A highly-efficient linear amplifier for satellite and cellular applications

This paper presents a scheme to linearise highly-efficient amplifiers over a broad bandwidth, whilst retaining most of their efficiency. Present wideband linearisation techniques are normally restricted to either feedforward or analogue predistortion. Feedforward has been shown to provide excellent linearity, but only modest efficiency; whilst analogue predistortion has little effect on efficiency, but limited linearity improvement. However, the combined use of both techniques has enormous potential, since the linearity improvement is greater than that attainable with feedforward alone, whilst the efficiency approaches that of the main amplifier. Practical results are presented which confirm the above predictions in terms of overall efficiency and linearity, and illustrate the effectiveness of the technique.