Method and apparatus for reducing distortion in an output signal of an amplifier

A method for reducing distortion contained in an output signal of an amplifier circuit, the method comprising the steps of:

• a) modulating an input signal of the amplifier circuit with a reference modulation to produce a modulated signal;
• b) amplifying the modulated signal to produce an amplified modulated signal;
• c) determining the reference modulation contained in the amplified modulated signal to produce a determined modulation;
• d) adjusting a characteristic of the determined modulation in response to a control signal to produce an adjusted modulation;
• e) combining the adjusted modulation with the amplified modulated signal to produce a corrected signal;
• f) demodulating the corrected signal to recover residual modulation contained therein to produce recovered residual modulation;
• and
• g) adjusting the control signal based on the recovered residual modulation, such that the residual modulation is reduced in the corrected signal.

A feed forward amplifier network comprising:

• an amplifier circuit having an input responsive to an input signal and an output producing an output signal;
• a first coupler sampling the input signal to produce a sampled input signal;
• a second coupler sampling the output signal to produce a sampled output signal;
• a modulation device coupled to the input of the amplifier circuit, said modulation device modulating the input signal with a reference modulation;
• a combination circuit responsive to the sampled output signal, and the sampled input signal and producing a determined modulation by subtracting the sampled input signal from the sampled output signal;
• means for reducing distortion contained in the output signal of the amplifier circuit based on the determined modulation;
• and
• an envelope detector responsive to the output signal.

A feed forward amplifier network comprising:

• an amplifier circuit;
• a modulator, coupled to an input of the amplifier circuit, that modulates an input signal of the amplifier circuit with a reference modulation;
• a modulation determination circuit, coupled to an output of the amplifier circuit, that determines the reference modulation contained in an output signal of the amplifier circuit to produce a determined modulation;
• an adjustment circuit, coupled to the modulation determination circuit and the output of the amplifier circuit, that adjusts a characteristic of the determined modulation in response to a control signal to produce an adjusted modulation, and combines the adjusted modulation with the output signal of the amplifier circuit to produce a corrected signal;
• and
• a residual modulation detection circuit, coupled to the output of the amplifier circuit and the adjustment circuit, that recovers residual modulation contained in the corrected signal and produces the control signal based on the residual modulation.

A feed forward amplifier network comprising:

• an amplifier circuit;
• a reference signal generator that generates a reference signal;
• an input signal characteristic adjuster, coupled to the reference signal generator and an input of the amplifier circuit, that modulates an input signal of the amplifier circuit with a reference modulation based on the reference signal;
• a modulation determination circuit, coupled to an output of the amplifier circuit, that determines the reference modulation contained in an output signal of the amplifier circuit to produce a determined modulation;
• an adjustment circuit, coupled to the modulation determination circuit and the output of the amplifier circuit, that adjusts a characteristic of the determined modulation in response to a control signal to produce an adjusted modulation;
• a first coupler, coupled to an output of the adjustment circuit and the output of the amplifier circuit, that combines the adjusted modulation with the output signal of the amplifier circuit to produce a corrected signal;
• a second coupler, coupled to the output of the amplifier circuit, that samples the corrected signal to produce a sampled corrected signal;
• an amplitude detector, coupled to the second coupler, that detects an amplitude of residual modulation contained in the sampled corrected signal to produce a recovered residual modulation;
• and a reference signal receiver, coupled to an output of the amplitude detector and the adjustment circuit, that produces the control signal based on the recovered residual modulation.