Digitally Assisted Load Modulated Balanced Amplifier for 200W Cellular Infrastructure Applications

Abstract

The paper demonstrates, for the first time, a high power (200W) load modulated balanced amplifier (LMBA) targeting 5G cellular infrastructure applications. Both amplitude and phase of the injected signal applied to the control power amplifier (CPA) are configured using a dynamic phase shaping function along with a pre-distortion digital front-end. Digital baseband processing provides flexibility in varying both amplitude and phase of the injected signal to the CPA which improves efficiency and overall linearizability of the LMBA. Under real-time modulated signal excitation, excellent linearization is achieved using a segmented digital predistortion (DPD) approach applied to the balanced power amplifier (BPA) branch and a power-dependent phasing function applied to the CPA branch. The LMBA prototype implementation is carried out using NXP's 100 W gallium nitride (GaN) on silicon carbide (SiC) pre-match device in the balanced branch. Measured results achieve peak output power of 53 dBm (200 W) with 44% linearized efficiency at 8 dB back-off and corrected ACPR of -52 dBc across LTE Band-41 (~2.6 GHz).