Abstract: The TWT amplifier exhibits nonlinear distortions in both amplitude(AM/AM) and phase(AM/PM), which can lead to signal distortion. So linearization technique is needed for amplifiers. Among a lot of techniques proposed, the pre-distorter based on direct maping is simple and effective. Based on the vector quantization technique, this paper impves the "direct mapping pre-distorter," presents a new adaptive predistorion technique for compensating for nonlinear distortions. Compared with the "direct mapping pre-distorter," this technique not only can decrease memory while maintaining compensation precision, but also can be aplied to input signals with different quantization bits, thus resulting in a great flexibility.

Key words: TWTA, predistortion technique, direct mapping, vector quantization