Detecting overequalization for adapting equalization and offset for data transmissions

Abstract

A method for tuning an adaptive equalizer in order to receive digital signals from a transmission medium both coarse and fine tuning methods to adaptively equalize a signal received from the transmission medium. The coarse tuning method adjusts an equalizer such that the post equalized signal starts to resemble a known data pattern, such as an MLT3 data pattern. The coarse tuning method monitors and corrects for several things: illegal transitions, over equalization, statistical data pattern anomalies and saturation conditions. Fine tuning methods operate concurrently with the coarse tuning methods and function from the point at which the coarse tuning methods stop being efficient. Additionally, the fine tuning methods hold the waveform locked in. In addition to coarse tuning and fine tuning of the equalizer, one embodiment also adjusts gain of the overall signal such that the post equalized signal is always a certain amplitude. One embodiment corrects for offsets that may get superimposed on the signal as it passes through the receive channel and which may lead to erroneous bit decisions. The method is applicable to a variety of data communication standards including 100 Base-X, FDDI and ATM-155.

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