本論文利用數位預失真技術來改善WiMAX基地台高功率放大器的線性度，使功率放大器在同樣線性度之條件下輸出功率與效率在表現上皆會優於傳統功\率倒退方法。由於WiMAX基地台系統之OFDM調制訊號具有相當高之PAPR值，使其對功率放大器線性度要求極為嚴格，本論文採用極座標架構之查表法數位預失真器，以FPGA實現基頻數位預失真電路，來提升一應用於WiMAX 2.6GHz頻段的Lateral MOSFET 15W AB類功率放大器之線性度，使其能滿足WiMAX基地台之發射頻譜遮罩與EVM規範要求，有預失真可比無預失真情況下操作在更高輸出功率範圍，進而提升轉換效率。

This thesis utilizes the digital predistortion technique to improve the linearity of high power amplifiers for WiMAX basestation applications. The power amplifier with the proposed technique can achieve higher output power and efficiency than with the conventional output power backoff technique. Owing to a very high PAPR value of the OFDM modulation signals applied to WiMAX basestation, the linearity requirement for the basestation power amplifiers is very strict. This thesis adopts a look-up table predistorter based on a polar scheme and realizes the digital predistorter circuitry using FPGA. As a result, the implemented digital predistorter successfully enhances the linearity of a 15W Lateral MOSFET Class-AB power amplifier operating in 2.6 GHz WiMAX band. Under the conditions that satisfy the spectrum mask and EVM requirement, the power amplifier with the digital predistorter can operate at higher output power and conversion efficiency than without the digital predistorter.

第一章 序論 1
1.1 背景簡介 1
1.2 章節規劃 1
第二章 功率放大器線性化技術 3
2.1 非線性特性 3
2.1.1 增益壓縮 4
2.1.2 交互調變失真 5
2.1.3 三階交越點 7
2.1.4 多音交互調變比例 8
2.1.5 鄰近通道功率比例 9
2.1.6 雙音訊號與多音訊號交互調失真之關係 10
2.2 AM/AM與AM/PM之非線性特性 11
2.2.1 AM/AM與AM/PM的轉換特性 12
2.3 線性化技術 14
2.3.1 前饋式線性化技術 15
2.3.2 回授式線性化技術 18
2.3.3 預失真線性化技術 19
第三章 基頻數位預失真技術 24
3.1 基頻數位預失真技術 24
3.1.1 多項式基頻預失真器 24
3.1.2 查找表基頻預失真器 26
3.2 基頻數位預失真電路設計 30
3.2.1 極座標數位預失真技術 30
3.2.2 基頻數位預失真電路設計 33
3.2.3 LUT及其索引函數之建立方法 36
第四章 WiMAX標準調制測試訊號之產生與設置 38
4.1 WiMAX標準調制訊號 38
4.2 WiMAX之射頻前端規格 44
4.3 WiMAX輸出訊號測試平台之建立 47
第五章 數位基頻預失真技術應用在WiMAX基地台高功率放大器 50
5.1 WiMAX基地台高功率放大器 50
5.1.1 AM/AM與AM/PM非線性特性之量測結果 52
5.2 CW測試訊號之量測結果 53
5.2.1 單音訊號測試之量測結果 54
5.2.2 雙音訊號測試之量測結果 55
5.2.3 多音訊號測試之量測結果 63
5.3 WiMAX輸出訊號測試之量測結果 73
5.3.1 WiMAX輸出訊號頻譜增長量測結果 73
5.3.2 WiMAX輸出訊號調制品質量測結果 79
第六章 結論 88
參考文獻 90
附錄A WiMAX在調制頻寬為3.5MHz的測試結果 94
附錄B WiMAX在調制頻寬為5MHz的測試結果 98

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