On the Spectral Regrowth in Polar Transmitters

The envelope elimination and restoration (EER) or so called polar transmission concept proposes significant power efficiency increase for the power amplifier (PA). Up to now no products or prototypes have been published, which are able to handle complex and wideband modulation standards like WCDMA, and concurrently fulfill the spectrum emission mask completely. This paper shows the background, why polar modulation causes spectral regrowth, and why it is not possible to overcome this by simple filtering.