Patent ID: 6973138

Claim:
In a power amplifier system in which a digital input transmission signal is adaptively predistorted to compensate for non-linearities in an amplification process based on a difference between a desired and an observed amplifier output, a method of generating a digital error signal that accurately represents said difference, comprising: adaptively processing the digital input transmission signal at least partially in response to the digital error signal to generate a first modified signal that complements non-linearities resulting from the amplification process; converting the first modified signal to analog form to produce an analog modified signal which is related to a signal that is amplified by the amplification process; down-converting a radio frequency (RF) signal that represents an actual output of the amplifier system to generate a feedback signal; processing the digital input transmission signal to providing the desired output signal; converting the desired output signal to analog form to produce an analog delayed signal; taking a difference between the feedback signal and the analog delayed signal to generate an analog error signal; scaling the analog error signal to produce a scaled error signal that substantially corresponds to a range of an analog-to-digital converter; using the analog-to-digital converter to convert the scaled error signal to digital form to produce the digital error signal; and wherein processing the digital transmission signal to provide the desired output signal further comprising adaptively adjusting the processing to reduce a magnitude of the analog error signal.