Abstract:

In this paper, we propose an efficient system approach to improve the power efficiency of dual-input Doherty power amplifier (DIDPA) with maintaining its linearity level. Firstly, an auto-tuning process based on a hybrid heuristic search control (HHSC) is applied to optimally define DIDPA configuration by optimizing its free parameters, including peak- to-average power (PAPR) reduction threshold. The HHSC is driven by a cost function designed to moderate the inherent trade-off between linearity and power efficiency. The digital predistortion (DPD) is then integrated to linearize DIDPA using an optimal reduced-complexity model based on the segmentation approach. The coefficients of the cost function are updated optimally based on the linearity improvement by DPD. An optimal prun- ing process of the free parameters, based on hill-climbing (HC) heuristics, is proposed to reduce the HHSC complexity in order to refine the optimal DIDPA configuration with the updated cost function. The system ap- proach has been approved by experimental results, in different scenarios, using an LTE 20 MHz signal with a PAPR of 8 dB PAPR. In the first step where HHSC is applied, DIDPA exhibited a drain efficiency of 61%. DPD linearization improved linearity using a low-complex model with only 30 coefficients, which exhibited an error vector magnitude (EVM) of 2.5% and an adjacent channel power ratio (ACPR) of -50 dB at an averaged output power of 34 dBm. By updating the cost function coefficients and pruning the free parameters, DIDPA exhibited an EVM of 3%, an ACPR of -50 dB, and a drain efficiency of 47% at an average output power of 39 dBm.