On Power Amplifier Efficiency with Modulated Signals

We have investigated the performance in terms of overall efficiency and maximum output power of a real high power amplifier with various modulated signals, ranging from constant envelope signals to orthogonal frequency division multiplexing based signals having large envelope variations. We show that there are large differences on the overall amplifier efficiency as well as its maximum output power depending on the modulated signal and also on the operation mode. In particular, we show that for high overall efficiency it is important to operate the amplifier close to the maximum output power level as often as possible, and we show that this has consequences for the resource allocation in especially packet based multicarrier systems. We also show that the amplifier performance with various Single-Carrier Frequency Division Multiple Access signals is very similar, and that the peak-to-average-power ratio can be used to predict the overall efficiency for the traditional amplifier drive method. Finally, we show that with advanced, today infeasible, amplifier operation methods the overall amplifier efficiency depends less on the modulation scheme, thus motivating further research in that domain.