Researches And Applications On Analog-Digital Hybrid Chaotic System Based On Electro-Optical Devices

Chaotic systems and theory have be widely applied in various aspects of scientific research.Analog chaotic system have the virtue of high output speed-rate and complex dynamic behavious,but usually suffer from their weak robustness and difficulty to control;digital system could be easily controlled and reproduced,however often facing the challenge of limited performance.In practical applications,the complex dynamic characteristic is in need to obtain a superior performance.Simultaneously,the robustness and controllability are required to ensure the reliability and stability of system function.There is always a trade-off between them and a balanced selection should be taken into consideration.According to the concept of analog-digital dynamic system,a novel theoretical model of analog-digital hybrid chaotic system is designed,which could be implemented by electro-optical devices.In the proposed hybrid system,complex dynamic characteristic,ultra-high operation frequency and robustness can be satisfied at the same time.Based on the designed hybrid chaotic system,the performance on radar and nonlinear computing is investigated further.The detailed contents are listed below:(1)Aiming at the requirements of controllability and superior performance for practical engineering applications,a novel anlog-digital hybrid chaotic model is proposed.Based on the concept of reverse-time chaos and PM-to-IM conversion mechanism respectively,two typical chaotic systems are established.By means of numerical simulation and experimental method,the dynamic behaviours of system have been studied in detail.Furthermore,the performances of generated chaos signal,including the complexity,statistical property and robustness,are also inverstigated.The results show that two dynamical systems exhibit complicated dynamical properties.The produced chaos signal owns a flat and broad frequency spectrum(effective bandwidth:7.3GHz and 12.4GHz),high complexity(permutation entropy:0.98 and 0.9918),no obvious time-delay signatures and other advantages.The system states and intial values could be controlled digitally and a large parameter space(?2¹⁴⁴)can be obtained.Besides,a robust reproduction of chaos signal in different places is feasible with the information of digital sequence.(2)With the development of electronic countermeasure technology,current radar systems have a higher demand on the detection resolution,anti-jamming and anti-intercept capability.Aiming at the requirments of radar system,a novel bistatic noise radar structure based on the hybrid chaos system and digital synchronization mechanism is proposed.The simulation and experimental results indicate that the generated chaos signal have a stochasitic temporal waveform,broadband spectrum,nearly-ideal shape of ambigurity function and excellent correlation.When applied in radar system,high detection resolution(6cm and 15m/s),low probability of intercept,and strong anti-jamming campability could be obatained.Besides,a novel digital synchronization scheme is adopted,where the replicated analog reference signal is replaced by digital sequence.In the receiver,the reference signal could be regenerated using the digital sequence.Simulation results show that the proposed scheme could be helpful in reducing the mutual interferences between the echo and reference signal,regardless of the digital transmission by wireless or fiber channel.Compared with the traditional bistatic radar,the detection SNR of the receiver in the proposed scheme improve 11.12d B and 9.98d B repsectively,which could make an enhancement on the detection performce.(3)Aiming at the problems of the limited computing capability and complex physical configuration existing in optical digital computing systems,an optical reconfigurable Boolean function generator based on the analog-digital hybrid chaotic system is put forward.Theoretically,all poosible Boolean function could be acquired by virtue of the ergodicity of nonlinear dynamical system.A different Boolean function could be implemented by setting the control signal.The four-input one-output Boolean function is selected as an example.Simulation results show that all 65536 Boolean functions coud be obtained in a single nonlinear system after adequent iterations.Furthermore,the contamination of noise on the iteration loop is discussed in detail.19640 reliable Boolean functions could be obtained under the degradation of noise,with no need of changing its physical configuration.