Written by: Bo Berglund, Thorsten Nygren and Karl-Gösta Sahlman

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Multicarrier transmitters traditionally have one power amplifier per carrier and a combiner circuit at the output, or they combine the carriers at low power level and then utilize a common multicarrier power amplifier (MCPA) for power generation. This latter solution seems to be simpler, but the need for high linearity—to avoid intermodulation distortion—makes the multicarrier amplifier more complex.

The modulation scheme in third-generation (WCDMA) mobile systems involves a high degree of amplitude modulation, which requires a certain amount of linearization even for single-carrier amplifiers. Notwithstanding, the high capacity and flexibility of the multicarrier amplifier makes it a logical choice for third-generation systems. The authors describe the technical challenges and Ericsson’s solution for building the MCPA for WCDMA.

[First published in Ericsson Review no. 04, 2001]