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噪扰下数字化多频连续波雷达的测距模糊问题 总被引:22,自引:2,他引:20
数字化多频连续波测距雷达是一种新体制雷达.它具有能同时测定多个目标、便于同时得到目标多个运动参数等突出优点.为了解决增大最大测距不模糊距离与提高测距精度之间的矛盾,我们将会在多频雷达中采用参差频差关系进行测距,这样我们可以大大提高测距最大不模糊距离.但此时噪声对测距结果有着各种有待讨论的影响,包括:能否正确解模糊;对输入信号信噪比有何要求;理论测距精度有何变化;直至对参差系数有何要求等.数字化多频雷达的这些问题,本文对这些问题进行了详细的讨论,并给出了本文结论的计算机仿真结果.从而在理论上为这种雷达的深入研究提供了一个很好的基础. 相似文献
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介绍了二次相差法测距的基本原理,并对二次相差法多频连续波测距体制在分离多目标的问题上进行了研究分析。通过对二次相差法测距性能进行了仿真分析,仿真结果表明,基于双频比相测距的二次相差法多篇连续波雷达,只能求解速度不同的目标的距离值,无法求解同速度不同距离目标的距离值。 相似文献
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FMCW雷达差频信号的非线性分析 总被引:1,自引:0,他引:1
FMCW雷达具有大的时宽带宽积,可达到较高的测距精度,但由于压控振荡器等器件非线性的存在,使测距精度大大降低。通过理论分析这一非线性对用于测距的差频信号频谱的影响,结合直接采集和实测相应的差频信号,确定非线性误差的来源和频率范围。采用模拟窄带滤波,降低扰频信号干扰,并通过实验测量,验证了利用该方法可以达到提高测距精度的效果。 相似文献
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提出了平衰落信道中阵列天线多输入多输出(MIMO)系统的基于广义高斯分布近似的最小互信息盲接收器(GGMIR)。该接收器采用输出信号的广义高斯分布近似,基于互信息目标函数最小化的方法自适应调整接收器的系数。比较了基于广义高斯分布近似和非线性变换(NLMIR)的两种最小互信息盲接收算法。实验表明基于广义高斯分布近似自适应盲接收算法GGMIR比NLMIR算法有更快的收敛速率,得到的信号星座图有更大的距离和更好的误码性能。 相似文献
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We present a least squares (LS) algorithm for blind channel equalization based on a reformulation of the Godard algorithm. A transformation for the equalizer parameters is considered to convert the nonlinear LS problem inherent in the Godard algorithm to a linear LS problem. Unlike the Godard (1980) algorithm, the proposed LS approach does not suffer from ill-convergence to closed-eye local minima. Methods for extracting the equalizer parameters from their transformed version are developed. Offline and recursive implementations of the LS algorithm are presented. The algorithm requires only a small number of channel output observations to estimate the equalizer parameters and is therefore fast vis-a-vis the Godard algorithm. The channel input correlation does not impose any restriction on the application of the algorithm, as long as a weak sufficient-excitation condition is satisfied. Simulation examples are presented to demonstrate the LS approach and to compare it with the Godard algorithm 相似文献
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He Shichun He Zhenya 《通信学报》1997,18(3):65-69
ApplicationofRecurrentWaveletNeuralNetworkstotheDigitalCommunicationsChannelBlindEqualization**ThisworkwassupportedbytheClimb... 相似文献
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A multiuser automatic modulation classifier (MAMC) is an important signal processing component of a multiantenna cognitive radio (CR) receiver that helps the radio in identifying modulation format employed by multiple users in a frequency band simultaneously. In a typical wireless communication, transmitted signals are subjected to multipath fading and interference from other users. Multipath fading not only affects symbol detection performance but also affects the performance of the automatic modulation classifier. A multi input multi output (MIMO) blind equalizer is another important component of a multiantenna CR receiver that improves symbol detection performance by reducing inter symbol interference and inter user interference. In a CR scenario it is preferable to consider the performance of the AMC also while adapting the parameters of the blind equalizer. In this paper we propose MIMO blind equalizers that improves the performance of both multiuser symbol detection and cumulants based MAMC. Computer simulations are provided to illustrate this concept and the proposed algorithm. 相似文献
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Timing phase offset recovery based on dispersion minimization 总被引:1,自引:0,他引:1
Wonzoo Chung Sethares W.A. Johnson R. Jr. 《Signal Processing, IEEE Transactions on》2005,53(3):1097-1109
This paper presents a blind timing phase offset recovery scheme that attempts to optimize the baud spaced equalizer output mean square error (MSE) for a realistic equalizer length that is usually shorter than the ideal length. Among the existing blind timing recovery schemes, few are designed for equalizer output MSE optimization, and none are designed for the realistic case when the equalizer is short. The proposed algorithm (that is based on a cost function that minimizes the dispersion of the received signal) attempts to minimize the MSE of a one-tap equalizer output. It also exhibits good performance for relatively short equalizers. Conditions for the unimodality of the dispersion minimization cost are investigated, and a geometric relationship to the minimum MSE (MMSE) timing offset is shown qualitatively. The detailed MSE performance of the algorithm is investigated for the representing classes of channels by comparing existing blind timing offset estimation schemes. 相似文献
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为了提高多径衰落信道下的盲解调性能,提出了一种结构简单的MPSK信号盲解调算法。首先利用超指数迭代分数间隔盲均衡器实现联合定时同步与均衡,然后对均衡器输出信号进行非线性变换实现载波频偏的估计,最后利用二阶数字判决锁相环跟踪相位变化纠正剩余频偏和相偏。仿真结果表明,在多径衰落信道条件下,与现有算法相比,基于超指数迭代分数间隔盲均衡器的盲解调算法实现简单,误码率低,而且具有收敛速度快、性能稳定等优点。 相似文献
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针对频率选择性衰落信道下的多天线盲接收问题,本文提出了一种新的"合成器-均衡器"盲空间分集均衡器结构.基于频域波形合成、均衡器与软符号信息的联合处理框架,首先设计了频域BLOCK-SUMPLE迭代算法,对多路信号频域合成权值进行联合估计,实现频率选择性衰落信道下的波形合成.在此基础上,利用均衡器输出软符号信息重构合成参考,对权值相位予以修正,实现对等效合成信道的优化补偿.与传统盲空间分集均衡算法相比,上述算法实现无需训练序列辅助,并且优化了信号分集合并性能,降低了均衡器的设计难度.仿真结果表明,采用新型结构可有效改善衰落信道下的盲接收效果,逼近最佳空间分集均衡器性能. 相似文献
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Santamaria I. Erdogmus D. Principe J.C. 《Signal Processing, IEEE Transactions on》2002,50(5):1184-1192
This paper investigates the application of error-entropy minimization algorithms to digital communications channel equalization. The pdf of the error between the training sequence and the output of the equalizer is estimated using the Parzen windowing method with a Gaussian kernel, and then, the Renyi's quadratic entropy is minimized using a gradient descent algorithm. By estimating Renyi's entropy over a short sliding window, an online training algorithm is also introduced. Moreover, for a linear equalizer, an orthogonality condition for the minimum entropy solution that leads to an alternative fixed-point iterative minimization method is derived. The performance of linear and nonlinear equalizers trained with entropy and mean square error (MSE) is compared. As expected, the results of training a linear equalizer are very similar for both criteria since, even if the input noise is non-Gaussian, the output filtered noise tends to be Gaussian. On the other hand, for nonlinear channels and using a multilayer perceptron (MLP) as the equalizer, differences between both criteria appear. Specifically, it is shown that the additional information used by the entropy criterion yields a faster convergence in comparison with the MSE 相似文献