The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 08, 2005
Filed:
Jun. 06, 2001
Behrooz Rezvani, Pleasanton, CA (US);
Sam Heidari, Menlo Park, CA (US);
Dale Smith, Fremont, CA (US);
Behrooz Rezvani, Pleasanton, CA (US);
Sam Heidari, Menlo Park, CA (US);
Dale Smith, Fremont, CA (US);
Ikanos Communication, Inc., Fremont, CA (US);
Abstract
An apparatus and method is provided for minimizing frequency distortion in the transmit path of an XDSL modem implementing digital multi-tone (DMT) line code. The current invention provides a means for both determining and correcting for distortion in the frequency domain. The apparatus may be incorporated in an existing X-DSL architecture without additional circuitry. In an embodiment of the invention the apparatus may include a calibration phase which may be implemented using the existing analog-to-digital (ADC) conversion and demodulation capabilities on the receive path of the modem. This calibration phase takes place before the training phase associated with establishing communications with a remote site. During the calibration phase a calibration sequence with known spectral characteristics in the frequency domain is injected digitally at the beginning of the transmit path into each of the tone bins of the inverse Fourier Transform engine (IFFT). The receive path is configured to receive feedback of a resultant analog output signal from the transmit path. A frequency analyzer is used to determine the spectral properties of the feedback from the analog output signal and a normalizer is used to compute a local gain table with gain factors for each tone bin which effect the required normalization.