Method and device for compensating bandwidth mismatches of time interleaved analog to digital converters

Patent metadata

Field	Value
Publication number	US-9608653-B2
Application number	US-201415039184-A
Country	US
Kind code	B2
Filing date	Nov 21, 2014
Priority date	Dec 4, 2013
Publication date	Mar 28, 2017
Grant date	Mar 28, 2017

Abstract

A device can be used for compensating bandwidth mismatches of time interleaved analog to digital converters. A processor of the device determines, for each original sample stream, an estimated difference between the time constant of a low pass filter representative of the corresponding converter and a reference time constant of a reference low pass filter, and uses this estimated difference and a filtered stream to correct the original stream and deliver a corrected stream of corrected samples.

First claim

The invention claimed is:

1. A method of direct compensation of bandwidth mismatch, the method comprising:
receiving M original trains of M original samples from of M time-interleaved converters, M being greater than two, each converter being considered in the first order as comprising a first order low-pass filter;
digitally filtering the M original trains delivering M corresponding filtered trains of filtered samples, the filtering having a transfer function substantially equal to the product of a transfer function of a reference low-pass filter and a transfer function of a derivative filter multiplied by a reference time constant of the reference low-pass filter; and
for each original train of original samples,
performing an estimation process to deliver an estimated difference between the time constant of the first order low-pass filter associated with the corresponding converter and the reference time constant, the estimation process comprising a first generation of a first item of differentiated power information relative to the original train and a second generation of a second item of information of differentiated power relative to at least one of the M filtered trains, and
performing a correction process of the original samples of the original train using the filtered samples of the corresponding filtered train and the corresponding estimated difference, in such a way as to deliver a corrected train of corrected samples.

2. The method according to claim 1 , wherein the M corrected trains are considered as coming from the corresponding M converters, the first order low-pass filters of which all have the reference time constant as their time constant.

3. The method according to claim 1 , wherein digitally filtering the M original trains comprises filtering each original train of original samples by a filter having a transfer function of that is substantially equal to jωτref/(1+jωτref), where τref denotes the time constant of the first order reference low-pass filter.

4. The method according to claim 1 , wherein the first generation comprises a first filtering of the corresponding original train with a first filter any determination of a first indication of power of the original train filtered by this first filter, and a second filtering of the corresponding original train with a second filter, which is different from the first filter, and a determination of a second indication of power of the original train filtered by this second filter, the first differentiated power information comprising the first and second power indications.

5. The method according to claim 4 , wherein the second generation comprises a third filtering of the at least one of the M trains filtered with the first filter and a determination of a third indication of power of the at least one of the M filtered trains filtered by this first filter, and a fourth filtering of the at least one of the M trains filtered with the second filter and a determination of a fourth indication of power of the at least one of the M filtered trains filtered by this second filter, the second differentiated power information comprising the third and fourth power indications.

6. The method according to claim 5 , wherein the estimation process further comprises a determination of a first averaged power indication obtained by an average of the M first power indications and a determination of a second averaged power indication obtained by average of the M second power indications, and the estimated difference is obtained for the corresponding original train from the first corresponding power indication, from the second corresponding power indication, from the third power indication, from the fourth power indication, from the first averaged power indication and from the second averaged power indication.

7. The method according to claim 1 , wherein the correction process comprises, for each original train, an addition to each original sample of the product of the homologous filtered sample of the filtered train corresponding to this original train and the corresponding estimated difference.

8. A device for direct compensation of bandwidth mismatch of M time-interleaved converters, M being greater than two, each converter being considered in the first order as comprising a first order low-pass filter, the device comprising:
an input to receive M original trains of original samples respectively coming from the M converters;
an output to deliver M corrected trains of corrected samples;
a processor comprising:
a digital filter configured to carry out a filtering process on the M original trains in such a way as to deliver M corresponding filtered trains of filtered samples, the filter having a transfer function substantially equal to the product of a transfer function of a reference low-pass filter and a transfer function of a derivative filter multiplied by a reference time constant of the reference low-pass filter;
an estimator configured to carry out an estimation process delivering, for each original train, an estimated difference between a time constant of the first order low-pass filter associated with the corresponding converter and the reference time constant, and comprising a first generation of a first item of differentiated power information relative to each original train and a second generation of a second item of differentiated power information relative to at least one of the M filtered trains; and
a correction circuit configured to carry out a process of correction of the original samples of each original train using the filtered samples of the corresponding filtered trains and the corresponding estimated difference, in such a way as to deliver a corresponding corrected train of corrected samples.

9. The device according to claim 8 , wherein the M corrected trains are considered as having come from the corresponding M converters, the first order low-pass filters of which all have the reference time constant as their time constant.

10. The device according to claim 8 , wherein the filter comprises a filter whose transfer function is substantially equal to jωτref/(1+jωτref), where τref denotes the time constant of the reference first order low-pass filter.

11. The device according to claim 10 , wherein the filter comprises a finite impulse response filter.

12. The device according to claim 8 , wherein the estimator comprises:
a first stage comprising a first filter intended to filter the corresponding original train and a first module configured to determine a first power indication of the original train filtered by the first filter, and a second filter, different from the first filter, intended to filter the corresponding original train and a second module configured to determine a second power indication of the original train filtered by the second filter, the first differentiated power information comprising the first and second power indications; and
a second stage comprising the first filter intended to filter the at least one of the M filtered trains and a third module configured to determine a third power indication of the at least one of the M filtered trains filtered by the first filter, and the second filter intended to filter the at least one of the M filtered trains and a fourth module configured to determine a fourth power indication of the at least one of the M filtered trains filtered by this second filter, the second differentiated power information comprising the third and fourth power indications.

13. The device according to claim 12 , wherein the estimator comprises a third stage configured to determine a first averaged power indication obtained by an average of the M first power

Assignees

• St Microelectronics Sa
• St Microelectronics Sa

Inventors

• Le Dortz Nicolas
• Simon Thierry
• Urard Pascal
• Lelandais-Perrault Caroline
• Parida Rakhel Kumar

Classifications

• H03M1/1215

  using time-division multiplexing · CPC title

• H03M1/0626

  by filtering · CPC title

• H03M1/1245

  Details of sampling arrangements or methods · CPC title

• H03M1/0617 Primary

  characterised by the use of methods or means not specific to a particular type of detrimental influence · CPC title

• H03M1/0614 Primary

  of harmonic distortion (H03M1/0617 takes precedence) · CPC title