Highly linear and efficient Doherty amplifier employing power tracking bias supply scheme for WCDMA applications

This paper presents a power tracking Doherty power amplifier (DPA) for high linearity and high efficiency. To achieve maximum linearity while preserving high efficiency of the DP A, the drain bias voltage of the carrier amplifier and the gate and drain bias voltages of the peaking amplifier are adaptively controlled using the power tracking method. For experimental verification, a 2-way DPA has been implemented at the wide-band code division multiple access (WCDMA) band of 2.11-2.17 GHz and tested using one-tone, two-tone, and 4-carrier WCDMA signals. Two-tone and WCDMA test results show notable cancellation of the IM3 components and significant improvement in adjacent channel leakage ratio (ACLR) over a wide range of output power levels, while obtaining high efficiency.