一种改进的四阶累积量波束形成算法

波束形成算法需要使用训练序列,或需要预先掌握期望信号的DOA信息,并且在多径环境中工作性能急剧下降。基于四阶累积量的CUM2算法在理论上可以收集期望信号的各多径干扰并使系统输出信干噪比达到最大,但对于四阶累积量的估计误差使得CUM2抑制干扰信号的性能受到了较大的影响。提出将四阶累积量矩阵进行Toeplitz预处理的思想,进而得到了一种改进算法。仿真试验也证明在同等条件下,改进算法与CUM2相比有着更强的干扰抑制性能。     

基于Volterra滤波器的混沌背景弱信号检测

针对混沌背景弱信号检测问题,提出了一种基于Volterra滤波器的混沌背景弱信号检测算法.在Volterra滤波系数计算过程中,采用了解线性方程组算法代替原有的自适应算法,提高了混沌预测精度以及混沌背景中弱信号检测性能.仿真结果表明,本文所提出的算法在信混比达到-70dB时,仍能检测混沌背景中微弱信号.     

Wigner-Ville distribution and cross Wigner-Ville distribution of noisy signals

The Wigner-Ville distribution （WVD） and the cross Wigner-Ville distribution （XWVD） have been shown to be efficient in the estimation of instantaneous frequency （IF）. But the statistical result of the IF estimation from XWVD peak is much better than using WVD peak. The reason is given from a statistical point of view. Theoretical studies show that XWVD of the analyzed signal can be estimated from XWVD of the noise-contaminated signal. The estimation is unbiased, and the variance is equal to that of noise. In this case, WVD cannot be estimated from W-VD of the noise-contaminated signal. Therefore, higher SNR is required when WVD is used to analyze signals.     

单点公交优先感应控制策略效益分析与仿真验证

单点交叉口信号优先可以降低公交车辆延误且易于实现.研究了公交相位绿灯延长、红灯早断和插入相位三种单点公交优先感应控制策略;应用延误三角形方法建立了以公交车辆车均延误变化量和非优先相位车均延误变化量为指标的三种单点公交优先策略效益计算模型.以两相位信号控制为对象,计算对比分析了三种公交优先策略的正负效益及其影响因素,并通过仿真进行了验证分析.研究表明:公交相位绿灯延长、公交相位红灯早断和插入公交相位三种策略都能够降低公交车均延误,与此同时也都会带来非优先相位车流延误的增加,但影响的程度不同.公交相位绿灯延长策略的效益略小于公交相位红灯早断策略,而相位插入策略的效益与插入时刻等多因素相关.     

基于伪谱方法的自适应鲁棒实时再入制导律研究

为了提高飞行器再入制导的鲁棒性和自适应性,将再入弹道跟踪问题转化为再入弹道状态调节问题,得到了一个LTV系统最优控制问题.在此基础上,利用基于伪谱算法的最优反馈控制算法,设计了一种便于在线实现的自适应鲁棒再入制导律.仿真结果表明,这种再入制导律对于再入点误差不敏感,具有良好的鲁棒陛.在气动参数模型存在较大误差的情况下,依然能够取得较高的再入制导精度.它不需要显示增益调度和积分,并且在不同情况下控制结构和参数无需改变.     

跳频同步信号的干扰仿真研究

跳频信号的同步过程是跳频通信系统的关键.一旦同步信号被干扰,整个跳频系统将无法正常工作.在分析了跳频同步信号侦收的可行性及目前干扰跳频同步信号方法的局限性的基础上,提出了一种新的干扰方法--部分驻留时间干扰,并将干信驻留时间比作为影响跳频同步信号的又一重要指标.仿真结果表明该干扰方法可在较小干扰功率下有效干扰跳频同步信号.     

单车型确定性动态车辆调配问题

给出了单车型确定性动态车辆调配问题的定义,引入网络图描述该问题.建立了问题的线性规划模型,鉴于线性模型的缺点,利用函数逼近技术构造一个特殊的线性函数来近似目标函数中未来时段部分,从而建立起问题的时空分解模型,把问题从时间和空间上分解为多个单时段单节点问题,并根据单时段单节点问题特点设计简单的排序求解方法.最后,给出了模型的完整求解过程,从而使问题得到有效地解决.     

Interval Time Series Analysis with an Application to the Sterling-Dollar Exchange Rate

Traditional econometrics has long employed ＂points＂ to measure time series data. In real life situations, however, it suffers the loss of volatility information, since many variables are bounded by intervals in a given period. To address this issue, this paper provides a new methodology for interval time series analysis. The concept of ＂interval stochastic process＂ is formally defined as a counterpart of ＂stochastic process＂ in point-based econometrics. The authors introduce the concepts of interval stationarity, interval statistics （including interval mean, interval variance, etc.） and propose an interval linear model to investigate the dynamic relationships between interval processes. A new interval-based optimization approach for estimation is proposed, and corresponding evaluation criteria are derived. To demonstrate that the new interval method provides valid results, an empirical example on the sterling-dollar exchange rate is presented.     

Robust model predictive control of continuous uncertain systems*

The authors concern robust model predictive control for linear continuous systems with polytopic uncertainties and input constraints. At each sampling time, a piecewise constant control sequence is obtained by solving a set of linear matrix inequalities. The sufficient conditions on the existence of the model predictive control are given, and the robust stability of the closed-loop systems is guaranteed. A simulation example illustrates the efficiency of the proposed method.     

高频雷达中LFMCW信号的分析

高频雷达在现代战争和民用事业上发挥着越来越重要的作用 ,线性调频连续波 ( L FMCW)信号是高频雷达常采用的信号形式。就 L FMCW信号在高频雷达中的应用作了具体分析 ,并导出了其差频相位的具体表达式 ,它表现出了要检测的各量的物理意义 ,对检测的方法提供了理论依据。在此基础上 ,利用二维 FFT处理技术对目标回波信号的信息提取进行了仿真 ,并对仿真结果进行了分析