A wideband envelope tracking Doherty amplifier for WiMAX systems

Abstract

We have demonstrated a wideband envelope tracking Doherty amplifier. The amplifier is implemented using Eudyna 10-W GaN high electron mobility transistor. For world interoperability for microwave access (WiMAX) signals of the 802.16d and 802.16e, the Doherty amplifier covers the 90 MHz bandwidth (2.3-2.39 GHz) of the Korea's mobile WiMAX (WiBro). The performance of gain, power-added efficiency (PAE), and relative constellation error (RCE) are nearly uniform for the bandwidth. In order to improve the linearity, we have applied the envelope tracking technique to the gate of the Doherty amplifier. The envelope tracking amplifier delivers a significantly improved RCE performance of -35.3 dB, which is an enhancement of about 4.3 dB, maintaining the high PAE of about 30% for the 802.16d signal at an average output power of 35 dBm.