Ikanos Communications, Inc.

John Zhongxuan Zhang

Dale Smith

Behrooz Rezvani

Sam Heidari

Ali K Al-Shamma

Peter Gunadisastra

Mong Yang

Caesar Seehoi Wong

An apparatus and method is provided for minimizing in channel distortion in an X-DSL line driver is disclosed. The apparatus may be incorporated in an existing X-DSL architecture without additional circuitry. Out of band monitoring of a channel is implemented to adaptively minimize out of band interference and in band distortion. A unique training sequence, suitable for DMT line codes is set forth. The training sequence allows a full spectral characterization of the downstream signal space with a single upstream monitoring tone. The invention may be used with multi-channel X-DSL line drivers interfacing with any of a number of multi-channel supply architectures. The apparatus may be applied with equal advantage to communication protocols other than X-DSL. The apparatus may be applied with equal advantage in wired and wireless media.

Method and apparatus for pre-distortion of an X-DSL line driver

An apparatus and method is disclosed for minimizing in band distortion in the transmit path of an XDSL modem. The transmit path of an XDSL modem introduces various non-linearities into transmissions in both the frequency and time domains. The current invention provides a means for both determining and correcting for distortion in the time domain. In an embodiment of the invention the apparatus may include a calibrator which may be implemented using the existing analog-to-digital (ADC) conversion and demodulation capabilities on the receive path of the modem or alternately, a dedicated module. During a calibration phase a training signal is injected digitally into the digital-to-analog converter of the transmit path. The analog portion of the transmit path is coupled to a calibrator which measures the corresponding analog response. The correlation between input and response is stored in an analog model. During subsequent training and run-time phases of modem operation an oversampled digital input stream is subject to digital Delta Sigma Modulation (&Dgr;&Sgr;M) with the analog model injected into the feedback path from the quantizer. The injection of the analog model into the feedback improves the noise transfer function (NTF) associated with the &Dgr;&Sgr;M.

Method and apparatus for digital to analog conversion with distortion calibration

An apparatus and method for reducing power requirements in X-DSL and other communication protocols is disclosed. The apparatus may be applied with equal advantage in wired and wireless media Power is supplied selectively to input lines in which input signals exceed selected threshold levels. The apparatus is configured to support statistical multiplexing of the input signal lines across a plurality of amplification means which support amplification at up to either of at least two power levels. This reduces overall power requirements for the combined input lines. In an embodiment of the invention an apparatus for providing amplification of input signals on corresponding ones of a plurality of input signal lines is disclosed. The apparatus includes primary amplifiers and at least one secondary amplifier with higher output levels than the primary amplifier which can be statistical multiplexed to whichever of the input signal lines requires additional amplification. In an alternate embodiment of the invention each input signal line is coupled to a corresponding amplifier which can be statistically multiplexed to a power supplies of varying output levels depending on the amplification requirements of each of the input signal lines.

Method and apparatus for multi-channel X-DSL line driver

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Fremont, CA, United States of America

John Zhongxuan Zhang