Bandwidth reduction techniques for the Supply Modulated RFPAs (ET) usable for wideband- and multicarrier signals.

The demand for higher signal bandwidths in the next generation transmitters challenges the efficiency of the drain modulator in ET PAs. A simple, but powerful technique has been developed reducing the required bandwidth of the drain modulator. The technique is called Power Envelope Tracking (PET). PET and 2nd order PET are used to shape the drain voltage, resulting in a significant reduction of the required bandwidth of the drain supply compared to classical ET. The bandwidth is well defined and have a clear “cut-off”. Other significant properties are inherent detroffing of the drain voltage for both PET and 2nd order PET. The 2nd order PET also has an inherent soft shape for high drain voltages. In multicarrier scenarios the envelope bandwidths can be extreme, witch makes supply modulation impossible. A new method have recently been published using the sum-of-envelopes instead of the envelope of signals.