蔡氏电路混沌同步保密通讯

两个相同的蔡氏电路(Chua’s Circuit)互相耦合可以实现混沌(Chaos)同步是混沌研究的一个重要成果．也是探索蔡氏电路开发应用的基础。应用蔡氏电路的同步特性实现保密通讯是当前蔡氏电路开发应用研究的一个主要方向。本文在介绍蔡氏电路混沌同步特性的基础上，讨论主—从式蔡氏电路同步保密通讯系统及实现双向通讯和无线传输的可行性．并对这种保密通讯系统的安全性与鲁棒性(Robustness)作了简要的分析.     

基于状态观测器的超混沌同步方法研究

研究超混沌系统同步问题,指出现有超混沌同步方法存在的缺点,及基于状态观测器的超混沌同步方法,并且应用于单向耦合蔡氏电路构成的超混沌系统同步设计.     

耦合蔡氏电路中混沌同步的充分必要条件

本文从系统稳定方面分析了系统同步，给出了一个耦合蔡氏电路同步的判定准则，由此扩大了同步耦合参数的判定范围。我们还依据准则给出了一个近似判定方法。数据模拟表明了近似判断方法的正确性和可行性。     

非直接耦合蔡氏电路超混沌系统同步新方法

基于状态观测器理论，研究超混沌系统同步问题，提出超混沌系统同步新方法，解决现有超混沌同步方法存在的问题。该方法应用于非直接耦合蔡氏电路构成的超混沌系统的同步设计。     

用连续控制法实现变型蔡氏电路的同步

在蔡氏电路的L臂上加入RC并联电路,用数值模拟研究这种变型蔡氏电路的分岔,控制和同步特性.     

一类混沌系统耦合同步的充分条件及其应用

针对一类非线性项满足Lipschitz条件的混沌系统，利用Lyapunov定理研究了耦合混沌系统的同步问题，提出了耦合混沌系统同步的一个充分条件。利用经性矩阵不等式（LMI）方法和Gerschgorin定理，给出了该混沌同步条件的LMI形式和代数不等式形式。将结果应用于蔡氏电路，证明了其正确性。     

用连续控制法实现变型蔡氏电路的同步

在蔡氏电路的Ｌ臂上加入ＲＣ并联电路，用数值模拟研究这种变开明蔡氏电路的分岔，控制和同步特性。     

蔡氏电路连续变量反馈同步的优化设计

本文研究蔡氏电路连续变量反馈同步的优化设计。从控制电路简单实用出发，选择双变量线性反馈单点控制同步方案，并对反馈向量实行抗干扰优化设计。设计实例的数字仿真和电路实验表明，用该方法设计的蔡氏电路同步系统具有较强的抗干扰能力。     

一种语音混沌保密通信方案的研究与硬件实现

在硬件实验研究的基础上，建立一种环形蔡氏电路，提出用环蔡氏电路实现语音混沌保密通信的一种闭环逆系统方案，其特点是利用环形蔡氏电路的单向耦合原理，通过反馈的方法形成一个包括有用信号在内的极联闭合环路，从而实现改善端与接收端之间混沌系统的严格同步而不受有用信息调制的影响。理论分析与硬件实验结果证明，该方案同现有的其它混沌通信方案相比较，具有非线性失真小、保真度高的优点，完全能够满足传送语音信号的要求。     

基于超混沌的保密通信系统

建立一种基于变型蔡氏电路的超混沌语音保密通信方案,在发端,利用变型氏电路对发送信号进行调,在收端对其进行逆变换解调出原信号。根据单向耦合法实现收发系统之间的同步,分析了同步的收敛特性。在此基础上设计硬件实验电路,进行传送语音信号的硬件实验研究,给出了实验结果。     

Coupled Nonuniform Transmission Line and Its Applications

Theory and applications of coupled nonuniform transmission lines are described. Matrix representations of a general coupled nonuniform transmission line are presented, by means of which the behavior of any coupled nonuniform transmission line maybe completely described. Among a wide variety of applications of coupled nonuniform transmission lines, two typical networks, one the coupled nonuniform transmission-line folded all-pass network and the other the coupled nonuniform transmission-line directional coupler, are treated in detail. Equivalent circuit representatious of these two networks are presented, which enable the designer to synthesize them in a greatly simplified manner by making use of the theories now available for more conventional single nonuniform transmission lines. In addition, the properties of these two networks using coupled exponential line are investigated. Design procedure is also given for asymmetrical coupled exponential-line directional couplers having excellent characteristics.     

Realization of new mutually coupled circuits using mutators

A method for realizing new mutually coupled circuits by using mutators is described. Various types of mutually coupled circuits, such as a mutual inductance, a mutual frequency-dependent negative resistance, and a frequency-dependent negative inductance, are realized by connecting a network between two mutators which have the suitable transmission matrix. New mutually coupled circuits composed of three impedances of different kinds, that is, two self-impedances and one mutually impedance, are also described. The theoretical frequency responses of the transfer functions of coupled tuned circuits composed of these mutually coupled circuits are shown, and experimental results of a coupled tuned circuit using mutual inductance are shown.     

Novel Schiffman phase shifters

In a standard Schiffman phase shifter a coupled section and a uniform transmission line are used to give a differential phase shift. In order to achieve larger bandwidth it is necessary to use tight coupled sections which are difficult to realize. It is shown how different configurations of coupled lines or parallel connected coupled lines can be used together with a uniform transmission line, other coupled lines, or parallel connected coupled lines in order to obtain a differential phase shifter with loose coupled lines and the same performance as for the standard case. The measurements confirm the calculated results, leading to a more realizable structure     

A Dispersion Model for Coupled Microstrips

The frequency-dependent propagation characteristics of symmetrical, nonsymmetrical, and multiple coupled microstrips are evaluated by utilizing a directly coupled parallel-plate ideal waveguide model. The closed-form expressions for the frequency-dependent parameters of this proposed semi-empirical utility model are derived in terms of the quasi-static parameters of the coupled microstrip structure. These model parameters are then used to evaluate the frequency-dependent propagation characteristics, including the normal-mode effective dielectric constants and impedances of the coupled microstrips. These results are found to be in good agreement with all the published experimental results and the numerically computed values for symmetrical and nonsymmetrical coupled microstrips. The model should be useful in the computer-aided design of coupled microstrip structures at higher frequencies where the dispersion effects become important.     

Coupled Power Equations for Backward Waves

Two waves traveling in opposite directions that are coupled by a random coupling function are considered. These two waves can be described in a standard way by coupled wave equations. It is possible to derive coupled equations for the power carried by these two waves. The form of the coupled power equations differs depending on the assumptions that are made for the initial conditions. The validity of the coupled power equations has been confirmed by a computer-simulated experiment.     

Characterization of picosecond pulse crosstalk between coupledmicrostrip lines with arbitrary conductor width

The propagation and crosstalk properties of picosecond electrical pulses along coupled microstrip lines with arbitrary strip widths are investigated. The current distributions and propagation constants of the dominant c- and π-modes in these asymmetric coupled striplines are calculated using the spectral domain approach; and the full-wave analysis results obtained are incorporated into a fast Fourier transform (FFT) algorithm to simulate pulse distortion and crosstalk in the coupled transmission lines. Several samples of asymmetric coupled microstrip lines are fabricated and their characteristics are measured. The results of experiments are found to be in good agreement with those of computer simulations. For the first time, rigorous results of picosecond pulse distortion and crosstalk in asymmetric coupled transmission lines are provided     

Introduction to modeling of transformers and coupled inductors

A tutorial paper is presented on modeling and design of transformers and coupled inductors. Beginning with a brief review of electromagnetic laws and magnetic circuit models, the magnetic and electric models of transformers and coupled inductors are developed, including both magnetizing and leakage effects. It is shown that while the voltage waveforms on the windings are primarily related by the turns ratio for both devices, the winding currents of transformers and coupled inductors are determined by very different mechanisms. An integrated structure with both transformer and coupled inductor on the same core is also discussed, as well as the special case of the coupled inductor used on a multiple-output transformer-isolated converter     

Reduction of mode Q-factor due to coupling between fundamental and first order whispering-gallery modes in coupled microdisks

The mode characteristics for twin coupled microdisks are investigated by finite-difference time-domain technique. In the coupled microdisks,the same order whispering-gallery(WG) modes can form coupled modes with split mode wavelengths. We find that the coupled fundamental and first order WG modes can have anticrossing mode coupling as their wavelengths approach the same value in some case,which prevents the cross of the coupled mode wavelengths. The anticrossing mode coupling greatly reduces the coupled mode Q-factor,because the coupled mode field distribution transfers between the fundamental and the first order WG modes.     

Coupled-mode theory

The authors give a brief historic perspective of the coupled mode theory. The development and applications of the theory in microwaves in early years and in optoelectronics and fiber optics in recent years are described. They then consider lossless coupling of two modes in time. Two coupled resonance circuits, or two coupled microwave or optical resonators, are the physical examples. The start-up of a parametric oscillator is another example. Then they look at the formal derivation of coupled mode theory and consider the more general case when the modes are not energy-orthogonal and the energies are not necessarily positive. A more detailed account of the nonorthogonal coupled mode theory developed in the last five years for optical waveguides is given     

A planar-lumped model for coupled microstrip lines anddiscontinuities

A convenient model for analyzing coupled microstrip line discontinuities is presented. A planar-lumped model similar to the planar waveguide model for single microstrip lines is developed for coupled microstrip lines. Fields underneath the two strips and those fringing at the outer edge are modeled by two equivalent planar waveguides. Electric and magnetic field coupling in the gap region is modeled by a lumped network. The lumped network parameters are evaluated such that [C] and [L] matrices for the model are identical with those for coupled lines. The model is verified by comparing coupler characteristics with those obtained by the conventional coupled line analysis. Just as the planar model of a single microstrip has been used for characterizing microstrip discontinuities, the planar-lumped model developed is used for coupled line discontinuities. Examples given include coupled microstrip sections with chamfered bends located at right angles to single microstrip lines, for which the results are in good agreement with experimental values