Extended ambiguity function for bistatic MIMO radar

This paper derives the extended ambiguity function for a bistatic multiple-input multiple-output (MIMO) radar system,which includes the whole radar system parameters:geometric sensor configuration,waveforms,range,range rate,target scattering and noise characteristics.Recent research indicates the potential parameter estimate performance of bistatic MIMO radars.And this ambiguity function can be used to analyze the parameter estimate performance for the relationship with the Cramer-Rao bounds of the estimated parameters.Finally,some examples are given to demonstrate the good parameter estimate performance of the bistatic MIMO radar,using the quasi-orthogonal waveforms based on Lorenz chaotic systems.     

Ultrasonic signal classification based on ambiguity plane feature

Ambiguity function (AF) is proposed to represent ultrasonic signal to resolve the preprocessing prob-lem of different center frequencies and different arriving times among ultrasonic signals for feature extraction, as well as offer time-frequency features for signal classification. Moreover, Karhunen-Loeve (K-L) transform is considered to extract signal features from ambiguity plane, and then the features are presented to probabilistic neural network (PNN) for signal classification. Experimental results show that ambiguity function eliminates the difference of center frequency and arriving time existing in ultrasonic signals, and ambiguity plane features extracted by K-L transform describe the signal of different classes effectively in a reduced dimensional space. Classification result suggests that the ambiguity plane features obtain better performance than the features extracted by wavelet transform (WT).     

机载双站合成孔径雷达模糊函数分析

针对机载双站合成孔径雷达的几何构型,推导了任意构型双站SAR模糊函数的表达式。根据该表达式,对单站、平行双站和任意构型双站SAR系统的模糊函数进行了仿真分析。仿真结果表明：单站SAR的模糊函数仅由发射信号的带宽和天线尺寸决定,双站SAR的模糊函数受到其几何构型、接收机、发射机各自速度的影响,而且还和目标点的位置有关。仿真结果验证了该函数的正确性,为双站SAR的构型设计提供了依据。     

基于任意平面阵的一阶模糊问题研究

基于平面阵的阵列测向系统中,一阶模糊是对测向性能影响最大的一类模糊.为了避免一阶模糊,推导了一个不存在一阶模糊的充分条件,并且可以据此判断任意平面阵列是否存在一阶模糊问题.此外,分析了阵元间距都大于半波长与阵列是否存在一阶模糊问题的关系,指出阵元间距都大于半波长并不必然导致产生一阶模糊.最后通过计算机仿真说明了上述结论的正确性.     

岸-舰双基地SIAR雷达距离-速度分辨率分析

双基地脉冲综合孔径雷达SIAR在发射站采用多个天线同时辐射不同载频的调频中断连续波FMICW信号,在接收站用一个全向天线接收目标回波。推导了该雷达发射信号的模糊函数,分析了影响其距离和速度分辨率的因素以及波形参数选取原则,结合双基地雷达的特点,给出了模糊函数与目标位置的关系。分析表明,该信号形式具有较高的距离和速度分辨率。但由于是双基地雷达,分辨率比单基地雷达差,而且从距离维不能分辨基线的目标。     

多LFM信号自适应时频表示方法

提出了一种多线性调频信号自适应时频表示方法及其快速算法:首先采用分数阶傅里叶变换的快速算法计算出模糊函数,再通过Radon-Ambiguity变换设计出信号的最优核函数,以滤除噪声和多线性调频信号在模糊域中的互项,最后通过二维傅里叶变换得到信号的时频表示。在多分量线性调频信号情况下借助"clean"的思想来抑制强分量对弱分量的干扰。仿真表明该方法在低信噪比环境下也十分有效,且运算复杂度小。     

奈特不确定性下的行为决策理论研究综述

现代经济、金融理论主要研究决策者在面临不确定性条件下的个体选择的理论,这里的不确定性是指有一个确定概率测度的不确定性,也就是风险.所谓奈特不确定性是指不能用一个确定概率测度来描述的不确定性,它与风险是两个不同的概念.本文首先对有关奈特不确定性的行为决策理论的文献作了全面的综述;在此基础上,分析了行为决策科学发展过程中存在的问题,提出了进一步的研究领域.     

余差查表法解多目标距离模糊算法

研究多重脉冲重复频率体制的脉冲多普勒雷达,利用余差查表法解多目标距离模糊的问题.对于一个四重脉冲重复频率的雷达系统,利用真实目标在任何两个脉冲重复频率上检测得到的视在距离,经过余差查表法匹配解得的目标距离是相同的这一特性,可以对多目标进行解距离模糊.提出的基于余差查表法的算法,可以有效地对多目标环境进行求解.尤其是在目标个数较少、系统设计脉冲重复频率选择合适的情况下更为有效.     

高校学生角色转换适应研究

我国正处于市场经济的转型期，巨大的社会变革使高校学生心理困惑加剧，本文试图运用角色理论埃里克森和凯利的人格发展理论，分析高校学生角色转换和适应过程中存在的较普遍的问题：角色认同混乱、自我认同危机、社会认同误差，寻求一些带有共同性的主要影响因素，提出促进学生角色转换，顺利适应的几点措施，以及在心理咨询中应注重的几个方面。     

An Analysis on English Grammatical Ambiguity and Lexical Ambiguity

Ambiguity exists in English as it exists in other natural languages,which leads to people＇s misunderstanding some sentences in some conditions,so it has an impact on the communication of people.Generally speaking,English ambiguity is divided into 3 classifications：phonetic ambiguity,lexical ambiguity and grammatical ambiguity.This paper intends to analyses English grammatical ambiguity and lexical ambiguity,and aims to make the English learners to know this complicated phenomenon wholly,so that English learners can express themselves accurately in writing,speaking and reading.