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

The paper demonstrates, for the first time, a 200W load modulated balanced amplifier 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 DPD approach applied to the balanced PA branch and a power-dependent phasing function applied to the CPA branch. The LMBA prototype implementation is carried out using 100W GaN on SiC pre-match device in the balanced branch. Measured results achieve peak 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.