Chaotic oscillator configuration using a frequency dependent negative resistor

A chaotic oscillator configuration employing a frequency‐dependent negative resistor (FDNR) as the only active element is proposed. The configuration relies on a simple two‐terminal passive device; namely a general purpose signal diode, to provide the necessary non‐linearity. The structure requires no floating elements and is independent of any circuit specific realization of the FDNR. Experimental results, PSpice simulations and numerical simulations of the derived mathematical models are included. Copyright © 2000 John Wiley & Sons, Ltd.     

Adaptive function Q‐S synchronization of chaotic systems with unknown parameters

This work investigates the adaptive function Q‐S synchronization of non‐identical chaotic systems with unknown parameters. The sufficient conditions for achieving Q‐S synchronization with a desired scaling function of two different chaotic systems (including different dimensional systems) are derived based on the Lyapunov stability theory. By the adaptive control technique, the control laws and the corresponding parameter update laws are proposed such that the Q‐S synchronization of non‐identical chaotic systems is to be achieved. Finally, four illustrative numerical simulations are also given to demonstrate the effectiveness of the proposed scheme. Copyright © 2009 John Wiley & Sons, Ltd.     

High output impedance CMQOs using DVCCs and grounded components

In this paper a new circuit topology for realizing second‐order current‐mode quadrature oscillator is proposed. Three additional circuits are further derived from it, thus resulting in four distinct circuits. Each circuit employs three differential voltage current conveyors and all grounded passive components, ideal for IC implementation. All the circuits possess high output impedance. The circuits exhibit non‐interactive frequency control and low THD. The effects of non‐idealities are also analyzed. PSPICE simulations using 0.5 µCMOS parameters confirm the validity and practical utility of the proposed circuits. Copyright © 2010 John Wiley & Sons, Ltd.     

基于Duffing振子的微弱正弦信号检测方法研究

利用混沌振子系统的初值敏感性和对噪声的免疫力检测微弱正弦信号，可以获得很高的检测灵敏度和很好的抗噪性能。文中分析了待测正弦信号幅值和相位对混沌系统状态的影响。基于Duffing振子系统的相变特性，提出了检测微弱正弦信号幅值和相位的新方法，即：反相补偿幅值检测方法和三分对称相位检测方法，介绍了检测的原理和具体实现步骤；利用Duffing方程的位移X波形的包络特性，提出了适合于含噪声情况的混沌特性自动判别方法，以正确判别混沌系统的状态并应用于文中的信号检测方法之中。最后，将该方法和最大似然法进行了比较。数字仿真结果证明了文中所提方法的可行性和有效性。只需改变策动力的频率，该方法即可适用于检测各种频率的微弱正弦信号，对于扩大光传感器的测量范围、电力系统谐波分析等应用具有实用价值。     

Circuit implementation and model of a new multi‐scroll chaotic system

In this paper, a multi‐scroll chaotic system from the improved Chua's system is proposed. Moreover, non‐linear dynamics are analyzed including phase‐space trajectories, bifurcation diagrams, Poincaré maps and so on. The most important thing is that we discovered phase‐space trajectories, bifurcation diagrams and Poincaré maps are unified and closely related, which can describe different aspects of the multi‐scroll chaotic system. Furthermore, the corresponding improved module‐based circuits are designed for realizing two to four‐scroll chaotic attractors, and the experimental results are also obtained, which are consistent with the numerical simulations. Copyright © 2012 John Wiley & Sons, Ltd.     

Multiscroll floating gate–based integrated chaotic oscillator

In this work, we proposed a voltage‐to‐current cell based on a Complementary metal‐oxide‐semiconductor (CMOS) inverter designed by using floating gate transistors. We demonstrate its usefulness for the design of stair‐type and sawtooth functions to be used in the implementation of a multiscroll chaotic oscillator. The main advantage of using floating gate transistors to design the nonlinear functions is the elimination of external reference DC sources, as is typically done in most of the nonlinear functions that generate multiscroll attractors. The key guidelines for the design of our proposed voltage‐to‐current cell are given to provide good performances in the design of an integrated multiscroll chaotic oscillator. HSPICE simulations are presented to demonstrate the usefulness of the proposed cell to generate multiscroll attractors. Finally, simulation results before and after layout are presented to show the good agreement with respect to theoretical results. HSPICE simulations of the post‐layout design are in accordance with the system behavior. Copyright © 2011 John Wiley & Sons, Ltd.     

Optimum design of high power and high efficiency mm‐wave fundamental oscillators

A systematic method to design high power and high efficiency mm‐wave fundamental oscillators is presented. By using a linear time variant method, we first obtain the optimum conditions and show that these conditions can be significantly different for high power and high efficiency fundamental oscillation. Next, we propose a modified multistage ring oscillator with interstage passive networks to exploit the full capacity of the transistors in terms of output power or efficiency. Analytical expressions are also derived to determine the value of passive elements used in the oscillator. To verify the validity of the method, a 77‐GHz two‐stage (differential) VCO is designed in a 65‐nm CMOS process. Careful electromagnetic and circuit simulations demonstrate that the designed VCO has 2‐GHz tuning range, maximum output power of 10.5 dBm and maximum DC to RF efficiency of 24.1%. The designed VCO shows 54.8% and 108.7% improvement in terms of maximum output power and efficiency compared with a conventional cross‐coupled VCO with the same tuning range.     

Truly random number generators based on non‐autonomous continuous‐time chaos

A novel non‐autonomous continuous‐time chaotic oscillator suitable for high‐frequency integrated circuit realization is presented. Simulation and experimental results, verifying the circuit feasibility, are given. Two methods for using this oscillator as the core of a random number generator are also proposed. Numerical binary data obtained according to the proposed methods pass the four basic tests of FIPS‐140‐2, while experimental data pass the full NIST‐800‐22 random number test suite. Copyright © 2008 John Wiley & Sons, Ltd.     

Analysis of discontinuities in rectangular ducts and higher order mode excitations using TLM and FEM methods

In acoustic waveguide, it is believed that higher order modes have a dramatic effect on the behaviour of the global acoustic waves when the frequency of the source is above the cut‐off frequency of the duct. In this paper, we are going to study the influence of the discontinuities on the excitation and the propagation of higher order modes in symmetrical and non‐symmetrical ducts using theoretical analysis and numerical simulations. As for numerical simulations, transmission line matrix (TLM) method and finite element method (FEM) will be used. Moreover, we will try here to compare the two numerical methods, showing their advantages and disadvantages. The transfer functions of symmetrical and non‐symmetrical ducts will also be shown and discussed as well as numerical simulations of the acoustic pressure into the duct in three‐dimensional (3‐D) system. Copyright © 2004 John Wiley & Sons, Ltd.     

EVALUATION OF THE ELECTRICAL PERFORMANCE OF CYLINDRICAL,SOLID CONDUCTING ROTOR,ASYNCHRONOUS MACHINES USING FOURIER ANALYSIS TO DETERMINE THE INTERNAL MAGNETIC |FIELD DISTRIBUTION

ABSTRACT

This paper describes a simple method of analysing the two dimensional electric and magnetic field distribution within a cylindrically symetrical machine driven from a non sinusoidal (inverter) current supply. The method is based on a double space-time Fourier analysis of the non sinusoidal magnetic field and current distribution. Its principal advantage is the very short computer time required for the complete analysis of the machine.     

Convergence analysis of blind image deconvolution via dispersion minimization

A new non‐linear adaptive filter called blind image deconvolution via dispersion minimization has recently been proposed for restoring noisy blurred images blindly. This is essentially a two‐dimensional version of the constant modulus algorithm that is well known in the field of blind equalization. The two‐dimensional extension has been shown capable of reconstructing noisy blurred images using partial a priori information about the true image and the point spread function in a variety of situations by means of simulations. This paper analyses the behaviour of the algorithm by investigating the static properties of the cost function and the dynamic convergence of the parameter estimates. The theoretical results are supported with computer simulations. Copyright © 2006 John Wiley & Sons, Ltd.     

Fully nonlinear oscillator noise analysis: an oscillator with no asymptotic phase

Oscillators exist in many systems. Detailed and correct characterization and comprehension of noise in autonomous systems such as oscillators is of utmost importance. Previous approaches to oscillator noise analysis are based on some kind of perturbation analysis, some linear and some nonlinear. However, the derivations of the equations for perturbation analysis are all based on information that is produced by a linearization of the oscillator equations around the periodic steady‐state solution, where it is assumed that the oscillator is orbitally stable and it has the so‐called asymptotic phase property. In this paper, we first discuss these notions from a qualitative perspective, and demonstrate that the asymptotic phase property is crucial in validating all of the previous approaches. We then present the case of a simple oscillator that is orbitally stable but without asymptotic phase, for which previous approaches fail. We then present a fully nonlinear noise analysis of this oscillator. We derive and compute nonlinear, non‐stationary and non‐Gaussian stochastic characterizations for both amplitude and phase noise. We arrive at results that are distinctly different when compared with the ones obtained previously for oscillators with asymptotic phase. We compare and verify our analytical results against extensive Monte Carlo simulations. Copyright © 2006 John Wiley & Sons, Ltd.     

Relaxation for online frequency estimator of bias‐affected damped sinusoidal signals based on Dynamic Regressor Extension and Mixing

This paper considers the problem of continuous‐time online frequency estimation for a biased damped sinusoidal signal. The previous result for a sinusoidal signal with time‐varying amplitude requires a persistency of excitation condition for regressor, which is not satisfied in the considered case. To relax this condition, we propose to use Dynamic Regressor Extension and Mixing method on the first step to replace nth‐order regression with n first‐order regression models. On the second step, two simple relaxation methods are proposed to establish necessary excitation for the first‐order gradient‐based estimator. The efficiency of the proposed approach is demonstrated through the set of numerical simulations for the exponentially damped sinusoidal signal.     

Adaptive switching control of uncertain fractional systems: Application to Chua's circuit

Since the introduction of fractional‐order differential equations, there has been much research interest in synthesis and control of oscillatory, periodic, and chaotic fractional‐order dynamical systems. Therefore, in this article, the problem of stabilization and control of nonlinear three‐dimensional perturbed fractional nonlinear systems is considered. The major novelty of this article is handling partially unknown dynamics of nonlinear fractional‐order systems, as well as coping with input saturation along the existence of model variations and high‐frequency sensor noises via just one control input. The method supposes no known knowledge on the upper bounds of the uncertainties and perturbations. It is assumed that the working region of the input saturation function is also unknown. After the introduction of a simple finite‐time stable nonlinear sliding manifold, an adaptive control technique is used to reach the system variables to the sliding surface. Rigorous stability discussions are adopted to prove the convergence of the developed sliding mode controller. The findings of this research are illustrated using providing computer simulations for the control problem of the chaotic unified system and the fractional Chua's circuit model.     

Role of the temperature distribution on the PN junction behaviour in the electro‐thermal simulation

Electro‐thermal simulations of a PIN‐diode based on the finite‐element method, show a non‐uniform temperature distribution inside the device during switching transients. Hence, the implicit assumption of a uniform temperature distribution when coupling an analytical electrical model and a thermal model yields inaccurate electro‐thermal behaviour of the PIN‐diode so far. The idea of including non‐uniform temperature distribution into power semiconductor device models is not new, as accurate electro‐thermal simulations are required for designing compact power electronic systems (as IC or MCM). Instead of using a one‐dimensional finite difference or element method, the bond graphs and the hydrodynamic method are utilized to build an electro‐thermal model of the PIN‐diode. The results obtained by this original technique are compared with those obtained by a commercial finite‐element simulator. The results are similar but the computation effort of the proposed technique is a fraction of that required by finite‐element simulators. Moreover, the proposed technique may be applied easily to other power semiconductor devices. Copyright © 2004 John Wiley & Sons, Ltd.     

Hyperchaos and horseshoe in a 4D memristive system with a line of equilibria and its implementation

We study a four‐dimensional system modified from a three‐dimensional chaotic circuit by adding a memristor, which is a new fundamental electronic element with promising applications. Although the system has a line of infinitely many equilibria, our studies show that when the strength of the memristor increases, it can exhibit rich interesting dynamics, such as hyperchaos, long period‐1 orbits, transient hyperchaos, as well as non‐attractive behaviors frequently interrupting hyperchaos. To verify the existence of hyperchaos and reveal its mechanism, a horseshoe with two‐directional expansion is studied rigorously in detail by the virtue of the topological horseshoe theory and the computer‐assisted approach of a Poincaré map. At last, the system is implemented with an electronic circuit for experimental verification. Copyright © 2013 John Wiley & Sons, Ltd.     

基于采样数据的非线性阻尼振荡器的混沌控制研究

本文针对Duffing模型非线性阻尼振荡器提出了一种新的基于采样数据的混沌控制算法。直接由采样数据构造控制器 ,并不断进行控制项的迭代与更新 ,在每个采样周期内控制项保持不变。给出了这样一个由连续时间动态和离散时间动态构成的混合动态系统的控制渐进稳定性分析结果。仿真表明了控制算法的有效性     

双振子差分混沌特性判别方法

利用混沌振子检测微弱信号具有灵敏度高、抗噪性好等优点,其检测的关键在于对混沌特性的判别。该文在对Duffing振子混沌特性研究的基础上,提出了一种利用双振子差分来进行混沌特性判别的新方法。该方法具有直观、计算量小、抗噪性好和易于实现等优点。文中阐述了该方法的原理,提出混沌牵引的概念,给出相应的判别程序流程,最后对该方法进行了数字仿真,并应用该方法处理小电流接地故障保护现场数据,仿真试验结果证明了该方法的可行性和有效性。     

A generalized family of memristor‐based voltage controlled relaxation oscillator

Recently, memristive oscillators are a significant topic in the nonlinear circuit theory where there is a possibility to build relaxation oscillators without existence of reactive elements. In this paper, a family of voltage‐controlled memristor‐based relaxation oscillator including two memristors is presented. The operation of two memristors‐based voltage relaxation oscillator circuits is demonstrated theoretically with the mathematical analysis and with numerical simulations. The generalized expressions for the oscillation frequency and conditions are derived for different cases, where a closed form is introduced for each case. The effect of changing the circuit parameters on the oscillation frequency and conditions is investigated numerically. In addition, the derived equations are verified using several transient PSPICE simulations. The power consumption of each oscillator is obtained numerically and compared with its PSPICE counterpart. Furthermore, controlling the memristive oscillator with a voltage grants the design an extra degree of freedom which increases the design flexibility. The nonlinear exponential model of memristor is employed to prove the oscillation concept. As an application, two examples of voltage‐controlled memristor‐based relaxation oscillator are provided to elaborate the effect of the reference voltage on the output voltage. This voltage‐controlled memristor‐based relaxation oscillator has nano size with storage property that makes it more efficient compared with the conventional one. It would be helpful in many communication applications.     

A family of Wien-type oscillators modified for chaos

A family consisting of four Wien-type oscillator circuits are modified for chaos by direct replacement of one of the linear resistors with an asymmetrical-type non-linearity introduced by a junction field effect transistor (JFET) operating in its triode region and the addition of a single capacitor. The internal op amp dominant pole is found to play a major role in understanding the chaotic behaviour of the proposed circuits. Mathematical models that describe the observed behaviours are derived. The well known Wien bridge oscillator design equations are shown to be useful as a starting point for chaos modification. Experimental laboratory results, PSpice simulations and numerical simulations of the mathematical models are provided for this family of autonomous RC chaos generators. © 1997 John Wiley & Sons, Ltd.