06501405 is referenced by 8 patents.

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.

Title
Method and apparatus for digital to analog conversion with distortion calibration
Application Number
9/881857
Publication Number
6501405 (B1)
Application Date
June 13, 2001
Publication Date
December 31, 2002
Inventor
Ali Al Shamma
San Jose
CA, US
Mong Yang
San Jose
CA, US
Dale Smith
Fremont
CA, US
Peter Gunadisastra
Palo Alto
CA, US
John Zhongxuan Zhang
Fremont
CA, US
Agent
IP Creators
US
Agent
Charles C Cary
US
Assignee
IKANOS Communication
CA, US
IPC
H03M 3/00
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