A new design of linear piezoelectric actuator using "A-shaped" structure was proposed, designed, fabricated, and tested. By fusion the transducer mechanical structure, proposed only uses first bending vibration center to work. Frequency degeneration is no longer needed, which enables adjust its structural parameters according application conditions. When applying an alternating voltage at resonance frequency, will be stimulated in vibration. The energy transmitted two driving arms generates...

Spectral analysis is a significant technique applied in many fields to infer the signal spectral contents. However, frequency resolution of spectrum estimation result limited by its finite data length, especially when using Fourier-based method. Extra processing gain [i.e., signal-to-noise ratio (SNR) improvement] always required for weak target detection. In this paper, high-resolution method deconvolution algorithm proposed. According classical analysis, power derived from length related...

Abstract For the detection of underwater moving target with constant speed at low signal-to-noise ratio (SNR), a track-before-detect method is proposed based on motion parameters estimation and hidden Markov model (HMM). Optimization algorithm used for parameter cost function obtained by energy accumulation along line spectrum tracked 1-D Hidden in spatially filtered LOFAR spectrum. This suitable detecting weak targets fast changes azimuth.

The Hilbert-Huang transform (HHT) has the advantage in dealing with non-stationary signals, for its data driving. However there are some limitations of original HHT. For getting more benefits frequency resolution, an improved HHT is applied this paper. In version, instantaneous harmonic retrieval method to calculate frequencies intrinsic mode functions, which overcomes limitation Hilbert transform. simulation result shows, HHT, we can get resolution than At same time experimental prove...

An optimal all-digital phase generated carrier (PGC) demodulation scheme for optical interferometric sensors is presented in order to reduce the effect of frequency and difference between reference signals. First, influence on signal from PGC discussed when are inconsistent with signal. It reveals that different frequencies phases will cause modulation fading phenomena output scheme. Second, a track algorithm proposed lock real time these influences The can be tracked by analysis,...

Aiming at the passive impulse wideband source range problem in shallow water waveguides, a method with single hydrophone which is applied to waveguide bottom of liquid semi-infinite space presented this paper by combining group delay theory and warping transformation. The receive signal composed several normal modes, each mode represents many characteristics environment. Warping transformation good tool can achieve separation extraction modes from received signal, it also an unitary...

With the advances of ship noise reduction technology, working frequency passive sonar must be reduced in order to detect a target. For conventional array, it requires large array aperture, comparable wavelength, achieve an acceptable angular resolution. Arrays small physical size with high resolution are thus attractive for low-frequency direction-of-arrival estimation underwater sound source. In this paper, we consider 33 uniform rectangular which consists vector sensors inter-sensor...

On the basis of time-reversal focusing theory, time frequency analysis combining with reversal mirror (TRM) on detection linear modulation (LFM) signal in inhomogeneous medium is studied. The simulation experiment carried out a lab water tank. Time manifested by taking time-domain scattered fields received an array, reversing them, and then propagating them back into same medium. re-transmitted near source Wigner-Ville Distribution(WVD) performed. varying spectrum gives more useful...

The Oceans cover around 70 percent of entire earth's surface and contain a volume 1.3 billion cubic kilometers. According to few analysts roughly 95 the world ocean 99 floor are yet be explored. more interesting fact is that mid-water which region between ocean's sea bottom least This study aimed at various sensors, system, platforms involved in measuring autonomously providing situ data real-time or near real-time. encompasses working types such systems provide atmospheric, physical,...

This paper presents the design and realization of a buoy for coastal ocean acoustic tomography based on narrowband-internet things (NB-IoT) technology. The body is made unplasticised polyvinyl chloride (PVCU) pipe material. consists two main parts: surface pharos body. part further NB-IoT global positioning system (GPS) modules which realize buoys networking, distributed time synchronization, remote real-time monitoring control. Whereas, built-in data reception system, signal transmission,...

Super-directivity sensor arrays are quite promising in target finding, due to their small size and enhanced directivity. An array design method which can build a desired beam pattern using compact multi-pole is presented this paper. The proposed extracts modes of different order from the spatial differentials sound field, square that consists vector sensors having dipole directivities. differential extraction procedure approximated by difference, decreases performance. performance...

Conventional beamforming and classical spectral estimation methods are widely used in array signal processing to estimate the angular frequency spectrum, respectively. But spectra provided by these algorithms appear as low resolutions high side lobes because of limited aperture number snapshots. Then a multi-dimensional window function is defined, which composed snapshot aperture. Based on theories space-time joint estimation, power spectrum about azimuthal angle can be deduced convolution...

A new method based on Volterra filter is introduced to extract weak signal in strong chaotic noise.A nonlinear prediction model established by combining phase space reconstruction and adaptive filter.Self-noise of ship used for training the model.The has a good performance noise without signal, but when mixed with noise, modal mismatches error varies dramatically.The cross-correlation extracted real calculated, similarity waveforms compared.It had been shown that algorithm powerful regular...

Super-directive sensor arrays, due to their small size and enhanced directivity, are quite promising in signal-to-noise enhancement target direction finding. An array design method, which can build a desired beam pattern using compact multi-pole is presented this paper. The proposed method extracts modes of different order from the spatial differentials sound fields measured by uniform square composed with hydrophones particle velocity sensors. It achieve more benefits employment sensors...

摘要: 瞬态干扰的存在会严重影响矢量信号处理方法性能，必须对其抑制。该文提出一种基于偏振分析的瞬态干扰抑制方法。该方法提取矢量信号的偏振参数，构建极化滤波器，对接收信号滤波，去除瞬态干扰。通过极化滤波器的调制函数判断瞬态干扰的存在位置，再利用信号的偏振模型恢复瞬态干扰处信号。仿真结果和实验数据表明该方法可以有效地抑制瞬态干扰。 关键词: 矢量信号处理 / 偏振分析 瞬态干扰

The characteristics of cross-correlation function for two receivers at different depths in deep sea are analyzed. For the near surface, peaks close to main peak, which is difficult be distinguished, and their positions change minor with variation source range depth. While large depths, beyond peak separate more apart from when decreases, depth increases or water increases. impact variations vertical sound speed profile on relatively minor. Based these characteristics, a method matching...

The focusing resolution effects of time reversal mirror (TRM) are studied based on time-reversal theory. Using the coherence multi-path effective aperture TRM is enlarged and gain can be obtained more than 10dB. Focusing with a through random medium much better that in homogeneous medium.

A new technology for spatially localizing acoustic backscatter called VS-CAATI (Virtual and Sub-array Computed Angle-of-Arrival Transient Imaging) is proposed in this paper. The can jointly estimate DOA amplitude at the same time. principles underlying VS-CAATI, which are based on virtual array processing sub-array technology, presented detail easily implemented offers dramatic improvements over conventional CAATI. Furthermore, technique superior to some other estimation methods.