| Hydrophone is an important instrument for ocean exploration and communication,and it is one of the key directions of ocean instrument and equipment research.Due to the rapid development of Underwater Unmanned equipment such as Unmanned Submarine Vehicle(UUV)and Underwater Robot,there is an urgent need for the development of new low-cost hydrophones.Because of its low power consumption,low cost,miniaturization and lightweight,the MEMS hydrophone is suitable for Underwater Unmanned equipment.In this paper,based on Al N piezoelectric film and MEMS technology,a MEMS hydrophone is designed and manufactured.The design and processing of the structure and packaging of the MEMS chip,the analysis and design of the signal conditioning circuit,the design and construction of the automatic measurement system of the hydrophone,and the comprehensive test of the performance of the MEMS system hydrophone are mainly studied.Firstly,the influence of the structure parameters,such as silicon support thickness,Al N piezoelectric layer thickness,and film element size,on the acoustic pressure sensitivity and frequency response of the hydrophone is studied by finite element simulation.MEMS hydrophone chips were fabricated by Al N film sputtering,Al N-on-SOI etching,and SOI back cavity vacuum packaging.Further,the external packaging structure of the MEMS hydrophone chip is designed,and the packaging process of the MEMS hydrophone chip is implemented by using 3D printing technology.Another important component of the MEMS hydrophone is its signal conditioning circuit,which amplifies weak signals and overcomes the high internal resistance of MEMS chip.In this paper,the equivalent electrical model of the MEMS chip is analyzed,and the signal conditioning circuit is designed according to the equivalent electrical model of the MEMS chip.In order to solve the noise problem of the chip signal conditioning circuit,the self-noise at the output of the MEMS hydrophone is further analyzed,and the simulation,fabrication and test of the signal conditioning circuit are completed.In order to meet the urgent need of the automated measurement system of the MEMS hydrophone,an automated measurement system of hydrophone sensitivity and self-noise based on Lab VIEW platform is designed and developed.Based on this self-developed test system,the sensitivity,self-noise and linearity of the designed and manufactured MEMS hydrophone are measured experimentally.Further,the test results of the self-developed measurement system are compared with those of the national first-level measurement stations.The test results show that the sensitivity measurement of the self-developed system is within+1.5 d B in the frequency band from 10 Hz to 20 k Hz,and within +2 d B in the frequency band from 1,000 Hz to 20 k Hz in the noise measurement.Good results are achieved,which can effectively improve the testing and development efficiency of MEMS hydrophone.Finally,the results of the hydrophone index test show that the sensitivity of the developed MEMS hydrophone is-186.1d B～-182.6d B(Ref.1V/μPa)from 10 Hz to 20 k Hz and the self-noise is 65.6d B@1000Hz(Ref.1 μPa/ Hz),linearity 0.144%,power consumption15.3m W,all meet the design expectations.In addition,the designed hydrophone has certain environmental adaptability by measuring the effect of operating temperature and storage temperature on the sensitivity of the hydrophone.The test results of various performance indexes show that the MEMS hydrophone designed and developed in this paper has high engineering application value. |
