混沌扩频通信系统及其干扰技术研究

【作者】 刘雪松；

【导师】 李立萍；

【作者基本信息】 电子科技大学 ， 信息与通信工程， 2009， 硕士

【摘要】 混沌科学作为一门新兴学科,越来越多的学者对其进行了研究,并被广泛应用于扩频通信技术中。随着混沌在扩频通信中的应用,使得电子侦察工作越来越困难,因此对混沌扩频通信系统的对抗研究成为现代电子战争的一个关键。本文中,对基带混沌扩频通信系统的特性进行了深入的分析,并对该系统的干扰技术做了进一步的研究。本文的主要工作如下:第一部分重点研究了四种混沌序列优于传统扩频序列的统计特性。主要研究了四种常用于扩频通信的混沌映射:Chebyshev映射、Logistic、改进型Logistic映射和Tent映射,仿真研究表明,在一定的条件下,这四种混沌映射都存在着一个或几个收敛点,因此在构造混沌序列时应避免这些收敛点;四种混沌序列误码性能要优于传统扩频序列--m序列和Gold序列。第二部分采用了一种基于Gold序列的混沌扩频同步方法。本文对一种基于Gold序列的混沌扩频同步方法进行了仿真分析。从仿真结果可以看出,该同步方法有效的实现了混沌扩频通信系统的同步问题,解扩后接收到的信息码比原始信息码延迟了一秒的时间,这在扩频通信系统的要求中是可以允许的。第三部分重点研究了多用户基带混沌扩频通信系统原理及其性能。理论分析了多用户基带混沌扩频通信系统的原理,强调了该系统的抗干扰能力强的特点,重点研究了产生混沌扩频码的映射参数对基带混沌扩频通信系统的影响,通过仿真比较,我们可以知道,该系统具有比传统扩频通信系统更优良的系统特性。第四部分重点分析了对基带混沌直接序列扩频通信系统的四种干扰样式和比较。首先对通信对抗技术的发展、干扰的不同分类以及干扰通信系统的分类进行了简单的介绍,其次,针对基带混沌直接序列扩频通信系统,说明影响通信系统性能的指标为系统输出端误码率,并说明了对混沌扩频通信系统的最佳干扰理论为具有混沌时频特性的随机信号。随后采用高斯白噪声信号、单频信号、线性调频信号、噪声调幅、噪声调频和噪声调相六种压制式干扰信号,对基带混沌直接序列扩频通信系统进行干扰仿真实验,分析各种信号的特性及在不同频率和不同带宽下的对其干扰效能的影响。更多还原

【Abstract】 Chaos spread-spectrum communication has become a hotspot in the field of chaotic application research. Combined theoretical analysis with simulation approaches, the key technologies of multi-user chaotic direct sequence spread spectrum(DS-SS) communication are analyzed, especially in the generation of chaotic sequence, the optimizing of the chaotic sequence, the method of chaotic synchronization, and the simulation and performance analysis of the system. The chaos DS-SS communication’s availably jamming becomes the key to get the electronic war’s victory, so it is very important to research the effectiveness of jamming and interference referred to the chaos DS-SS communication system.In the first part, the relation between the performance of balance and the parameter of four typical chaotic maps (Chebyshev, Logistic, Improved Logistic and Tent) is studied. The new numeric ranges of initial value and fractal parameter are decided, which provides reference for the generation of chaotic spread-spectrum sequence. The performance of balance and correlated characteristic of these four chaotic sequences with the length of 2000 to 3000 are studied. Compared with conventional spreading sequence (m sequence and Gold sequence), they have better performance of balance and correlated characteristic.In the second part, the techniques of Costas carrier tracking and non-coherent PN sequence tracking in digital receiver are studied. Besides, based on m sequence, a new chaotic sequence synchronization method which has excellent anti-jamming capability is proposed. Through the capture of m sequence, the synchronization of chaotic sequence between transmitter and receiver is realized. This method not only solves the synchronization of the chaotic sequences with the finite length, but also founds the technology foundation for the practical application of chaotic DS-SS communication. In the third part, multi-user chaotic DS-SS communication systems are designed. The error-bit rate performance of this system with parameter of chaotic maps, signal to noise ratio, number of users, the length of sequence is investigated, and the results show that it has many merits, such as good anti-interference, low BER, great capacity, ideal secure properties, and good flexibility.In the fourth part, the optimum jamming bandwidth and optimum jamming frequency for direct sequence system are mathematically analyzed. Based on DS-SS technology, the proposed chaos-based noise jamming technology is studied. Based on chaos DS-SS technology, this Master Dissertation profoundly studies five kinds of different jamming signals, including the white noise, the chirp signal, the noise AM jamming, the noise FM jamming and the noise PM jamming, evaluates the effectiveness of them and makes simulation. Combined theoretical deduction and the computer simulation results, jamming strategy in different situations and get relevant jamming condition is analyzed.更多还原