DPP-MP: An Area-Efficient Digital Predistortion Model for Quadrature Digital Transmitters

Although quadrature digital transmitters (DTXs) are particularly useful in wideband scenarios, the interaction between I and Q paths would lead to a non-negligible distortion. Unfortunately, traditional DPD models have not performed well in solving this kind of distortion. For example, memory polynomial (MP) model uses signal amplitude as the fundamental term which is not accurate enough to solve this issue, while 2-D lookup table (2D-LUT) model requires a large number of entries which leads to significant hardware resource consumption. In view of this, we propose an area-efficient dual-path piecewise memory-polynomial (DPP-MP) model, which improves model accuracy while reducing hardware resource consumption. To further reduce the area cost, the model is pruned to 8 terms only and 4 of them are reused. To reduce the logic delay, a new squared multiplier is proposed to replace the default one, which reduces delay by 13.51% and power consumption by 2.56%. This model achieves 36.86% and 66.98% area optimization compared to MP and 2D-LUT, respectively. When applied to a 9-bit quadrature DTX with a 40 MHz 256-QAM signal, this model improves the error vector magnitude (EVM) from -16.38 dB to -35.89 dB with a target average power (Pavg) of 21.07 dBm.