舰艇编队对空防御队形优化配置模型

分析了海上机动编队中防空舰的位置配置对舰艇编队拦截目标效果的影响,通过舰艇对来袭目标拦截概率的推导,建立了被掩护舰的生存概率模型,从而提供了一种解算编队防御队形最佳配置的方法。     

Signal‐to‐interference‐plus‐noise ratio estimation for wireless communication systems: Methods and analysis

The Signal‐to‐Interference‐plus‐Noise Ratio (SINR) is an important metric of wireless communication link quality. SINR estimates have several important applications. These include optimizing the transmit power level for a target quality of service, assisting with handoff decisions and dynamically adapting the data rate for wireless Internet applications. Accurate SINR estimation provides for both a more efficient system and a higher user‐perceived quality of service. In this paper, we develop new SINR estimators and compare their mean squared error (MSE) performance. We show that our new estimators dominate estimators that have previously appeared in the literature with respect to MSE. The sequence of transmitted bits in wireless communication systems consists of both pilot bits (which are known both to the transmitter and receiver) and user bits (which are known only by the transmitter). The SINR estimators we consider alternatively depend exclusively on pilot bits, exclusively on user bits, or simultaneously use both pilot and user bits. In addition, we consider estimators that utilize smoothing and feedback mechanisms. Smoothed estimators are motivated by the fact that the interference component of the SINR changes relatively slowly with time, typically with the addition or departure of a user to the system. Feedback estimators are motivated by the fact that receivers typically decode bits correctly with a very high probability, and therefore user bits can be thought of as quasipilot bits. For each estimator discussed, we derive an exact or approximate formula for its MSE. Satterthwaite approximations, noncentral F distributions (singly and doubly) and distribution theory of quadratic forms are the key statistical tools used in developing the MSE formulas. In the case of approximate MSE formulas, we validate their accuracy using simulation techniques. The approximate MSE formulas, of interest in their own right for comparing the quality of the estimators, are also used for optimally combining estimators. In particular, we derive optimal weights for linearly combining an estimator based on pilot bits with an estimator based on user bits. The optimal weights depend on the MSE of the two estimators being combined, and thus the accurate approximate MSE formulas can conveniently be used. The optimal weights also depend on the unknown SINR, and therefore need to be estimated in order to construct a useable combined estimator. The impact on the MSE of the combined estimator due to estimating the weights is examined. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004     

振荡器相位噪声对GNSS接收机载波跟踪数字锁相环性能的影响

关于振荡器相位噪声引起的GNSS接收机载波跟踪数字锁相环相位抖动,目前的解析结论仍是基于模拟锁相环的,不能说明相位抖动大小与中频积累时间的关系,因此不能有效指导高灵敏度、高精度载波跟踪锁相环参数设计.本文首先推导中频积累输出的频率白噪声、频率游走噪声序列的功率谱,然后基于数字二阶锁相环离散线性模型导出了环路相位抖动公式并进行了仿真验证,最后对公式进行了解析和数值分析.分析结果表明:频率白噪声、频率游走噪声引起的二阶载波跟踪锁相环相位抖动,均随中频积累时间单调递增,随环路带宽先递减后递增.本文推得的相位抖动公式及其随参数变化特征的分析结论,可用于具体指导GNSS载波跟踪锁相环参数设计.     

模2n加与模2加相对结合律相容程度的分析

模2n加和模2加是密码算法设计中经常使用的两个编码环节,二者对于结合律的相容程度是指改变二者形成的混合等式中两个变量的运算顺序所造成的误差大小.本文研究了模2n加与模2加相对于结合律的相容程度,给出了在改变[(χ(+)y)+z]mod 2n的运算顺序时,产生的噪声函数ξ(x,y,z)=[(x(+)y)+nz](+)[x(+)(y+nz)]在各点取值的概率分布规律,以及对噪声函数所有取值点的概率值平方求和的计算公式.这些结论在区分攻击中有一定的应用价值.     

潜艇自航发射鱼雷的若干问题

潜艇自航发射鱼雷可以降低发射过程的辐射噪声,有利于提高发射艇的安全性。通过分析自航发射需具备的基本条件、现有533mm口径潜艇鱼雷发射管实现自航发射的可能性、后端补水的自航发射、有动力后端补水的自航发射等几个问题,得出了533mm口径的潜艇鱼雷发射管不可能实现自航发射的结论。另外,对降低潜艇发射鱼雷时的出管速度给鱼雷和发射艇带来的风险作了分析,得出了为保证潜艇发射鱼雷时的安全不能随意降低鱼雷出管速度的结论。     

舰船成本预测系统中的自变量约简方法

针对舰船成本预测系统中自变量众多且相互关系错综复杂的特点,提出了用模糊粗糙集方法对舰船成本预测系统中的自变量进行约简。在模糊粗糙集方法的框架下,给出了模糊不可分辨关系和相对约简的定义,构建了基于模糊粗糙集的舰船成本预测系统自变量约简模型,并且针对实际的舰船成本预测系统一般是混合数据系统的问题,对广义差别矩阵的定义进行了改进,设计了相应的启发式约简算法。实例分析结果表明:文中所提的方法不仅能使约简的自变量大为减少,而且约简的效果较传统方法更好,且计算过程也更简单。     

激光成像自动对焦系统的散斑噪声滤波算法

针对激光主动探测成像的散斑（Speckle）噪声影响自动对焦系统的清晰度评价函数曲线,从而影响对焦性能的问题,提出一种多方向线型加权形态滤波方法。实验证明：基于该方法构造的滤波器明显改善了激光图像清晰度评价曲线（即自动对焦曲线）的形状,降低了误对焦率,提高了自动对焦系统的稳定性。     

高灵敏度GPS软件接收机捕获算法

针对传统方法难以实现室内环境下GPS信号的捕获以及传统弱信号捕获算法的一系列弊端,介绍了一种新的捕获算法。由于数据段通过“先累加后相关”的方式进行相干积分可以减少运算量,以此方法改进的半位捕获法进行数据段选择可以避免导航数据位翻转,并且改进后的差分相干积分能够减小非相干积分造成的“平方损失”和改善信噪比,融合上述优点,提出了一种新的算法,为高灵敏度GPS软件接收机的实现提供了保证。仿真结果表明,此算法极大的提高了接收机的捕获性能,并且能够快速捕获到载噪比低至25dB/Hz的微弱信号。     

舰载相控阵雷达对空搜索仰角上的资源分配

针对舰载相控阵雷达对空搜索的特点和规律,分析了影响仰角上资源分配的因素,根据不同空域,不同目标的威胁度划分了搜索屏,并确定其优先级别。详细研究了舰载相控阵雷达对空搜索性能的优化模型,给出了相控阵雷达搜索帧周期和驻波时间的优化选取的最佳准则和方法。利用模型进行了相关的仿真计算,得到的结果验证了该方法的有效性。     

夺占小型岛屿作战综合登陆舰编队展开点选择优化模型

针对综合登陆舰编队夺占小型岛屿作战中的威胁特点,确定了岸基航空兵对综合登陆舰的有效掩护区,建立了综合登陆舰展开点选择的优化模型,并给出了简单方便的图上作业法,为合理确定综合登陆舰的展开点提供了方法和依据。