Effects of Look-Up Table Size on Adaptive Predistortion Linearizer Systems with Error Sources

Adaptive predistortion is one of the most promising methods to linearize RF power amplifiers. The size of gain look-up table is a performance limiting factor and so are various error sources existing in the system. In this paper, we study the table size effects in combination with system imperfections. It is shown that errors introduced in the adaptation path can cause an inverse relationship between the table size and the output adjacent channel power ratio. Thus, this implies that there exists an optimal table size in practice and a further increase of the table size beyond that value can even result in linearity degradation instead of improvement. The reason behind this unexpected result is discussed. This study indicates that the table size shall be properly chosen based on a good understanding of various error sources located in the system.