A linear assisted switching envelope amplifier for an UHF polar transmitter

Spectrally efficient wireless communication standards impose stringent linearity specifications, which would require traditional IQ transmitters to operate with back-offed and power inefficient linear RF power amplifiers (PAs). In order to overcome such a significant limitation, alternative architectures have been proposed, as those based on the Envelope Elimination and Restoration (EER) technique. In this paper, a UHF polar transmitter is presented, combining switching and linear stages in the envelope amplifier as to achieve both great bandwidth and high efficiency, when drain modulating a GaN HEMT Class E RF PA. Several tests, using EDGE, TETRA, and WCDMA standards have been performed with good results.