Patent ID: 7471739
Filing Date: 2008-12-30
Classification: H04L

Abstract:
1. 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 output signal and an observed amplifier output, a method of generating a digital error signal that accurately represents said difference, comprising: in a forward path, adaptively processing the digital input transmission signal in response to the digital error signal to generate a predistorted signal that complements non-linearities resulting from the amplification process, wherein power in the digital error signal is minimized; in the forward path, converting the predistorted signal to analog form to produce an analog predistorted signal, which is related to a signal that is amplified by the amplification process; in a return path, down-converting a radio frequency (RF) signal that represents an actual output of the power amplifier system to generate a feedback signal; in a side path separate from the forward path, delaying the digital input transmission signal to provide the desired output signal such that an analog delayed signal is substantially time aligned with the feedback signal; in the side path, converting the desired output signal to analog form to produce the 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; and using the analog-to-digital converter to convert the scaled error signal to digital form to produce the digital error signal.