An Integrated Scheme of Cross-FIR-LUT Harmonic Cancellation Digital Predistortion Model for Short-Wave Power Amplifier

Abstract

Intermodulation distortion (IMD) and higher harmonics caused by the nonlinearity of power amplifier (PA) are the main problems of multioctave PA used in high-frequency (HF) transmitter. In this letter, the integrated structured digital predistortion (DPD) method is proposed based on the characteristics of short-wave signal systems. Based on the integrated cross-memory polynomial DPD model, the FIR structure with low-pass filtering characteristics is further employed to achieve the goal of improving baseband IMD while suppressing higher order harmonics of multioctave HF PAs. Experimental results on a real HF PA illustrate that the proposed CROSS-FIR-lookup table (LUT) improves the baseband IMD about <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{10}$</tex-math> </inline-formula> dB, while the second and third harmonics are below <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 55 dB, compared with the conventional MP and GMP schemes without increasing the algorithm complexity.