Adaptive frequency domain equalizer circuits, systems, and methods for discrete multitone based digital subscriber line modem

摘要

A method of modem communications between first and second modems (10, 20k) over a communications facility (TWP). The method operates the first modem (20_k) to issue communications to the second modem (10) over the communications facility. These communications comprise a plurality of subchannel signals (n). The method also operates the second modem to perform various steps. In one of these steps, the second modem converts (33) the communications from time domain communications to frequency domain communications, where the frequency domain communications signals comprise a plurality of subchannel signals. Each of these plurality of subchannel signals comprises an amplitude portion and a phase portion. In another of these steps, the second modem equalizes (36) the amplitude portion of each of the plurality of subchannel signals using fixed gain factors (GE(n))corresponding to each of the plurality of subchannel signals. In still another of these steps, the second modem equalizes (37) the phase portion of each of the plurality of subchannel signals using adjustable phase factors (PE(n)) corresponding to each of the plurality of subchannel signals. The adjustable phase factors are adjusted in response to previous communications from the first modem to the second modem.