A wideband linearization method using low-sampling ADCs and DACs

Wireless communication systems are evolving to the next generation to cover larger bandwidth to provide higher data rates, higher connection density, and higher reliability. Broadband Communication such as millimeter wave (mmWave) communications and teraHertz (THz) communications are both key enablers of 6G networks. Due to the inherent nonlinearity of the radio frequency (RF) components, such as power amplifiers (PAs) and mixers, larger bandwidth with high-speed modulation would cause serious nonlinear distortion, which would significantly degrade the quality of the transmission signal.If simply transmitting signal at a power level with large back-off, the power efficiency of the transmitter would dramatically drop to a unacceptable level, which would deviate from green communications with less power consumption.The digital pre-distortion (DPD) technique usually be used to correct the nonlinearity from these RF component and integration module. However, in the conventional DPD, the sampling rate of analog-to-digital (ADC) and digital-to-analog (DAC) is ten times as bandwidth for the transmitting signal, which is impractical for broadband applications, such as THz communication. Therefore, this paper proposed a novel linearization method to use ADC and DAC with low sampling rates. A nonlinearity correction model with under sampling signals are derived. Finally, simulation results verify the effectiveness of the theoretical analysis and demonstrate that the proposed linearization method could improve the EVM from 9% to 2% for a 64-QAM signal of 2 GHz bandwidth.