Vector Hydrophone Research Articles

Correction to: Design and modeling of a novel high sensitive MEMS piezoelectric vector hydrophone

In the original article, one of the co-author’s (Morteza Dardel) family name has been published incorrectly. The correct family name should be Dardel. The original article has been corrected.

Redundancy-Removed MUSIC-like Algorithm Based on Single Vector Hydrophone

To reduce the operation time of the MUSIC-like algorithm on a single vector hydrophone, a redundancy-removed MUSIC-like algorithm was proposed. For the extended steering vector, this algorithm removes the repetitive elements directly. For the fourth-order cumulant matrix, the algorithm removes the redundancy using the conjugate symmetry. Simulation experiments show that the proposed algorithm lose a little performance compared with the regular MUSIC-like algorithm. However, the computational cost of the proposed algorithm is reduced greatly.

Design and modeling of a novel high sensitive MEMS piezoelectric vector hydrophone

In this paper, a novel micro electromechanical systems (MEMS) piezoelectric hydrophone with the ability to detect the direction of the sound in two dimensions was designed and analyzed. Piezoelectric hydrophones are widely used today. These devices constitute the main part of the sonar systems. Sonars are used in marine vessels and for transportation of marine military equipment, such as submarines and battleships. Hydrophones work by converting received sound pressure to electrical signals. The idea of the present paper for designing hydrophones is taken from sea creatures and use artificial hair cell structure. This structure not only has the advantages of piezoelectric sensors such as being active and having optimal sensitivity, but it is also able to detect the direction of the sound and work at low frequencies, the performance of the sensor has been improved compared with the previous works (Ito et al. in Sens Actuators, 2008; Choi et al. in Sens Actuators, 2010; Guan et al. in Microsyst Technol, 2011; Sens Actuators, 2012; Zhang et al. in Design of a monolithic integrated three-dimensional MEMS bionic vector hydrophone, 2014), in a way that its sensitivity is ź 191 dB in the frequency range of below 10.4 kHz (0 dB re 1 V/μPa).

Realization of a composite MEMS hydrophone without left-right ambiguity

A sound-pressure sound-pressure-gradient composite MEMS vector hydrophone has been proposed and demonstrated to solve the problem of left-right ambiguity that is intrinsic to existing MEMS hydrophones measuring the pressure gradient of a vector sound field. A newly-designed capacitance scalar microstructure is added into a MEMS vector hydrophone that otherwise consists of only a regular cilium-four-beam microstructure. Theoretical model shows that the left-right ambiguity problem can be artfully solved by synthesizing the output signals from the vector and scalar structures. The hydrophone’s ability of azimuth measurement is tested with a standing-wave tube and the error of direction of arrival (DOA) estimation is within 1°. Moreover, the composite hydrophone remains the frequency response trend of the cilium MEMS vector hydrophone. We believe that this work is a significant advance in the development of MEMS hydrophone and should place a solid base for relevant engineering applications.

Design and optimization of stress centralized MEMS vector hydrophone with high sensitivity at low frequency

Abstract A micro hydrophone based on piezoresistive effect, “MEMS vector hydrophone” was developed for acoustic detection application. To improve the sensitivity of MEMS vector hydrophone at low frequency, we reported a stress centralized MEMS vector hydrophone (SCVH) mainly used in 20–500 Hz. Stress concentration area was actualized in sensitive unit of hydrophone by silicon micromachining technology. Then piezoresistors were placed in stress concentration area for better mechanical response, thereby obtaining higher sensitivity. Static analysis was done to compare the mechanical response of three different sensitive microstructure: SCVH, conventional micro-silicon four-beam vector hydrophone (CFVH) and Lollipop-shaped vector hydrophone (LVH) respectively. And fluid–structure interaction (FSI) was used to analyze the natural frequency of SCVH for ensuring the measurable bandwidth. Eventually, the calibration experiment in standing wave field was done to test the property of SCVH and verify the accuracy of simulation. The results show that the sensitivity of SCVH has nearly increased by 17.2 dB in contrast to CFVH and 7.6 dB in contrast to LVH during 20–500 Hz.

Extrinsic Fabry–Perot Cantilever Accelerometer Based on Micromachined 45° Angled Fiber

High-sensitivity extrinsic Fabry-Perot cantilever accelerometers were proposed and tested. Micromachined 45° angled fiber was adopted to form the cantilever to measure the acceleration. The Fabry-Perot cavity was formed by the sidewall of the fiber and the inner surface of commercial ceramic sleeves. The stepped cantilever fiber was fabricated by etching method to improve the sensitivity without enlarging the cantilever's length or adding extra proof-mass. Detailed theoretical analysis, simulation, and experimental results of the proposed accelerometers were given. The measured results were in good agreement with the simulated results. The proposed accelerometers show the advantages of high flexibility, simplicity, compactness, and low cost, which are expected to be applied in the field of miniaturized vector hydrophone and seismic monitoring.

Spatial-division-multiplexing in time-variant and multi-path channel based on vector adaptive time reversal technique

In the field of multistatic remote detection for underwater target, as a time-variant and multi-path channel interfered by environmental noise, complex underwater acoustic environment limits the spatial share of channel and poses a great challenge against spatial-division-multiplexing (SDM) in multistatic detection. In this paper, a kind of method of spatial-division-multiplexing(SDM) based on vector adaptive time-reversal technique is proposed. By use of time-reversal technique, multi-path structure of channel is efficiently restrained; Meanwhile, with adaptive filtering applied, time-variant characteristic of channel is effectively suppressed. Moreover, with single vector hydrophone, spatial focus of target echoes and noise interference suppression is accomplished by spatial filtering. Finally, excellent results are performed in SDM of multistatic detection, supported by the experimental simulation.

Research on near field acoustic source localization algorithm based on arbitrary planar vector array

In order to solve the problem of near acoustic target location, vector hydrophone array with arbitrary formation is proposed to locate near field acoustic source. In this paper, firstly, the near field measurement model of vector hydrophone array is derived detailed. Then, introduces the conventional beamforming and MVDR algorithm based on vector hydrophone array. Finally, the performance of the algorithm is verified by simulation. The results show that the vector MVDR has higher target resolution, and the error decreases with the increase of SNR. It is more suitable for underwater near field regional warning.

Short cavity DFB fiber laser based vector hydrophone for low frequency signal detection

A short cavity distributed feedback (DFB) fiber laser is used for low frequency acoustic signal detection. Three DFB fiber lasers with different central wavelengths are chained together to make three-element vector hydrophone with proper sensitivity enhancement design, which has extensive and significant applications to underwater acoustic monitoring for the national defense, oil, gas exploration, and so on. By wavelength-phase demodulation, the lasing wavelength changes under different frequency signals can be interpreted, and the sensitivity is tested about 33 dB re pm/g. The frequency response range is rather flat from 5 Hz to 300 Hz.

Analysis of a thickness-shear mode vibrator for the accelerometer in vector hydrophones

Typical hydrophones in line array sensors used to detect covert underwater targets can measure only sound pressure magnitude with the limitation of being unable to identify the direction of an incoming wave. In this paper, a thickness-shear mode vibrator is proposed as the main component of an inertia-type vector hydrophone to measure both the magnitude and direction of acoustic signals from targets. The piezoelectric single crystal lead magnesium niobate-lead titanate with rhombohedral 3m symmetry constitutes the vibrator. The directional voltage response of the vibrator to an external force is derived, and the validity of the derived response is verified through fabrication of a piezoelectric single crystal vibrator and by comparison of its measured characteristics with the analysis results.

Method for measuring self-noise of vector hydrophones

The Vector Hydrophone (VH) is widely used to remotely detect underwater targets. Accurately measuring the self-noise of the VH provides an important basis for evaluating the performance of the detection system in which it is utilized, since the ability to acquire weak signals is determined by the VH self-noise level. To accurately measure the VH self-noise level in actual working conditions, the Dual-channel Transfer Function Method (DTFM) is proposed to reduce ambient background noise interference. In this paper, the underlying principles of DTFM in reducing ambient background noise is analyzed. The numerical simulations to determine the influence of ambient background noise, and the sensitivity difference of the two VHs on the measurement results are studied. The results of measuring the VH self-noise level in a small laboratory water tank by using DTMF indicate that ambient background noise interference can be reduced effectively by employing DTMF, more accurate self-noise level can be obtained as well. The DTMF provides an effective method for accurately measuring the self-noise level of VHs and also provides technical support for the practical application of the VH in underwater acoustics.

Cross-supported planar MEMS vector hydrophone for high impact resistance

The high g shock resistance and sensitivity are two dominant factors to impact the airdropped sonobuoy reliability. In order to improve the high g shock resistance and sensitivity of MEMS vector hydrophones for airdropped application, cross-supported planar MEMS vector hydrophone is presented in this paper. The planar-shaped vibration unit with the Wheatstone bridge is defined on the wafer, and stress concentration region (SCR) is etched on the back of wafer. After theoretical and numerical calculation, the acceleration shock reaches up to 2000m/s2 when the sonobuoy is thrown in the sea and contacted the water. According to the simulation, the max equivalent stresses respectively are 91.3MPa (along the direction of X axis), 92.3MPa (along the direction of Y=X axis) and 16.2MPa (along the direction of Z axis), whereas the fracture strength of Si is reported 175MPa. Optimum parameters are determined in view of the sensitivity, frequency and impact resistance of hydrophone. The test results demonstrated the hydrophone has favorable sensitivity and directivity. In brief, the cross-supported planar MEMS vector hydrophone was fabricated and its superiority was preliminarily confirmed.

The Development of the Differential MEMS Vector Hydrophone.

To solve the problem that MEMS vector hydrophones are greatly interfered with by the vibration of the platform and flow noise in applications, this paper describes a differential MEMS vector hydrophone that could simultaneously receive acoustic signals and reject acceleration signals. Theoretical and simulation analyses have been carried out. Lastly, a prototype of the differential MEMS vector hydrophone has been created and tested using a standing wave tube and a vibration platform. The results of the test show that this hydrophone has a high sensitivity, Mv = −185 dB (@ 500 Hz, 0 dB reference 1 V/μPa), which is almost the same as the previous MEMS vector hydrophones, and has a low acceleration sensitivity, Mv = −58 dB (0 dB reference 1 V/g), which has decreased by 17 dB compared with the previous MEMS vector hydrophone. The differential MEMS vector hydrophone basically meets the requirements of acoustic vector detection when it is rigidly fixed to a working platform, which lays the foundation for engineering applications of MEMS vector hydrophones.

벡터 하이드로폰을 위한 두께 전단형 진동자의 빔 패턴 해석

수중에서 은밀하게 움직이는 표적을 조기에 탐지하기 위한 선배열센서에 적용되는 통상의 하이드로폰은 표적신호의 크기만 측정할 뿐, 외부에서 들어오는 음향신호의 방향은 파악할 수 없는 한계가 있다. 이에 본 연구에서는 표적으로부터의 음향신호의 크기와 방향을 동시에 탐지할 수 있는 관성형 벡터 하이드로폰의 기본 구성품으로 두께 전단형 진동자를 제안하였다. 외력에 대한 진동자의 출력 전압을 해석할 수 있는 수식을 유도하였으며, PMN-PT 단결정 진동자에 대한 유한요소해석을 통해 수식의 타당성을 검증하였다. 본 연구에서 얻어진 해석 결과는 향후 두께 전단형 진동자로 구성된 관성형 벡터 하이드로폰 설계에 활용될 것이다. Typical hydrophones in line array sensors for early detection of covert underwater targets can measure only sound-pressure-magnitude with the limitation of being unable to identify the direction of an incoming wave. In this study, a thickness shear mode vibrator was proposed as the main component of an inertia type vector hydrophone to measure both magnitude and direction of acoustic signals from targets. The equation to analyze the output voltage of the vibrator to an external force was derived, and the validity of the equation was verified through finite element analysis of a PMN-PT single crystal vibrator. The analysis results from this study will be utilized in the future for the design of inertia type vector hydrophones made of thickness shear vibrators.

Influence of beat phenomenon on direction of arrival estimation based on a single vector hydrophone

The vector hydrophone can measure sound pressure and orthogonal components of particle velocity co-locately in space and simultaneously in time. DOA (direction of arrival) estimation based on a single vector hydrophone has attracted extensive attention. Beat phenomenon can cause confusion in the DOA estimation results. In this paper, the impact mechanism of beat phenomenon to DOA estimation by cross spectrum method and average acoustic intensity method is explored through theoretical study and simulation. The result shows that beat phenomenon causes the change of sound pressure and vibration velocity amplitude with time and leads to DOA estimation results of these two methods are instability eventually. First, DOA is estimated by the average sound intensity method, if the temporal resolution is smaller than the minimum envelope period, the DOA estimation will change over time; Second, DOA is estimated by the cross spectral method, if the FFT frequency resolution is greater than frequency difference, it is unable to distinguish the frequency of these two signals. Subsequent operations will also be confused by two signal energy, causing error estimates. In the end, the solutions and application examples are proposed. The conclusion could be applied to improve the DOA estimation performance of a single vector hydrophone.

Spatial-division-multiplexing (SDM) in time-variant channel based on vector adaptive time-reversal technique

In the field of multistatic remote detection for underwater target, as a time-variant and multi-path channel interfered by environmental noise, underwater acoustic environment limits the spatial share of channel and poses a great challenge against spatial-division-multiplexing(SDM) in multistatic detection. In this paper, a kind of method of spatial-division-multiplexing(SDM) in time-variant channel based on vector adaptive time-reversal technique is proposed. By using time-reversal technique, multi-path structure of channel is efficiently restrained ; Applied adaptive filtering, time-variant characteristic of channel is effectively suppressed; With single vector hydrophone, spatial focus of target echoes and noise interference suppression is accomplished by spatial filtering. Finally, excellent results are performed in spatial-division-multiplexing(SDM) of multistatic detection, supported by the experimental simulation.

Design of automatic testing system for sensitivity of MEMS vector hydrophone

Due to the single, heavy and time-consuming testing task and the uncertain errors of manual operation of MEMS vector hydrophone sensitivity testing, this paper uses AD9850, AD8599, PGA205, MK60DN512ZVLQ110 micro-controller chips, to design an auto testing device of MEMS vector hydrophone sensitivity based on the analysis of the testing principle of vector hydrophone sensitivity. This device integrates signal excitation source, weak signal detection, signal conditioning, sampling and transmission module. It shrinks testing instrument, integrates multi module and connects PC to make quick and timely calibration testing of vector hydrophone sensitivity, which not only saves testing time greatly, but also can optimize the hydrophone rapidly. It has the advantages of small size, lightweight and simple testing, which brings convenience to field testing and accelerate engineering application of MEMS vector hydrophone.

A ‘fitness-wheel-shaped’ MEMS vector hydrophone for 3D spatial acoustic orientation

For the purpose of acquiring precise underwater 3D spatial orientation, a ‘fitness-wheel-shaped’ MEMS vector hydrophone (FWVH) is developed, which achieves monitoring of a tri-axial acoustic pressure differential via appropriate constructional design and strain readout. Compared to the previously reported T-structure-combined vector hydrophone (TSVH) which has a nonlinear relationship between output and external force, using the FWVH it is feasible in principle to achieve a tri-axial match, which make it promising in accurate acoustic orientation. A theoretic model for sensitivity is developed, where torque moment is taken into consideration to match the simulation and practical results. Superior to 3D force sensors, bandwidth is taken as the key index for the FWVH and is designed in detail with a compromise of sensitivity. In view of the bandwidth, the parameters are determined for detecting the signal in the range 20–300 Hz. A vibration test demonstrates tri-axial resonance frequencies. Finally, the frequency response curve of the FWVH shows that tri-axial sensitivities are consistent, agreeing with the analysis and simulation results, which reach −174 dB (0 dB referring to 1 V µPa−1) at 300 Hz.

一种改进的矢量阵常规波束形成方法研究

为了更好的探测低信噪比目标，我们研究了矢量阵的常规波束形成，理论和仿真分析了常规时延方法最近邻法、矩形窗sinc函数插值法以及FFT相移法对信号的影响，结果表明矩形窗sinc函数插值法以及FFT相移法对信号进行时延补偿可以提高矢量阵接收信号之间的相关度，性能优于最近邻法。我们给出了频域分子带相移的矢量阵常规波束形成算法以及实现流程，并进行了仿真分析，比较了利用三种延时方法所到的矢量阵波束形成结果，虽然sinc-VCBF有较好性能，但是运算速度较慢，而VFFTABF比sinc-VCBF和最近邻VCBF执行速度更快，且性能与sinc-VCBF相当。 In order to detect low signal ratio underwater targets, we studied conventional beamforming for vector sensor array and analyzed nearest conventional time delay method, rectangular window sinc function interpolated method, and FFT phase-shifting method through theory and simulation. The results showed that rectangular window sinc function interpolated method and FFT phase- shifting method could improve the coherence degree between signals receive by vector sensor array. Their capability was better than nearest conventional time delay method. An improved beamforming technique for vector hydrophone array based on FFT was developed. The flow chart of this algorithm was given. The simulation result showed that though sinc-VCBF had better capability, its calculation speed was slower. VFFTABF calculation speed was faster than sinc-VCBF and VCBF, and had almost the same capability with sinc-VCBF.

Analysis of MEMS Piezoelectric Hydrophone at High Sensitivity for underwater application

Micro-electromechanical systems (MEMS), is a technology that is used to design small integrated devices that combines both electrical (voltage, resistance) and mechanical components (stress, displacement). These devices are assembled using integrated circuit batch processing methods and their size can vary from Micrometers (µm) to Millimeters (mm). MEMS devices have the capability to sense and control the environment. These devices are fabricated using System Integrated chip technology and micro-level segments are manufactured using silicon. To remove the selective parts of silicon i.e. extra silicon parts, Processes such as back etching, high-aspect-ratio micromachining are used to remove selective parts of silicon or to add the extra layers to form the electromechanical components. The study is concerned to design a T- Shape vector Hydrophone using MEMS Technology and to analyses mechanical properties like induced stresses, deformation and to analyses the piezoelectric hydrophone characteristics like frequency response, sensitivity and Voltage to achieve improved sensitivity. MEMS Directional Hydrophone PZT is simulated. Both the structure resembles the fish lateral line and auditory cilia system which converts acoustic pressure into voltage