Method and apparatus for tracking the magnitude of channel induced distortion to a transmitted signal

The present invention relates to a receiver for an amplitude modulated signal and more particularly to tracking the amplitude of an incoming signal and recovering the desired signal (amplitude) from distortion imposed by the transmission channel by reconstructing the channel-induced amplitude distortion. Channel induced distortion is cancelled from a QAM or similarly modulated signal that has both a signal component and a distortion component. Using digital signal processing, the information component of the received signal is removed by canceling magnitude variations arising from the information content. This is accomplished by normalizing the received signal to the magnitude value of one ring on the QAM constellation. Once the distortion component of the received signal is reconstructed, a compensation factor can be derived and applied to the received signal in order to remove the effects of the channel distortion prior to further processing and decoding of the received signal. Applications include radio communications including cellular telephones and two way radio, as well as wire-based communications in which the transmission channel induces distortion to the signal