High efficiency GaN wideband Doherty amplifier for LTE-Advanced applications

In this paper, a high efficiency GaN Doherty power amplifier (PA) with broad signal bandwidth for LTE-Advanced applications is presented. The carrier and peak amplifier of the Doherty PA, which operate at different classes, have different matching circuits in order to optimize the performance of each amplifier. To validate the performance of the proposed Doherty PA in wideband system, it was tested with LTE-Advanced signals with modulation of 16-QAM and bandwidth of 20 MHz, 40 MHz and 50 MHz, individually. Measurement results show that drain efficiency (DE) of the proposed PA can achieve 60% at the maximum output power of 47 dBm, and it maintains higher than 43% at the output power range of 40-47 dBm. Meanwhile, adjacent channel leakage ratio (ACLR) of PA output are -38 dBc, -38 dBc, -37 dBc respectively to the three signal bandwidth at 3.43 GHz. Furthermore, with the PA linearization technique combined of digital pre-distortion (DPD) and peak-to-average power ratio (PAPR) reduction, ACLR can be improved to -45dBc.