两步法提高时延差估计精度的分析和实验验证

为提高短基线水声定位系统的定位精度,对利用两次估计提高时延差计算精度的方法进行了理论分析、仿真和实验验证,并给出了具体的实现步骤。该方法将时延差估计值分解成了时延差初测值和时延差修正值,前者直接利用相关函数包络求解,后者与相关函数相位差之间存在映射关系,通过频域的相位差估计获得。仿真和实验的结果显示,采用这一方法能够获得很高的时延差估计精度。两步法具有很强的实用性,可以有效的提高短基线水声定位系统定位精度。     

单矢量水听器稀疏近似最小方差方位估计算法

针对单矢量水听器海上目标探测问题,利用稀疏近似最小方差(Sparse Asymptotic Minimum Variance,SAMV)算法进行目标方位估计,该算法利用单矢量水听器自身具有阵列流形的特点,将整个扫描空间离散化,目标方位分布于某一离散方向位置上,利用空间信号的稀疏性可提高目标方位估计性能。仿真结果表明,SAMV算法在各信噪比条件下方位估计噪声背景级明显优于常规波束形成(Conventional Beam Forming,CBF)算法和最小方差无失真响应(Minimum Variance Distortionless Response,MVDR)算法,当信噪比大于0dB时,该算法测向结果均方根误差小于2°,且SAMV算法具有更好的空间方位分辨能力。消声水池和海上声学浮标海上试验数据处理结果表明,SAMV算法给出了噪声背景级更低的目标方位历程图,有效验证了SAMV算法对海上目标的探测性能及其有效性。     

利用随机共振技术的微弱信号方位估计

提出了基于随机共振技术的微弱目标方位估计方法。通过自适应调节系统参数,包括两种方法:自适应调节系统结构参数和自适应调节外加噪声,使系统进入随机共振状态,经随机共振器输出后得到信噪比较大提高的阵列信号,再由方位估计算法估计出目标方位。并进行了仿真和实验研究,结果表明:实验结果与理论分析符合良好,该方法可应用于微弱低频信号的目标方位估计。     

随机共振研究进展

全面介绍了随机共振的概念、机理、理论和实验研究的主要进展及研究现状，对随机共振研究的可能应用也做了富有建设意义的展望性介绍。     

随机共振实验

介绍了随机共振现象的基本原理、模拟电路,给出了一组实验结果,并绘制了实验曲红,分析了随机共振产生的原因。     

二次加权频域自适应时延估计算法与应用

时延估计问题在许多工程应用中具有重要的意义。本文提出了一种二次加权频域自适应时延估计模型,给出了二次加权频域SCOT和ML自适应时延估计算法,推导了二次加权频域SCOT自适应时延估计的方差。把该算法应用于对武装直升机的声测无源定位中,用实测直升机噪声数据进行了计算机仿真。结果表明,在低信噪比情况下,二次加权频域自适应时延估计具有更好的时延估计性能。     

自适应滤波器在时延估计中的应用——广义二次内插时延估计法

两个或多个接收信号之间的延时估计问题在许多工程应用中具有重要的意义。本文提出一种在接收信号的统计特性的先验知识了解甚少,或不了解的情况下,仍能准确地估计出接收信号间时延的方法,并推导了这一估计的方差。该方法是基于自适应噪声抵消器,在其收敛时,用权系数进行内插估计,与传统的用采样函数内插不同,本方法对F.A.Reed等人提出的二次内插法进行了改进,保证了估计精度,在实现上也比较简单。计算机模拟实验与海上实验结果与理论上的分析是一致的。     

基于声程差的多通道广义相关时延估计及其DSP实现

本文将基于声程差的广义相关法时延估计应用于六基元阵,同时成功地将中值滤波及可变门限算法用于相关峰的自动跟踪,为了提高精度,导出了新的内插公式。最后给出了时延估计的结果。     

基于振动共振的随机共振控制

分析了非线性双稳系统在高、低两种不同频率信号作用下的动力学特性，给出了高频信号参数与双稳系统输出信号的信噪比和功率谱放大率关系的解析表达式，提出了基于振动共振的随机共振控制方法.理论分析和数值仿真结果表明，通过调节高频信号的幅值或频率大小，能有效地控制双稳系统输出信号的信噪比和功率谱放大率.     

随机共振的模拟实验

用模拟电路的方法对随机共振现象进行多方面的实验研究,讨论随机共振机制,测量输出信噪比(SNR),由于在随机共振过程中部分噪声能量可转变为信号能量,利用这个机制可能在强噪声对信号的抑制下取出信号。 关键词：     

Experimental evidence of binary aperiodic stochastic resonance

A novel kind of aperiodic stochastic resonance is experimentally studied in a vertical cavity surface emitting laser. We characterize the response of the system to a random, binary signal as a function of an applied external noise. A maximum in the input-output correlation is found for a nonzero added noise. We present analytic results with a good agreement with the measurements. We also discuss the physical meaning of the phenomenon using simple arguments, and we compare it to stochastic resonance.     

Combined action of time-delay and colored cross-associated multiplicative and additive noises on stability and stochastic resonance for a stochastic metapopulation system

In this paper, the transition between the stable state of a big density and theextinction state and stochastic resonance (SR) for a time-delayed metapopulation systemdisturbed by colored cross-correlated noises are investigated. By applying the fastdescent method, the small time-delay approximation and McNamara and Wiesenfeld’s SRtheory, we investigate the impacts of time-delay, the multiplicative, additive noises andcolored cross-correlated noise on the SNR and the shift between the two states of thesystem. Numerical results show that the multiplicative, additive noises and time-delay canall speed up the transition from the stable state to the extinction state, while thecorrelation noise and its correlation time can slow down the extinction process of thepopulation system. With respect to SNR, the multiplicative noise always weakens the SReffect, while noise correlation time plays a dual role in motivating the SR phenomenon.Meanwhile, time-delay mainly plays a negative role in stimulating the SR phenomenon.Conversely, it could motivate the SR effect to increase the strength of thecross-correlation noise in the SNR-β plot, while the increase of additive noiseintensity will firstly excite SR, and then suppress the SR effect.     

单水听器波导不变量被动测距

本文主要讨论利用声场干涉现象由单水听器被动测距的可行性及测距性能,为此提出了单水听器波导不变量被动测距方法,通过提取LOFAR图上干涉条纹、使用简正波模型计算波导不变量、频域相关法估计相对速度,最后依据干涉条纹方程得到声源距离估计量。数值仿真和海上实验结果验证了单水听器被动测距的可行性,并具备一定测距性能,在3 dB信噪比环境中,对于7 km处的运动声源,平均测距误差小于5%。本文方法具有设备简单、易于推广至阵列信号处理等特点,为声纳信号处理环境宽容性的提高及环境适配声纳的设计开拓了思路。     

Study of stochastic resonance by method of stochastic energetics

Stochastic resonance (SR) is numerically analyzed by the method of the stochastic energetics that enable us to analyze the energetics of non-equilibrium processes described by the Langevin equations. The work done by the external agent which drives the potential to fluctuate periodically is shown to be a good quantitative measure of SR. If the phase lag of the inter-well resonant motion before the periodic force is investigated, the good measure of SR can be devised by extracting the inter-well resonant motion. Thus, we numerically investigate the phase lag of the Brownian motion. The value of phase lag at the optimal noise intensity is found to depend on the frequency of the periodic force.     

浅海环境中矢量水听器角度谱特性

为探明远场舰船噪声和近场平台噪声声能流相互作用的机制对矢量水听器角度谱特性的影响,基于简正波矢量场理论,构建舰船平台噪声声场模型,获得与海上实验结果相符的声能流角度谱特性,声能流方向均随频率变化。对远场舰船噪声声能流和近场平台噪声声能流相互作用进行仿真,两者声能流强度的此消彼长使角度谱出现4种条纹,与海上实验获得的角度谱特性一致,导致目标方位估计出现误差,且不同频带上的结果不一致。说明两个声能流相互作用时,影响合成能流角度谱特性的主要因素是两者的声压级之差,为浅海中同时存在多个声源时的目标方位估计提供参考。     

The characteristics of frequency-time azimuth spectrum estimation by a vector hydrophone in shallow water

The mechanism of interaction between the energy flows of the far-field ship noise and the near-field platform is studied, and the characteristics of frequency-time azimuth spectrum is discussed. Based on normal modes theory in acoustic vector fields, the model of the near-field platform is established, and the simulated result is similar to the investigation in shallow water. The frequency-time azimuth spectrum of the energy flow is investigated by the vector hydrophone changes with frequency. The energy flow of the far-field ship noise interacts with the near-field platform, so four kinds of stripes are shown in the frequency-time azimuth spectrum, which is the same with the investigation of sea trial. The estimation of direction of arrival appears inaccuracy, and varies with frequency. The main factor that affects the characteristics of frequency-time azimuth spectrum of resultant energy flow is the difference of sound pressure level. The estimation of the direction of arrival benefits from this when a number of sources exist in shallow water.     

单矢量水听器估计目标方位的方法与实验

为评估基于单矢量水听器的方位估计能力,在黄海海域对矢量水听器进行实验。矢量水听器吊放于接收船尾部,采用平均声强器和复声强器方位估计方法,并提出以概率密度值最大的方位角作为目标方位估计值的具体处理准则,对恒定方向、匀速行驶的目标船方位进行估计,并求出两种方法的方位估计误差。结果表明,水听器布放深度10 m时,对正横距离为0.42 km的航速10 kn的目标船,平均声强器方法的水平方位角估计误差18°,极角估计误差为5°,可以在离目标船最远1.17 km处估计其方位;复声强法的水平方位角估计误差为13°,极角估计误差为8°,可以在离目标船最远2.35 km处估计其方位。在有接收船的噪声干扰情况下,复声强器比平均声强器方法估计的方位更准确,可以对更远处的噪声源进行方位估计。