Diagnostics of the generalized synchronization in microwave generators of chaos

The generalized synchronization of chaos in a system of microwave generators based on klystron amplifiers with delayed feedback has been studied. A modification of the nearest neighbors method for diagnostics of generalized synchronization of chaos in systems with delayed feedback is developed. The efficiency of the modified method for processing experimental data is shown.     

Robust hyperchaotic synchronization via analog transmission line

In this paper, a novel experimental chaotic synchronization technique via analog transmission is discussed. We demonstrate through Field-Programmable Gate Array (FPGA) implementation design the robust synchronization of two embedded hyperchaotic Lorenz generators interconnected with an analog transmission line. The basic idea of this work consists in combining a numerical generation of chaos and transmitting it with an analog signal. The numerical chaos allows to overcome the callback parameter mismatch problem and the analog transmission offers robust data security. As application, this technique can be applied to all families of chaotic systems including time-delayed chaotic systems.     

一种利用CPRNG实现的混沌同步加密通信方案

提出了一种利用新型的基于混沌的伪随机数发生器(CPRNG)系统实现的数据加密通信方案.在该方案中,发、收两端的CPRNG系统将驱动系统产生的混沌序列转换为加密密钥序列,利用这些密钥序列对明文数据按字节切换交替加密. 系统的主要优点是在通信的安全性和同步性上有所改善,且便于用软件实现. 关键词： 密钥 基于混沌的伪随机数发生器 混沌同步     

双向耦合混沌系统广义同步

提出了用条件熵来测定双向耦合混沌系统的广义同步，随着耦合强度的增大，当条件熵有一突出的最小值出现时表明两系统达到广义同步.为了证明这种方法的有效性，将这种方法用 于Rssler-Lorenz与Rssler-Rssler混沌系统的双向耦合情况，数值模拟结果表明该方 法非常有效且具有较强的鲁棒性. 关键词： 广义同步 双向耦合 条件熵     

相空间压缩实现时空混沌系统的广义同步

提出了一种通过相空间压缩实现时空混沌系统广义同步的方法. 以Fitzhugh-Nagumo反应扩散时空混沌系统为例,仿真模拟说明了该方法的有效性与实用性. 通过研究有界噪声作用下该系统的同步效果,表明这种同步方法具有较强的抗干扰能力. 此方法可以实现任意时空混沌系统的广义同步,具有普适性. 同步控制器结构简单、易于应用. 关键词： 时空混沌 广义同步 相空间压缩     

1.5-GHz message transmission based on synchronization of chaos in semiconductor lasers

Sinusoidal message transmission up to 1.5 GHz is performed based on synchronization of chaos in experimental nonlinear systems of semiconductor lasers with optical feedback. In the chaotic systems the message is almost entirely suppressed in the receiver output, even if the message has nonnegligible power in the transmitter.     

Adaptive chaos control and synchronization in only locally Lipschitz systems

In the existing results on chaos control and synchronization based on the adaptive controlling technique (ACT), a uniform Lipschitz condition on a given dynamical system is always assumed in advance. However, without this uniform Lipschitz condition, the ACT might be failed in both theoretical analysis and in numerical experiment. This Letter shows how to utilize the ACT to get a rigorous control for the system which is not uniformly Lipschitz but only locally Lipschitz, and even for the system which has unbounded trajectories. In fact, the ACT is proved to possess some limitation, which is actually induced by the nonlinear degree of the original system. Consequently, a piecewise ACT is proposed so as to improve the performance of the existing techniques.     

Effect of transmission fiber and amplifier noise on optical chaos synchronization

Optical chaos propagation has few constraints peculiar to itself which do not become as significant in conventional nonchaotic optical communication. We have investigated the effects of transmission fiber nonlinearities, dispersion and noise of erbium doped fiber amplifier (EDFA) on chaotic signal synchronization in lumped and distributed configuration. It is found that the effects of fiber dispersion can be easily compensated; however, the effects of fiber nonlinearity on chaos cannot be overdone and must be avoided. Three distinct configurations with different combinations of standard telecommunication fiber, dispersion compensation fiber and lumped and distributed EDF for amplification are analysed. The results are compared in terms of sync diagrams and noise figure. The chaos after propagation through distributed amplification performs better as compared to lumped amplification. Also, a new quantitative measure for the calculation of deviation in sync diagram of chaos is introduced.     

Globally exponential multi switching-combination synchronization control of chaotic systems for secure communications

This article introduces the global exponential multi switching combination synchronization (GEMSCS) for three different chaotic systems with known parameters in the master-slave system configuration. The proposed GEMSCS scheme establishes the global exponential stability of the synchronization error at the origin with different combinations of state variables of the two master chaotic systems with the state variables of a slave chaotic system in diverse manners. Consequently, it increases the complexity level of the information signal in secure communications. To study the GEMSCS, an efficient nonlinear control algorithm is designed. The Lyapunov direct theorem is used to accomplish the global exponential stability of the synchronization error at the origin. The stability conditions are derived analytically. To show the effectiveness and advantages of the proposed GEMSCS control approach, two numerical examples are presented. The computer based simulation results are compared with the reported works in the relevant literature. This article also extends the idea of GEMSCS to the secure communication using the chaotic masking technique. Using the GEMSCS strategy, the information signal is recovered at the receiving system with good accuracy and high speed while the parameters of the transmitter and receiver systems mismatch. At the end, some future research problems related to this work are suggested.     

Phenomenon of generalized synchronization in klystron chaos generators with delayed feedback: Experiment and numerical simulation

The system of unidirectionally coupled klystron chaos generators with delayed feedback has been experimentally and theoretically investigated. A new technique for diagnostics of generalized chaotic synchronization is proposed, which is based on the spectral analysis of a signal from a response klystron generator. Comparison of the obtained experimental and theoretical results is performed.     

Experimental study on tracking the state of analog Chua's circuit with particle filter for chaos synchronization

The aim of this Letter is to study by experiment the feasibility of tracking the state of analog Chua's circuit with particle filter for chaos synchronization. The structure of this digital-filter-based synchronization approach is proposed and depicted. The transmitted signals, generated from PSpice simulations and a physically implemented Chua's circuit, get through an additive white Gaussian noise (AWGN) channel to a receiver consisting of an analog-to-digital converter (ADC) and a particle filter (PF). The ADC is used to sample the analog signals and the PF is used to estimate and track the state of the transmitting circuit to obtain synchronized oscillation signals. Experiment results indicate that it is possible to use this approach to synchronize analog Chua's circuit, even if the circuit parameters are not known exactly and time-varying. In addition, the effects of different signal-to-noise ratio (SNR), ADC sampling frequency and PF state sampling time on synchronization performance are also studied for further understanding of this synchronization approach.     

Robust chaos synchronization of noise-perturbed chaotic systems with multiple time-delays

The aim of this paper is to propose an output coupling and feedback scheme, which is not only to guarantee the asymptotic synchronization between the master and the slave chaotic systems with multiple time-delays but also to attenuate the effects of noise perturbation on the overall error system to a prescribed level in terms of the performance index H_∞-norm. The output coupling and feedback gain is derived on the basis of the Lyapunov theory and the linear matrix inequality (LMI) technique. Some numerical examples are given to demonstrate the effectiveness of the main results.     

广义混沌同步中的多稳定同步流形

从构造驱动系统和响应系统之间的函数关系出发,一般性地研究了广义混沌同步中同步流形的多值性问题,并对同步流形的稳定性进行了分析,提出了多稳定同步流形存在的条件.利用该稳定性条件对两个实例进行了分析,一个为Genesio-Rssler耦合系统,另一个为具有二次、三次非线性的耦合Duffing系统,结果表明前者仅有唯一的稳定同步流形,而后者随着耦合强度的增加,从具有两个稳定的同步流形变为只存在一个稳定同步流形. 关键词： 混沌同步 多稳定性 同步流形     

基于鼠标轨迹和混沌系统的真随机数产生器研究

提出了一种基于鼠标轨迹的真随机数产生器,并对该类产生器的优缺点、总体设计和基本技术进行了研究.为了消除相同用户鼠标轨迹中存在的相似性,利用混沌系统的敏感性,分别采用图像加密算法和Hash函数两种方法对鼠标轨迹进行后处理.大量严格的测试和实验表明,改进的基于混沌Hash函数的真随机数产生器具有安全、快速、方便和廉价的优点,可以在个人电脑上实际使用. 关键词： 混沌 真随机数产生器 鼠标轨迹     

Generalized synchronization of chaos in identical systems with hidden degrees of freedom

We demonstrate generalized synchronization of chaos in a two-mode laser system. The total intensity of the laser output (the sum of the individual mode intensities) is used as the drive signal. This lumped variable transmitted to the identical response system does not generate identical synchronization. Generalized synchronization is observed instead of identical synchronization because of the hidden internal degrees of freedom.     

Multimodal synchronization of chaos

An elementary notion of master-slave synchronization that accepts multimodal synchronization is introduced. We prove rigorously that the attractor of a coupled pair in a regime of multimodal synchronization is the graph of a multivalued function. Our framework provides the theoretical basis for some practical tools for detection of multimodal synchrony in experiments. Results are illustrated with the analysis of experiments with coupled electronic oscillators.     

Impulsive control of stochastic systems with applications in chaos control, chaos synchronization, and neural networks

Real systems are often subject to both noise perturbations and impulsive effects. In this paper, we study the stability and stabilization of systems with both noise perturbations and impulsive effects. In other words, we generalize the impulsive control theory from the deterministic case to the stochastic case. The method is based on extending the comparison method to the stochastic case. The method presented in this paper is general and easy to apply. Theoretical results on both stability in the pth mean and stability with disturbance attenuation are derived. To show the effectiveness of the basic theory, we apply it to the impulsive control and synchronization of chaotic systems with noise perturbations, and to the stability of impulsive stochastic neural networks. Several numerical examples are also presented to verify the theoretical results.     

Photonic integrated device for chaos applications in communications

A novel photonic monolithic integrated device consisting of a distributed feedback laser, a passive resonator, and active elements that control the optical feedback properties has been designed, fabricated, and evaluated as a compact potential chaotic emitter in optical communications. Under diverse operating parameters, the device behaves in different modes providing stable solutions, periodic states, and broadband chaotic dynamics. Chaos data analysis is performed in order to quantify the complexity and chaoticity of the experimental reconstructed attractors by applying nonlinear noise filtering.     

Generalized chaos synchronization theorems for bidirectional differential equations and discrete systems with applications

Two constructive generalized chaos synchronization (GCS) theorems for bidirectional differential equations and discrete systems are introduced. Using the two theorems, one can construct new chaos systems to make the system variables be in GCS. Five examples are presented to illustrate the effectiveness of the theoretical results.