A Broadband Doherty Power Amplifier Using Class B/J Continuum

Abstract

This brief presents implementation of a broadband Doherty power amplifier with enhanced performance in terms of bandwidth and efficiency. The bandwidth enhancement is achieved by incorporating continuous class B/J mode in designing main power amplifier of the architecture. A novel broadband combiner has been proposed in this paper. It takes care of the non-infinite impedance of the auxiliary power amplifier such that the back-off load trajectory of main power amplifier matches with that of class B/J continuum. The proposed theory is validated with a 20W Doherty power amplifier designed at 1.725 GHz. The measured results show that the circuit gives 45%-53% drain efficiency around 6-7 dB back-off, where, around 55% fractional bandwidth is achieved. The circuit also qualifies the spectral mask when characterized with a single carrier 5 MHz modulated signal.