Improved baseband digital predistortion for linearising PAs with nonlinear memory effects using linearly interpolated LUT

Abstract

International audienceAn improved baseband Digital PreDistortion (DPD) solution to reduce the nonlinearity of Power Amplifiers (PAs) with memory effects is proposed. It is based on the Memory Polynomial (MP) model and linearly interpolated Look-Up Table (LUT). This predistorter reduces significantly the computational time needed in MP based DPD by using a LUT. A linear interpolation technique is introduced to enhance the indexing of LUT, such that good performance with small table size and low computational complexity is achieved. The proposed solution is validated on a test bench using a PA ZFL-2500 driven by a 16QAM modulated signal

Analysis on LUT based digital predistortion using direct learning architecture for linearizing power amplifiers

“…(8) and (9), respectively. In [13,21,22], only the amplitude calculation in (8) is considered. The approaches based on LUT are used instead of the root-finding process.…”

“…where LILUT is the linear-interpolated LUT [21]. Similarly, for the algorithm of proposed DPD based on QILUT, the step 4) is as follows…”

“…In our previous work [21,22], some interpolated LUTs are introduced based on MP/LUT DPD. Thanks to the interpolation techniques, the improved DPDs achieve good performance in terms of computational efficiency and LUT size.…”

“…Thanks to the interpolation techniques, the improved DPDs achieve good performance in terms of computational efficiency and LUT size. In [21], the linear interpolation is introduced based on MP/LUT DPD. In [22], the quadratic-interpolated LUT is combined with the nonuniform MP model.…”

“…In [22], the quadratic-interpolated LUT is combined with the nonuniform MP model. It is worth noting that, in [21,22], LUTs are only used to determine the amplitude of the predistorted signal. While the predistorted signal's phase must be calculated by another separated time-consuming process.…”