Analysis and characterization of a load modulated balanced amplifier for base-station applications

Abstract

This paper discusses the analysis and the experimental results of a load modulated balanced amplifier designed for base-station applications. The hardware, employing commercially available GaN packaged devices, operates in the 1.7–2.5 GHz band, with maximum output power higher than 63 W, and with power added efficiency higher than 43% and 39% at 6 dB and 8 dB output power back-off, respectively. The analysis reveals that the proposed topology has some advantages when compared to other load modulated amplifiers, such as the Doherty, but on the other hand it shows an intrinsic non-linear behaviour. This is confirmed by experimental results, where it is shown that employing a non-linear splitting function between the two branches of the amplifier improves the performances with respect to a linear splitter. Moreover, through the adoption of a proper digital splitting function and predistortion it is possible to linearize the amplifier to a level acceptable for Long Term Evolution (LTE) base-stations while maintaining a competitive average efficiency.