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  本文選題：寬帶　切入點：數(shù)字預(yù)失真　出處：《電子科技大學(xué)》2017年碩士論文

【摘要】：功率放大器作為通信系統(tǒng)的核心單元,其性能一直是研發(fā)人員重要的關(guān)注點。在通信信號帶寬持續(xù)增長的背景下,功放的非線性失真問題將愈加嚴(yán)重。目前,數(shù)字預(yù)失真技術(shù)已經(jīng)成為補償功放非線性失真的主流技術(shù)。本文主要圍繞寬帶通信中數(shù)字預(yù)失真技術(shù)展開,包括功率放大器的行為模型提取和數(shù)字預(yù)失真模型修剪兩個方面。對于寬帶通信中功率放大器的行為模型提取,本文搭建了一個單輸入單輸出射頻器件特征提取平臺。整個平臺使用了16位1Gbps采樣率的DAC和14位250Mbps采樣率的ADC,可工作在400MHz-4GHz頻率范圍內(nèi),實現(xiàn)基帶帶寬達125MHz。文中使用ADI公司的FMCOMMS1射頻評估板和Xilinx公司的高性能FPGA開發(fā)板VC707實現(xiàn)了一個寬帶高效的零中頻收發(fā)單元,并對其發(fā)射和接收通路中存在的本振泄露和I/Q不平衡問題,以及行為模型建立時存在的延時對齊問題進行了深入的分析,并實現(xiàn)了相應(yīng)的補償。寬帶通信中功放建模需要更多的非線性項,這會導(dǎo)致計算復(fù)雜度的增加。本文使用OMP(Orthogonal Matching Pursuit,正交追蹤基)算法和VS-SAMP(Variable Step-size Sparsity Adaptive Matching Pursuit,變步長稀疏度自適應(yīng)匹配追蹤)算法對功放行為模型進行修剪。通過仿真可以看到,OMP和VS-SAMP均可在保證功放建模精度的情況下有效地減少模型系數(shù)個數(shù),即使在功放模型的系數(shù)個數(shù)(稀疏度)未知的情況下,VS-SAMP辨識算法仍能通過變步長的方式,使用盡可能少的系數(shù)滿足功放建模精度的要求。最后,本文使用VS-SAMP算法實現(xiàn)了數(shù)字預(yù)失真器,實驗驗證了其對混合類功放失真的改善效果。實驗結(jié)果表明,在使用20M和40M LTE信號進行測試時,功率放大器輸出信號的ACLR(Adjacent Channel Leakage Ratio,鄰信道泄露功率比)可改善16dB,達到-45dBc以下,實現(xiàn)了預(yù)期的效果。相比于傳統(tǒng)的LS辨識算法,VS-SAMP算法使用了更少的系數(shù)。
[Abstract]:Power amplifier as the core unit of communication system, its performance has been an important concern of researchers. In the context of the continuous growth of communication signal bandwidth, the nonlinear distortion of power amplifier will become more serious. Digital predistortion technology has become the mainstream technology to compensate nonlinear distortion of power amplifier. It includes two aspects: the behavior model extraction of power amplifier and the pruning of digital predistortion model. In this paper, a single input and single output RF device feature extraction platform is built. The whole platform uses 16-bit 1Gbps sampling rate DAC and 14-bit 250Mbps sampling rate ADC.The platform can work in the 400MHz-4GHz frequency range. The baseband bandwidth of 125MHz is achieved. In this paper, a wideband and efficient zero-if transceiver unit is implemented by using ADI's FMCOMMS1 radio frequency evaluation board and Xilinx's high performance FPGA development board VC707. The problems of local oscillation leakage and I / Q imbalance in the transmission and reception channels, and the problem of delay alignment when the behavior model is established, are analyzed in detail. And the corresponding compensation is realized. In wideband communication, more nonlinear items are needed for power amplifier modeling. This will increase the computational complexity. This paper uses OMP(Orthogonal Matching pursuit (orthogonal tracking basis) algorithm and VS-SAMP(Variable Step-size Sparsity Adaptive Matching pursuit (variable step size sparse adaptive matching tracking) algorithm to prune the performance model of power amplifier. Both OMP and VS-SAMP can effectively reduce the number of model coefficients under the condition of ensuring the modeling accuracy of power amplifier. Even when the number of coefficients (sparsity) of the power amplifier model is unknown, the VS-SAMP identification algorithm can use as few coefficients as possible to meet the requirements of the modeling accuracy of the amplifier by changing the step size. Finally, In this paper, the digital predistorter is realized by using VS-SAMP algorithm, and the effect of improving the distortion of hybrid power amplifier is verified by experiments. The experimental results show that, when using 20m and 40M LTE signals, the digital predistorter is tested. The ACLR(Adjacent Channel Leakage Ratio (adjacent channel leakage power ratio) of the output signal of the power amplifier can be improved by 16dBs, below -45dBc, and the expected effect is achieved. Compared with the traditional LS identification algorithm, the VS-SAMP algorithm uses less coefficients.
【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】：2017
【分類號】：TN722.75;TN929.5

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本文編號：1672568