Research On Self-noise Suppression Of Multi-cilia Array Vector Hydrophone

Vector hydrophones can detect vector information such as underwater particle vibrational velocity.So it is an important tool for acquiring underwater target sound sources.And it can be applied to underwater detection platforms such as sonar systems,underwater unmanned submersibles,air-dropped sonar buoys,etc.Research on their performance and application promotes the development of vector hydrophones.Currently,with the development of hydroacoustic combat and technology,the noise emitted by underwater platforms is being reduced substantially every year.In order to achieve the monitoring of low-noise platforms,reducing the self-noise of vector hydrophones to achieve the detection of weak signals is one of the current research hotspots.For the suppression of self-noise of cilium MEMS vector hydrophones,this thesis proposes a scheme to suppress sensor self-noise by arraying.The multi-cilia array vector hydrophone is a two-dimensional extension of the cilium MEMS vector hydrophone.Compared with the cilium MEMS vector hydrophone,the arraying can average the received voltage signal amplitude of each array with a pre-circuit.At the same time,this process averages the power of the uncorrelated self-noise of each array unit,thus achieving the suppression of the self-noise on the scale of amplitude.In this thesis,we start from the self-noise analysis of cilium MEMS vector hydrophone.And we mainly introduce the self-noise suppression principle of multi-cilia array vector hydrophone.Then we analyze the performance of multi-cilia array vector hydrophone.Finally we introduce the process preparation of sensor sensitive chip,the design of pre-circuit,the packaging of sensor and the experimental testing of the prototype.Specific work includes the following.(1)Static analysis and frequency analysis of the cilium MEMS vector hydrophone from the measurement principle.Analyze the self-noise of the cilium MEMS vector hydrophone,and determine the main noise source of the sensor.Study the principle of self-noise suppression for the multi-cilia array vector hydrophone.Establish the hydroacoustic detection model of the multi-cilia array vector hydrophone and study the consistency of the output of each array unit.Analyze and simulate the stress and characteristic frequency on the beam of multi-cilia array vector hydrophone.(2)Design the processing flow of multi-cilia array vector hydrophone sensitive chip.Design the low-noise signal conditioning circuit of multi-cilia array vector hydrophone,and perform circuit simulation to verify the circuit function.Prepare the bridge conduction circuit board for the sensor sensitive chip and complete the chip-level packaging.Consistent integration of multi-cilia on the sensitive chip.Design the natural rubber as the sound transmission material and the steel mesh as the inner support of the sound transmission cap.Simulate and analyze the characteristic frequency of the natural rubber cap supported by the steel mesh.Carry out the sensor integration package,and complete the prototype preparation.(3)Calibration experiments of the prepared sensor prototype were conducted to verify its vector detection capability.And the sensitivity was obtained as-197.3 d B@400 Hz with an operating band of 20 Hz ～ 400 Hz.The directivity has a better ’ 8’ shaped and deeper concave point depth,the analysis shows that better positioning accuracy can be obtained.Then,noise tests were conducted.The white noise spectrum of the multi-cilia array vector hydrophone was6 d B lower than that of its four array units.In X-and Y-ways,the equivalent self-noise level in the operating frequency band of the array output is lower than the mean value of its four units,with results of 5.18 d B and 5.14 d B respectively.The results verify the theoretical analysis.