Analysis Of Effect Of Ionospheric Modification On Navigation Satellite Communication Link

The accurate and real-time communication of navigation satellite is gaining growing interests in domestic and foreign academia. As one of the most important links of navigation satellite communication, the ionosphere link can be influenced by many factors, such as the earth storm, the sun’s ultraviolet and the X-ray. These can lead to the ionospheric modification and affect the satellite communication, and this thesis is important to analyze the satellite communication.Based on the radio wave propagation theory and double-selective channel model, author gets the satellite communication link model and the ionosphere channel model by mathematical and simulates these models by the MATLAB.Firstly, author introduces the electric parameters of the ionosphere and analyzes how the radio wave propagates through the ionosphere. In this thesis, author also reaches that amplitude can be leaded by the wave’s large-scale fading and small-scale fading and phase can be leaded by Doppler frequency and delay. Based on the analysis, we get the maximum Doppler frequency is about one hertz and the maximum delay is about one microsecond.Secondly, based on the analysis of the satellite communication and spread spectrum modulation, author can get the satellite communication link model and reach the expression of signal to noise and bits error rate. By these expressions, author gets that the BER is small when the GPS signal propagates through the ionosphere, and the SNR caused by the heating ionosphere increases, and this change is more and more with the SNR caused by the no-heating ionosphere. Author analyzes how the BER is along with the SER change by using MATLAB.Thirdly, by using the study of the scattering characteristics of the ionosphere and the functions of the ionosphere scattering and the impulse response, author gets the ionosphere channel model. The channel is related to the Doppler frequency and the delay which caused by the ionosphere, and author reaches that the maximum delay does not much affect the SER and the Doppler frequency affects it. Author gets the expression of SNR and SER for different maximum Doppler frequency, when the QPSK signal and the spread spectrum QPSK signal propagates through the ionosphere channel. For different Doppler frequency, author analyzes the SER that the signal is used spread spectrum and not used spread spectrum by using the MATLAB. And author gets the SER is much smaller after the QPSK signal is used the spread spectrum through these analysis, and also reaches that the SER is approximately equal to the conclusion in the third chapter.At last, a conclusion of the dissertation is made and the shortcomings are pointed out.