"Carved Cilia" Composite MEMS Vector Hydrophone Based On Steel Mesh Packaging

The MEMS vector hydrophone independently developed by North University of China has the advantages of small volume,low power consumption and good low-frequency response characteristics.It can be applied to small platforms such as drag array,airdrop buoy and UUV.After years of development,by integrating piezoelectric ceramic tube as scalar channel on the basis of MEMS vector hydrophone,a composite MEMS vector hydrophone is designed,which can solve the problem that port and starboard cannot be distinguished in underwater orientation,and this design has been used all the time.However,as a vector acquisition channel,MEMS vector hydrophone still has the problems of low sensitivity and mutual restriction between natural frequency and sensitivity.The introduction of piezoelectric ceramic tube as scalar channel will increase the package volume,which leads to the reduction of package resonant frequency and the reduction of working frequency band of hydrophone.The polyurethane package of composite MEMS vector hydrophone has the problem of reducing the lowfrequency sensitivity of vector channel.To solve these three problems,this paper optimizes the cilia of MEMS vector hydrophone to improve the sensitivity of vector channel,and solves the problem of mutual restriction between natural frequency and sensitivity to a certain extent.A new package is designed for the composite MEMS vector hydrophone to enhance the engineering application ability.In the previous MEMS vector hydrophone(CVH)design,it is usually considered to add attachments to the cilia to increase the force area of the cilia,which improves the sensitivity of CVH,but will greatly reduce the natural frequency of the hydrophone and bring a heavier burden to the cantilever beam.In this paper,an engraved ciliated MEMS vector hydrophone(scvh)is designed,which has the same force area and smaller mass compared with cylindrical cilia.Compared with the traditional CVH,this carved ciliary microstructure increases the sensitivity of the hydrophone and maintains a certain working bandwidth.The polyurethane package of the composite MEMS vector hydrophone has little effect on the performance of the scalar channel at low frequency,but the vector channel has the problems of low frequency sensitivity(10-80hz)loss and narrow working band width.In order to eliminate these two problems,a new package with stainless steel mesh cap structure and parylene combination is proposed.The resonant frequency of the steel mesh package is higher than that of the MEMS vector hydrophone,so the working bandwidth of the MEMS vector hydrophone will not be reduced.Through size design optimization,the sensitivity of the hydrophone is hardly reduced,and due to its robustness,it also provides sufficient protection for the composite vector hydrophone.For these two optimization designs,the main work includes the design,theoretical analysis and simulation analysis of the vector sensitive structure of the composite MEMS vector hydrophone.Theoretical analysis of scalar channel and selection of piezoelectric ceramic tube.Then,the chip processing technology of the vector part of the composite MEMS vector hydrophone and the fabrication of the composite vector hydrophone are introduced.Finally,the sensitivity,directivity,hydrostatic pressure resistance,vibration test and field test of the composite vector hydrophone are carried out.It is proved that the composite MEMS vector hydrophone has the potential of engineering application.