RC oscillator admits negative frequency

The humble resistance–capacitance (RC) oscillator has held our attention for nearly seven decades. During that time many improvements have been made to enhance the performance and the range of applicability. In this letter we consider further refinements that extend the frequency range to include zero, and even negative frequencies. This allows the frequency to be swept through zero with no discontinuity in phase or amplitude. We then suggest an addition to the well‐known automatic level control (ALC) circuits to linearize the control function, with attendant benefits in modeling, simulation, and implementation. Closed‐loop dynamics for the improved ALC circuit are predicted, then verified by experiment. Copyright © 2010 John Wiley & Sons, Ltd.     

基于混沌振荡电路的频率测量方法

设计了一种基于混沌振荡电路来进行频率测量的新方法，该测量方法不需要基准时钟，测量精度不随被测频率的变化而受影响，且测量精度较高、电路简单、成本低廉。     

A voltage tunable CMOS differential active resistor and its application

We propose a novel CMOS differential voltage-controlled equivalent active resistor based on a modified common-source cross-coupled pair. The equivalent resistance exhibited by the circuit can be tuned to be either positive or negative through the tail current, which is controlled by a bias voltage. The complete cell comprises four transistors, two resistors in addition to the bias voltage, and tail current source. Application to the design of oscillators is demonstrated by theoretical analysis, circuit simulations, and verified experimentally through measurements on prototypes implemented using discrete transistors.     

变型蔡氏电路的混沌保密通信

为了产生更复杂的混沌系统,使通信更安全可靠,设计了一种产生丰富混沌行为的变型蔡氏电路,并进行了理论分析和计算机仿真.在此基础上根据驱动-响应同步原理设计了混沌保密通信电路,以方波作为输入信号进行了相应的硬件实验研究,给出了通信系统中各元件的参数和各部分的波形.结果表明:电路实验结果与计算机模拟结果完全符合,并且在响应电路和驱动电路的元件参数一致,其相对误差小于1%的条件下,当输入方波信号频率在约8 kHz～9 MHz时,该变型蔡氏电路的混沌保密通信系统可以实现保密通信.     

混沌超宽带通信调制方法研究

大量研究表明数据保密和高传输速率是现在通信领域的关键技术,由于混沌信号自身的类随机性和对初值的敏感性,用混沌信号进行保密通信有着很大的优势。因此,混沌超宽带通信成为通信领域一种非常有发展潜力的技术。着重介绍了混沌超宽带通信的3种调制方法：混沌脉位调制（CPPM）、混沌脉幅调制（CPAM）以及混沌脉宽调制（CPWM）,分析了它们各自的优缺点;最后展望了混沌超宽带通信技术的发展前景。     

Hyperchaos from two coupled Wien‐bridge oscillators

This paper proposes a simple inductorless approach to generating hyperchaos by coupling two Wien‐bridge oscillators with a resistor and a diode. The whole circuit is investigated both numerically and experimentally. Also, its hyperchaotic dynamics is studied theoretically by a topological horseshoe with two‐directional expansions which provides an immediate evidence of hyperchaos. Copyright © 2007 John Wiley & Sons, Ltd.     

Harmonic oscillators realized using current amplifiers and grounded capacitors

New configurations of harmonic oscillators, realized using current amplifier blocks and only grounded capacitors, are introduced in this article. The proposed configurations are based on a grounded inductor simulator scheme and on a loop constructed from first‐order sections, respectively. Comparison with the already published topologies shows that the new configurations have attractive characteristics concerning their implementation in integrated form. Copyright © 2006 John Wiley & Sons, Ltd.     

Systematic realization of a class of hysteresis chaotic oscillators

A systematic method for realizing a class of hysteresis RC chaotic oscillators is described. The method is based on direct coupling of a general second‐order sinusoidal oscillator structure to a passive non‐monotone current‐controlled non‐linear resistor. Owing to this passive non‐linearity, the power consumption, supply voltage and bandwidth limitations imposed upon the chaotic oscillator are mainly those due to the active sinusoidal oscillator alone. Tunability of the chaotic oscillator can be achieved via a single control parameter and the evolution of the two‐dimensional sinusoidal oscillator dynamics into a three‐dimensional state‐space is clearly recognized. The flexibility of this method is demonstrated by two examples using PSpice simulations and experimental results. Numerical simulations of derived mathematical models are also shown. Copyright © 2000 John Wiley & Sons, Ltd.     

Electronically controlled multiphase sinusoidal oscillators using current amplifiers

A novel current‐mode multiphase oscillator topology is introduced in this letter. This is realized by employing current amplifiers and only grounded capacitors. Attractive characteristics offered by the new topology are the electronic adjustment of the oscillation frequency, the absence of passive resistors, and the requirement of only grounded capacitors. Comparison with the corresponding already published current follower based structure shows that the proposed topology has better performance in terms of the number of required active elements, the employment of passive resistors, and the ability for electronic adjustment of the oscillation frequency. Copyright © 2008 John Wiley & Sons, Ltd.     

电压模式控制Buck变换器中的混沌吸引子重构技术

利用Buck变换器的输出电压时间序列可以进行变换器的混沌吸引子重构，其中延迟量可以通过时间序列的自相关函数来确定，而重构维数也可根据混沌吸引子的关联维来确定，仿真和特征参数计算均表明Buck变换器的重构混沌吸引子与原混沌吸引子拓扑等价，具有相同的动力学性质和几何性质，另外，构建了一个延迟重构实验电路，得到的实验波形也验证了上述结果。     

电压模式控制Buck变换器中的混沌吸引子重构技术

利用Buck变换器的输出电压时间序列可以进行变换器的混沌吸引子重构，其中延迟量可以通过时间序列的自相关函数来确定，而重构维数也可根据混沌吸引子的关联维来确定，仿真和特征参数计算均表明Buck变换器的重构混沌吸引子与原混沌吸引子拓扑等价，具有相同的动力学性质和几何性质，另外，构建了一个延迟重构实验电路，得到的实验波形也验证了上述结果。     

基于并行混沌搜索的非线性系统参数估计

提出了一种并行混沌搜索结合模式搜索法的混合优化算法,并应用于非线性系统参数估计.该算法采用并行混沌搜索机制,多个混沌变量同时映射一个优化变量.为了提高搜索速度,在每一次并行混沌搜索之后,由模式搜索法对并行混沌搜索结果再次寻优.该优化算法具有混沌优化的全局搜索能力,而模式搜索法则加快了局部寻优性能.该算法应用于三种不同非线性系统中,仿真结果表明其是一种有效的参数估计方法,参数估计精度优.     

电感式混沌测量

将混沌理论用于测量,是测量研究及非线性科学应用研究的一个突破,此方法具有极高的灵敏度和分辨率。但现有的混沌测量系统皆采用电容为敏感元件,这局限了混沌测量理论的发展,因此,提出一种以电感为敏感元件的混沌测量系统,实现微弱直流电压的测量,并且具有极高的精度和良好的线性度。此混沌测量系统的提出丰富了混沌理论。     

混沌时间序列预测在短期电力负荷预测中的应用

混沌吸引子具有空间的遍历性、总体的稳定性、吸引性和内部分形性，使得混沌预测成为可能。采用非线性系统理论对电力系统的历史数据进行分析，并基于改进的混沌吸引子模型对山西电网实际负荷数据进行短期预测，预测结果相对误差小、精度高，为电力系统短期负荷预测提供了一种新的预测方法。     

混沌时间序列预测在短期电力负荷预测中的应用

混沌吸引子具有空间的遍历性、总体的稳定性、吸引性和内部分形性,使得混沌预测成为可能。采用非线性系统理论对电力系统的历史数据进行分析,并基于改进的混沌吸引子模型对山西电网实际负荷数据进行短期预测,预测结果相对误差小、精度高,为电力系统短期负荷预测提供了一种新的预测方法。     

Mutiphase oscillator using dissipatively coupled transmission lines with regularly spaced tunnel diodes

A generation scheme is proposed for multiphase oscillatory signals based on mutual synchronization of the oscillating pulse edges developed in point‐coupled transmission lines periodically loaded with tunnel diodes (TDs). When supplied with an appropriate voltage at the end of a TD line, a pulse edge is shown to exhibit a spatially extended limit‐cycle oscillation on the line. When two TD lines are dissipatively coupled, such edge oscillations are mutually synchronized such that two edges simultaneously pass the connecting cells. Based on this observation, the scheme employs multiple point‐coupled TD lines, wherein the first and last lines are linked at the same position. Its design criterion is obtained by applying the phase reduction method to the transmission equation of a TD line. In addition, several time‐domain calculations demonstrate the validity of the scheme. Copyright © 2016 John Wiley & Sons, Ltd.     

Chaotic synchronization‐based communications using constant envelope pulse

We propose use of a constant‐envelope pulse for the purpose of improving noise‐rejection property in chaotic synchronization‐based communication systems. In a conventional system where discrete‐time chaotic signals are transmitted through the pulse amplitude modulation, the correlator output variance increases as the spreading factor decreases, while the synchronization error increases as the spreading factor increases. Therefore, it is difficult to control the bit error rate only by adjusting the spreading factor. In the proposed system, use of pulse width modulation keeps the envelope of transmitted signals constant, which leads to the correlator output with zero variance. The synchronization error is kept small because the spreading factor can be set to be one without increasing the correlator output variance. We have a result of computer simulation showing that the proposed system achieves a bit error performance better than the conventional system. In addition, a new blind adaptive algorithm is proposed which suppresses intersymbol interference. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(3): 47– 56, 2008; Published online in Wiley InterScience ( www. interscience.wiley.com ). DOI 10.1002/eej.20318     

Analysis and synthesis of oscillator systems described by perturbed double hump Duffing equations

This paper presents an analysis of oscillator systems described by double hump Duffing equations under polynomial perturbations of fourth degree. It has been proved that such a system can have unique hyperbolic limit cycle whose properties depend on the perturbation coefficients. The analytical condition for the arising of a limit cycle has been derived. Moreover, a method for the synthesis of oscillator systems of the considered type, having preliminarily assigned properties, is proposed. The synthesis consists of an appropriate choice of the perturbation coefficients in such a way that the oscillator equation is to have in advance assigned limit cycle. Both the analysis and the synthesis are performed with the aid of the Melnikov function. Copyright © 2010 John Wiley & Sons, Ltd.     

Observers for a Class of Chaotic Systems

The design of observers for a class of practical physical chaotic systems is discussed. By using only one state variable and its time derivatives, a control law is constructed to achieve the synchronization between the investigated chaotic systems and their observers, and the results are proved theoretically. Several observers of chaotic systems are designed by using this method. Translated from “Observers for a Class of Chaotic Systems” published in Journal of Southwest China Normal University (Natural Science), 2004, 29(1): 53–57 (in Chinese)     

Chaotic system identification using Wiener‐LSSVM model

In this paper, a new method is proposed for identifying chaotic system based on a Wiener‐least squares support vector machine (Wiener‐LSSVM) model. The model consists of a linear dynamic subsystem followed by a static nonlinear function, which is represented by LSSVM in this paper. The parameters of the linear dynamic part and those of LSSVM are estimated simultaneously by solving a set of linear equations using the least squares (LS) method. The proposed method incorporates partial structure information into the identification process and does not assume that the parameters of linear dynamic part are known. On the other hand, the LS algorithm is more efficient than gradient‐descendent‐based algorithms for estimating the parameters of Wiener‐LSSVM. Three identification examples are given to validate the effectiveness of the proposed method. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.