Tetsuo Hirota

Highly efficient feed-forward amplifier using a Class-F Doherty amplifier

A new feed-forward amplifier configuration is proposed that uses a Doherty amplifier with Class-F operation as the main amplifier. Due to the new configuration, the enhanced main amplifier operates well with less output back-off and achieves high efficiency under Class-F operation compared with Class-B amplifier (non Doherty amplifier). A 2-GHz band 1-W class feed-forward amplifier is investigated. A back-off improvement of 3 dB is experimentally achieved compared with a conventional feed-forward amplifier for the same intermodulation distortion level. The efficiency of the main amplifier is also improved from 33% to 52% when third-order intermodulation distortion of feed-forward amplifier is - 50 dB. The proposed technique can effectively reduce the power consumption of the power amplifiers for cellular base stations.