Highly Linear Power Tracking Doherty Amplifierfor WCDMA Repeater Applications

This letter presents a highly linear power tracking Doherty power amplifier (DPA) for wide-band code division multiple access (WCDMA) repeater system. To achieve maximum linearity without extra linearization circuits, the drain bias voltages of the carrier and peaking amplifiers as well as the gate bias voltage of the peaking amplifier are adaptively controlled using the power tracking method according to average power level of the input signal. For experimental verification, a two-way DPA has been implemented at the WCDMA band of 2.11~2.17 GHz and tested using one-tone, two-tone, and four-carrier WCDMA signals. Two-tone and WCDMA test results show the notable cancellation of the IM3 and IM5 components and the significant improvement in adjacent channel leakage ratio over a wide range of output power levels.