Method and a system for estimating errors introduced in a time-interleaved analog-to-digital converter system

• US 8,307,248 B2
• Filed: 06/30/2006
• Issued: 11/06/2012
• Est. Priority Date: 06/30/2006
• Status: Active Grant

• Current Assignee: Teledyne Signal Processing Devices Sweden AB (Teledyne Technologies Incorporated)
• Original Assignee: Signal Processing Devices Sweden AB (Teledyne Technologies Incorporated)
• Inventors: Johansson, Håkan, Löwenborg, Per
• Primary Examiner(s): Kerveros, James C
• Application Number:
  US12/306,942
• Publication Number:
  US 20100049483A1
• Time in Patent Office: 2,321 Days
• Field of Search: 714/704
• US Class Current: 714/704
• CPC Class Codes: H03M 1/1009 Calibration
• CPC Class Codes: H03M 1/1215 using time-division multiplexing

Abstract

A method and a module for estimating a plurality of relative channel-error for at least one signal with respect to a reference signal. The signals and are produced by an analog-to-digital module including parallel and time interleaved analog-to-digital converters and are received by an estimation module. The method is performed by the estimation module and includes defining a function representing a relationship between the reference signal and an arbitrary signal in the group of signals, selecting a first reference signal in the group of signals, selecting a second signal from the remaining signals in the group, optimizing the function so as to obtain an estimate of the plurality of relative channel-error, and repeating the selecting a second signal and optimizing the function for each remaining signal.

Claims

1. A method for estimating a plurality of relative channel-errors for at least one signal with respect to a reference signal belonging to a group of digitized signals received by an estimation module;

wherein said method is performed by said estimation module, the method comprising;

defining a loss function representing a difference between said reference signal and a remaining signal in said group of digitized signals, wherein said group of digitized signals are produced by an analog-to-digital module comprising a plurality of parallel and time interleaved analog-to-digital converters, each converter producing a respective one of said group of digitized signals;

selecting the reference signal in said group of digitized signals;

selecting the remaining signal from the remaining signals in said group of digitized signals; and

minimizing the loss function to thereby obtain an estimate or a representation of an estimate of said plurality of relative channel-errors for the selected remaining signal.

2. The method according to claim 1, wherein the optimizing is performed by an iterative process comprising:

feedback of the channel-error or channel-errors estimated in the previous iteration so as to adjust the channel-error in the sequence of the second signal;

updating the function with a sequence of the second signal having channel-errors adjusted by said feedback; and

repeating said feedback and said update until a satisfactory estimation is obtained.

3. The method according to claim 1, wherein said plurality of estimated channel-errors is calculated by defining said function as a measure of the difference between said sequences with respect to said plurality of channel-errors, and by performing an optimization by minimizing the defined function.

4. The method according to claim 2, wherein at least one of the estimated channel-errors is an estimated delay corresponding to a delay mismatch, which estimated delay is applied to the selected signal using a fractional delay filter.

5. The method according to claim 4, wherein said fractional delay filter is implemented using a Lagrange, Farrow Structure or Thiran Allpass.

6. The method according to claim 1, wherein the loss function is defined as

7. The method according to claim 1, further comprising:

repeating said further steps for each one of the other remaining signals.

8. The method according to claim 1, wherein the loss-function comprises a sum of squared values of differences between the reference signal and the selected remaining signal, or comprises a sum of absolute values of differences between the reference signal and the selected remaining signal.

9. The method according to claim 1, wherein the estimates of the channel-errors are obtained by minimizing the loss function

10. The method according to claim 1, wherein said relative channel-errors for the selected remaining signal belong to the group of aperture delay mismatch error, gain mismatch error and offset mismatch error.

11. An estimation module for estimating a plurality of relative channel-errors or a representation thereof for at least one signal with respect to a reference signal belonging to a group of digitized signals, where said estimation module is configured to operatively receive said digitized signals and to operatively select the reference signal in said group of signals, and wherein the estimation module is further configured to operatively:

select a remaining signal from the remaining signals in said group of digitized signals, wherein said group of digitized signals are produced by an analog-to-digital module comprising a plurality of parallel and time interleaved analog-to-digital converters, each converter producing a respective one of said group of digitized signals; and

minimize a loss function, representing a difference between said reference signal and the selected remaining signal to thereby obtain an estimate or a representation of an estimate of said plurality of relative channel-errors for the selected remaining signal.

12. The estimation module according to claim 11, wherein the module performs said optimizing by being further configured to operatively:

feedback the channel-error or channel-errors estimated in the previous iteration so as to adjust the channel-error in the sequence of the second signal;

update the function with a sequence of the second signal having channel-errors adjusted by said feedback; and

repeat said feedback and said update until a satisfactory estimation is obtained.

13. The estimation module according to claim 11, wherein the estimation module is further configured

to operatively calculate said plurality of estimated channel-errors by utilizing a function defining a measure of the difference between said sequences with respect to said plurality of channel-errors, and by performing an optimization by minimizing the defined function.

14. The estimation module according to claim 13, wherein the estimation module is further configured

to operatively estimate a plurality of channel-errors, wherein least one of the estimated channel-errors is an estimated delay corresponding to a delay mismatch, and to apply the estimated delay to the selected signal using a fractional delay filter.

15. The estimation module according to claim 14, wherein said fractional delay filter is implemented by using a Lagrange, Farrow Structure or Thiran Allpass.

16. The estimation module according to claim 11, wherein the estimation module is further configured

to operatively use the function:

17. The estimation module according to claim 11, further comprising:

repeating said selection and optimizing for each remaining signal in said group of signals.

18. The estimation module according to claim 11, wherein the loss-function comprises a sum of squared values of differences between the reference signal and the selected remaining signal, or comprises a sum of absolute values of differences between the reference signal and the selected remaining signal.

19. The estimation module according to claim 11, wherein the estimation module is configured to obtain the estimates of the channel-errors are by minimizing the loss function

20. The estimation module according to claim 11, wherein said relative channel-errors for the selected remaining signal belong to the group of aperture delay mismatch error, gain mismatch error and offset mismatch error.

21. A system for reducing or eliminating a plurality of relative channel-errors for at least one signal with respect to a reference signal belonging to a group of digitized, the system comprising:

an estimation module configured to operatively receive said group of digitized signals and to provide an estimate of the plurality of relative channel-errors or a representation of the estimate, wherein said group of digitized signals are produced by an analog-to-digital module comprising a plurality of parallel and time interleaved analog-to-digital converters, each converter producing a respective one of said group of digitized signals, and

a reconstruction module configured to operatively apply said estimate of said plurality of relative channel-errors or the representation of the estimate to said at least one signal to reduce or eliminate the plurality of relative channel-error for the at least one signal.