功率放大器在無線傳輸系統的收發端模組中是非常重要的零組件，而高效能功率放大器設計又相當依賴精準非線性元件模型；因此在本論文裡，我們提出一個可以準確描述元件非線性特性的模型以及一個高線性度的功率放大器，並且利用砷化鎵高電子遷移率電晶體的製程來實現。 我們提出新的電流方程式並利用平滑方程式去彌補傳統元件模型對於高電子遷移率電晶體電流特性與其微分特性的不精準，電容方程式的部分採用Statz Model 電荷模型來描述。透過AgilentTM ADS 模擬軟體SDD的環境下，完整地描述0.5 μm 砷化銦鎵增強型假晶格高電子遷移率電晶體的特性，並將模擬與量測結果做比較，如功率飽和、諧波失真等，證實此大訊號模型有不錯的準確性。 透過建立元件非線性模型，瞭解了元件失真的原因之後，本論文提出一線性器電路架構來設計高線性度功率放大器，並利用0.15 μm 高電子遷移率電晶體製程來實現此放大器。由於線性器電路提供共源極放大器功率增益及相位的補償，因此有較好的線性度表現。電路的量測結果靜態電流、功率增益、1 dB 輸出飽和功率、分別為320 mA、16 dB、27.5 dBm；注入3.5 GHz WiMAX 64 QAM 調變訊號時，相對星座圖向量誤差量測結果為3.5 %。 Power amplifier is a very important component in the wireless transmitter. The high performance power amplifier must depend on accurate nonlinear device model. In this thesis, an accurate nonlinear model and a high linearity power amplifier are designed, analyzed, and demonstrated for InGaAs pHEMT. We proposed a novel current model for 0.5 μm InGaAs pHEMTs enhancement-mode device. The model is differentiable for any order at full bias range by utilizing smooth function technique in the symbolical defined device environment (SDD). The Statz charge model is included for device capacitance in this model. The proposed model predicted the DC, S-parameters, microwave power, and nonlinear distortion characteristics more accurate in comparison with conventional compact model. Further, the model is convenient and direct to be embedded in commercial harmonic balanced simulator. Utilizing nonlinear model tools, the high performance power amplifier was realized for WiMAX applications. The predistortion method in this work was used to improve AM-AM and AM-PM distortion at high power operation without degrading the intrinsic performance. The power amplifier was successfully demonstrated at 3.5 GHz. The power performances were power gain of 16 dB, maximum power of 29.5 dBm, output linear power (P1dB) of 27.5 dBm. The measured EVM was smaller than 3.5 % using 3.5 GHz 64 QAM WiMAX signal.
