Adaptive linearization of a feedforward amplifier by complex gain stabilization of the error amplifier

A feedforward amplifier for amplifying an input signal in order to produce an amplified signal, comprising:

• a main amplifier circuit having an input responsive to the input signal and an amplified signal delivering output connected to feedforward amplifier output;
• a signal-comparing circuit having a first input responsive to the input signal, a second input responsive to the amplified signal on the output of the main amplifier circuit, and an error signal delivering output, said error signal being representative of a comparison between the input signal and the amplified signal and of distortion in the amplified signal;
• an adaptive linearization circuit comprising:
• a controllable signal feature-adjusting circuit having an input responsive to the error signal and a feature-adjusted error signal delivering output;
• and
• a comparator/controller circuit having a first input responsive to the error signal, a second input responsive to the feature-adjusted error signal, and a control output connected to the controllable signal feature-adjusting circuit so that, in operation, the signal feature-adjusting circuit is controlled in relation to a comparison between the error signal and the feature-adjusted error signal;
• and
• a coupling member between the output of the signal feature-adjusting circuit and the feedforward amplifier output, wherein, in operation, the coupling member combines the feature-adjusted error signal with the amplified signal in order to substantially cancel distortion in the amplified output signal.

A method for adaptively linearizing a feedforward amplifier which, in operation, supplies an amplified output signal on a feedforward amplifier output and produces an error signal representative of distortion in the amplified output signal, said adaptive linearization method comprising:

• controllably adjusting at least one feature of the error signal;
• and
• controlling the error signal feature adjusting in relation to the error signal and the feature-adjusted error signal;
• whereby the feature-adjusted error signal, when combined with the amplified output signal, substantially cancels distortion in said amplified output signal.

An adaptive linearization circuit for a feedforward power amplifier which, in operation, supplies an amplified output signal on a feedforward amplifier output and produces an error signal representative of distortion in the amplified output signal, said adaptive linearization circuit comprising:

• a controllable signal feature-adjusting circuit responsive to the error signal for producing a feature-adjusted error signal;
• and
• a comparator/controller circuit for comparing the error signal and the feature-adjusted error signal, and for controlling the signal feature-adjusting circuit in relation to the comparison between the error signal and the feature-adjusted error signal;
• whereby, in operation, the controllable signal feature-adjusting circuit supplies a feature-adjusted error signal which, when combined with the amplified output signal, substantially cancels distortion in said amplified output signal.

A feedforward amplifier for amplifying an input signal in order to produce an amplified output signal, comprising:

• a main amplifier circuit responsive to the input signal for producing the amplified output signal supplied on a feedforward amplifier output;
• a signal comparator circuit responsive to the input signal and the amplified output signal for comparing the input signal and the amplified output signal and, as a result of said comparison, supplying an error signal representative of distortion in the amplified output signal;
• an adaptive linearization circuit comprising:
• a controllable signal feature-adjusting circuit responsive to the error signal for producing a feature-adjusted error signal;
• and
• a comparator/controller circuit for comparing the error signal and the feature-adjusted error signal, and for controlling the signal feature-adjusting circuit in relation to the comparison between the error signal and the feature-adjusted error signal;
• and
• a coupling member for transmitting the feature-adjusted error signal to the feedforward amplifier output in order to combine the feature-adjusted error signal and the amplified output signal in order to substantially cancel distortion in the amplified output signal.