Low Frequency Optimization Of Inverse Memristor Emulator And Its Chaotic Circuit Application

The concept of memristor was put forward as early as 1971.It was not until 2008 that nano-scale memristor came out,which triggered a research boom in the field of memristor.Its unique nonlinearity and memory have a positive promoting effect on the development of non-volatile memory,digital circuits,chaotic systems,simulated brain synapses,and artificial neural networks.The pinched hysteresis loop is the most significant feature of memristor,and its blade area decreases with the increase of the input signal frequency,while the change trend of the inverse memristor is the opposite.The existing dissimilar properties of both can provide a certainly reference value to the design of memristor circuits.However,the research of the inverse memristor and its application is relatively few now.Therefore,two novel voltage-controlled inverse memristors and a reversible memristor with inverse memristor-memristor states switching are proposed in this thesis firstly inspired by the existing models.Then,the fourth and fifth order chaotic circuits are designed by using the reversible memristor based on the traditional Chua’s circuit.Finally,the chaotic sequences of the more complex fifth order system are combined with the two-dimensional code to carry out simple image encryption application.The main research work and innovation of this thesis are as follows:(1)In order to study the characteristics of the inverse memristor,a new voltage-controlled inverse memristor emulator model was proposed.In its structure,an alterable shaping function module was preset and set as voltage quadratic function and hyperbolic sine function,which completes two novel inverse memristors in turn.When the lower frequency excitation is applied,they have better low frequency characteristics and adaptability compared with the existing models.And their inverse memristor behavior is more obvious.In addition,an improved invertible memristor with inverse memristor-memristor states transition is designed,which not only analyzes and displays its switching behavior with the change of input frequency under certain parameters,but also deeply investigates the influence of model integral parameters on the internal state quantity.(2)The proposed reversible memristor emulator is added to the classical Chua’s circuit as a nonlinear element,then the fourth order chaotic circuit is designed.Its chaotic characteristics and rich dynamic behaviors follow with the changing key parameter under the initial state is unchanged are analyzed by the conventional dynamics perspective,as Lyaponuv index,equilibrium stability,variable phase diagram and so on.Furthermore,a fifth order chaotic circuit of higher structural complexity is designed by added an inductor based on the fourth order model,its hyperchaos state is researched emphatically.The results of Matlab numerical simulation are consistent with the LTspice circuit simulation,which effectively verifies the accuracy of theoretical analysis.(3)Based on the strong secrecy of chaotic encryption and the ability of two-dimensional code scanning query and anti-external attack,the simple memristor chaotic encryption application is completed by combining the two.The traditional row and column scrambling encryption has limitations,so a complementary scrambling and diffusion encryption method is adopted,which applies the hyperchaotic sequence generated by the fifth order system to the information image encryption firstly,then the generated ciphertext is transformed into a two-dimensional code and subjected to external attack testing.The histogram before and after encryption,the contrast of adjacent pixel gray level and the result of resisting external attack all show that it has good security and defense effect.