Research On Channel Modeling And High Precision Simulation Methods For Space Ionization Media

In recent years, the world’s major countries have begun a new round of space exploration activities,which formed a space exploration wave around the world. With the rapid development of China’s space industry, space exploration has become one of the important researches of China’s aerospace technology. Communication system occupies a pivotal position in the design of satellites, which is an important link between the space and the earth. In order to effectively shorten the development cycle of satellite communication system, reduce the test cost and simulate the real space channel propagation environment on the ground, it is very important to study the channel characteristics and establish channel model of the space.The tangible media in most of the space is present in the form of ionization, so the electromagnetic wave used by satellite communication system will be mainly affected by this space ionization medium (SIM) during the propagation process. The most closely related spatial ionization media is in the interplanetary space and the Earth’s ionosphere. At present, these two parts of the ionization media are still researched separately. But in space, these two parts directly connected and there is no obvious dividing line between them. So modeling and analysis unitedly can illustrate influence on electromagnetic waves more precisely. Therefore, the main contents of the dissertation are as follows:1. The space ionization media is regarded as a random media. Based on the analysis and research of ionization media in the interplanetary space and Earth ionospheric, the unified space electron density expression is deduced by using the Savitzky-Golay algorithm. The influences of the space ionization media on the communication are the intensity scintillation, the spectral broadening and the time broadening. Then the scintillation index, the coherence bandwidth and the coherence time of the SIM are deduced based on the propagation and scattering theory of the electromagnetic wave in the random media. At last the correctness is verified by theoretical proof and simulation analysis.2. Based on the study of the scintillation index, the coherence time and the coherence bandwidth, the cascade effect of interplanetary space and Earth ionospheric is analyzed. Considering the random variation of signal amplitude, the spectral broadening, the time broadening, the noise in the space, the propagation delay of the long distance and the Doppler shift, a more complete model of the space ionization media fading channel model is proposed. The fading channel model is closer to the real space environment. At the same time, this model is used to classify the spatial ionization media channel according to frequency selectivity and fading speed.3. The simulation methods of spatial ionization media channel model are studied from the time domain and frequency domain. The channel fading is simulated by using the Tapped Delay Line (TDL) and the frequency domain cyclic convolution.Using the linear feedback shift register and Box-Muller method simulates the space complex electromagnetic environment noise. The optimal boundary fitting Remez algorithm from the time domain and the complex multiplication from the frequency domain are used to simulate the spatial high precision delay. Finally, through the analysis and discussion of time complexity and spatial complexity, the conclusion of time domain simulation is obtained.4. The hardware simulation system is established by means of fixed-point simulation and the time domain channel simulation methods. The influence of the loss of the space ionization media simulator is reduced to an acceptable range. And then the hardware simulation system error analysis and processing methods are given.Finally, the simulation and implementation results are tested by standard instrument and equipment, which proves the correctness and validity of spatial channel model simulation.