The Performance Analysis And Received Algorithm Research Of Chirp-BOK System In Fading Channel

In order to deal with the complex and changeable electromagnetic environment,realize the higher rate information transmission and meet the requirements of communication system for low interception,low detection and anti-interference ability,the Chirp Spread Spectrum(CSS) communication technology is proposed to replace the single frequency wave for covert communication.The shortcomings of receiving algorithm for Chirp Binary Orthogonality Keying(Chirp-BOK) system based on the background of covert communication electronic warfare in the fading channel are analyzed.Then,the new methods combined with Fractional Fourier Transform(FrFT) are given to improve the communication performance of the Chirp-BOK system in the fading channel.The details are as follows:Firstly,the character of Chirp signal in Time Domain and Fractional Fourier Transform Domain are studied.The matched filter(MF) demodulation method in time domain and the coherent demodulation method and the non-coherent demodulation method in fractional fourier domain for Chirp-BOK system are given.The results of simulation show that the BER performance of coherent demodulation is affected and the BER performance of non-coherent demodulation in fractional fourier domain is not affected when there is phase error in the system.Secondly,a demodulation method of area peak search based on FrFT(APS-FrFT) is given to improve the fractional domain demodulation algorithm of Chirp-BOK system,which has better BER performance of system under the condition of frequency offset.The results of simulation show that the new demodulation method has strong adaptability to frequency offset.Then,a secondary search synchronization method based on FrFT domain is proposed to improve the bit synchronization algorithm of Chirp-BOK system,which has better synchronization performance of Chirp-BOK system.Finally,the communication performance of Chirp-BOK system in multipath channels is analyzed.A new demodulation method is proposed by combining the transmitted reference(TR) and FrFT.According to the different ways of obtaining the reference template,it can be divided into: the transmission reference demodulation method based on FrFT domain(TR-FrFT) and the improved TR-FrFT demodulation method(ITR-FrFT).The results of simulation show that the BER performance of Chirp-BOK system is improved in multipath channels when the methods of TR-FrFT and ITR-FrFT are used effectively.The methods of TR-FrFT has better BER performance of Chirp-BOK system compared to that of ITR-FrFT in AWGN channels and multipath channels.