Research On DFS Adaptable Performance Analysis And Suppression Methods Of SNCK Communication Systems

With the rapid development of society, people demand more and more on the quality of communication and the capacity of the communication system , and put forward higher requirements to the adaptability of the communication system. The demand for wireless communication is also increasing. The current wireless communication technology is moving forward in high speed,high capacity,high security and high reliability direction. Because the traditional way is mostly single frequency wave modulation, and the communication system of single-frequency waves has high error rate due to Doppler performance , therefore non-single-frequency wave communication system is gradually into sight. Nonlinear frequency modulation signal,as representative of the non-monochromatic wave,has the advantage of gathering more energy, higher bandwidth utilization rate and having better performance in the Doppler resisting. So researching on nonlinear frequency modulated signal gradually becomes the hot direction in modern wireless communication system. In this paper,study the SNCK( Sine Non-linear Chirp Keying)deeply, and the main contents are as follows:Firstly , the modulation principle and mathematical model of SNCK communication signal are introduced, so the basic structure of SNCK signal is established in mathematics,as a result , have an essential understanding of the nonlinear frequency modulation characteristics. Then, based on the mathematical model,the performance and power spectrum of SNCK signal is analyzed under the condition of Gaussian white noise. The demodulation of discrimination demodulation method is proposed from its nonlinear characteristics of frequency and detailed proposed its coherence and non-coherent demodulation scheme. Each module of the two schemes are introduced and the physical model is established.Secondly, the effect of Doppler frequency shift on the performance of SNCK signal is discussed. Because of the high speed movement of the mobile terminal in modern society,there is a clear Doppler shift in the communication process, which has a significant effect on the performance of the signal and the system. Therefore , the third chapter focuses on the impact of Doppler frequency shift on the SNCK,and the simulation analysis, especially on the consequences of SNCK demodulation. At the same time , the error rate of SNCK under Doppler and non Doppler is derived.Finally,the principle of Doppler frequency shift suppression method based on SNCK demodulation method is introduced,and the structure block diagram of the method is given. Simulation of different Doppler channel model is realized, and the signal spectrum is studied before and after the baseband filter. It is proved that the method has the ability to restrain the Doppler effect.