| 摘要 |
An adaptive equalization filter system and method [including a controllable equalization filter] which filters a signal received over a transmission link in response to feedback indicative of channel characteristics. The system uses closed loop feedback to control [the] an equalization filter to achieve cancellation of each pole of the channel transfer function with a zero of the equalization filter, by moving the zero of the filter in response to feedback indicative of the difference in transmission delay between received and equalized high and low frequency signals (e.g., high and low transition density portions of a received and equalized data signal, or received and equalized high and low frequency clocks transmitted over the channel in parallel with a data signal) until the feedback indicates equal delays for the two equalized signals. In some embodiments, phase comparison is performed on clocks recovered from high and low transition density portions of a received and equalized data signal. Preferred embodiments operate in a selected one of an amplitude based equalization mode (in which feedback is indicative of detected amplitudes of transitions in a signal received over the channel and then equalized) and a delay based equalization mode in which feedback results from phase comparison between received and equalized high and low frequency signals. Preferably, a state machine causes the system to operate initially in the amplitude based equalization mode to tune the equalization filter coarsely, and then in the delay based equalization mode (to fine tune the filter). [Other embodiments are adaptive equalization methods implemented by embodiments of the system.
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