Skew compensation and tracking in communications systems
AssigneeViaSat, Inc.
InventorsYuri Zelensky, Fan Mo
Life of this patent
Estimating the term…
Abstract
Compensation for in-phase (I) and quadrature (Q) timing skew and offset in an optical signal may be achieved based on the correlation between derivatives of I and Q samples in the optical signal. The magnitude of the correlation between derivatives is measured to determine the presence of skew. Correlation between derivatives may be coupled with frequency offset information and/or with trials having additional positive and negative skew to determine presence of skew. Correlations are determined according to pre-defined time periods to provide for continued tracking and compensation for timing skew that may result from, for example, thermal drift.
Claims22
A method of skew compensation, the method comprising:
- receiving a plurality of in-phase and quadrature samples of a received optical signal;
- measuring a correlation between a derivative of the in-phase samples and a derivative of the quadrature samples, wherein measuring the correlation comprises:
- receiving frequency offset information corresponding to a difference between the frequency of the received samples and a baseband modulation frequency;
- and
- multiplying the frequency offset information by the derivative of the in-phase samples and the derivative of the quadrature samples;
- and
- generating a skew correction factor responsive to the correlation.
An apparatus for skew compensation between in-phase and quadrature channels in an optical signal, comprising:
- a skew compensation module configured to receive a plurality of in-phase and quadrature samples of a received optical signal, receive skew update information, and output skew-compensated in-phase and quadrature samples based on the skew update information;
- a skew correlation module configured to receive in-phase and quadrature samples of the received optical signal, and measure a correlation between a derivative of the in-phase samples and a derivative of the quadrature samples;
- and
- a skew update module configured to receive the measured correlation information and generate a skew correction factor responsive to the correlation,
- wherein the skew correlation module is further configured to receive frequency offset information corresponding to a difference between the frequency of the received samples and a baseband modulation frequency and measure correlation between a derivative of the in-phase samples and a derivative of the quadrature samples based on a product of the frequency offset information and the derivatives of the in-phase and quadrature samples.
A system of skew compensation, the system comprising:
- means for receiving a plurality of in-phase and quadrature samples of a received optical signal;
- means for measuring a correlation between a derivative of the in-phase samples and a derivative of the quadrature samples;
- and
- means for generating a skew correction factor responsive to the correlation,
- wherein the means for measuring a correlation comprises:
- means for receiving frequency offset information corresponding to a difference between the frequency of the received samples and a baseband modulation frequency;
- and
- means for multiplying the frequency offset information by the derivative of the in-phase samples and the derivative of the quadrature samples.
Dependencies are inferred from the claim text.