Radio frequency power amplifier system and method of linearizing an output signal thereof

A method of linearization of an output signal of a radio frequency power amplifier system, the system including:

• a first and a second input port arranged to receive a first and a second input signal respectively;
• a main amplifier having an input and an output;
• a first and a second auxiliary amplifier having respective inputs and outputs;
• an internal load connected to the output of the first auxiliary amplifier;
• a feedback network arranged to linearize the first input signal and having an input end connected to the output of the first auxiliary amplifier and an output end connected to the input of the first auxiliary amplifier;
• and,
• a feedforward amplifier having an input and an output;
• wherein:
• the inputs of the main amplifier and the auxiliary amplifiers are interconnected with the first input port at a common input node;
• the output of the second auxiliary amplifier and the second input port are interconnected with the input of the feedforward amplifier at a common node;
• the outputs of the feedforward amplifier and the main amplifier are interconnected at a common output node;
• and wherein;
• the main amplifier is a replica of the first and second auxiliary amplifiers with an increased gain;
• and, the second auxiliary amplifier is a replica of the first auxiliary amplifier;
• the ratio of the second input signal over the first input signal input is the same as the ratio of the gain provided by the second auxiliary amplifier over the gain provided by the first auxiliary amplifier;
• the method comprising:
• obtaining the deviation from an ideal response on the first auxiliary amplifier by means of the feedback network;
• isolating said deviation by removing the second input signal from the output of the second auxiliary amplifier;
• amplifying the isolated deviation by means of the feedforward amplifier;
• and
• adding said amplified deviation to the output of the main amplifier,