Patent ID: 9735814
Date: 2017-08-15
CPC Classifications: H03F,H04B

Claim:
1. A method executed at a digital predistortion (DPD) coefficient finder of an amplifier module in a cable network, the method comprising: receiving a first signal and a second signal at the DPD coefficient finder, wherein the second signal comprises a transformation of the first signal including distortions due to channel effects and distortions due to amplifier nonlinearity, the first signal being transformed into the second signal after being passed in sequence through a pre-network circuit, an amplifier, and a post-network circuit, wherein the pre-network circuit and the post-network circuit introduce the distortions due to channel effects and the amplifier introduces the distortions due to amplifier nonlinearity; synchronizing the first signal and the second signal, wherein the synchronizing removes the channel effects of the pre-network circuit and the post-network circuit from the second signal, wherein the synchronizing comprises finding a vector w representative of a combination of the channel effects; computing a first vector representing an inverse of the nonlinearity of the amplifier based on the vector w; computing a second vector representing an inverse of the channel effects of the pre-network circuit based on the first vector; and providing DPD coefficients to a DPD actuator in the amplifier module, wherein the DPD coefficients comprise the first vector and the second vector, wherein the DPD actuator predistorts an input signal to the amplifier module with the DPD coefficients, wherein an output signal from the amplifier module retains linearity relative to the input signal, wherein the input signal comprises upstream (US) transmission of a cable modem, wherein the second signal comprises a reflection of the input signal looped back at a combiner in the cable modem into a downstream (DS) receiver path, wherein a cable modem termination system (CMTS) schedules a DS silent period during which the CMTS does not send any DS transmission to the cable modem, wherein the cable modem schedules US transmission comprising the input signal during the DS silent period and listens to the input signal during the DS silent period.