CMOS high bandwidth envelope tracking and power amplifiers for LTE carrier aggregation

The demand for higher data rated has lead to the utilization of both higher frequency bands, where power amplifiers (Pas) are inherently less linear, as well as carrier aggregation (CA) where linearity requirements are more stringent. In addition, cost reducing tactics for large volume applications naturally lead to CMOS based PAs which are less linear than the commonly used GaAs PAs. Envelope tracking techniques, together with digital signal processing (DSP), provide a method for achieving the linearity and efficiency required for CMOS PAs. This paper reviews the new technical challenges associated with envelope tracking methods for high data rate PAs utilized in carrier agg regation systems.