Calibrating timing, gain and bandwidth mismatch in interleaved ADCs using injection of random pulses
A method and a corresponding device for calibrating an interleaved analog-to-digital converter (ADC) involve injecting a pulsed, substantially-random signal into a plurality of channels in the ADC. After the substantially-random signal is injected, a gain correlation value is determined for each channel, which value indicates a degree of correlation between the injected substantially-random signal and an output of the respective channel. The gain correlation values are then compared to determine a degree of mismatch between the channels. At least one of the channels is calibrated as a function of the determined degree of mismatch.
1. A method for calibrating an interleaved analog-to-digital converter (ADC), comprising:
injecting a pulsed, substantially-random signal into a plurality of channels in the ADC;
after the substantially-random signal is injected, determining for each channel a gain correlation value indicating a degree of correlation between the injected substantially-random signal and an output of the respective channel;
comparing the gain correlation values to determine a degree of mismatch between the channels; and
calibrating at least one of the channels as a function of the determined degree of mismatch.
2. The method of claim 1 , wherein the substantially-random signal is injected onto an analog input of the ADC, the analog input forming an input to each of the plurality of channels.
3. The method of claim 1 , wherein the calibrating includes at least one of an analog and a digital adjustment to the at least one channel.
4. The method of claim 3 , further comprising:
performing the adjustment by phase-shifting a clock input of the at least one channel.
5. The method of claim 3 , further comprising:
performing the adjustment by changing an RC time constant of a stage in the at least one channel.
6. The method of claim 5 , wherein the RC time constant is changed by adjusting a capacitance in the at least one channel.
7. The method of claim 5 , wherein the RC time constant is changed by adjusting a resistance in the at least one channel.
8. The method of claim 3 , further comprising:
performing the adjustment by changing a value of a multiplier applied to an output of the least one channel.
9. The method of claim 1 , further comprising:
determining the degree of mismatch by calculating a difference between the gain correlation value of the at least one channel and the gain correlation value of at least one additional channel.
10. The method of claim 1 , further comprising:
controlling a timing of the substantially-random signal so that each of the plurality of channels samples an amplitude of a respective pulse of the substantially-random signal.
11. The method of claim 1 , further comprising:
controlling a timing of the substantially-random signal so that each of the plurality of channels samples an edge of a respective pulse of the substantially-random signal.
12. The method of claim 1 , wherein the substantially-random signal is injected into a common input point of the plurality of channels.
13. A device for calibrating an interleaved analog-to-digital converter (ADC), comprising:
an injection arrangement configured to inject a pulsed, substantially-random signal into a plurality of channels in the ADC;
a correlation arrangement configured to, after the substantially-random signal is injected, determine for each channel a gain correlation value indicating a degree of correlation between the injected substantially-random signal and an output of the respective channel; and
a correction arrangement configured to:
compare the gain correlation values to determine a degree of mismatch between the channels; and
calibrate at least one of the channels as a function of the determined degree of mismatch.
14. The device of claim 13 , wherein the injection arrangement injects the substantially-random signal onto an analog input of the ADC, the analog input forming an input to each of the plurality of channels.
15. The device of claim 13 , wherein the calibrating includes at least one of an analog and a digital adjustment to the at least one channel.
16. The device of claim 15 , wherein the correction arrangement performs the adjustment by phase-shifting a clock input of the at least one channel.
17. The device of claim 15 , wherein the correction arrangement performs the adjustment by changing an RC time constant of a stage in the at least one channel.
18. The device of claim 15 , wherein the correction arrangement performs the adjustment by changing a value of a multiplier applied to an output of the least one channel.
19. The device of claim 13 , wherein the correction arrangement determines the degree of mismatch by calculating a difference between the gain correlation value of the at least one channel and the gain correlation value of at least one additional channel.
20. The device of claim 13 , wherein the injection arrangement controls a timing of the substantially-random signal so that each of the plurality of channels samples an amplitude of a respective pulse of the substantially-random signal.
21. The device of claim 13 , wherein the injection arrangement controls a timing of the substantially-random signal so that each of the plurality of channels samples an edge of a respective pulse of the substantially-random signal.
22. The device of claim 13 , wherein the injection arrangement injects the substantially-random signal into a common input point of the plurality of channels.