【摘要】：時(shí)域同步正交頻分復(fù)用(TDS-OFDM)調(diào)制技術(shù)具有諸多優(yōu)點(diǎn),如抗多徑衰落能力強(qiáng)、頻譜利用率高等。然而,TDS-OFDM技術(shù)也存在其固有的缺點(diǎn)：對(duì)接收端同步系統(tǒng)的性能要求較為苛刻。我國的數(shù)字電視地面廣播DTMB標(biāo)準(zhǔn)的多載波模式中采用TDS-OFDM作為其調(diào)制方式。因此,針對(duì)DTMB標(biāo)準(zhǔn)的多載波模式的同步系統(tǒng)的設(shè)計(jì)顯得尤為重要,其同步系統(tǒng)的性能直接關(guān)系到接收端的質(zhì)量。本文將基于DTMB標(biāo)準(zhǔn)的多載波模式提出一種同步系統(tǒng)的設(shè)計(jì)方案,并且對(duì)其進(jìn)行FPGA實(shí)現(xiàn)。本文首先著重介紹了現(xiàn)有的DTMB多載波系統(tǒng)的同步技術(shù),并對(duì)DTMB多載波系統(tǒng)的發(fā)送端和接收端的系統(tǒng)結(jié)構(gòu)、系統(tǒng)幀結(jié)構(gòu)以及同步問題進(jìn)行了分析。接著,本文提出一種實(shí)現(xiàn)DTMB多載波系統(tǒng)同步的流程,設(shè)計(jì)了其同步系統(tǒng)的運(yùn)行機(jī)制。然后,給出了同步系統(tǒng)的FPGA實(shí)現(xiàn)的總體結(jié)構(gòu),對(duì)各個(gè)模塊進(jìn)行了實(shí)現(xiàn)。最后,將各個(gè)模塊進(jìn)行連接,構(gòu)建完整的同步系統(tǒng)。在系統(tǒng)的同步流程設(shè)計(jì)方面,將同步系統(tǒng)劃分為捕獲和跟蹤兩種狀態(tài)。所設(shè)計(jì)的同步流程如下：系統(tǒng)依次進(jìn)行定時(shí)初調(diào)整、幀頭模式檢測(cè)及幀頭位置粗估計(jì)、頻偏粗估計(jì)及頻偏校正、幀頭相位捕獲、幀頭位置細(xì)估計(jì)、采樣細(xì)同步、頻偏細(xì)估計(jì)及頻偏校正、頻偏精估計(jì)及頻偏校正。借助Matlab軟件對(duì)該同步流程進(jìn)行了仿真驗(yàn)證。仿真結(jié)果表明,該同步流程能夠很好地實(shí)現(xiàn)系統(tǒng)同步。在系統(tǒng)的運(yùn)行機(jī)制方面,介紹了捕獲和跟蹤狀態(tài)的信號(hào)處理流程,并且提出了實(shí)現(xiàn)捕獲／跟蹤狀態(tài)切換的機(jī)制以及突發(fā)頻偏的處理方法。在狀態(tài)切換機(jī)制上,提出了通過判斷定時(shí)誤差提取器輸出的互相關(guān)序列的相關(guān)峰的尖銳程度以及位置是否發(fā)生改變實(shí)現(xiàn)狀態(tài)切換的方法。最后,通過Simulink搭建同步系統(tǒng),驗(yàn)證了該運(yùn)行機(jī)制的可行性。在同步系統(tǒng)的FPGA實(shí)現(xiàn)方面,首先提出了同步系統(tǒng)的FPGA實(shí)現(xiàn)的總體架構(gòu)；接著著重介紹系統(tǒng)各個(gè)模塊的實(shí)現(xiàn)結(jié)構(gòu),對(duì)其中一些模塊的實(shí)現(xiàn)進(jìn)行了優(yōu)化,并對(duì)主要模塊的實(shí)現(xiàn)結(jié)果進(jìn)行了驗(yàn)證；最后將各個(gè)模塊進(jìn)行級(jí)聯(lián),構(gòu)建完整的同步系統(tǒng)。在FPGA實(shí)現(xiàn)過程中,通過采用“乒乓操作”和“串并轉(zhuǎn)換”的方法,提高了系統(tǒng)的處理速度,同時(shí)通過采用模塊復(fù)用、線性逼近法以及數(shù)據(jù)交織等方法,有效節(jié)省了硬件資源。
[Abstract]:Time Domain synchronous orthogonal Frequency Division Multiplexing (TDS-OFDM) has many advantages, such as strong anti-multipath fading ability and high spectral efficiency. However, TDS-OFDM technology also has its inherent shortcomings: the performance of the receiver synchronization system is demanding. In the DTMB standard of digital TV terrestrial broadcasting in China, TDS-OFDM is adopted as the modulation mode in multicarrier mode. Therefore, the design of multi-carrier synchronization system based on DTMB standard is particularly important. The performance of the synchronization system is directly related to the quality of the receiver. In this paper, we propose a design scheme of synchronization system based on multi-carrier mode of DTMB standard, and implement it with FPGA. In this paper, the existing synchronization technology of DTMB multicarrier system is introduced, and the system structure, frame structure and synchronization of DTMB multicarrier system are analyzed. Then, this paper presents a process to realize the synchronization of DTMB multicarrier system, and designs the operation mechanism of the synchronization system. Then, the overall structure of the FPGA implementation of the synchronization system is given, and each module is implemented. Finally, each module is connected to build a complete synchronization system. In the design of synchronization process, the synchronization system is divided into two states: capture and trace. The designed synchronization flow is as follows: the system performs timing initial adjustment, frame head mode detection and frame head position coarse estimation, frequency offset estimation and frequency offset correction, frame head phase capture, frame head position fine estimation, sampling fine synchronization, frame head phase acquisition, frame head position fine estimation, frame head position coarse estimation and frequency offset correction. Frequency offset fine estimation and frequency offset correction, frequency offset precision estimation and frequency offset correction. The synchronization process is verified by Matlab software. Simulation results show that the synchronization process can achieve system synchronization well. In the aspect of system running mechanism, the signal processing flow of acquisition and tracking state is introduced, and the mechanism of acquisition / tracking state switching and the processing method of burst frequency offset are put forward. In the mechanism of state switching, a method is proposed to realize state switching by judging the sharpness of the correlation peak of the cross-correlation sequence outputted by the timing error extractor and whether the position is changed or not. Finally, the synchronization system is built by Simulink, and the feasibility of the operation mechanism is verified. In the aspect of the FPGA implementation of the synchronization system, the overall architecture of the FPGA implementation of the synchronization system is put forward firstly, and then the realization structure of each module of the system is introduced emphatically, and some of the modules are optimized. The implementation results of the main modules are verified. Finally, each module is concatenated to construct a complete synchronization system. In the process of FPGA implementation, the processing speed of the system is improved by using the methods of "ping-pong operation" and "serial-parallel conversion". At the same time, the hardware resources are saved effectively by using the methods of module reuse, linear approximation and data interleaving.
【學(xué)位授予單位】：福州大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TN949.197

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