Study On Synchronization In Hyperchaotic Circuit Systems And Its Application To Secure Communication

Chaos is the most important discovery in physics in the 20th century, then chaos control is becoming the advanced field with the further research in chaos theory.Chaos synchronization which is the part of chaos control has been the important content of the research in nonlinear complex science recently.Because of the property including non-period,consective BW spectrum and noise-like, chaos signal is apt to secure communication.In this thesis,synchronzation in hyperchaotic circuit systems and its application to secure communication are studied.The main research work of this dissertation has six parts as follows: First,expound the chaos definition, basic property and the route to chaos in detail, introduce the concept of chaos synchronization, criterion and several typical synchronous methods, explain the feasibility of synchronous chaos applying to secure communication, analyses the applicable actuality of chaos synchronization and secure communication, meanwhile describe the method and signification of hyperchaotic synchronization which implementing secure communication. Second, Base on Lyapunov stability theorem, several parameters in the 5th order hyperchaotic autonomous circuit system are adjusted adaptively to synchronize. Furthermore, the fewer control signal in the engineering practice is, the easier the hardware for manipulative process will be. So certain parameter in the circuit system is regulated to achieve adaptive synchronization successfully, and the parameter can be tracked during the synchronization. Third,the proportional synchronization between drive system and response system in 6-D hyperchaotic chua's circuit was achieved by using the concept of generalized synchronization. The phase space of response system can be expanded and compressed flexibly. Meanwhile, focusing on the shortcoming of the long transient behavior during the process of synchronization, a feedback method was adopted to shorten the transitional time of synchronization, which will provide an effective way for speeding up the transmitting velocity of code in chaotic multiple access communication. Forth,a scheme about digital secure communication is proposed by using different drive functions of hyperchaotic systems based on APD approach. The two different drive functions can be alternately sent according to the transmission of binary signal "0"and "1", which will enhance the complexity and decrease the relativity of transmitted signal. Meanwhile, by designing compound nonlinear function transformation for transmitted signal to intercalate secret key further, a determined intruder is very difficult to retrieve the contents of message signal using forecasting method. Fifth,a method about linear and nonlinear mixing feedback synchronization based on hyperchaotic LC oscillator circuit is proposed. Meanwhile, we study the secure communication based on the signal injected method. The method can strengthen the security of communication and possesses better robustness towards noise, which make the scheme adapt for the application of engineering practice. Sixth, the synchronization in random small-world coupled network whose single node exhibiting hyperchaotic behavior is studied. The network synchronization is achieved by analysis and numerical simulation, furthermore, several parameters such as coupled strength, probability for implementing synchronization are given, so we can synchronize and anti-synchronize according to the practical work...