FPGA Implementation For A Quaternary Chaotic Digital Receiver Using Duffing Oscillator

Chaotic signal is suitable for secure communication because of its covert,unpredictability,high complexity and easy implementation.Therefore,this paper propose a FPGA design scheme of a quadrature chaotic receiver based on a Duffing oscillator array to receive the quadrature chaotic signals.The correctness of the scheme is proved by software simulation and hardware verification.The chaotic quadrature receiver consists of four modules: RF front-end module,quadrature demodulation module,chaotic signal detection module and bit synchronization module.The RF front-end module is composed of AD831 module and A/D conversion module.The AD831 module is mainly used to convert the analog signal received by the antenna to lower frequency band,which is convenient for data acquisition and processing.A/D conversion module adopts AD9433 chip for digital-to-analog Conversion.The quadrature demodulation module is used for quadrature demodulation,bandpass filtering and CIC filtering,which is convenient for the following signal processing.The chaotic signal detection module mainly includes two modules: The Duffing oscillator array demodulation module and the Duffing oscillator optimization module.The Duffing oscillator array demodulation module uses four Duffing oscillator arrays to detect the chaotic modulation signal,and then four-channel baseband signal will be recovered by circle zone partition and integrate-dump filter.The Duffing oscillator optimization module is used to select the oscillator with better detection performance,which can improve the receiver's overall performance.The bit synchronization module is used to recover the baseband code element information.This paper utilized the amplitude sensitivity of the signal and shielded its phase sensitivity by using Duffing oscillators array,so that it can demodulate binary chaotic signal with arbitrary phases.Taking account the time-domain signal of chaotic Duffing oscillator has concealment and noise-like characteristics,it can be used to construct a more secure communication information in signal modulation.This design adopts the quaternary transmission systems,which improves the transmission rate of the signal to some extent.Under the condition of conventional receiver,a Duffing oscillator optimization is added to improve the receiver's overall performance.This design realizes the traditional theory research with hardware,so that it can be really applied in practice.In order to test the quaternary chaotic receiver designed in this paper,Modelsim simulation and on-board verification are used to give the verification results.It is tested that the quaternary chaotic receiver can receive and demodulate the chaotic signal correctly,and the performance is good,which achieves the goal of this design.