Features Analyzing And Parameters Estimating Of CSS And DSSS-Chirp

Spread spectrum communication is the technology mainstream means currently in the field of wireless communication,it can be completed the reliability of data transmission in the low signal to noise ratio,and has good anti interception ability.Spread spectrum signal in this paper is divided into two kinds,the first kind is CSS signal with large time bandwidth product,The second is a signal to be direct sequence spread spectrum,and then modulated by the Chirp-rate of the Chirp signal,with lower bandwidth product,spread spectrum signal generated at this time could be called DSSS-Chirp.The non stationary transformation of the above two kinds of spread spectrum signal,analysis of signal characteristics in transform domain,so as to provide the corresponding algorithm for the estimation of important parameter.The main work and conclusions are specifically as follows:Firstly,it introduces the basic concept of Chirp signal,analyzes the pulse compression characteristics of its unique,on the basis of the analysis,gives CSS and DSSS-Chirp signal modulation and demodulation principle and concrete realization of the model,and in the white Gauss noise channel and 802.15.4a protocol standard multi path channel model,the BER performance of two kinds of spread spectrum technology has carried on the comparative analysis,further illustrate the BER performance of two kinds of Chirp modulated signals are dependent on the correlation between each Chirp symbols.Secondly,for the CSS and the DSSS-Chirp two kinds of non-stationary signal,using cyclostationary transform and fractional Fourier transform theory,research and analysis of signal characteristics of two spread spectrum signal in circular correlation domain and fractional domain.It can be concluded that in cyclic domain,if the observation time is not more than a single Chirp symbol duration,circulation domain characteristics of the second order cyclic statistics reflect the frequency parameters,but when the time is long enough,the interval of adjacent cycle frequency value are symbol rate signals in the second order cyclic statistics.Finally,by the signal characteristics of CSS and DSSS-Chirp signal in the circular domain,estimation of its main parameters.For the CSS signal,presents an algorithm for theestimation of the center frequency based on maximum peak search,and an algorithm for the estimation of Frequency modulation rate based on maximum peak search,and combining the observation time value of different conditions,gives the complete selection scheme of the algorithm for parameter estimation;for DSSS-Chirp signals,the symbol rate estimation algorithm is proposed based on the adjacent peak spectral line.By the characteristics analysis of the two spread spectrum signals in transform domain and the comparison of the parameter estimation algorithm simulation,in the same system parameters,DSSS-Chirp compared with CSS,it has better anti-interception performance.