Digital predistortion for a frequency-selective channel

A method comprising:

• in a Data-Over-Cable Service Interface Specification (DOCSIS) transmitter comprising a first reverse tilt filter circuit, a digital predistortion circuit downstream from the first reverse tilt filter circuit, a forward tilt filter circuit downstream from the digital predistortion circuit, an equalizer circuit downstream from the forward tilt filter circuit, a digital-to-analog converter circuit downstream from the equalizer circuit, a second reverse tilt filter circuit downstream from the digital-to-analog converter circuit, and a power amplifier downstream from the second reverse tilt filter circuit:
• receiving, by the first reverse tilt filter circuit, a first signal occupying a band of frequencies;
• filtering, by the first reverse tilt filter circuit, the first signal to decrease strength of lower-frequency components of the first signal and/or increase strength of higher-frequency components of the first signal.
• distorting, by the digital predistortion circuit, a signal input to the digital predistortion circuit to compensate for distortion introduced by circuitry of the transmitter;
• filtering, by the forward tilt filter, a signal input to the forward tilt filter to increase strength of lower-frequency components of the signal input to the forward tilt filter and/or decrease strength of higher-frequency components of the signal input to the forward tilt filter;
• equalizing, by the equalizer circuit, a signal input to the equalizer circuit;
• converting, by the digital-to-analog converter circuit, a digital signal input to the digital-to-analog converter circuit to an analog signal;
• filtering, by the second reverse tilt filter circuit, a signal input to the second reverse tilt filter circuit to decrease strength of lower-frequency components of the signal input to the second reverse tilt filter circuit and/or increase strength of higher-frequency components of the signal input to the second reverse tilt filter circuit;
• and
• amplifying, by the power amplifier, a signal for output onto a coaxial cable.

A system comprising:

• a transmitter circuit comprising a first reverse tilt filter circuit, a digital predistortion circuit, and a forward tilt filter circuit, wherein:
• the first reverse tilt filter circuit is operable to:
• receive a first signal occupying a band of frequencies;
• and
• generate a reverse-tilted signal by filtering of the first signal to decrease strength of lower-frequency components of the first signal and/or increase strength of higher-frequency components of the first signal.
• the digital predistortion circuit is operable to generate a pre-distorted, reverse-tilted signal by distortion of the reverse-tilted signal;
• and
• the forward tilt filter circuit is operable to generate a third signal by filtering of the pre-distorted, reverse-tilted signal to increase strength of lower-frequency components of the pre-distorted, reverse-tilted signal and/or decrease strength of higher-frequency components of the pre-distorted, reverse-tilted signal.