在通訊系統中，高功率放大器是一個非線性的元件。由於放大器的非線性關係，訊號經過放大器後，會對訊號產生振幅和相位失真項。這樣的影響不是我們所希望的，為了改善此現象，預扭器方式便被提出。預扭器針對放大器的振幅和相位項，產生一個反函數，使得訊號經過預扭器補償後，能得到線性的效果。在本篇論文中，分析一個複數增益數位預扭器，它是由轉換對照表所組成，用來補償功率放大器所造成的非線性效應。轉換對照表更新的方式可以分為三種（正割法、線性法、極坐標法）。本篇論文中，針對無記憶性的放大器模型比較三種轉換對照表更新方法對於放大器輸出的錯誤誤差收斂快慢。亦比較錯誤率、功率頻譜密度函數的影響。本篇論文系統架構於寬頻分碼多工系統下.

Power amplifiers (Pas) are inherently nonlinear devices and are used in virtually all communications systems. However, they produce distortions by creating AM/AM and AM/PM responses in the transmitting signal. The predistortion is accomplished by inverse modeling of the AM/AM and AM/PM responses of a high power amplifier. This thesis analyzes a complex gain digital predistorter (CGDP), which is composed of a look-up table (LUT), that can compensate for the distortion produced by a PA. LUT adaptation is investigated by using three methods (Secant method, Linear method, Polar method). We compare which method has the best convergence of the squared magnitude of the power amplifier output error for a memoryless Travelling Wave Tube Amplifier (TWTA). We also investigate the bit error rate (BER) and power spectrum density（PSD）function for different adaptation algorithms. The performance of the proposed algorithm is demonstrated on a WCDMA system.

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