Simplified Temperature Compensation Technique for Digital Predistorter Using Fixed Coefficients

An adaptive digital predistorter (ADPD) promises accurate nonlinear compensation and can automatically follow the change of output power of PA, a gain of transmitter consisting of DAC, mixer, PA, etc., and nonlinearity of PA by temperature fluctuation. However, an ADPD needs costly, large-power-consuming, and bulky equipment for calibration-loop. To overcome these drawbacks, we propose a simplified digital pre-distorter (DPD) using fixed coefficients with a variable gain amplifier (VGA), which requires no adaptive estimation block. The proposed DPD alleviates the performance degradation due to the change in temperature. The results show that error vector magnitude (EVM) of 2% and adjacent channel power ratio (ACPR) of -48 dBc can be achieved from -20 to 70 degrees Celsius using single-carrier 64-QAM signal.