Linearization of broadband Doherty amplifier by baseband signal that modulates second harmonic

The linearization approach that exploits the modified baseband signal is applied in this paper to linearize a two-way broadband Doherty power amplifier. The required linearization signal formed as a product of the second-order nonlinearity of a nonlinear system is adequately processed in amplitude and phase in the digital domain. Then, the fundamental carrier second harmonic is modulated by the tuned baseband signal and injected to the input and output of the carrier amplifier transistor in the Doherty configuration. The assessment of the linearization technique effects is considered on a two-way Doherty amplifier for quadrature amplitude modulated signals characterized with frequency spacing between spectral components up to 30 MHz for different input power levels. Additionally, impact of the linearization method is tested on the WCDMA digitally modulated signal.