Patent ID: 8675714

Claim:
A trace canceller for canceling distortions on a transmission line comprising: an equalizer input connected to a far end of a first segment of a transmission line driven at a near end by a transmitter; a trace-canceller output connected to a near end of a second segment of the transmission line connected at a far end to a receiver; an equalizer connected to the equalizer input and having a trace-length control input for adjusting a degree of compensation performed by the equalizer to compensate for the first segment of the transmission line to generate an equalized signal; a variable gain amplifier, receiving the equalized signal from the equalizer, for amplifying the equalized signal by a gain determined by a variable-gain input to the variable gain amplifier to generate an amplified signal; an output buffer, receiving the amplified signal from the variable gain amplifier, for generating an output signal on the trace-canceller output; and an automatic gain control circuit, connected to the equalizer input and to the trace-canceller output, for comparing low-frequency voltage swings of the trace-canceller output to low-frequency voltage swings of the equalizer input to generate the variable-gain input to the variable gain amplifier, wherein the gain of the variable gain amplifier is adjusted by the automatic gain control circuit to prevent saturating voltage swings of the amplified signal and prevent the output buffer from clipping voltage peaks of the output signal.