一种新的二维非线性提升小波变换方法

根据图像的统计信息,本文构造了一种新的非线性算子即统计算子,提出了基于该算子的一种新的非线性提升小波分析方法.使图像经过该方法变换以后,在无量化失真的前提下,以较大概率取得零高频系数.本文将该方法与现存文献中所提出的非线性形态学小波等分析方法,进行了标准图像的测试分析,实验结果显示,利用本文所提出的基于统计算子的提升小波分析的方法所得到的高频子带的熵都低于其它几种非线性小波变换,取得了很好的分析结果.     

非线性电路平衡点全局渐近稳定的冻结系数法

本文提出了一种新的分析非线性电路平衡点全局渐近稳定的方法.这种方法利用冻结系数的相关概念,结合平衡点的渐近稳定判据从而决定平衡点的全局渐近稳定性.与目前该问题所采用的LIYAPUNOV直接法相比,该方法具有无须判断非线性系统平衡点的唯一性和构造LYAPUNOV函数的优点.同时,该方法对于其它形式的非线性系统的分析,也有重要的启发性及应用价值.     

电视台非线性节目制作网的安全性设计

本文结合天津电视台非线性节目制作网的建设过程,分析了非线性制作网络的主要故障,并针对故障原因,介绍和分析该非线性制作网络一系列高可用性、安全性的设计方案.     

解非线性方程组的神经网络方法

本文提出了一种求解非线性方程组的神经网络方法,该方法对非线性方程组的任意给定的初始点,都能稳定地收敛到它的一个实根.文中首先严格地证明了该方法的稳定性、收敛性及可行性,然后给出了一个模拟算法及其应用.最后的数值试验结果表明该方法是有效的.     

非线性编辑在电视专题片制作之运用

在制作电视专题片中,非线性编辑属于重要的制作技术.因此,在制作电视专题片中研究非线性编辑技术具有实用价值.本文分析了制作电视专题片中应用非线性编辑技术,体现出该技术的重要性.     

归一化峰度及其在弱非线性系统盲辨识中的应用

本文主要研究信号的归一化峰度及其在弱非线性系统辨识中的应用策略问题.首先简要介绍了几类常见的无记忆/有记忆非线性模型及其表示方法;给出了信号的归一化峰度定义及重要性质;在此基础上,分别针对非线性系统的记忆效应和非线性阶数对系统输出信号归一化峰度的影响进行了理论推导和仿真分析,揭示了该参数随系统特性的变化规律,表明归一化峰度具备精确辨识弱非线性系统的潜力.最后,针对SFDR(无杂散动态范围)高达85dBFS(dB Full Scale)的弱非线性系统,本文提出了一种分步辨识的方法,并结合所提出的方法阐明了此规律对于弱非线性系统盲辨识和失真补偿的潜在应用价值及其精度优势.     

一类非线性系统的单尺度小波框架 网络自适应观测器

本文提出了一类MIMO非线性系统的小波网络自适应观测器设计方法,可对一类非线性未知或具有不确定性的非仿射系统进行状态估计.文中给出了小波网络参数的在线自适应调节律,从理论上分析了观测器增益矩阵的选择对状态估计误差的影响.根据Lyapunov理论证明了整个自适应观测器的稳定性,仿真试验表明了该方法的有效性.     

扬声器非线性的几种数字补偿方法

对扬声器非线性的数字补偿方法作了综述,扼要介绍分析了该领域研究人员所采用过的5种主要方法.展望了扬声器非线性数字处理方法的应用前景.     

相关乘性噪声背景下的三次非线性耦合谐波分析

本文利用特殊四阶时间平均多矩谱对任意均值乘性噪声与任意均值加性噪声共存,并且乘性噪声之间相关、乘性噪声与加性噪声之间相互独立的噪声背景下的三次非线性耦合进行了分析,该方法能够有效地估计出观测信号中参于三次非线性耦合的频率和耦合产生的频率.并且该方法无需限制乘性噪声与加性噪声的颜色和分布.最后,文中把此方法拓广到二维,用此二维四阶时间平均多矩谱方法分析了二维三次非线性耦合问题,同样取得了良好的效果.仿真实验验证了文中结论.     

基于局部方差中值滤波的 极/超低频信道噪声抑制方法

针对极/超低频信道噪声模型参数估计复杂度高而难以实施最优非线性处理的问题,根据噪声时域波形分析,本文提出了一种基于局部方差中值滤波的抑噪方法.该方法利用局部方差提取结构信息以强化噪声脉冲性,提高中值滤波抑噪性能;采用基于恒虚警率的奇异值检测方法实现含噪样点的盲判决,利用自适应中值滤波算法实现噪声的盲抑制.仿真和实测结果验证了该方法的有效性.相比最优非线性处理,该方法无需噪声参数估计,因而更具实用性.     

Application of sliding-mode control to the design of a buck-basedsinusoidal generator

This paper is devoted to the design of a sliding-mode control scheme for a buck-based inverter, with programmable amplitude, frequency, and DC offset, with no external sinusoidal reference required. A general procedure for obtaining an autonomous (time independent) switching surface from a time-dependent one is presented. For this surface, the system exhibits a zeroth-order dynamics in sliding motion. On the other hand, from the sliding-domain analysis, a set of design restrictions is established in terms of the inverter output filter Bode diagram and the output signal parameters (amplitude, frequency and DC offset), facilitating the subsequent design procedure. The control scheme is robust with respect to both power-stage parameter variations and external disturbances and can be implemented by means of conventional electronic circuitry. Simulations and experimental results for both reactive and nonlinear loads are presented     

Nonlinear analysis of microwave FET oscillators using Volterraseries

A novel approach for determining the amplitude and frequency of nonlinear FET oscillators is presented. The nonlinear elements of the active device are modeled by the Volterra series method. The frequency and amplitude of oscillation are then calculated by solving two algebraic equations. Experimental results obtained from a constructed oscillator confirm the validity of the theory, the discrepancy between measured and calculated frequency and amplitude values being less than 10%     

恒压源驱动下的扬声器低频跳跃

通过能量法求解扬声器非线性振动系统的非线性微分方程的一阶近似解，得出幅频关系方程和幅频关系曲线，并着重分析讨论磁场的非线性对扬声器低频跳跃的影响，得出一些结论。     

Oscillating circuit using nonlinear inductance

An oscillating circuit with nonlinear inductance is examined. A general characteristic of an inductance is used. Using the method of Samoilo, expressions for the oscillation frequency, the current harmonics, the characteristics of the forced oscillations and the characteristics of the parametric resonance are obtained, without limitations on the oscillation amplitude.     

单片CDCTA-C低功耗电控调谐双模式三阶正交振荡器的设计

针对振荡器功耗大和振荡频率低的问题,提出了一种基于电流差分级联跨导放大器的三阶正交振荡电路.该电路仅使用一个电流差分级联跨导放大器和三个接地无源电容,可以同时产生两组等幅正交电流信号和一组等幅正交电压信号.电路结构简单,功耗低至1.8mW,最大灵敏度绝对值仅0.5,振荡频率可达10MHz数量级,而且振荡条件和震荡频率可相互独立地电控调谐.计算机模拟和流片芯片测试结果验证了理论分析的正确性.     

Wigner-Ville分布在电力系统低频振荡中的应用

研究了基于Wigner-Ville分布（WVD）对电力系统低频振荡信号进行检测和时频分析的新方法,Wigner-Ville（wVD）分布是一种优良的时频分析方法,能够在时域频域上对非平稳信号进行联合时频分析。利用WVD的时间边缘特性和频率边缘特性,能精确地估计各模式信号的幅值、频率与主导时间;精确地分析非平稳信号的局域动态行为和特性。更好地反映振荡过程中所包含的多个模式随时间的变化规律以及模式间的相互影响,还可提高识别能力和处理效果。通过多个试验验证了该方法的有效性。     

A Stable Loss Control Feedback Loop for VCO Amplitude Tuning

In practical implementations of LC oscillators in which the quality factor of the tank is dominated by the quality factor of the inductor, due to dependence of the oscillation amplitude on the square of the oscillation frequency and the bias current of the LC tank, a stable amplitude control loop is essential to maintain a constant oscillation amplitude over the tuning range of the voltage-controlled oscillator (VCO) and to optimally bias the VCO over different conditions. In this paper, an enhanced loss control scheme incorporating an integral feedback to automatically tune the oscillation amplitude of LC oscillators is proposed. The proposed loss control feedback (LCF) loop is conditionally stable with an easy stability requirement to meet and its stability is examined: 1) by linearizing the system around the stable point using a perturbation method; and 2) by numerically solving the nonlinear differential equation of the LCF loop describing the transient behavior of the step response of the loop. A prototype including the LC VCO and the proposed LCF loop has been implemented in TSMC 0.35-mum CMOS process and occupies an area of 0.057 mm² and consumes 8.1 mA from a 2.8-V power supply. The LCF loop, with respect to the VCO, has an overhead of 25% on the area and consumes only 1.3% of the total power. Measurement results of the proposed LCF loop show an 11 dBm amplitude tuning range from -16 dBm to -5 dBm at any frequency over the 2-2.5-GHz tuning range of the VCO. The step response of the loop has a settling time less than 0.5 ns     

Noise Analysis of Nonlinear Feedback Oscillator with AM-PM Conversion Coefficient

The noise of a microwave nonlinear feedback oscillator with AM-PM conversion coefficient is analyzed. The oscillation wave is divided into a carrier and noise sidebands. It is assumed that the noise sideband is the first-order perturbation to the carrier wave and can be superposed with each other. The amplitude and frequency of the carrier are graphically determined by the "device-load line" method, considering the nonlinearity of the amplifier. In order to take the AM-PM conversion effect of a nonlinear amplifier into account, the "transfer matrix" for the small AM and PM sideband components which has amplitude-dependent diagonal and off-diagonal terms is introduced as an extension of the incremental describing function. The spectra of the oscillator noise and their dependence on operating conditions can be easily calculated by using these transfer matrices. The AM and PM noise spectra are measured when a traveling-wave tube is used as an amplifier. The measured values well agree with the calculated ones.     

Wireless-Control Strategy for Parallel Operation of Distributed-Generation Inverters

In this paper, a method for the parallel operation of inverters in an ac-distributed system is proposed. This paper explores the control of active and reactive power flow through the analysis of the output impedance of the inverters and its impact on the power sharing. As a result, adaptive virtual output impedance is proposed in order to achieve a proper reactive power sharing, regardless of the line-impedance unbalances. A soft-start operation is also included, avoiding the initial current peak, which results in a seamless hot-swap operation. Active power sharing is achieved by adjusting the frequency in load transient situations only, owing to which the proposed method obtains a constant steady-state frequency and amplitude. As opposed to the conventional droop method, the transient response can be modified by acting on the main control parameters. Linear and nonlinear loads can be properly shared due to the addition of a current harmonic loop in the control strategy. Experimental results are presented from a two-6-kVA parallel-connected inverter system, showing the feasibility of the proposed approach     

Perturbation solution of self-pulsing in semiconductor lasers witha saturable absorber

We solve the three-component rate equations for semiconductor lasers with a saturable absorber or for multi-section semiconductor lasers by using a singular perturbation method. The effects of nonlinear gain and spontaneous emission are included in the rate equations. By transforming the rate equations to the generalized coordinates, we eliminate the most rapidly varying term adiabatically for the fast saturable absorber. Then, we solve the two-component nonlinear equations to obtain analytic expressions for parametric dependence of self-pulsing amplitude and self-pulsing frequency. the self-pulsing frequency shifts from the small-signal oscillation frequency to the lower-frequency side as we increase the self-pulsing amplitude. The square of the self-pulsing frequency does not linearly depend on the injection current, in agreement with experimental observations. We also derive an optimum saturable absorber recovery time for the shortest optical pulse generation