【作者】 赵柏山；

【导师】 朱义胜；

【作者基本信息】 大连海事大学 ， 通信与信息系统， 2008， 博士

【摘要】 在过去的几十年里,信息安全问题越来越受到人们的重视,混沌保密通信作为一个重要的分支得到了飞速的发展。本文主要研究了混沌通信系统中高性能混沌信号制取及混沌调制系统性能等基础性问题。本文中的方法是从基本系统的角度进行论证,但结论和成果同样可以应用到其他复杂的混沌系统中。论文首先针对混沌信号设计缺乏规律可循的问题,论述了在Lorenz系统基础上通过引入系统参数,对混沌吸引区域及状态变量的控制,实现具有可选特性参数混沌信号的制取方法。并在此基础上提出了利用同构混沌系统作为混沌键控信号产生系统的设计方法,有效地消除了混沌信号在相图中的分叉现象,提高了混沌键控系统的保密性能。其次针对当前广泛讨论的混沌掩盖系统中信息安全性出现的问题,提出了一种混沌掩盖技术的改进方法。通过对混沌信号频谱分布的调整,实现信息的安全传输,解决了混沌掩盖系统易受攻击方破解的问题。同时为降低突发噪声对混沌通信系统的影响,提出了一种降低混沌接收系统混沌同步时间的方法,通过对系统模型状态变量导数的系数进行调整,增强系统的同步能力,缩短同步所需的时间。此外针对现有基于混沌同步的混沌调制系统对信道干扰及信道特性极为敏感的问题,提出了一种基于半同步解调的混沌调制方案。通过仿真,说明方法能够有效地对信息进行加密调制及信号恢复,系统的抗干扰能力以及系统的安全性也得到增强。同时针对现有混沌信号存在较大直流和低频分量的问题,提出了一种抑制混沌信号直流和低频分量的方法。通过仿真说明该系统在抑制混沌信号直流和低频分量方面的效果以及系统设计时应注意的问题。文章最后介绍了对无源通信网络的研究。首先提出一种利用预先选定的电路模型,通过分析耦合矩阵及传递函数,实现并联谐振实现交叉耦合谐振滤波器的方法。其次提出了一种多端口元件散射参数测试参数进行校正的方法,解决了接入阻抗反射系数的精度导致的测试误差问题,有效提高了这类测试方法的测试精度。更多还原

【Abstract】 In the past decades, the security of the information is more and more important to people, and the chaotic communication system has been developed rapidly as a part of secure communication system. This thesis discusses the problems of the generation of the chaotic signal with proper characteristic and the improvement of the chaotic modulation method, which are focused on the basic theory of chaotic communication system, comparing with the methods of adding affixation or using more complex structure to enhance the securitiy of the system. The results can also be combined with the methods presented in literature.First in order to find a principle to design chaotic signal, this paper presents a method of producing chaotic signals with arbitrary magnitude and spectrum, which is based on the Lorenz system by introducing some parameters of the system to realize the selective magnitude and spectrum. Furthermore, this paper has shown the validity of this method by theory and simulation. In addition, this kind of generators is easily implemented, and the signal is suitable for protecting the information in communication systems. By the way, a new chaotic shift keying modulation is proposed by using the same structure systems designed by the method of producing chaotic signals with arbitrary magnitude and spectrum. The same structure systems have the same attractors and attracting region, so the bifurcation of the attractors in return maps can be eliminated. The binary information can not be attacked easily by the return map breaking method.Then the reason of the security weakness of generalized state-space observers-based approaches for secure communication is discussed which is used chaotic masking and chaotic nodulation of a Lorenz system and a method is proposed to solve this problem. Theory analysis and simulation show this improvement realized chaotic masking. By contrast with the original system, this method improves the performance of secure communication system based on chaotic masking. At the same time, in order to reduce the affect of the gusty noise to the chaotic communication system, a method is developed to enhance the synchronization ability and reduce time expenditure by adjusting the differentiation with respect to the state variables in the chaotic system. This method also has the ability to resist the gusty noise in the channel and improve the quality of the chaotic communication.Furthermore, since the chaotic modulation systems based on chaotic synchronization are very sensitive to the noise or the distortion of the channel, a new chaotic modulation method is proposed based on Lorenz system, the information signal is introduced into the modulation system as the parameter of the nonlinear part. In the receiver, the information signal is derived from the error of the partial synchronization. The system did not require the synchronization process, and the sensitivity of this modulation system to the noise is reduced. The simulation shows this system has realized secure communication and enhanced the ability to resist the noise in the channel and to secure information.In addition, a multidimentional chaotic signal generator is introduced to restrain the DC and the spectrum component in the low frequency. The n+1 dimentional system is deduced from an n dimentional system, the output signal of which is added an integration to its derivative. The characteristic of the original system is kept and the purpose is realized by analysis and simulation.At last, the study of another domain of the communication system is discussed, which is about the theory of passitive communication networks.This contained two aspects: first, a method to design cross-coupled resonator filters with parallel resonance circuits is presented in this paper. The procedure includes selecting a circuit model, introducing a scaling factor and bandwidth condition, and calculating the values of the coupling and resonance admittances of the circuit model by the coupling matrix and the given transfer function. Finally, an example is given to illustrate the designing procedure, and the simulation results show the validity of the presented approach. Second, a method used to reduce the errors in the scattering parameters measurement of N-ports based on two-port vector network analyzer (VNA) is presented, which is based on the normalization and renormalization of the scattering matrix and an optimization procedure. The method is proved by measured results.更多还原