Doherty Power Amplifier Distortion Correction Using an RF Linearization Amplifier

This paper presents a linear Doherty power amplifier (DPA) topology suitable for low-powered small cell and multiantenna fifth generation transceivers. The proposed topology relies on augmenting the conventional two-way DPA with a linearization amplifier (LA) in order to enhance its efficiency versus linearity tradeoff when driven with wideband modulated signals. For this, a study of the interactions between the LA and DPA circuitries is conducted, and a design strategy is developed to determine the circuit's parameters that maximize the adjacent channel leakage ratio (ACLR) improvement while minimizing its power overhead. For validation purpose, this strategy is applied to design a proof of concept prototype with a center frequency of 800 MHz and an output peak envelope power of 12 W. Compared with the case where the LA is not integrated, more than 11-dB improvement of the ACLR was obtained at the prototype output when driven with modulated signals of up to 40 MHz of modulation bandwidth. Furthermore, an ACLR of about -45 dBc or better was maintained over a wide average power range.