Analysis of Resolution of Bistatic SAR

In this paper, the spatial resolutions at different directions of bistatic synthetic aperture radar （BiSAR） have been derived from the ambiguity function. Compared with monostatic signal to noise ratio, BiSAR＇s resolutions of a fixed point target are varying with slow time since BiSAR system is space-variant. Constraints for the assumption of space-invariant bistatic topology are proposed in the paper. Moreover, under the assumption of invariance, the change of resolutions at different point in the image scene is taken into account, and we have specified two key parameters that affect resolutions directly and analyzed the way how they influence on the resolutions.     

ANALYSIS AND PROCESSING OF LMF－COSTAS STEPPED FREQUENCY RADAR SIGNAL

Linear Modulated Frequency (LMF) Costas Stepped Frequency Radar (SFR) signal is introduced. Its ambiguity function is derived and analyzed in detail and its feasibility is validated in theory. The scheme of the proposed signal processing is also presented. The results of theoretic analysis and simulation show that, by using the proposed signal and increasing the bandwidth of the total stepped frequency, the ambiguity sidelobe is well suppressed and the range-velocity coupling in the stepped frequency radar is also greatly weakened.     

ACCELERATION AMBIGUITY FUNCTION OF RADAR SIGNALS AND ITS APPLICATION

High acceleration of radar targets is analyzed using Acceleration Ambiguity Function(AAF). The acceleration resolution based on AAF is defined. The AAF and acceleration resolution of rectangle pulse signal are derivated and the conclusion that its acceleration resolution is in inverse proportion with the square of its duration is drawn. In the end, these conclusions are applied to the parameter designing and performance evaluation for a certain type of pulse Doppler radar.     

基于CITAF-HAF的立方调频信号参数估计

针对立方调频（Cubic Frequency Modulated,CFM）信号的参数估计问题,提出了一种基于高阶模糊函数（High order Ambiguity Function,HAF）和相参积累三阶自相关函数（Coherently Integrated Trilinear Autocorrelation Function,CITAF）的参数估计方法。利用HAF将立方相位信号降阶为二次调频（Quadratic Frequency Modulated,QFM）信号,再利用CITAF完成参数估计。由于CITAF能够在时域和时延域完成信号能量的二维相参积累,其实现过程利用复乘、傅里叶变换和加法操作即可完成,因此该方法能够提高参数估计的分辨率和抗噪声干扰能力,并保持较低的计算量。实验结果证实了该算法的有效性和性能上的优越性。     

Neural network wind retrieval from ERS-1 scatterometer data

This paper presents a neural network methodology to retrieve wind vectors from ERS1 scatterometer data. First, a neural network (NN-INVERSE) computes the most probable wind vectors. Probabilities for the estimated direction are given. At least 75% of the most probable wind directions are consistent with ECMWF winds (at ±20°). Then the remaining ambiguities are solved by an adapted PRESCAT method, which uses the probabilities provided by NN-INVERSE. Several statistical tests are presented to evaluate the accuracy of the method. Its good performance is mainly due to the use of a spatial context and to the probabilistic approach for estimating the direction. Comparisons with other methods are also presented. The good performance of the neural method suggests that self-consistent wind retrieval is possible.     

系统可靠性的计算机仿真方法

随着各种新型复杂系统的建立和工程项目的实施，常规可靠性设计理论与工程实践的矛盾日益突出。当进行可靠性计算时，由随机应力和随机强度的概率密度函数来获取功能函数的概率密度函数较困难，该文就如何将常规可靠性仿真方法推广进行计算机可靠性仿真，提出了将模糊可靠性设计问题转化为常规可靠性设计问题求解的思路，给出了转化的基本原理和方法，由此推出了一系列的计算公式及其仿真方法，从而使得可靠性设计方法能同时处理设计中的随机性和模糊性。     

编队卫星SAR系统的模糊函数分析

从编队卫星SAR的特点出发,定义了编队卫星SAR的模糊函数,推导出了模糊函数的数学表达式,并进行了计算机仿真。仿真结果充分验证了本函数的有效性。通过分析模糊函数可以直观地看出编队卫星构型对系统分辨率的影响,这为卫星构型的选择提供了依据。     

反向训练 影像传媒与空间知觉的多义性

作者从视知觉心理学的角度出发,论述当代影像媒介对空间知觉所进行的反向训练,并以“深度”、“框”和“序列”为例,具体分析有关空间的概念在这一训练过程中发生了怎样的变化,进而指出空间知觉在当代传媒环境下的一种总体趋向,以及这一转变的认知心理机制。     

基于盲源分离的多幅顺序图像加密方法

根据许多加密方法利用数学难题保障其安全性的思想,盲源分离欠定难题可用于高度安全的多幅图像加密。然而,由于盲源分离存在顺序和幅度模糊性,通过盲源分离得到的解密图像可能发生顺序变化和像素值反转。这在加密多幅顺序图像时可能导致解密错误。针对这一问题,该文利用数字水印技术,加密前在每幅明文图像中嵌入与其对应的顺序信息;解密后,通过在各解密图像中检测该顺序信息而消除其顺序和幅度的模糊性。计算机仿真结果表明,该方法在恢复解密图像顺序的同时也能检测其是否反转,从而有效地解决了多幅顺序图像的盲源分离加密问题。     

LFMCW雷达信号模糊函数分析

本文从ＬＦＭＣＷ雷达体制特点出发，导出了ＬＦＭＣＷ信号模糊函数，分析了它的特点以及它与ＬＦＭＣＷ雷达接收机中点目标回波信号的关系，阐明了它与脉冲雷达ＬＦＭ信号模糊函数的差别，并从模糊函数角度说明了运动目标回波的距离速度耦合及波形畸变现象。