【摘要】：陸地移動通信系統(tǒng)飛速發(fā)展,第四代陸地移動通信系統(tǒng)已經(jīng)開始大規(guī)模組網(wǎng)并且商用,第五代也開始了全面的研究,數(shù)據(jù)傳輸速率和載波頻率都在不斷提高。同時,衛(wèi)星移動通信系統(tǒng)也發(fā)展到了以提供高速寬帶Internet的接入和無線多媒體通信服務(wù)的第三代,衛(wèi)星移動通信系統(tǒng)正朝著信號寬帶化和載波的高頻化演進。寬帶信號將經(jīng)歷頻率選擇性衰落,引起碼間串?dāng)_,使得信號波形失真,而衛(wèi)星系統(tǒng)中的高頻載波在通過大氣層與地面站進行信息傳輸時將不可避免地受到大氣吸收損耗、降雨衰減、電離層閃爍等影響。因此,寬帶衛(wèi)星移動信道特性的研究對于提高寬帶衛(wèi)星系統(tǒng)服務(wù)質(zhì)量具有重要意義,本文從以下幾方面進行研究。首先,分析了無線電波的傳播機制,包括多徑效應(yīng)、陰影遮蔽、多普勒頻移的形成原因及其對電波信號的影響,并研究高頻信號在星地鏈路傳播過程中大氣損耗、降雨衰減對其影響,并對這些影響進行量化分析,建立統(tǒng)計模型,對成都地區(qū)的降雨衰減進行了計算機仿真實現(xiàn),對比分析了星地之間的通信仰角、工作頻率和降雨率對降雨衰減的不同影響,給出了Rician、Rayleigh和Lognormal概率分布函數(shù)的推導(dǎo)及其物理意義。然后,介紹了寬帶衛(wèi)星移動信道與傳統(tǒng)的窄帶衛(wèi)星移動信道的區(qū)別,研究了寬帶信號頻率選擇性衰落的形成原因,給出了基于廣義平穩(wěn)非相關(guān)散射模型的寬帶衛(wèi)星移動信道沖擊響應(yīng)函數(shù),進一步建立了基于抽頭延遲線原理的寬帶衛(wèi)星移動信道模型,重點研究了成形濾波法、正弦波疊加法和隨機數(shù)生成法模擬平坦性衰落信道并進行了計算機仿真實現(xiàn),對正弦波疊加法進行了改進,對于每個正弦波的頻移和相移引入隨機性,使得模擬得到的平坦性衰落序列更符合實際情況,對建立的寬帶衛(wèi)星移動信道分別從時域和頻域進行了仿真分析,并和實測數(shù)據(jù)進行了統(tǒng)計特性的對比,驗證了所提模型的正確性。最后,設(shè)計并實現(xiàn)了基于STK和MATLAB GUI的寬帶衛(wèi)星移動信道模擬器。該模擬器的信道模型采用本文建立的基于抽頭延遲線的寬帶衛(wèi)星移動信道模型,對使用到的STK衛(wèi)星工具包進行了二次開發(fā),利用其強大的分析報告能力實時地計算出衛(wèi)星通信仰角、多普勒頻移和星地鏈路距離,并通過與MATLAB的聯(lián)合仿真將這些數(shù)據(jù)實時傳送到信道模擬器中,既可以形象地觀測衛(wèi)星運行軌跡,還可在信道模擬器上分析其信道傳輸特性和鏈路特性,具有較高的實用價值。
[Abstract]:With the rapid development of land mobile communication systems, the fourth generation of land mobile communication systems have begun to form a large-scale network and commercial, the fifth generation has also started a comprehensive study, the data transmission rate and carrier frequency are constantly improving. At the same time, the satellite mobile communication system has been developed to provide high-speed broadband Internet access and wireless multimedia communication services of the third generation, the satellite mobile communication system is moving towards signal broadband and carrier high-frequency evolution. Wideband signals will undergo frequency-selective fading, causing inter-symbol crosstalk, resulting in distortion of signal waveforms, while high-frequency carriers in satellite systems will inevitably suffer from atmospheric absorption losses when transmitting information through the atmosphere to earth stations. Rain attenuation, ionospheric scintillation and so on. Therefore, the research on the characteristics of broadband satellite mobile channel is of great significance to improve the quality of service of broadband satellite system. Firstly, the propagation mechanism of radio wave is analyzed, including multipath effect, shadow shadowing, Doppler frequency shift and its influence on radio wave signal, and the atmospheric loss of high frequency signal in the process of satellite and ground link propagation is studied. The influence of rainfall attenuation on it is analyzed quantitatively, and a statistical model is established. The computer simulation of rainfall attenuation in Chengdu area is carried out, and the elevation angle of communication between satellites and ground is compared and analyzed. The effects of operating frequency and rainfall rate on rainfall attenuation are different. The derivation of probability distribution function of Rician,Rayleigh and Lognormal and its physical significance are given. Then, the difference between wideband satellite mobile channel and traditional narrowband satellite mobile channel is introduced, and the reason of frequency selective fading of wideband signal is studied. The impulse response function of wideband satellite mobile channel based on generalized stationary uncorrelated scattering model is given. The wideband satellite mobile channel model based on tap delay line principle is further established. Sine wave superposition method and random number generation method are used to simulate flat fading channel and computer simulation is carried out. The sine wave superposition method is improved to introduce randomness into frequency shift and phase shift of each sine wave. The flattening fading sequence obtained by simulation is more in line with the actual situation. The established wideband satellite mobile channel is simulated and analyzed in time domain and frequency domain respectively, and the statistical characteristics of the established channel are compared with the measured data. The correctness of the proposed model is verified. Finally, a broadband satellite mobile channel simulator based on STK and MATLAB GUI is designed and implemented. The channel model of the simulator adopts the wideband satellite mobile channel model based on tap delay line established in this paper. The second development of the STK satellite toolkit is carried out. The satellite communication elevation angle, Doppler frequency shift and satellite-ground link distance are calculated in real time by using its powerful analytical reporting ability, and these data are transmitted to the channel simulator in real time through the joint simulation with MATLAB. Not only can the satellite track be observed vividly, but also the channel transmission and link characteristics can be analyzed on the channel simulator, which is of high practical value.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TN927.23

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本文編號：2316959