Doherty amplifier with envelope tracking for high efficiency

A Doherty amplifier assisted by a supply modulator is presented using 2.14 GHz GaN HEMT saturated power amplifier (PA). A novel envelope shaping method is applied for high power-added efficiency (PAE) over a broad output power range. Experimental comparison with the Doherty and saturated PAs with the supply modulator is carried out. For the 8 dB crest factor WCDMA 1FA signal, the Doherty PA supported by the modulator presents the improved PAE over the broad output power region compared to the standalone Doherty PA. In addition, it achieves better PAE than the saturated PA with the supply modulator due to the lower crest factor envelope signal applied to the Doherty PA. At the maximum average output power, back-off by 8 dB from the peak power, the Doherty amplifier employing bias adaptation shows the PAE of 50.9%, while the comparable saturated PA with supply modulator and standalone saturated Doherty amplifier and saturated PA provide the PAEs of 42.3%, 49.7%, and 35.0%, respectively.