本文選題：電力線通信 + 擴頻��； 參考：《電子科技大學(xué)》2015年碩士論文

【摘要】：電力線通信(Power line communication,PLC)技術(shù)使用電力線作為傳輸媒介進行數(shù)據(jù)傳輸,具有投資少、用戶多、布線安裝簡單、覆蓋范圍廣等特有的優(yōu)勢在智能電網(wǎng)中已得到廣泛運用,但是由于電力線傳輸環(huán)境復(fù)雜,高噪聲、高衰減和多徑特性等因素使得電力線通信的傳輸質(zhì)量大大降低,本文重點對電力線通信系統(tǒng)中的同步算法進行研究與改進。首先,本文研究了電力線信道的特點,給出了本文使用的電力線信道的仿真模型,接著分析了幾種常見的電力線載波通信的傳輸方式,通過分析各自的優(yōu)缺點,給出了本論文選擇直接擴頻通信的理由,接著介紹了擴頻通信的理論基礎(chǔ)和系統(tǒng)結(jié)構(gòu),并設(shè)計了電力線擴頻系統(tǒng)的幀結(jié)構(gòu)。然后,本文在深入研究直接擴頻通信同步理論的基礎(chǔ)上,提出了一種新穎的基于線性調(diào)頻Chirp信號的定時同步算法,具體而言,主要工作及創(chuàng)新點如下:研究了直接擴頻系統(tǒng)中傳統(tǒng)的定時同步算法,這類算法都是依據(jù)偽隨機序列的自相關(guān)特性,在接收端通過尋找相關(guān)峰值點來獲得同步,這種算法的不足之處在于同步時間過長,同步精度不高。接著研究了基于Chirp信號脈沖壓縮特性的同步方法,該算法使用Chirp信號作為訓(xùn)練序列,在接收端對接收信號進行匹配濾波可得到一個很尖銳的窄脈沖,由此獲得同步。接著研究了基于Chirp信號分數(shù)階傅里葉變換(Fractional Fourier Transform,FRFT)的同步算法,由于Chirp信號的FRFT在最優(yōu)分數(shù)域上產(chǎn)生“能量匯聚”,根據(jù)能量匯聚點位置的偏移量確定定時同步的位置,該算法在零頻偏環(huán)境下定時同步精度高,但頻偏存在時算法性能大大降低。根據(jù)普通的FRFT法會受頻偏的影響,提出了改進的FRFT法,設(shè)計了新的訓(xùn)練序列結(jié)構(gòu),利用首尾相接的兩個Chirp信號作為同步頭。分別對接收信號做最優(yōu)分數(shù)域上的分數(shù)階傅里葉變換可得到兩個能量匯聚點,由這兩個能量匯聚點的偏移量計算出定時同步的位置,該位置已消除掉頻偏的影響,定時同步準確度高。最后,本文就提出的改進FRFT算法在DSP(TMS320C6455)上進行了代碼轉(zhuǎn)換和驗證,分析了DSP實現(xiàn)和matlab仿真的性能差異,結(jié)果表明改進算法的硬件實現(xiàn)是有效的。
[Abstract]:Power line communication (PLC) technology has been widely used in smart grid because of its advantages such as less investment, more users, simple wiring, wide coverage and so on, which uses power line as a transmission medium for data transmission. However, due to the complexity of power line transmission environment, high noise, high attenuation and multipath characteristics, the transmission quality of power line communication is greatly reduced. This paper focuses on the research and improvement of synchronization algorithm in power line communication system. Firstly, this paper studies the characteristics of power line channel, gives the simulation model of power line channel used in this paper, then analyzes several common transmission modes of power line carrier communication, and analyzes their advantages and disadvantages. The reason for choosing direct spread spectrum communication in this paper is given. Then, the theoretical basis and system structure of spread spectrum communication are introduced, and the frame structure of power line spread spectrum system is designed. Then, on the basis of deeply studying the synchronization theory of direct spread spectrum communication, this paper proposes a novel timing synchronization algorithm based on linear frequency modulation (LFM) Chirp signal. The main work and innovations are as follows: the traditional timing synchronization algorithms in direct spread spectrum systems are studied. These algorithms are based on the autocorrelation characteristics of pseudorandom sequences and can be synchronized at the receiving end by finding correlation peak points. The shortcoming of this algorithm is that the synchronization time is too long and the precision of synchronization is not high. Then the synchronization method based on the pulse compression characteristic of Chirp signal is studied. The algorithm uses Chirp signal as training sequence and matches the received signal to obtain a very sharp narrow pulse at the receiving end. Then, the synchronization algorithm based on Fractional Fourier transform (FRFT) of Chirp signal is studied. Because the FRFT of Chirp signal produces "energy convergence" in the optimal fractional domain, the position of timing synchronization is determined according to the offset of the position of energy convergent point. The algorithm has high precision of timing synchronization in zero-frequency offset environment, but the performance of the algorithm is greatly reduced when frequency offset exists. According to the influence of frequency offset on the common FRFT method, an improved FRFT method is proposed, and a new training sequence structure is designed. Two Chirp signals are used as synchronization heads. Two energy convergent points can be obtained by using fractional Fourier transform in the optimal fractional domain respectively. The position of timing synchronization is calculated from the offset of these two energy convergent points, and the influence of frequency drop is eliminated. Timing synchronization accuracy is high. Finally, the improved FRFT algorithm is implemented on DSP (TMS320C6455) for code conversion and verification, and the performance difference between DSP implementation and matlab simulation is analyzed. The results show that the hardware implementation of the improved algorithm is effective.
【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】：2015
【分類號】：TM73

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相關(guān)期刊論文 前1條

1 茍先太;;大多普勒頻移下DS/FH混合擴頻測控機理與方法研究[J];學(xué)術(shù)動態(tài);2010年02期

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本文編號：2090493