High-power amplifier linearization using the Doherty amplifier as a predistortion circuit

Abstract

This paper presents the application of a Doherty power amplifier (DPA) as a predistortion circuit for the linearization of high PA. When the DPA is employed as the driver amplifier, its nonlinearity is used as predistorted components to cancel the strong nonlinearity of the main amplifier. To verify the proposed method, the DPA is implemented with two 30-W silicon metal-oxide semiconductor field-effect transistors and tested with a 180-W main amplifier at a wideband code-division multiple access (WCDMA) band of 2.14 GHz. For a two-tone signal with 2-MHz tone spacing and a one-carrier WCDMA signal, the significant cancellation of the third- and fifth-order intermodulation (IM3 and IM5) components and a superior adjacent channel leakage ratio improvement are achieved.