A System Approach for Efficiency Enhancement and Linearization Technique of Dual-Input Doherty Power Amplifier

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. An auto-tuning process based on a hybrid heuristic search control (HHSC) is applied to optimally define DIDPA configuration by optimizing its free parameters. Digital predistortion (DPD) is then integrated to linearize DIDPA using an optimal reduced-complexity model based on the segmentation approach. An optimal pruning 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. The system approach has been approved by experimental results, in different scenarios, using an LTE 20 MHz signal with a PAPR of 8 dB. DPD linearization under optimal DIDPA configuration 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.