主动声纳的自适应显示数据缩减算法

本文讨论了主动声纳系统中主动检测结果的数据显示问题.首先介绍传统显示数据缩减的几种算法,在这些基础上,我们提出一种新颖的自适应显示数据缩减算法.此算法利用宽带信号特征和主动检测统计特征,通过分段加权平均并取用子段平均最大值的方法,自适应地缩减待显示数据.仿真结果表明,此算法可以提高数据输出的信息量,减小输出信噪比损失,其性能优于传统的几种显示数据缩减算法,有助于提高人机交互的可靠性,并且算法简单,适于实时实现.     

雷达、遥感技术及声纳

 1.雷达雷达是一种空中通讯技术。它是利用无线电技术来测量空中飞机、导弹,海洋中的船只、礁石,陆地上的高山、湖泊、建筑物或行进的汽车、坦克,太空中的行星及航行中的宇宙飞船等位置的一种测量技术。雷达的工作原理雷达是如何利用电磁波来侦察远方目标的呢?让我们举一个回声测距的例子来说明。当我们面对高山用双手在嘴旁合成一个圆形喇叭,大声地短促地呼叫时(见图1),声音便从呼叫的地方出发向着高山的方向传播开去,瞬间,声音又从高山那边返回来,传播到我们的耳朵里,于是我们听到了回声。     

DFT用于检测未知线谱信号的应用研究

本文介绍了DFT谱估计线谱检测器的原理和C25－DSP系统的硬件、软件构成，分析了该系统的性能，并给出了部分实验室测试结果和湖上试验结果．     

Beam pattern of sparse array for passive sonar

This work aims at sparse array without grating lobe for passive sonar, in order to increase frequency band of the passive sonar and reduce the cost. According to traditional method, the distance between two contiguous sensors in sonar array should be less than the wavelength of highest frequency of the signal; otherwise the grating lobe appears on beam pattern. The paper realizes that the conclusion of the grating lobe emergence it is not fit to the passive sonar due to the sine wave signal model in traditional method, in fact the input of passive sonar is random signal. Prom three aspect of the computer simulation, real passive sonar signal and theory analysis, it is revealed that the grating lobe does not appear on beam pattern when the distance between two contiguous sensors in passive sonar array is longer than wavelength of highest frequency. Whitening of the radiated noise can widen the frequency band, to ensure the beam pattern without the grating lobe. The conclusion of the paper is: if the band of radiated noise is wide enough (broader than 1 octave), that the wavelength of signal can be shorter than the distance between two contiguous sensors in passive sonar without grating lobe.     

A passive synthetic aperture phase correction algorithm for the asymmetric twin-line array sonar

A passive synthetic aperture based on phase correction algorithm for solving the port-starboard discrimination problem in the non-aligned towed twin-line array sonar,is de- scribed.This method creates a virtual array through applying the estimated phase correction into one array of twin-line arrays.Because the synthetic virtual array is aligned with the other array in twin-line arrays,the right port-starboard discriminated results can be obtained by array processing based on the new synthetic twin-line array.The effect of proposed method has been shown by simulated and sea-trials results in towed twin-line array sonar.With low extra computational loads,the proposed method is easy to apply to the practice.     

基于线性预测倒谱的被动声纳目标特征提取技术

从声纳员的角度出发，被动声纳目标可以被看作为一个发声体，利用线性预测倒谱从声纳目标噪声中分离出目标作为发声体的冲激响应在倒谱域中的表示，提取一组识别特征，设计神经网络分类器，对三类目标进行分类。实测数据验证了基于线性预测倒谱的被动声纳目标特征提取方法是可行的。     

基于混合能量模型水平集的合成孔径声纳图像分割方法

本文讨论了合成孔径声纳图像分割问题。首先介绍了Chan-Vese模型水平集方法,针对该模型存在的边界定位和重复初始化等问题,提出了一种改进的水平集方法。该方法的能量模型由区域信息项、边界信息项和距离约束函数构成的内部能量项三部分混合形成,既兼顾了全局优化特性和局部定位精度,又避免了水平集函数重复初始化,提高了运算效率。实验结果表明,该模型对于噪声干扰严重、边缘模糊的合成孔径声纳图像分割效果良好。     

基于直接数字频率合成技术任意波形声纳信号源的设计

基于直接数字频率合成技术的声纳信号源,重点解决了调频波的相位连续性和波形光滑度的难题。该信号源在硬件电路不改变的情况下,只通过更改软件就可以产生任意的波形。由于直接数字频率合成芯片的高度集成化和简单的外围电路,设计出的信号源是小型化的,可直接应用于声纳浮标的发射源。此外这种技术的高可靠性,又在很大程度上保证了浮标的成活率,具有良好的应用前景。     

Research on beamforming method for dual-line array with space mismatch between the two line arrays

The performance of port/starboard discrimination of dual-line array will be seriously degraded when the space between the two line arrays of the dual-line array is mismatched. The directivity function of the delay-sum and delay-subtract beamforming is deduced and the port/starboard discrimination of the delay-sum and delay-subtract beamforming is also studied both under the ideal status and the status under which the space between the two line arrays of the dual-line array is mismatched. Analysis results show the delay-subtract beamforming has better performance of port/starboard discrimination. At last, the sea trial results demonstrate the theoretical results.