【摘要】：在過去的幾十年里,無線通信系統(tǒng)所傳輸?shù)臄?shù)據(jù)率按照摩爾定律的速度增長。特別是近些年來多媒體信息的爆炸式增長給移動回傳網(wǎng)絡(luò)的速度和容量帶來了巨大的挑戰(zhàn)。采用點對點的微波無線回傳技術(shù)是一種比傳統(tǒng)的光纖或者同軸電纜回傳技術(shù)更經(jīng)濟有效的方法,尤其是在人煙稀少的農(nóng)村或是地形復(fù)雜的區(qū)域更具優(yōu)越性。然而微波回傳通信面臨著很多技術(shù)上的挑戰(zhàn),特別是我國所主導(dǎo)的TDD通信模式下,高速的收發(fā)切換導(dǎo)致了對載波同步時間的要求非常高。本文研究了一種減少同步時間的技術(shù)。為了減少同步時間,載波同步不能用數(shù)字電路實現(xiàn),所以本文提出了一種模擬電路解決方案。模擬方案中必須讓QPSK信號先同通過四倍頻來移除調(diào)制得到載波的四倍頻,引入了距離載波很近的雜散,這需要非常窄帶的濾波器才能濾除。SIR濾波器和開口環(huán)濾波器都可以實現(xiàn)窄帶的功能,但是為了實際應(yīng)用的考慮,選擇了開口環(huán)濾波器作為載波恢復(fù)中的一個部件。最終設(shè)計出的濾波器的中心頻率在1.2GHz,相對帶寬達到了3%,插入損耗也在3dB以下,實際應(yīng)用中的效果良好。為了保證載波恢復(fù)的質(zhì)量,使用PLL設(shè)計了一個自同步電路。PLL用的是取樣鎖相鑒相器,解決了對高碼速率信號的載波恢復(fù)。自同步技術(shù)使兩路鑒相信號通過相同路徑產(chǎn)生了相位對消,從而免除了移相器的使用。然后用信號源分別產(chǎn)生了不同符號率的QPSK信號來測試電路的同步性能。測試結(jié)果表明恢復(fù)出的載波相位噪聲優(yōu)于-80 dBc/Hz@1kHz,VCO的調(diào)諧電壓達到穩(wěn)定的時間也小于22毫秒。接下來是外同步方案的分析。相比于傳統(tǒng)的同步方案,它的鎖定閾值要更低,在比較低的信噪比情況下也可以保持良好的環(huán)路穩(wěn)定性。TDD通信模式的上下行的數(shù)據(jù)量并不固定,隨時間會有很大的變化,在這種情況下外同步方案可以很到地追蹤到載波的變化情況。
[Abstract]:Over the past few decades, wireless communication systems have been transmitting data at the rate of Moore's law. Especially in recent years, the explosive growth of multimedia information has brought great challenges to the speed and capacity of mobile return network. The point to point microwave wireless transmission technology is a more economical and effective method than the traditional optical fiber or coaxial cable technology, especially in the rural areas where people are sparsely populated or in areas with complex terrain. However, microwave return communication faces many technical challenges, especially in the TDD communication mode, which is dominated by our country. The high speed transceiver switching results in a very high requirement of carrier synchronization time. In this paper, a technique to reduce synchronization time is studied. In order to reduce synchronization time, carrier synchronization can not be realized by digital circuit, so this paper proposes an analog circuit solution. In the simulation scheme, the QPSK signal must be removed from the modulation to get the quadruple frequency of the carrier by four times frequency first, and the spurious signal is introduced very close to the carrier. It takes very narrow band filter to filter out. SIR filter and open loop filter can realize narrow band function, but for practical application, open loop filter is chosen as a component of carrier recovery. Finally, the center frequency of the filter is 1.2 GHz, the relative bandwidth is 3 and the insertion loss is below 3dB. The effect of practical application is good. In order to guarantee the quality of carrier recovery, a self-synchronization circuit is designed by using PLL. The PLL uses a sampling phase-locked detector to solve the problem of carrier recovery for high code rate signals. The self-synchronization technique enables the phase cancellation of the two signals through the same path, thus eliminating the use of the phase shifter. Then the synchronization performance of the circuit is tested by using the signal source to generate QPSK signals with different symbol rates. The test results show that the recovered carrier phase noise is less than 22 milliseconds when the tuning voltage of the recovered carrier phase noise is better than -80 dBc/Hz@1kHz,VCO. Next is the analysis of the external synchronization scheme. Compared with the traditional synchronization scheme, the locking threshold is lower, and the loop stability can be maintained under the condition of low SNR. The data volume of TDD communication mode is not fixed, and will vary greatly with time. In this case, the external synchronization scheme can track the carrier changes very well.
【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】：TN919.34

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相關(guān)碩士學(xué)位論文 前1條

1 謝睦寬;小型腔體濾波器設(shè)計技術(shù)研究[D];電子科技大學(xué);2011年

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本文編號：2337588