Patent ID: 6831954
Filing Date: 2004-12-14
Classification: H03F,H04L

Abstract:
Apparatus for a sending station operable to transmit a send signal, once amplified by an amplifier, the send signal formed of successive symbols, each symbol selected from a constellation of symbols, of said apparatus for compensating for distortion introduced upon the send signal when amplified by the amplifier, said apparatus comprising:a phase rotator coupled to receive indications of the send signal prior to amplification by the amplifier, said phase rotator for selectably rotating a phase component of the send signal responsive to a characterization of an AM (amplitude modulated)-to-PM (phase modulated) response of the amplifier that defines a phase distortion characteristic of the send signal, the phase distortion characteristic responsive to an input power level of the send signal and of a substantially constant level when the input power level of the send signal is less than a first threshold; and a distortion estimator coupled to receive the indications of the send signal prior to amplification by the amplifier and to receive indications of the send signal subsequent to amplification by the amplifier, said distortion estimator for estimating an indicia of distortion of the send signal due to amplification thereof by the amplifier, the indicia of distortion at least related to a normalized, standard deviation of differences determined between values of the symbols, prior to amplification by the amplifier and subsequent to amplification by the amplifier and for providing a distortion estimate signal to said phase rotator, values of the distortion estimate signal determinative of rotation by said phase rotator of the phase component of the send signal.