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浅海内波及声场起伏数值研究 总被引：2，自引：0，他引：2
为探讨声学方法监测(反演)海洋内波的可行性，分析ASIAEX2001亚洲海海洋声学实验定点温度链实验数据，结果表明：实验期间存在M2内潮波、周期10～30min非线性内波现象，并观测到双温跃层同相传播“双非线性内波”。分别对垂直和平行于内波传播方向传播声场进行了数值计算分析。垂直于内波传播方向的声传播计算结果表明：简正波波数时间演化函数的频谱与内波引起的声速剖面变化频谱基本一致；简正波系数(模值)时间演化函数的频谱与内波引起的声源位置处的声速演化函数的频谱基本一致；高阶简正波波数差随时间的变化要比低阶简正波波数差小约1个量级。平行于内波传播方向的声传播计算结果表明：内潮波主要导致相邻简正波间耦合；非线性内波包能够导致跨号甚至垮多号简正波间耦合。讨论了2种海洋内波声学监测方法。 相似文献
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《中国海洋大学学报(自然科学版)》2015,(11)
基于简正波理论的波导不变量在声传播特性描述中已得到广泛应用,而当环境与距离无关或存在轻微扰动时,基于射线理论的声场特性可以用一个新的物理量—射线稳定性参数来描述。本文通过简正波干涉声场数值模拟,通过分析简正波相长干涉形成的能量包传播路径与射线传播路径相互关系,利用简正波水平干涉结构距离上的周期性与射线水平跨距相等的特点,采用简洁方式证明了射线稳定性参数与简正波波导不变量间的等价性,从而在射线和简正波理论中建立了一个新的联系。对远距离射线模型声传播仿真结果的分析表明,与射线传播时间相比,射线稳定性参数作为射线理论的一个新的参数,可有效用于描述声传播特性,并能够反映海洋环境变化,应用于海洋环境参数声学反演。 相似文献
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从射线声学和简正波声学的角度，概述了海洋声层析的基本理论，包括射线走时反演、简正波走时反演、简正波相位反演和简正波水平折射层析。海洋声层析以反演海水温度和流速为基础。还总结了声层析在海洋学研究中的应用。 相似文献
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文章简要介绍了浅海声传播损失的研究背景和基本理论方法。通过1/3倍频程滤波对浅海爆炸宽带信号的不同频段在浅海的传播损失情况进行了分析,描述了浅海环境对声传播损失的影响;同时在不知道先验信息的条件下,利用垂直阵声压数据成功地进行了简正波分离,并与理想条件下Kraken简正波模型计算出的结果进行了比较分析。 相似文献
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通过构建中尺度涡的数学模型,利用射线-简正波-抛物方程(RMPE)声学模型进行传播损失计算,进而分析在深海声道、深海会聚区、海底反射3种传播模式下,中尺度涡对深海声效应的影响。数值仿真结果显示,暖涡对深海声道、会聚区产生下压效果,使会聚区水平距离变大,深海声道深度方向上变宽;冷涡使会聚区上抬,距离变短,对声场散射现象明显。研究结果表明,涡旋环境条件下,声场特征会产生显著变化。试验结果揭示了中尺度涡对深海声场效应的影响,对指导海上运用中尺度涡现象开展的科学研究、工程实践、军事运用具有积极的指导意义。 相似文献
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浅海中的平滑平均声场 总被引：14，自引：0，他引：14
浅海声传播问题虽然已进行过许多研究,但由于浅海声场往往包含大量简正波或射线,形成复杂的空间干涉结构,计算起来十分困难.实践表明,由于海洋环境与实验条件的不稳定性,使复杂的干涉结构很难与实验相吻合.有时实验点落在图1所示的理论曲线附近就认为是理论与实验基本一致,而不能验证曲线的精细结构.这种情况下人们就考虑用比较简便的方法计算声场的空间平滑结构,以避免繁琐的数值计算. 相似文献
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由于传统情况,匹配场处理器主要针对接收信号为高斯信号,而海洋环境中存在大量的有色噪声,因此设计基于高阶累积量的匹配场处理器具有一定价值。本文介绍了一种在海洋声层析环境下用高阶累积量来降低匹配场处理中高斯有色噪声的算法,对比研究了基于高阶累积量的简正波声场匹配场处理器、传统线性匹配场处理器、自适应匹配场处理器及二阶MUSIC算法匹配场处理器在相同声场环境条件下的匹配场定位效果。研究结果表明,在不考虑参数失配与计算量前提下,接收信号经过基于高阶累积量的简正波声场匹配场处理器后再进行匹配场定位,能有效降低旁瓣,且使用高阶累积量可显著消除海洋传播环境中高斯有色噪声和高斯白噪声对信号的干扰,其匹配效果优于另外三种匹配场处理器。 相似文献
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采用简正波方法对海水中的声传播特性进行了研究，介绍了简正波方法的原理，给出了一般情况下声传播损失的大体趋势和规律。 相似文献
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水声宽带信号波形预报技术研究 总被引：1，自引：0，他引：1
为了实现远程水下目标微弱信号检测,掌握远程传输后信号波形的特征,水声宽带信号波形预报技术是研究水下信号精细化特征研究的重要突破口之一.针对宽带信号,采用波束位移射线简正波(BDRM)频域合成波形预报算法和 BELLHOP 射线时域波形预报算法,获得宽带信号远程波形预报模型,并在浅海负跃层和深海声道两种典型海洋环境下,利用上述两种宽带波形预报算法,仿真计算了宽带信号远程波形,比较了两种波形预报算法精度.结果表明,在一定条件下,两种模型具有同等计算精度,可满足不同条件下的信号波形预报需求. 相似文献
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海洋中声速起伏导致水声信道发生变化,进而引起声线到达结构的变化,对水声传播及定位精度产生一定影响。为讨论这一效应,基于TDOA体制建立了考虑声线弯曲的水下目标无源定位模型,分析了声速起伏对水下声传播路径及传播时间的影响,进而研究了声速起伏对水下无源定位测量精度影响程度。结果表明:当水平传播距离较大时,声速剖面起伏对声传播路径及传播时间的影响更为显著;以典型四元阵为例,若基线长度为20 km,接收阵位于水下5 km处,在不考虑其它随机误差影响下,海洋声速起伏造成的声源定位误差量级在0.5 m以内。分析结果有助于更好地利用环境特征优化无源定位测量方案,可为高精度水下无源定位系统设计及精度评估提供依据。 相似文献
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Monitoring the thickness changes of channel siltation is paramount in safeguarding navigation and guiding dredging.This paper presents a novel method for realizing the field monitoring of channel siltation in real time.The method is based on the bistatic scattering theory and concerned more with the receiving and processing of multipath signal at high-frequency and small grazing angle.By use of the multipath propagation structure of underwater acoustic channel,the method obtains the silt thickness by calculating the relative time delay of acoustic signals between the direct and the shortest bottom reflected paths.Bistatic transducer pairs are employed to transmit and receive the acoustic signals,and the GPS time synchronization technology is introduced to synchronize the transmitter and receiver.The WRELAX (Weighted Fourier transform and RELAX) algorithm is used to obtain the high resolution estimation of multipath time delay.To examine the feasibility of the presented method and the accuracy and precision of the developed system,a series of sea trials are conducted in the southwest coast area of Dalian City,north of the Yellow Sea.The experimental results are compared with that using high-resolution dual echo sounder HydroBoxTM,and the uncertainty is smaller than ±0.06 m.Compared with the existing means for measuring the silt thickness,the present method is innovative,and the system is stable,efficient and provides a better real-time performance.It especially suits monitoring the narrow channel with rapid changes of siltation. 相似文献
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Two computer models are presented, one for short-range and one for long-range propagation of acoustic signals through an underwater channel from a transmitter to a receiver. In the short-range model, the received signal is due to a direct path (steady component) and a random path (diffused component) that could be the result of boundary scattering. For the long-range case, the received signal is the superposition of a number of time-delayed, randomly propagated components arriving by different paths. Both models assume perfect transmitter-receiver synchronization but use realistic channel time delays. They demonstrate the time-varying characteristics of underwater acoustic channels and are used in simulations to evaluate the performance of the detection technique 相似文献
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Buck J.R. Preisig J.C. Johnson M. Catipovic J. 《Oceanic Engineering, IEEE Journal of》1997,22(2):281-291
The shallow-water acoustic channel supports far-field propagation in a discrete set of modes. Ocean experiments have confirmed the modal nature of acoustic propagation, but no experiment has successfully excited only one of the suite of mid-frequency trapped modes propagating in a coastal environment. The ability to excite a single mode would be a powerful tool for investigating shallow-water ocean processes. A feedback control algorithm incorporating elements of adaptive estimation, underwater acoustics, array processing, and control theory to generate a high-fidelity single mode is presented. This approach also yields a cohesive framework for evaluating the feasibility of generating a single mode with given array geometries, noise characteristics, and source power limitations. Simulations and laboratory wave guide experiments indicate the proposed algorithm holds promise for ocean experiments 相似文献
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An underwater acoustic local area network (ALAN) provides multipoint-to-point telemetry between many high-rate, ocean-bottom sensors and a central, surface-deployed receiver in the 10-30 kHz vertical acoustical channel. Ocean-bottom modems initiate the transmission process by requesting data channel time slots via a common narrow-band request channel. Request packets overlap in time and frequency in this channel, and the throughput and average transmission delay rely heavily on the successful resolution of the request packet collisions. This paper presents the design, analysis, and experimental demonstration of a request channel receiver capable of resolving collisions between several asynchronous and cochannel packets. The receiver algorithm differs from standard capture schemes (by demodulating the data from both strong and weak transmitters), conventional spread-spectrum receivers (by overcoming the near-far problem), and existing multiple-access demodulation techniques (by adapting to the number of interfering signals, and the unknown phase, Doppler, amplitude, and timing of each signal in the collision). The receiver demodulates the collided packets by decision-directed techniques through a novel method of estimating the interference for each user which minimizes error propagation due to inaccurate tentative decisions. An inwater experiment illustrates that this technique is extremely desirable for collision resolution in underwater acoustic local area networks, and also for underwater autonomous vehicles with both sidescan sonar as well as acoustic telemetry links 相似文献
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以多传感器信息融合理论为指导,结合现代信息处理技术与数据驱动建模及科学计算技术,研究浅海超低频声源目标激发共存地震波的复合声场中超低频声波传播特性和数据驱动建模的水下目标深度识别等关键技术,并论证了技术实现方案及路径。结果表明:以复合矢量水听器、地震波监测仪等多传感器信息融合理论为指导研究前海超低频声源目标可以克服传统声场建模存在的问题,有助于浅海超低频声源目标探测及改善海洋水下声学监测手段。在提高声呐探测设备的测量准确度、精度方面具有重要的理论意义,对周边海域为浅海的我国海防具有实战价值。 相似文献
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Recent advances in high-speed underwater acoustic communications 总被引：4，自引：0，他引：4
In recent years, underwater acoustic (UWA) communications have received much attention as their applications have begun to shift from military toward commercial. Digital communications through UWA channels differ substantially from those in other media, such as radio channels, due to severe signal degradations caused by multipath propagation and high temporal and spatial variability of the channel conditions. The design of underwater acoustic communication systems has until recently relied on the use of noncoherent modulation techniques. However, to achieve high data rates on the severely band-limited UWA channels, bandwidth-efficient modulation techniques must be considered, together with array processing for exploitation of spatial multipath diversity. The new generation of underwater communication systems, employing phase-coherent modulation techniques, has a potential of achieving at least an order of magnitude increase in data throughput. The emerging communication scenario in which the modern underwater acoustic systems mill operate is that of an underwater network consisting of stationary and mobile nodes. Current research focuses on the development of efficient signal processing algorithms, multiuser communications in the presence of interference, and design of efficient modulation and coding schemes. This paper presents a review of recent results and research problems in high-speed underwater acoustic communications, focusing on the bandwidth-efficient phase-coherent methods. Experimental results are included to illustrate the state-of-the-art coherent detection of digital signals transmitted at 30 and 40 kb/s through a rapidly varying one-mile shallow water channel 相似文献
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In this paper, we investigate the performance of adaptive modulation （AM） orthogonal frequency division multiplexing （OFDM） system in underwater acoustic （UWA） communications. The aim is to solve the problem of large feedback overhead for channel state information （CSI） in every subcarrier. A novel CSI feedback scheme is proposed based on the theory of compressed sensing （CS）. We propose a feedback from the receiver that only feedback the sparse channel parameters. Additionally, prediction of the channel state is proposed every several symbols to realize the AM in practice. We describe a linear channel prediction algorithm which is used in adaptive transmission. This system has been tested in the real underwater acoustic channel. The linear channel prediction makes the AM transmission techniques more feasible for acoustic channel communications. The simulation and experiment show that significant improvements can be obtained both in bit error rate （BER） and throughput in the AM scheme compared with the fixed Quadrature Phase Shift Keying （QPSK） modulation scheme. Moreover, the performance with standard CS outperforms the Discrete Cosine Transform （DCT） method. 相似文献
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The conventional matched field processing (MFP) uses large vertical arrays to locate an underwater acoustic target. However, the use of large vertical arrays increases equipment and computational cost, and causes some problems such as element failures, and array tilting to degrade the localization performance. In this paper, the matched field localization method using two-hydrophone is proposed for underwater acoustic pulse signals with an unknown emitted signal waveform. Using the received signal of hydrophones and the ocean channel pulse response which can be calculated from an acoustic propagation model, the spectral matrix of the emitted signal for different source locations can be estimated by employing the method of frequency domain least squares. The resulting spectral matrix of the emitted signal for every grid region is then multiplied by the ocean channel frequency response matrix to generate the spectral matrix of replica signal. Finally, the matched field localization using two-hydrophone for underwater acoustic pulse signals of an unknown emitted signal waveform can be estimated by comparing the difference between the spectral matrixes of the received signal and the replica signal. The simulated results from a shallow water environment for broadband signals demonstrate the significant localization performance of the proposed method. In addition, the localization accuracy in five different cases are analyzed by the simulation trial, and the results show that the proposed method has a sharp peak and low sidelobes, overcoming the problem of high sidelobes in the conventional MFP due to lack of the number of elements. 相似文献