Design And Performance Optimization Of MEMS Vector Hydrophone

In order to solve the detection of underwater far-field targets and the detection of quiet submarines,low-frequency detection and high SNR detection have become an important trend in the development of sonar systems.The hydrophone is the core component of the sonar system to receive the acoustic signal,and the performance of the hydrophone will directly affect the performance of the sonar system.Since the vector hydrophone can synchronously acquire the scalar and vector information in the sound field,and has good low-frequency directivity and anti-same noise,it can effectively improve the detection range and positioning accuracy of the sonar system.The MEMS vector hydrophone can realize the miniaturization,integration,low cost and low power consumption of the underwater acoustic sensor,especially in the low frequency range,it shows good sensitivity and directivity.MEMS vector hydrophone has become one of the research focuses of the water sound field.However,there are still some problems,such as the sensitivity and resonant frequency is a pair of inherent contradictions,and device reliability issues in high-impact applications,etc.Based on the previous research work,this paper studies the above problems of MEMS vector hydrophones,including:Firstly,based on the working principle of MEMS vector hydrophone to convert acoustic signals into electric signals,a complete multi-physics coupling simulation model is established by using COMSOL Multiphysics software.The simulation results of characteristic frequency,stress response and frequency response characteristics of the sensor are carried out.Meanwhile,the acoustic simulation of the influence of the package structure on the external water field is carried out,and the acoustic attenuation of the acoustic signal through the polyurethane package structure is calculated.It provides a theoretical basis for the subsequent optimization of hydrophone performance.Then,in order to solve the inherent contradiction between sensitivity and bandwidth performance of MEMS vector hydrophone chip,a stress-concentrated hydrophone chip structure design is proposed to improve the bandwidth performance of MEMS vector hydrophone sensitivity.By introducing a through-hole structure design at the root of the cross beam of the hydrophone chip,a stress concentration area(SCR)is formed to improve the device's ability to pick up stress.Using COMSOL software,three different stress concentration structure design schemes were compared,and the design with the highest stress response was selected as the final solution.And the stress-concentrated MEMS vector hydrophone sample was successfully prepared,and the test results show that the sensitivity of the stress-concentrated MEMS vector hydrophone can reach-187.9 dB(ref=1 V/?Pa,@1000 Hz),compared to the traditional MEMS vector hydrophone sample,at 20 Hz~1000Hz.The sensitivity is increased by approximately 5 dB over the frequency response range.Finally,based on the optimization of MEMS vector hydrophone chip structure,this paper proposes a new type of gel package design to solve the device reliability problem of hydrophone in high impact applications.The gel is potted in the hollow portion of the chip cross beam and the surrounding support structure,thereby realizing the packaging of the MEMS chip and improving the impact resistance of the cross beam structure.In this paper,the finite element model simulation is used to compare the stress response of the chip structure with or without gel package under 1000 m/s~2 impact.The simulation results show that the gel package method effectively improves the impact resistance of MEMS vector hydrophone chip.In order to verify whether the application of the package affects the key performance of vector hydrophone sensitivity,bandwidth,directivity,etc.,a gel encapsulated MEMS vector hydrophone sample was fabricated and calibrated in the standing wave tube.The test results show that the sensitivity of the gel encapsulated MEMS vector hydrophone can reach-164.3 dB(ref=1 V/?Pa,@1000 Hz),and the first-order resonant frequency of the hydrophone is appropriately increased,and the frequency response range is extended from 20 Hz~630 Hz to 20 Hz~1000 Hz.Simulation and test results show that the gel encapsulated MEMS vector hydrophone has good impact resistance,and has good sensitivity,working bandwidth and directivity.