Phase noise analysis of oscillators with Sylvester representation for periodic time-varying modulus matrix by regular perturbations

Phase noise analysis of an oscillator is implemented with its periodic time-varying small signal state equations by perturbing the autonomous large signal state equations of the oscillator. In this paper, the time domain steady solutions of os- cillators are perturbed with traditional regular method; the periodic time-varying Jocobian modulus matrices are decomposed with Sylvester theorem, and on the resulting space spanned by periodic vectors, the conditions under which the os- cillator holds periodic steady states with any perturbations are analyzed. In this paper, stochastic calculus is applied to disclose the generation process of phase noise and calculate the phase jitter of the oscillator by injecting a pseudo sinusoi- dal signal in frequency domain, representing the white noise, and a δ correlation signal in time domain into the oscillator. Applying the principle of frequency modulation, we learned how the power-law and the Lorentzian spectrums are formed. Their relations and the Lorentzian spectrums of harmonics are also worked out. Based on the periodic Jacobian modulus matrix, the simple algorithms for Floquet exponents and phase noise are constructed, as well as a simple case is demonstrated. The analysis difficulties and the future directions for the phase noise of oscillators are also pointed out at the end.     

ADC动态特性测试中采样率的选取研究

从ADC的模型建立出发,通过分析量化误差的频域特性和采样过程,提出了一种在频域对ADC进行动态特性测试时,如何根据输入信号频率f0选取恰当的ADC采样率fs的方法,从而有效避免谐波混叠现象,提高测试准确度.实验结果证明了理论分析的正确性,分析结果对ADC的测试和设计具有理论指导意义.     

Beyond synchronization: String instability in coupled harmonic oscillator systems

In this paper, we consider the problem of disturbance response and error amplification for a simple system of coupled harmonic oscillators. We first suppose that identical oscillators are connected in a string in which each oscillator attempts to track its predecessor by using the same control law that depends on the relative position information from its immediate predecessor. Such an oscillator string is called a homogeneous oscillator string with predecessor‐following architecture. Motivated by terminology from the problem of vehicle platooning, we say that the synchronized oscillator system is string unstable if the effect of a disturbance to the lead oscillator is amplified as it propagates along the string. With the use of a new Bode‐like integral relation that must be satisfied by the complementary sensitivity function, we provide sufficient conditions for string instability. The sufficient conditions show that any string of oscillators that satisfies certain time domain performance specifications and bandwidth limitations must necessarily be string unstable. We further introduce a concept of time headway for the oscillator system and extend our analysis of string instability to consider the heterogeneous oscillator string and a more general communication range. Copyright © 2014 John Wiley & Sons, Ltd.     

基于Matlab的绝缘材料电气性能测试系统设计

针对传统的绝缘性能测试仪存在功能单一和无法兼容频域介电响应等新方法的问题,通过选用常见设备,设计了一套基于Matlab绝缘材料电气性能测试系统。该系统利用前置滤波器消除了频率响应函数对系统输出的不利影响,使系统不仅拥有常规的直流跟工频检测功能,也具备在50Hz-1kHz频率范围内进行电压试验的能力,测试时的最高电压能够达到10kV。通过测量试验中流过介质的漏电流,该系统适用于对被测物的绝缘性能进行综合的评估。试验结果表明该系统达到了设计指标,并且能够满足日常工作中的测试需要     

A testability strategy for microprocessor architecture

The authors present a method for fully testing chips designed using synthesis and silicon compilation. The method is targeted for a multiprocessor architecture that implements low-speed to medium-speed signal-processing algorithms. By taking advantage of the specific properties of the architecture, the method allows a chip to be partitioned into several functional units. The authors use the C-test concept instead of the traditional automatic test-pattern generation to derive a compact set of test vectors. The fault model covers both the stuck-at class and part of the transistor stuck-open and stuck-closed cases. For large units with embedded memory, the authors adopt a self-test approach     

时频分析在复合材料无损检测中的应用研究

随着复合材料检测的发展,Lamb波无损检测技术日益受到重视。根据Lamb波多模式和频散的特点,以群速度-频厚积曲线为基础,采用短时傅利叶变换（STFT）的时频分析方法,以层合板复合材料为实验对象,与单独在时域、频域中分析相比较,结果表明：STFT可有效地识别Lamb波的传播模式,并可准确地对能量成分进行分析。     

基于调制域分析的自动测试系统设计

调制域分析已经成为现代测试技术不可或缺的部分,在显现频率变化信号时优于时域测量和频域测量.可是建立在调制域基础上的自动测试设备在国内却很少见到.基于调制域分析,设计了电子产品频率调制参数测试方法.借助GPIB高速数据传输总线,设计了无须人工干预的自动测试方案,该方案数据传输快速稳定,并且能适应用户多种测试要求,智能性强.实际使用证明,开发出的系统能够持续稳定地工作,大大提高劳动生产率.     

小波域利用Duffing振子检测的图像水印算法

为了提高图像Chirp类水印的鲁棒性能,提出一种利用混沌振子检测微弱水印信号的方法。将嵌入在载体低频小波域的非周期Chirp信号通过分块平滑转化为单频周期信号,然后通过Duffing振子阵列检测器检测微弱的周期信号,使水印检测问题转化为超低信噪比下,确定性微弱周期信号的检测。实验表明信噪比为－40dB时仍然能有效检测到水印的存在。     

光伏组件测试仪的光辐照度不均匀性检验系统的研究和设计

通过对传统光伏组件测试设备检验方式的分析,提出了一种一次闪光就能够完成对测试仪工作平面辐照不均匀性测试的方法,在设计中充分使用了国际知名公司新生产的元器件,设计了信号调理电路和数据采集电路,电路设计简单,成本低廉易于实现,采集精度符合设计要求。并编写了上位机的测试程序,对辐照不均匀性测试进行了验证,结果表明测试工艺简单,数据可靠,生产效率高。     

A parallel computing approach to creating engineering conceptspaces for semantic retrieval: the Illinois Digital Library Initiativeproject

This research presents preliminary results generated from the semantic retrieval research component of the Illinois Digital Library Initiative (DLI) project. Using a variation of the automatic thesaurus generation techniques, to which we refer to as the concept space approach, we aimed to create graphs of domain-specific concepts (terms) and their weighted co-occurrence relationships for all major engineering domains. Merging these concept spaces and providing traversal paths across different concept spaces could potentially help alleviate the vocabulary (difference) problem evident in large-scale information retrieval. In order to address the scalability issue related to large-scale information retrieval and analysis for the current Illinois DLI project, we conducted experiments using the concept space approach on parallel supercomputers. Our test collection included computer science and electrical engineering abstracts extracted from the INSPEC database. The concept space approach called for extensive textual and statistical analysis (a form of knowledge discovery) based on automatic indexing and co-occurrence analysis algorithms, both previously tested in the biology domain. Initial testing results using a 512-node CM-5 and a 16-processor SGI Power Challenge were promising     

Implementation of phase-locked loop control for MEMS scanning mirror using DSP

The present study has employed the phase-locked loop control method to ensure the operating of MEMS actuators at their resonant frequency. In this study, the control algorism was simulated by the MATLAB. Further, the digital signal processing (DSP) technique was adopted to implement the concept of phase-locked loop control algorithm. Thus, a wide VCO lock-in dynamic range was achieved. In applications, the optical scanners fabricated using the SOI wafer and MOSBE process were respectively employed to demonstrate the present technique. The test show that the resonant frequency was tracked for various driving voltages, loop gains, and initial frequency offsets. Thus, the variation of the scanning angle resulted from the offset of the resonant frequency of the devices can be prevented.     

基于频率跟踪方式的智能滤波信号处理系统研究

频域模式化分析或时域波形理论等方法在实现与应用上存在一定局限性.介绍了一种较新颖的自适应滤波系统的实现方法,它是利用FFT谱分析抽取的信号主频来实现滤波中心频率实时跟踪及带宽分段变化.实验测试结果表明：该系统具有在较强背景噪声下,跟踪提取有用信号并精确计算信号频率的功能,可为涡街流量计信号处理等工程实际中信号的进一步应用提供研究基础.     

New applications of harmonic balance analysis

This article shows how the theory of averaging extends applications of harmonic balance analysis. Two examples are given: (i) a new approach to high-Q oscillators, which results in an analysis of slowly varying envelope of oscillations rather than the oscillations themselves; and (ii) a rigorous analysis of frequency lock and of stability of multiple solutions in synchronized oscillators. Both results can be directly applied to diode and transistor oscillators and can also serve as benchmarks in testing nonlinear simulators. © 1995 John Wiley & Sons, Inc.     

基于共振隧穿二极管的矢量水声传感器设计

提出了一种基于共振隧穿二极管(RTD)的矢量水声传感器,传感器采用共振隧穿二极管作为敏感元件,共振隧穿二极管布置在传感器结构中柱体的四周边缘.两个反方向变化的基于共振隧穿二极管的振荡器的输出信号通过信号处理电路预处理后输入微处理器,计算出声源水平方位角和声压.分析并设计了基于共振隧穿二极管的振荡电路、矢量水声传感器物理结构以及制作工艺,讨论了传感器信号处理方法.     

光伏系统直流串联故障电弧特征研究

应用时域分析和频域分析相结合的方法,研究了光伏系统串联电弧故障问题.搭建了新型光伏系统故障电弧实验平台,获得了光伏系统正常运行和发生串联故障电孤时电流峰峰值和电流平均值的特征差异,分析了电流时域特征在串联故障电弧识别方面的可行性.得到了光伏系统发生串联故障电弧时,电流一层小波分解细节分量均值是正常状态下的2.5～4倍,两层小波分解细节分量均值是正常状态下的10～16倍的结论.以上结论可通过有效的数据融合形成串联电孤故障识别判据,为光伏系统串联电弧故障保护装置的研制提供理论支持.     

毫米波低相噪捷变频高分辨率雷达频率源设计

设计了一种由直接数字频率合成(DDS)、倍频链构成的三次变频直接频率合成方案,实现了低相噪捷变频高分辨率毫米波雷达频率合成器设计.利用直接频率合成器的倍频输出取代传统三次变频毫米波频率源的锁相环(PLL),同时提供线性调频(LFM)信号,优化DDS和变频方案的频率配置关系.利用FPGA电路进行高速控制,较好地解决了毫米...     

泡沫夹层结构的超声检测特征成像

某型号直升机采用了碳纤维/聚甲基丙烯酰亚胺(CFRP/PMI)泡沫夹层结构制作旋翼,针对此结构内部存在分层、脱粘等缺陷识别困难的问题,通过预埋人工缺陷制作对比试块,从检测原理上分析了超声时域特征成像原理和频域特征成像原理,分别采用缺陷幅值、底波幅值、缺陷深度、频域幅值、频域相位5种特征成像效果进行了对比分析,寻找最优特征成像方法。结果表明：不管采用时域信号特征成像还是频域信号特征成像都能够清晰地发现CFRP中的分层缺陷。但是对于CFRP/PMI泡沫的脱粘缺陷,时域幅值特征成像效果优于深度特征成像;频域信号特征成像优于时域信号特征成像;相-频特征成像优于幅-频特征成像效果。     

Fractional dynamical model for the generation of ECG like signals from filtered coupled Van-der Pol oscillators

In this paper, an incommensurate fractional order (FO) model has been proposed to generate ECG like waveforms. Earlier investigation of ECG like waveform generation is based on two identical Van-der Pol (VdP) family of oscillators, which are coupled by time delays and gains. In this paper, we suitably modify the three state equations corresponding to the nonlinear cross-product of states, time delay coupling of the two oscillators and low-pass filtering, using the concept of fractional derivatives. Our results show that a wide variety of ECG like waveforms can be simulated from the proposed generalized models, characterizing heart conditions under different physiological conditions. Such generalization of the modelling of ECG waveforms may be useful to understand the physiological process behind ECG signal generation in normal and abnormal heart conditions. Along with the proposed FO models, an optimization based approach is also presented to estimate the VdP oscillator parameters for representing a realistic ECG like signal.     

低成本的两级扫描测试结构

提出了一种两级扫描测试结构：根据电路结构信息对时序单元进行分组,同组的时序单元在测试生成电路中共享同一个伪输入;将时序单元划分到不同的时钟域,在测试向量的置入过程中只有很小一部分时序单元发生逻辑值的翻转;引入新的异或网络结构,消除了故障屏蔽效应.实验结果表明,该两级测试结构与以往的方法相比,在保证故障覆盖率的同时,大大降低了测试时间、测试功耗和测试数据量.     

标准接口仪器测试应用软件辅助开发工具

领域工程是目前软件工程领域的一个重要研究方向,通过对基于特定领域的核心资产库的复用,可以提高开发效率和质量,降低维护成本．该文通过对基于标准接口仪器测试软件的领域分析,提出了该领域软件的体系结构,并开发了相应的支持工具．文章最后是使用该工具的体会和进一步的工作．