Impact of Excitation Signal Statistics in the Selection of the Optimum Load for Future Wideband Power Amplifiers

This article presents a new perspective on the characterization of the performance parameters of wideband power amplifiers (PAs) based on signal statistics’ figure of merits (FoMs), such as complementary cumulative distribution function (CCDF) and peak-to-average power ratio (PAPR). First, the importance of the use of multi-tone over the continuous wave (CW) excitation in the selection of optimum load for the wideband PAs is discussed. In the subsequent section, several factors which have an influence on the optimum load synthesis during wideband load–pull are discussed. Different sub-circuits of the PA, such as input-output match, intrinsic/extrinsic parasitics, and baseband impedance mismatch, affect the signal statistics, such as PAPR. In the load synthesis process, focusing on a specific PAPR value for a specific signal can lead to suboptimal performance conclusions. The influence of the PAPR of a signal on the PA behavior, PA design, and its characterization process is examined in-depth in this article. This article shows that the PA performance under modulated load–pull largely depends on the characteristics of the excitation signal and how it changes at the different sub-circuit nodes, specifically at the input section of the PA. Further optimization in terms of the linearity and efficiency of the PA can be obtained by improving the load–pull process using frequency-dependent load optimization under wideband modulation.