过采样Σ-Δ ADC中Σ-Δ调制器分析与研究

分析并讨论了过采样Σ-ΔADC中过采样技术和噪声整形技术的工作原理,Σ-Δ调制器的级数对整形效果的影响及调制器的结构选择,并用MATLAB语言的simulink工具箱进行了系统级的仿真。     

Maximum Likelihood (ML) Symbol Timing Recovery (STR) Techniques for Reconfigurable PAM and QAM Modems

A fast symbol timing recovery (STR) scheme suitable for flexible-symbol-rate, burst-mode M-ary QAM (M-QAM) and PAM (M-PAM) demodulators used in broadband communications is proposed. The maximum- likelihood (ML) estimation is used to derive a feed-forward STR strategy to achieve fast and accurate derivation of the optimum timing instant with a very short training preamble for applications requiring short packet transmission. In addition, the signal sample at the optimum timing instant is reproduced by interpolation. Analysis to derive the ML-based timing estimation algorithm and STR structure is presented. Analytical models are developed to evaluate the effects of imperfect interpolation and channel additive white Gaussian noise (AWGN) on the timing estimation performance. The derived expressions can be used for optimum interpolation filter design and selection of key parameters to achieve the required mean squared timing error. Simulation results are in good agreement with the analytical prediction.     

融合特征边界信息的不平衡数据过采样方法

针对实际应用中存在的数据集分布不平衡的问题，提出一种融合特征边界数据信息的过采样方法。去除数据集中的噪声点，基于少数类样本点的多类近邻集合，融合特征边界的几何分布信息获得有利于定义最优非线性分类边界的少数类样本点，通过其与所属类簇的结合生成新样本。对不平衡数据集采用多种过采样技术处理后，利用支持向量机进行分类，对比实验表明所提方法有效改善了不平衡数据的分类精度，验证了算法的有效性。     

采用多伯努利滤波器的过采样点目标检测前跟踪

为了提高过采样体制下点目标的探测能力,提出了基于多伯努利滤波器的过采样点目标检测前跟踪方法。分析了时空过采样体制的成像过程,给出了时空过采样体制下的点目标成像模型,并将过采样观测过程等效建模为多个单采样线阵同时观测的过程。利用提出的模型,将单采样条件下的图像处理方法自然地扩展到过采样条件下。然后,根据等效观测模型,给出了针对过采样点目标的多伯努利预测和更新过程,并用序贯蒙特卡罗的方式实现了该检测前跟踪方法。最后,通过仿真实验验证了本文算法的有效性。实验结果表明:本文提出的方法能够在图像信噪比≥3的条件下,有效检测和跟踪过采样体制下的多个点目标,目标估计误差≤0.25pixel;与单采样检测前跟踪相比,过采样检测前跟踪能够探测目标能量更弱的小目标。因此,本文方法能够满足高精度天基点目标检测跟踪的需求。     

新型空间红外扫描传感器

针对天基红外扫描传感器,实例分析了SBIRS-HIGH和SPIRITⅢ传感器的特性.总结了新型天基红外扫描传感器系统设计的技术特点,包括多工作波段,时间延迟积分,过采样,大动态测量范围以及与凝视传感器相互切换等技术方面.     

带有超长方体约束的少数类样本生成机制

合成少数类过采样技术（SMOTE）是解决类不平衡问题的有效方法之一。但是,SMOTE的线性插值机制将合成样本限制在原始样本的连线上,导致新样本缺乏多样性,并且这条连线穿过多数类区域时可能会生成噪声样本。针对上述问题,提出一种带有超长方体约束的少数类样本生成机制。该机制使用超长方体作为新样本的生成区域来代替线性插值,以增加合成样本与原始样本的差异性。并通过检测超长方体内是否存在多数类样本来决定是否修正此超长方体,从而防止新合成样本落入多数类区域内。使用所提机制替换线性插值,并集成在SMOTE、Borderline-SMOTE和ADASYN三种过采样方法中,然后在KEEL的11个标准数据集上进行了实验评估。结果表明,相比于原始方法,集成后的方法能够帮助分类器取得更高的F1值和相当的G-mean。这说明超长方体生成机制能够显著改善分类器对少数类样本的识别能力,并且能够兼顾到多数类样本。     

基于过采样的混合滤波器组性能优化

模拟误差是制约混合滤波器组信号重构精度的主要原因,如何降低由模拟误差导致的分解滤波器组系数误差成为了首要问题。引入过采样技术,研究在不同过采样率下8通道混合滤波器组的性能,寻找到过采样率最优值约等于7%。在不同模拟误差下对基于过采样的混合滤波器组的性能进行仿真,结果表明,原型结构和双阶型结构的混叠值相近,但后者对模拟误差的敏感度比前者大。信号重构阶段,在最小二乘法的基础上采用频带加权法进行误差校准。在1%模拟误差内,采用7%过采样率的原型混合滤波器组相比无过采样,平均混叠值下降了约50 dB,最大混叠值下降了约94 dB。仿真验证了引入过采样的有效性。     

An empirical comparison and evaluation of minority oversampling techniques on a large number of imbalanced datasets

Learning and mining from imbalanced datasets gained increased interest in recent years. One simple but efficient way to increase the performance of standard machine learning techniques on imbalanced datasets is the synthetic generation of minority samples. In this paper, a detailed, empirical comparison of 85 variants of minority oversampling techniques is presented and discussed involving 104 imbalanced datasets for evaluation. The goal of the work is to set a new baseline in the field, determine the oversampling principles leading to the best results under general circumstances, and also give guidance to practitioners on which techniques to use with certain types of datasets.     

基于N通道技术的带通Σ△A／D转换器

本文基于Ｎ通道技术，提出了一种新型的带通Σ△Ａ／Ｄ转换器，分析了其工作原理，并给出了性能的模拟结果。本文的思想对于带通Ａ／Ｄ转换系统的设计有明显价值。     

On-Chip Evaluation of Oscillation-Based-Test Output Signals for Switched-Capacitor Circuits

This work presents a simple and low-cost method for on-chip evaluation of test signals coming from the application of the Oscillation-Based-Test (OBT) technique. This method extracts the main test signal features (amplitude, frequency and DC level) in the digital domain requiring just a very simple and robust circuitry. Experimental results obtained from an integrated chip demonstrate the feasibility of the approach.