發(fā)布時(shí)間：2019-01-02 07:32

【摘要】：低軌衛(wèi)星移動(dòng)通信系統(tǒng)運(yùn)行軌道低、傳輸時(shí)延小和終端要求低等特點(diǎn)已使其成為衛(wèi)星通信系統(tǒng)的一個(gè)主要發(fā)展方向。在低軌衛(wèi)星移動(dòng)通信系統(tǒng)中,信號(hào)會(huì)受多普勒效應(yīng)、陰影效應(yīng)、多徑效應(yīng)和傳播噪聲等因素的影響。所以,在低軌衛(wèi)星移動(dòng)通信系統(tǒng)的研發(fā)過程中,為了驗(yàn)證系統(tǒng)的可靠性,必須要了解低軌衛(wèi)星信道對(duì)系統(tǒng)信號(hào)所產(chǎn)生的影響。在以往,人們大多采用外場(chǎng)試驗(yàn)的方法,租用實(shí)際衛(wèi)星鏈路進(jìn)行測(cè)試,但這種方法代價(jià)高昂且易受外界因素影響。所以,本課題設(shè)計(jì)了一種基于DSP的低軌衛(wèi)星信道模擬器,該信道模擬器能夠在實(shí)驗(yàn)室條件下實(shí)時(shí)模擬低軌衛(wèi)星信道的傳輸特性,為低軌衛(wèi)星移動(dòng)通信系統(tǒng)的研制提供測(cè)試方法,具有重要的實(shí)際意義。 本文主要工作包括以下內(nèi)容： (1)通過分析比較幾種常用衛(wèi)星信道模型,選擇了IMS (Land Mobile Satellite)模型作為本低軌衛(wèi)星信道模擬器的理論模型。 (2)針對(duì)LMS模型,提出了本低軌衛(wèi)星信道模擬器的實(shí)現(xiàn)結(jié)構(gòu)框圖,并利用Simulink對(duì)其中的數(shù)字下變頻系統(tǒng)進(jìn)行了仿真,仿真結(jié)果驗(yàn)證了數(shù)字下變頻系統(tǒng)中抽取濾波器的性能,為實(shí)際開發(fā)中數(shù)字下變頻(DDC)芯片的參數(shù)設(shè)置提供了數(shù)據(jù)驗(yàn)證。 (3)提出了一種結(jié)合專用數(shù)字下變頻芯片AD6620和DSP的低軌衛(wèi)星信道模擬器實(shí)現(xiàn)方案。設(shè)計(jì)了一塊中頻處理子卡,再結(jié)合SEED-DEC6713開發(fā)板,,完成了本低軌衛(wèi)星信道模擬器的硬件設(shè)計(jì),并對(duì)各模塊及模塊間的具體電路設(shè)計(jì)進(jìn)行了詳細(xì)介紹。 (4)利用AD6620濾波器設(shè)計(jì)軟件Fltrdsn得到了濾波器的最優(yōu)抽取率組合,使用單片機(jī)AT89LV51完成了對(duì)AD6620的初始化設(shè)置,并給出了TMS320C6713與AD6620的接口程序及信號(hào)處理程序的設(shè)計(jì)。 (5)搭建了系統(tǒng)測(cè)試平臺(tái),利用信號(hào)發(fā)生器為系統(tǒng)提供模擬中頻測(cè)試信號(hào),然后通過CCS (Code Composer Studio)軟件對(duì)測(cè)試結(jié)果進(jìn)行觀測(cè)與分析,測(cè)試結(jié)果表明,本低軌衛(wèi)星信道模擬器能夠模擬衛(wèi)星移動(dòng)通信信道的衰落和多普勒頻移效應(yīng),達(dá)到了預(yù)期的設(shè)計(jì)目標(biāo)。
[Abstract]:Low orbit satellite mobile communication system has become a main developing direction of satellite communication system due to its low orbit, low transmission delay and low terminal requirements. In Leo satellite mobile communication system, the signal is affected by Doppler effect, shadow effect, multipath effect and propagation noise. Therefore, in the research and development of Leo satellite mobile communication system, in order to verify the reliability of the system, it is necessary to understand the influence of Leo satellite channel on the system signal. In the past, people mostly used the method of field test to rent the actual satellite link for test, but this method is expensive and easy to be affected by external factors. Therefore, this paper designs a Leo satellite channel simulator based on DSP. The channel simulator can simulate the transmission characteristics of Leo satellite channel in real time under laboratory conditions, and provide a test method for the development of Leo satellite mobile communication system. It has important practical significance. The main work of this paper is as follows: (1) by analyzing and comparing several commonly used satellite channel models, IMS (Land Mobile Satellite) model is selected as the theoretical model of the Leo satellite channel simulator. (2) based on the LMS model, the implementation block diagram of the Leo satellite channel simulator is proposed, and the digital downconversion system is simulated by Simulink. The simulation results verify the performance of the decimation filter in the digital downconversion system. It provides the data verification for the parameter setting of the digital down conversion (DDC) chip in the actual development. (3) an implementation scheme of Leo satellite channel simulator based on AD6620 and DSP is proposed. In this paper, a sub-card of intermediate frequency processing is designed, combined with SEED-DEC6713 development board, the hardware design of the Leo satellite channel simulator is completed, and the specific circuit design of each module and module is introduced in detail. (4) the optimal decimation rate combination of the filter is obtained by using the AD6620 filter design software Fltrdsn, and the initialization setting of the AD6620 is completed by using the single-chip computer AT89LV51. The interface program between TMS320C6713 and AD6620 and the design of the signal processing program are given. (5) the system test platform is built, and the signal generator is used to provide the analog if test signal for the system. Then the test results are observed and analyzed by CCS (Code Composer Studio) software. The test results show that, This Leo satellite channel simulator can simulate the fading and Doppler frequency shift effect of satellite mobile communication channel and achieve the desired design goal.
【學(xué)位授予單位】：南京信息工程大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TN927.23

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本文編號(hào)：2398195