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During underwater acoustic detection, the positioning accuracy of the bionic cilia MEMS vector hydrophone is affected by its own sensitivity. MEMS vector hydrophone operate in different temperature environments, so studies on the environmental temperature and the sensitivity of the MEMS vector hydrophone are of great significance. In this paper, based on the sensitivity of the MEMS vector hydrophone at room temperature (22°C), its sensitivity variation is studied within the temperature range of 0–40°C. The relationship between the temperature and the piezoresistor in the MEMS vector hydrophone is theoretically analyzed, and it is concluded that the sensitivity change is within ±0.6dB. The sensitivity change of MEMS vector hydrophone is proved to be within ±0.3 dB via COMSOL 5.4 simulation software, and the MEMS vector hydrophone is verified experimentally by the hydrophone temperature characteristic testing system. The results show that the variation of the sensitivity is within ±0.5 dB, which is basically consistent with the theoretical analysis results and simulation results. It can be said that under normal non-extreme ambient temperature, the operating temperature has little effect on the sensitivity of the MEMS vector hydrophone.

A self-contained MEMS vector hydrophone with a scalar–vector integrated design is proposed in this paper. Compared with traditional MEMS vector hydrophones, this design solves the problem of ambiguity in the port and starboard during orientation, and also realizes the self-contained storage of acoustic signals. First, the sensor principle and structural design of the self-contained MEMS hydrophone are introduced, and then the principle of the combined beamforming algorithm is given. In addition to this, the amplitude and phase calibration method based on the self-contained MEMS vector hydrophone is proposed. Then, the sensitivity and phase calibrations of the sensor are carried out in the standing wave tube. The sensitivity of the vector channel is −182.7 dB (0 dB@1 V/μPa) and the sensitivity of the scalar channel is −181.8 dB (0 dB@1 V/μPa). Finally, an outdoor water experiment was carried out. The experimental results show that the self-contained MEMS vector hydrophone can accurately pick up and record underwater acoustics information. It realizes the precise orientation of the target by combining beamforming algorithms. The direction of arrival (DOA) error is within 5° under the outdoor experimental conditions with an SNR of 13.67 dB.

The polyurethane-encapsulated lateral line-inspired MEMS vector hydrophone has problems such as low-frequency sensitivity (10–80 Hz) loss and narrow working bandwidth. In order to eliminate these two problems, a new encapsulation with a stainless steel mesh cap structure was proposed. This paper first verified the sensitivity loss and narrow working bandwidth of the polyurethane encapsulation through experiments and simulations, analyzed the impact of the perforation rate, thickness, and aperture of the stainless steel mesh cap structure on the vector hydrophone through simulation, and finally made 8 types of stainless steel mesh cap with different apertures was tested experimentally. Finally, the experimental results show that the sensitivity of the stainless steel mesh encapsulation in the low frequency range (10–80 Hz) is improved by an average of 12 dB than that of the polyurethane encapsulation, and the working bandwidth has been increased from 10–210 Hz to 10–667 Hz.

The traditional design of cilium MEMS vector hydrophone (CVH) usually adds attachment to the cilium to increase the force-bearing area of the cilium, which improves the sensitivity of CVH but also greatly reduces the inherent frequency of hydrophone, and brings heavier burden to the cross-beam. Based on the radiation noise of ships that is generally below 1 kHz, this article designs a sculpture-shape cilium MEMS vector hydrophone (SCVH). Compared to traditional CVH, it enhances the sensitivity of hydrophone, increases the resolution of weak signal, and reaches the working frequency band of 1 kHz. In this paper, the stress analysis of cantilever beam is carried out, and then the appropriate size of SCVH is determined by simulation analysis. Finally, the sensitivity and directivity experiments in standing wave tube are carried out. The experimental results show that the sensitivity of SCVH at 1 kHz reaches -184.2 dB (0 dB = 1 V/μPa), 13.1 dB higher than traditional CVH. The working frequency band of SCVH is 20 Hz-1kHZ, and the depth of “8”-shaped directivity concave point is larger than 30 dB.

Ciliary MEMS vector hydrophone (CVH) has excellent performance in low-frequency detection, however, there is still the problem of poor sensitivity in some applications. A cap-shaped ciliary vector hydrophone (CCVH) is proposed in this paper. The microstructure not only ensures the working bandwidth of the hydrophone, but also increases the sensitivity. A single integration process is adopted to complete the pasting of the cap-shaped cilia and the cantilever beam, requiring no complicated secondary cilia integration process. Firstly, a mathematical model is established for theoretical derivation, and then the principle is verified via COMSOL simulation. Finally, test results show that the sensitivity of CCVH can reach −182.7 dB at 1 kHz (1 kHz, 0 dB@1 V/µPa). Compared with the CVH, the sensitivity has increased by 14.4 dB. Concave point depth of 8-shaped directivity is beyond 30 dB, which indicates that CCVH has an excellent ability to detect underwater ship noise.

In view of the problem that the increased difficulty of underwater moving targets detection caused by the development of acoustic stealth technology, a beaded cilia MEMS vector hydrophone (BCVH) is proposed in this paper. Compared with previous cilia structures, it can enlarge the receiving area of acoustic wave to improve sensitivity without the introduction of additional structures. Meanwhile, the introduction of additional mass and the loss of working frequency band are reduced, and the structure is manufactured at one time. In this paper, the design scheme and optimal size of BCVH are determined via theoretical analysis and simulation, then vector hydrophone calibration system is used to verify it. The experimental results show that the sensitivity of BCVH reaches −183.3 dB (@1kHz, 0 d B = 1 V / μ P a ), 13.7 dB higher than bionic cilia MEMS vector hydrophone (CVH). Moreover, the depth of concave point of BCVH is more than 30 dB, which has a good directivity.