Energy-Efficient Baseband DPD for Joint Harmonic and Intermodulation Distortion Suppression in HF communication

The nonlinear characteristics of power amplifiers (PAs) in high-frequency (HF) communication systems introduce both intermodulation distortion (IMD) and harmonic distortion (HD), which severely degrade spectral efficiency and transmission quality. To address these issues, this paper presents a novel baseband digital predistortion (DPD) technique capable of jointly suppressing both IMD and HD components. The proposed method employs a memory polynomial model to accurately characterize the nonlinear behavior of PAs, including the interactions among fundamental tones, harmonic components, and intermodulation products. An iterative optimization framework is then adopted to construct a composite predistorted signal that effectively compensates for the nonlinear distortions. Experimental validation using two-tone signals at carrier frequencies of 4 MHz and 8 MHz demonstrates that the proposed scheme achieves over 40 dB suppression of second- and third-order harmonics, and at least 15 dB reduction in third-order intermodulation distortion (IMD3).