Bounds on Time-Delay Estimation for Monochromatic Signals

Time-delay estimation (TDE) of monochromatic signals,observed by spatially separated sensors, is widely used for sourcelocalization in radar/sonar applications. We use lower bounds tostudy the accuracy of TDE as a function of signal to noise ratio(SNR), frequency, and sensor separation. We show that the Cramer-Rao bound, which is frequently used as a standard ofreference, yields optimistic predictions in many cases.     

吊放声纳与声纳浮标在应召搜潜中的联合运用

在介绍吊放声纳与声纳浮标各自在应召搜潜中的运用的基础上,针对两者在单独使用上的不足提出了一种新的搜潜策略,并从理论上说明了这种新的搜潜策略具有一定的优势。     

基于自适应线谱增强的LOFAR浮标信号处理及Doppler-CPA定位方法

LOFAR浮标是一种被动全向浮标,用于对潜搜索的初始阶段。常规的LOFAR谱图对于小信噪比和有色背景噪声处理性能下降。文中采用自适应线谱增强技术将目标辐射中的线谱成分从背景噪声中分离出来进行LOFAR谱图分析,提高LOFAR浮标的检测性能。在LOFAR分析的基础上利用目标的多普勒信息,采用Doppler-CAP方法测算目标的速度和目标与浮标的距离,初步估算出目标的航迹。仿真结果表明,新的LOFAR浮标数据处理算法检测性能更好,能够得到目标与浮标最接近点的距离。     

Signal Resolution via Digital Inverse Filtering

Research in numerous areas is directed toward the resolution of multiple overlapping signals in a noisy environment. These areas include radar, sonar, speech, seismology, and electrophysiology. Sometimes matched filters are used; other times inverse filters are employed. This paper discusses one approach to the analysis of the resolution of inverse filters. Our method is to compromise the trade-off between signal resolution and the output signal-to-noise ratio (SNR). A performance measure for the inverse or deconvolution filter is defined as a quantity proportional to the harmonic mean of the resolution and the SNR. An optimum output pulse duration is obtained using this criterion, where the pulse shape has been previously selected and the input signal waveform is known. In addition, upper and lower bounds for the output pulse duration are presented. Graphs are given which allow the designer to select the optimum inverse filter output pulse duration for a desired signal resolution and an estimated SNR.     

Space-time adaptive processing and adaptive arrays: specialcollection of papers

Space-time adaptive processing (STAP) and related adaptive array techniques hold tremendous potential for improving sensor performance by exploiting signal diversity. Such methods have important application in radar, sonar, and communication systems. Recent advances in digital signal processing technology now provide the computational means to field STAP-based systems. The objective of this special collection of papers is to examine the current state-of-the art in STAP technology and explore the remaining obstacles, practical issues and novel techniques required to implement STAP-based radar, sonar or communication systems     

Homodyned-K fluctuation model

The statistics of the matched filter output are examined for the case of a nonfluctuating target in K-type clutter. The resulting "homodyned-K" backscatter model is a generalization of the classic Rayleigh-Rice model and has applications in radar, sonar, optics, and ultrasonic medical imaging. This paper presents exact and asymptotic equations for the probability density function, survival function, moments, and parameter estimation. The exact equations are expressed as infinite series. Also provided are proof of the series' convergence and guidance for their numerical computation. Examples illustrating the model's application to radar and sonar are presented using electromagnetic and acoustic backscatter data     

A Confidence Bound for R90 from Direct Observations

Observed detection ranges instead of blip-scan ratios are used to construct lower confidence bounds for R90, a measure of radar performance.     

Composite Bound on Arrival Time Estimation Errors

Time of arrival (TOA) estimation of narrowband signals is a problem of considerable practical interest in radar and sonar applications. A new technique is presented to analyze the mean square error (MSE) performance of TOA estimation schemes, based on recently developed lower bound. We obtain a complete characterization of the MSE as a function of the signal and noise parameters. The results are given in a simple closed-form analytical expression.     

航空声纳浮标定位的数据融合方法研究

声纳浮标由于受到多种随机因素的干扰,定位精度相差很大,在对具有一定散布海域的潜艇目标进行探测时,往往会投放多枚定位浮标,出现数据冗余的现象。针对这一问题,本文提出了浮标定位算法中的一种数据融合算法;并分析了加权融合和非线性最小二乘数据融合的方法,最后通过仿真验证了这种算法的有效性和可行性。     

Estimating matched filter amplitude probability functions byfailure rate analysis

Performance analysis of echolocation systems requires knowledge of the probability density function (pdf) or cumulative distribution function (cdf) of a matched filter output. A method is presented to estimate these and other probability functions from data by estimating the failure rate function, a function employed in reliability theory. The method can also be used to derive approximations to closed-form probability functions. The method is demonstrated using experimental sonar and radar clutter data and a closed-form radar clutter model     

The Design of Huffman Sequences

The paper presents a method by which the zeros of the polynomial representing a Huffman (impulse-equivalent) pulse sequence can be chosen so as to exert a degree of control on the form of the energy distribution of the signal in the time-frequency plane. This makes it possible to design Huffman pulse sequences which are suitable for use as radar or sonar signals in situations where significant target velocity occurs.     

监听时间对声纳浮标阵检查性搜索效能影响仿真

以方形声纳浮标阵检查性搜索为背景,研究了监听时间对声纳浮标阵搜索效能的影响,给出了仿真结果并对仿真结果进行了分析。基本结论为:声纳浮标阵的搜索效能随监听时间的增加而提高;只要开始监听,就可以取得比较高的搜索概率;监听时间的增加和搜索效能的提高不是简单的线性关系,而是大致可区分为快速提高期、平稳提高期和滞涨期3个阶段。应根据作战条件和作战要求合理确定监听时间。     

Range and Bearing Estimation in Passive Sonar

Passive sonar systems are used for estimating the range and bearing of signal sources, such as ships or submarines. In this study, the Cramer-Rao bounds on estimation errors are used as measures of the accuracy of the estimates. The bounds show how parameters such as observation time, signal bandwidth, signal-to-noise ratio, and array geometry can be chosen to obtain maximum accuracy. When the array geometry satisfies certain conditions, the bound for range estimate is shown to be independent of the actual source bearing and the bound for bearing estimate independent of both the range and bearing of the source. It is also shown that the same conditions on array geometry ensure that the range or bearing estimation accuracy is not degraded when tne other pammeter is not known.     

检查性反潜时声纳浮标阵阵型优化

存总结检查性反潜要求与特点的基础上，分析了检查性反潜时声纳浮标阵的主要阵型，建立了声纳浮标阵作战效能的仿真模型，并在想定条件下对典型声纳浮标阵的搜索效能进行了仿真研究。比较、分析仿真结果，提出了检查性反潜时声纳浮标阵阵型的优化结果.     

Low observable target motion analysis using amplitude information

In conventional passive and active sonar system, target amplitude information (AI) at the output of the signal processor is used only to declare detections and provide measurements. We show that the AI can be used in passive sonar system, with or without frequency measurements, in the estimation process itself to enhance the performance in the presence of clutter where the target-originated measurements cannot be identified with certainty, i.e., for “low observable” or “dim” (low signal-to-noise ratio (SNR)) targets. A probabilistic data association (PDA) based maximum likelihood (ML) estimator for target motion analysis (TMA) that uses amplitude information is derived. A track formation algorithm and the Cramer-Rao lower bound (CRLB) in the presence of false measurements, which is met by the estimator even under low SNR conditions, are also given. The CRLB is met by the proposed estimator even at 6 dB in a cell (which corresponds to 0 dB for 1 Hz bandwidth in the case of a 0.25 Hz frequency cell) whereas the estimator without AI works only down to 9 dB. Results demonstrate improved accuracy and superior global convergence when compared with the estimator without AI. The same methodology can be used for bistatic radar     

反潜直升机搜潜效能分析

作为战术反潜的主要手段,反潜直升机已成各国海军的重点研制装备。考虑反潜直升机所搭载的众多探潜设备,包括雷达、红外前视仪、声纳浮标和磁探仪等,在详细分析上述搜索设备性能的基础上,针对应召和巡逻两种典型搜潜方式进行了典型组合搜潜方案的效能分析。仿真分析验证了组合搜潜方案的合理性与可行性。     

圆形声纳浮标阵搜潜效能模型研究

分析了建立圆形声纳浮标阵搜潜效能模型的重要意义。通过对圆形声纳浮标阵作战机理的分析,使用数学方法建立了圆形声纳浮标阵搜潜效能的计算模型,并对模型的应用进行了讨论。     

某直升机专用交流地面电源车PSPICE模型仿真分析

针对某直升机专用交流地面电源车系统,建立了PSPICE软件的仿真模型,且进行了系统仿真,研究了基于独立源及受控源的SPWM波产生方法,分析了滤波器参数分布对于系统性能的影响。仿真结果表明该电源系统对于雷达、吊声类冲击性负载有较好的适应性。     

Scanning, Tracking, and Mapping State Variable Estimation Algorithms

Recursive state equation estimation algorithms are derived to determine optimal estimation error covariance and state estimate for a linear dynamic system, driven by time-varying and positionverying (or angle-varying) functions whose a priori covariance are described. Retracing the same trajectory with the system measuring device causes the position varying function to repeat and can significantly reduce estimation errors. Applications for these algorithms include improving accuracy of a position dependent quantity to be mapped, or recursively processing radar or sonar data from repeating scans over the same area. Three types of return path patterns are considered: 1) multiple independent returns, 2) reverse returns, and 3) cyclical returns.     

Angle/Doppler estimation in heavy-tailed clutter backgrounds

This work describes new methods on the modeling of the amplitude statistics of airborne radar clutter by means of alpha-stable distributions. We develop joint target angle and Doppler, maximum likelihood-based estimation techniques from radar measurements retrieved in the presence of impulsive uncorrelated noise modeled as an alpha-stable random process. We derive the Cramer-Rao bounds (CRBs) for the additive Cauchy interference scenario to assess the best case estimation accuracy which can be achieved. In addition, we introduce a new joint spatial- and Doppler-frequency high-resolution estimation technique based on the fractional lower order statistics of the measurements of a radar array. Simulation results demonstrate that the proposed methods can be of interest in the study of space-time adaptive processing (STAP) for airborne pulse Doppler radar arrays operating in impulsive interference environments