Research On Time-Varying Parameters Communication System Based On Chirp Modulation

In recent years,with the increasing requirements for the security of information transmission in wireless communication systems,the demand for anti-interception of communication signals is also increasing.Based on the goal of enhancing the concealment,and the anti-interception of wireless communication signals,a timing-varing parameters DSSS-Chirp communication signal and its system are proposed,which combines the chirp modulation technology and direct sequence spread spectrum technology.The time-frequency energy distribution and statistical characteristics of the timing-varing parameters DSSS-Chirp communication signal are analyzed by different time-frequency analysis tools,and the communication performance of the system is analyzed and verified through simulation.It lays a theoretical foundation for further study and application of DSSS-Chirp communication technology.The main work and conclusions are as follow:Firstly,the basic concepts of the chirp signal and the basic principles of the two Chirp modulation technology are introduced.Based on the analysis of the essential characteristics of the chirp signal,we introduce a matched filtering demodulation scheme.Then,we give the definition of fractional Fourier transform and the scheme of fractional demodulation based on the energy aggregation characteristic of the chirp signal in the optimal transform order.The system performance of different demodulation schemes has carried on the comparative analysis in the Gaussian white noise channel.Secondly,we give the modulation and demodulation principle and specific implementation models of DSSS-Chirp-BOK and DSSS-Chirp-DM communication technologies.The spectral characteristics of the two modulation signals are analyzed,and the bit error rate performance of the two systems is comparatively analyzed in the Gaussian white noise channel.Then,the statistical characteristics of DSSS-Chirp signal in frequency domain,cyclic domain,fractional domain are simulated by using the traditional communication parameter detection methods,such as the frequency doubler detection,cyclostationary theory,and fractional Fourier transform.Finally,we propose the construction scheme of DSSS-Chirp communication signal with time-varying communication parameters in the time domain and frequency domain,and the time-frequency energy distribution characteristics of the time-varying parameters signal are analyzed by different detection methods.The simulation results show that the time-varying parameters DSSS-Chirp signal has better anti-detection performance than the fixed parameter DSSS-Chirp signal and the traditional spread spectrum hopping signal.In essence,the variable-parameter DSSS-Chirp communication system is a loss of communication performance in exchange for the improvement of anti-interception performance.