piezoresistive vector hydrophone.According to the above principle, a novel bionic microstructure was designed. The simplified analytical model of the microstructure was established to describe the microstructure's mechanical behaviour. Finite element modeling was also conducted to verify the analytical model and evaluate the performance of the microstructure. Comparison of the results obtained from the analytical model and finite element simulation was completed. Microfabrication technology based on MEMS has been employed for the fabrication of the vector hydrophone. By means of the simulation of fish's neuromast organ, the packaging the bionic microstructure has been accomplished and the prototype of the vector hydrophone has been fabricated.In order to verify sensor function, preliminary characterization tests of the hydrophone have been performed. The obtained results show that the artificial hydrophone can effectively be used as an underwater acoustic sensor for frequencies within its resonance frequency width. The novel hydrophone not only possesses satisfactory directional pattern and good low-frequency characteristic but also has miniature structure and lightweight quality as well as simple structure. The free-field voltage sensitivity is–197.2dB( 0 dB = 1v/μPa) at 400 Hz. The depth of pits of the directivity pattern is about 28.2dB. The experiment results on the sea were obtained and showed that the bionic hydrophone vector has good application value in engineering.The main research fruits are as following:(1) The design of the bionic microstructure is accomplished by means of the simulation of the fish's neuromast organ. (2) The application of the bionic theory and piezoresistive effect of semiconductor material as well as co-vibrating principle improves the low-frequency characteristic of the vector hydrophone, and which satisfies the requirements for low-frequency acoustic detection in underwater acoustic field.(3) By means of the microfabrication technology based on MEMS and acoustic packaging technique, a prototype of micromachined fish-like artificial vector hydrophone for underwater sound explorations at low-frequency had been obtained, and which effectively solve the bionic manufacture problem of complex structure and achieve the prospective objective for the miniaturization of vector hydrophone.