Linearisation of asymmetrical Doherty amplifier by the even-order non-linear signals

ABSTRACT

This paper considers the linearisation of an asymmetrical two-way Doherty amplifier by the method that uses the second harmonics and fourth-order non-linear signals for linearisation. These even-order signals for linearisation are extracted at the output of the peaking amplifier, adjusted in amplitude and phase and injected at the input and output of the carrier amplifier transistor in the Doherty configuration. The effect of linearisation has been experimentally confirmed on a fabricated asymmetrical Doherty amplifier with the additional circuit for linearisation. The suppression of the third-order intermodulation products has been carried out for two-tone test, 64QAM and WCDMA digitally modulated signals in a range of signal power.

KEYWORDS:

• Doherty amplifier
• linearisation
• second harmonics
• fourth-order non-linear signals
• intermodulation products

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was partially supported by German Academic Exchange Service-DAAD fund and Ministry of Education, Science and Technological development of Republic of Serbia within a bilateral programme between Germany and Serbia, the project name ‘Development of linearisation technique for broadband and/or dual band power amplifiers in terrestrial microwave links’, and by the Ministry of Education, Science and Technological development of Republic of Serbia [project number TR-32052].