Recovery error bounds on compressed sensing of noisy signals

Compressed sensing is an emerging technique in the field of digital signal acquisition. It promises almost exact recovery of high‐dimensional signals from a very small set of measurements. However, this technique is challenged by the task of recovering signals immersed in noise. In this paper, we derive upper and lower bounds on mean squared recovery error of noisy signals. These bounds are valid for any number of acquired measurements and at any signal‐to‐noise ratio. This work is highly useful for the design of any compressed sensing‐based real world application by quantifying recovery error entailed with realistic digital signal acquisition scenarios. Copyright © 2013 John Wiley & Sons, Ltd.     

基于Lawson范数的通用lncosh稀疏自适应算法

该文提出一种通用稀疏系统识别Lawson-lncosh自适应滤波算法,该算法采用系数向量的Lawson范数和误差的lncosh函数构建代价函数。Lawson范数约束引入参数p,实现稀疏约束滤波动态调整,所提算法可以提高稀疏系统识别时的收敛速度,减小了稳态误差。误差的lncosh函数具有良好的抗脉冲噪声性能。然后,算法分析了步长参数的取值范围和参数p对算法性能的影响。计算机仿真结果表明,在高斯信号输入和色信号输入情况下,所提算法的性能要明显优于其他现存算法,且具备稀疏约束可控特性。     

一种基于IBC的零信任安全解决方案

传统IT网络安全架构基于内网安全的假设,安全边界一旦被突破,传统网络安全防护就可能失效,导致网络系统受到严重破坏.为解决上述问题,设计了一种基于标识密码的零信任安全方案.在防护网络中,所有用户和设备都被赋予唯一访问标识,基于国产密码体系搭建标识密钥基础设施,构建统一身份认证体系,对系统主体及客体实施身份认证和加密传输,...     

具有双重稀疏机制的在线学习算法

针对大数据背景下数据分类问题,已有的在线学习算法通常引入L₁范数正则化增强预测模型的稀疏性,但单一的正则化约束不能高效的获取稀疏模型.基于此,提出了一种具有双重稀疏机制的在线学习算法（an online learning algorithm with dual sparse mechanisms,DSOL）.在DSOL算法中,一方面利用L_1/2正则化项约束目标函数以增强预测模型的稀疏性,提高算法的泛化性能.另一方面用改进的梯度截取法对数据特征进行选择,有效稀疏化预测模型.通过L_1/2正则化与改进的梯度截取策略的有机融合,有效利用了历史数据信息,提高了算法分类数据的性能.通过与另4种代表性稀疏在线学习算法在9个公开数据集的实验对比表明DSOL算法对数据分类的准确性更高.     

圆盘超声电机准零刚度转子设计及其优化

该文针对长时间储存和高冲击环境导致超声电机正常工作预压力发生改变的背景,设计了一种受到外部环境扰动保持预压力恒定的准零刚度碟簧转子。借鉴了开槽碟簧设计思路,建立其参数化有限元模型。采用灵敏度分析选择主要设计变量,建立了在选定工作预压力附近准零刚度段最长的目标函数。利用有限元数值模型对该碟簧转子进行参数优化设计。结果表明,优化后的碟簧转子在正常工作预压力附近准零刚度段的长度达到0.6 mm,且在冲击环境下满足强度要求,最终通过实验验证了装配有该碟簧转子超声电机的输出特性良好。     

一种线性相位LC滤波器的设计

为解决滤波器带外抑制和通带内相位波动之间的矛盾,该文介绍了一种线性相位LC滤波器的设计方法,通过对滤波器传输零点特性进行分析,根据指标要求灵活设计电路拓扑结构和零点位置,采用内、外均衡电路级联网络两种方法,来实现具有高矩形、线性相位特性的滤波器。设计了中心频率21.4 MHz、0.5 dB带宽大于10 MHz、矩形系数(45 dB/0.5 dB)小于2、带内相位波动绝对值小于5°和中心频率1 300 MHz、1 dB带宽大于200 MHz、矩形系数(35 dB/1 dB)小于2、带内相位波动绝对值小于5°两款滤波器。该方法工程实用化强,便于调试和制作,可应用于幅相特性要求高的微波系统中,提高了系统性能指标。     

基于自适应最优消零的无线传感器网络数据压缩算法研究

针对无线传感器网络采集数据存在的时空冗余,提出了一种自适应最优消零压缩算法(AOZS,adaptive op-timal zero suppression compression algorithm)。AOZS是一种无损的数据压缩算法,能够自适应地寻找最优位数因子对递增排列的数据序列进行消零运算和编码,使得数据序列的最终编码长度最短。仿真结果表明,AOZS算法能够对无线传感器网络采集的数据进行有效地压缩,降低了节点能耗,减小了网络延时,并且能精确地重构原始数据。     

一种具有动态零点补偿的电流模DC-DC降压型转换器

To achieve fast transient response for a DC-DC buck converter,an adaptive zero compensation circuit is presented.The compensation resistance is dynamically adjusted according to the different output load conditions, and achieves an adequate system phase margin under the different conditions.An improved capacitor multiplier circuit is adopted to realize the minimized compensation capacitance size.In addition,analysis of the small-signal model shows the correctness of the mechanism of the proposed adaptive zero compensation technique.A currentmode DC-DC buck converter with the proposed structure has been implemented in a 0.35μm CMOS process,and the die size is only 800×1040μm~2.The experimental results show that the transient undershoot/overshoot voltage and the recovery times do not exceed 40 mV and 30μs for a load current variation from 100 mA to 1 A.     

A Fast and Precise Blind I/Q Mismatch Compensation for Image Rejection in Direct‐Conversion Receiver

In this paper, we propose a new digital blind in‐phase/quadrature‐phase (I/Q) mismatch compensation technique for image rejection in a direct‐conversion receiver (DCR). The proposed image‐rejection circuit adopts DC offset cancellation and a sign‐sign least mean squares (LMS) algorithm with a unique step size adaptation both for a fast and precise I/Q mismatch estimation. In addition, several performance‐optimizing design considerations related to accuracy, speed, and hardware simplicity are discussed. The implementation of the proposed circuit in an FPGA results in an image‐rejection ratio (IRR) of 65 dB, which is the best performance with modulated signals, along with an adaptation time of 0.9 seconds, which is a tenfold increase in the compensation speed as compared to previously reported circuits. The proposed technique will be a promising solution in the area of image rejection to increase both the speed and accuracy of future DCRs.     

系统极零点与频率特性的关系

采用定量计算的方法,分析了单极点、单零点以及共轭极点、共轭零点对系统频率响应的影响.分析表明单极、零点时以及共轭极点、共轭零点位于特定区域时,系统频率响应的幅频峰值,谷值的频率与极、零点位置所在频率严格一致.通过对多极、零点系统幅频响应的分析得出结论,出现幅频峰值,谷值的频率相对极、零点位置所在频率可能有偏移,但是仍然可以说:极点所在频率位置附近频率响应幅度出现峰值,零点所在频率位置附近频率响应幅度出现谷点.