本文選題：行為建模 + 數(shù)字預(yù)失真��； 參考：《電子科技大學(xué)》2017年碩士論文

【摘要】：隨著無(wú)線通信系統(tǒng)的基帶帶寬需求越來(lái)越寬,信號(hào)的峰均比也急劇增加,這就要求作為無(wú)線通信系統(tǒng)基礎(chǔ)的射頻功率放大器有較高的回退區(qū)且保持高效率。為了解決這些問(wèn)題,出現(xiàn)了異相技術(shù)、包絡(luò)跟蹤和Doherty等功率放大器結(jié)構(gòu)。其中Doherty因其結(jié)構(gòu)簡(jiǎn)單、成本低、易于實(shí)現(xiàn)和便于改進(jìn)等特點(diǎn),成為當(dāng)前功率放大器設(shè)計(jì)的主流。而與功率放大器通信質(zhì)量息息相關(guān)的數(shù)字預(yù)失真技術(shù)也愈發(fā)受到重視。本文主要內(nèi)容是對(duì)Doherty功率放大器的數(shù)字預(yù)失真技術(shù)進(jìn)行研究。本文選取了1.8-2.6GHz的雙帶Doherty功率放大器作為研究對(duì)象,首先分析其非線性特性,然后對(duì)放大器行為模型和數(shù)字預(yù)失真算法進(jìn)行分析討論。同時(shí),引入了一種基于記憶多項(xiàng)式模型(Memory Polynomial,MP)的改進(jìn)模型--加權(quán)記憶多項(xiàng)式模型(Weighted Memory Polynomial,WMP),該模型可以應(yīng)用于射頻功率放大器的行為建模和預(yù)失真。加權(quán)記憶多項(xiàng)式模型在記憶多項(xiàng)式模型的靜態(tài)和動(dòng)態(tài)項(xiàng)上,引入了依賴于即時(shí)功率的權(quán)重函數(shù),本文所用的權(quán)重函數(shù)是雙曲正切函數(shù)。同時(shí)本文基于WMP模型,實(shí)現(xiàn)了WMP模型的多步迭代預(yù)失真器,可以獲得更好的線性化效果。為了更好的驗(yàn)證本文提出的基于WMP模型的多步迭代數(shù)字預(yù)失真結(jié)構(gòu)的有效性和優(yōu)越性,作者利用實(shí)驗(yàn)室現(xiàn)有儀器搭建了驗(yàn)證平臺(tái),并對(duì)平臺(tái)可能造成的非線性失真進(jìn)行了討論分析和校準(zhǔn)。本文以20MHz LTE(長(zhǎng)期演進(jìn)技術(shù))信號(hào),對(duì)放大器模型的建模和預(yù)失真進(jìn)行了實(shí)驗(yàn)驗(yàn)證,并以輸出信號(hào)的ACPR(Adjacent Channel Power Ratio,相鄰信道功率比)作為衡量功率放大器線性度的標(biāo)準(zhǔn)。將實(shí)驗(yàn)結(jié)果與傳統(tǒng)的記憶多項(xiàng)式模型和廣義記憶多項(xiàng)式模型進(jìn)行對(duì)比從而評(píng)估新模型。結(jié)果表明,本文使用的雙帶Doherty功率放大器在未進(jìn)行預(yù)失真處理時(shí),在其1.9GHz和2.6GHz的ACPR分別為-26.08dBc/-28.67dBc、-28.88dBc/-28.87dBc,而經(jīng)過(guò)基于WMP模型的多步迭代數(shù)字預(yù)失真處理后,ACPR至少可以改善26.19dBc,達(dá)到預(yù)期目標(biāo)-52dBc以下。
[Abstract]:As the baseband bandwidth of the wireless communication system becomes wider and wider, the peak to average ratio of the signal increases rapidly, which requires the RF power amplifier, which is the basis of the wireless communication system, to have a high fallback zone and high efficiency. In order to solve these problems, heterogeneous techniques, envelope tracking and Doherty power amplifier structures have emerged. Among them, Doherty has become the mainstream of power amplifier design because of its simple structure, low cost, easy to implement and easy to improve. Digital predistortion technology, which is closely related to the communication quality of power amplifier, has been paid more and more attention. The main content of this paper is to study the digital predistortion technology of Doherty power amplifier. In this paper, a 1.8-2.6GHz dual-band Doherty power amplifier is chosen as the research object. Firstly, the nonlinear characteristics of the amplifier are analyzed, and then the behavior model of the amplifier and the digital predistortion algorithm are analyzed and discussed. At the same time, an improved memory polynomial model, weighted memory polynomial model, is introduced, which can be applied to the behavior modeling and predistortion of RF power amplifiers. In the static and dynamic terms of the memory polynomial model, the weighted memory polynomial model introduces the weight function which depends on the instant power. The weight function used in this paper is hyperbolic tangent function. At the same time, based on the WMP model, the multi-step iterative predistorter of the WMP model is implemented, which can obtain better linearization effect. In order to better verify the validity and superiority of the multi-step iterative digital predistortion structure based on WMP model proposed in this paper, the author has built a verification platform using the existing instruments in the laboratory. The possible nonlinear distortion caused by the platform is analyzed and calibrated. In this paper, the modeling and predistortion of amplifier model are verified by using 20MHz LTE (long term evolution technique) signal, and the linearity of power amplifier is measured by the ACPRG adjacent channel power ratio of the output signal. The experimental results are compared with the traditional memory polynomial model and the generalized memory polynomial model to evaluate the new model. The results show that the dual-band Doherty power amplifier is used without predistortion. At 1.9GHz and 2.6GHz, the ACPR is -26.08dBc / -28.67dBc / -28.88dBc / -28.87dBcrespectively. After multi-step iterative digital predistortion processing based on WMP model, ACPR can improve at least 26.19dBc and reach the expected target of -52dBc.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TN722.75

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本文編號(hào)：2013091