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US 10,764,078 B2Granted
Digital predistortion for a frequency-selective channel
AssigneeMaxLinear, Inc.
InventorsMario Milicevic, Ioannis Spyropoulos
Life of this patent
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Abstract
A transmitter is configured to generate a DOCSIS signal for transmission onto a frequency-selective coaxial cable. The transmitter comprises a first reverse tilt filter circuit, a digital predistortion circuit, a forward tilt filter, a wideband equalizer, a second reverse tilt filter, and a power amplifier. The responses of the tilt filters may be set based on the frequency response of the frequency-selective coaxial cable to which the transmitter is intended to be coupled. The predistortion circuit may compensate for distortion introduced by circuitry of the transmitter. The equalizer circuit may be operable to compensate for undesired linear response of other circuitry of the transmitter.
Claims18
A system comprising:
- a transmitter configured to generate a Data-Over-Cable Service Interface Specification (DOCSIS) signal for transmission onto a frequency-selective coaxial cable, wherein the transmitter comprises:
- a first reverse tilt filter circuit 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;
- a digital predistortion circuit that is downstream from the first reverse tilt filter circuit and operable to distort the reverse-tilted signal input to the digital predistortion circuit to compensate for distortion introduced by the transmitter;
- a forward tilt filter circuit that is downstream from the digital predistortion circuit and is operable to filter a signal input to the forward tilt filter circuit to increase strength of lower-frequency components of the signal input to the forward tilt filter circuit and/or decrease strength of higher-frequency components of the signal input to the forward tilt filter circuit;
- an equalizer circuit that is downstream from the forward tilt filter circuit and operable to compensate for undesired linear response introduced by the transmitter;
- a digital-to-analog converter that is downstream from the equalizer circuit;
- a second reverse tilt filter circuit that is downstream from the digital-to-analog converter and is operable to filter 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
- a power amplifier that is downstream from the second reverse tilt filter circuit and operable to amplify a signal tilted by the second reverse tilt filter circuit for output onto the coaxial cable.
8 more elements
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 from the first reverse tilt filter circuit to compensate for distortion introduced by the transmitter;
- filtering, by the forward tilt filter circuit, a signal input to the forward tilt filter circuit from the digital predistortion circuit to increase strength of lower-frequency components of the signal input to the forward tilt filter circuit and/or decrease strength of higher-frequency components of the signal input to the forward tilt filter circuit;
- equalizing, by the equalizer circuit from the forward tilt filter 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 from the equalizer circuit to an analog signal;
- filtering, by the second reverse tilt filter circuit, a signal input to the second reverse tilt filter circuit from the digital-to-analog converter 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 tilted by the second reverse tilt filter circuit for output onto a coaxial cable.
7 more elements
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 second 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.
4 more elements
Dependencies are inferred from the claim text.