Verification of two linearization methods, applied on asymmetrical two-way microstrip Doherty amplifier in experiment and on symmetrical two-way Doherty amplifier in simulation, is performed in this paper. The laboratory set-ups are formed to generate the baseband nonlinear linearization signals of the second-order. After being tuned in magnitude and phase in the digital domain the linearization signals modulate the second harmonics of fundamental carrier. In the first method, adequately processed signals are then inserted at the input and output of the main Doherty amplifier transistor, whereas in the second method, they are injected at the outputs of the Doherty main and auxiliary amplifier transistors. The experimental results are obtained for 64QAM digitally modulated signals. As a proof of concept, the linearization methods are also verified in simulation, for Doherty amplifier designed to work in 5G band below 6 GHz, utilizing 20 MHz LTE signal.

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This paper represents the linearization of the RF power amplifier performed by a new approach that combines two different methods exploiting the modified baseband signals. The signals for linearization in both methods are formed and processed in digital domain. The required modified baseband signals for linearization are products of the second order nonlinearity of a nonlinear system fed by the useful baseband signal. In the first method, adequate part of the modified baseband signal is adjusted in amplitude and polarity and injected at the input and output of the amplifier transistor across the series LC resonant circuit. In the second method, the appropriate modified baseband signal set on the appropriate amplitude and phase modulates the fundamental carrier second harmonic, which is then inserted at the input and output of the amplifier transistor. The effects of the combined linearization method are considered on a single stage power amplifier for quadrature amplitude modulated signals characterized with frequency spacing between spectral components up to 60 MHz for different input power levels, as well as for WCDMA digitally modulated signal.

The linearization of broadband power amplifier for application in the frequency range 0.9-1.3 GHz is considered in this paper. The amplifier is designed for LDMOSFET characterized by the maximum output power 4W designing the broadband lumped element matching circuits and matching circuits in topologies that combines LC elements and transmission lines. The linearization of the amplifier is carried out by the second harmonics of the fundamental signals injected at the input and output of the amplifier transistor. The effects of linearization are considered for the case of two sinusoidal signals separated in frequency by different intervals up to 80 MHz ranging input power levels to saturation. [Projekat Ministarstva nauke Republike Srbije, br. TR-32052]