Analog-to-Digital Converter, Signal Processor, and Method for Analog-to-Digital Conversion

• US 20130194114A1
• Filed: 01/31/2012
• Published: 08/01/2013
• Est. Priority Date: 01/31/2012
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Mobile Communications GmbH (Intel Corporation)
• Inventors: Schimper, Markus, Schelmbauer, Werner, Ritter, Rudolf, Ortsmanns, Maurits
• Granted Patent: US 8,760,330 B2
• Time in Patent Office: Days
• US Class Current: 341/110
• CPC Class Codes: H03M 3/30 Delta-sigma modulation
• CPC Class Codes: H03M 3/368 of noise other than the quantisation noise already being shaped inherently by delta-sigma modulators
• CPC Class Codes: H03M 3/424 the quantiser being a multiple bit one
• CPC Class Codes: H03M 3/454 with distributed feedback, i.e. with feedback paths from the quantiser output to more than one filter stage
• CPC Class Codes: H04B 1/1036 with automatic suppression of narrow band noise or interference, e.g. by using tuneable notch filters H04B1/123 takes precedence; filter circuits H03H
• CPC Class Codes: H04B 1/123 using adaptive balancing or compensation means adaptive filter circuits and algorithms H03H

Abstract

An analog-to-digital converter for converting an input signal includes a sigma-delta modulator for receiving an analog modulator input signal and for providing a digital modulator output signal and an interference cancellation loop. The interference cancellation loop includes a digital filter, a digital-to-analog converter, and a signal combiner. The digital filter is configured to amplify the sigma-delta output signal in a frequency band, attenuate the sigma-delta output signal outside the frequency band and a transition band surrounding the frequency band, and provide a filtered digital feedback signal. The digital-to-analog converter is configured to convert the filtered digital signal to a cancellation signal. The signal combiner is configured to combine the input signal with the cancellation signal resulting in the modulator input signal, in order to at least partially cancel interference signal portions within the input signal.

Claims

1. An analog-to-digital converter for converting an input signal, the analog-to-digital converter comprising:

a sigma-delta modulator configured to receive an analog modulator input signal and provide a digital modulator output signal; and

an interference cancellation loop, comprising;

a digital filter configured to amplify the digital modulator output signal in a frequency band, attenuate the digital modulator output signal outside the frequency band and a transition band surrounding the frequency band, and provide a filtered digital feedback signal;

a digital-to-analog converter configured to convert the filtered digital feedback signal to a cancellation signal; and

a signal combiner configured to combine the analog modulator input signal with the cancellation signal resulting in the analog modulator input signal, in order to at least partially cancel interference signal portions within the analog modulator input signal.

2. The analog-to-digital converter according to claim 1, wherein the frequency band of the digital filter comprises, overlaps, or is within a frequency range of an expected interference signal.

3. The analog-to-digital converter according to claim 1, wherein the digital filter is configured to attenuate the digital modulator output signal in an in-band frequency range of the analog modulator input signal and amplify the digital modulator output signal in an out-of-band frequency range of the analog modulator input signal.

4. The analog-to-digital converter according to claim 1, wherein the digital filter comprises a digital resonator.

5. The analog-to-digital converter according to claim 1, wherein the interference cancellation loop further comprises a digital noise shaper between an output of the sigma-delta modulator and the digital-to-analog converter.

6. The analog-to-digital converter according to claim 1, wherein the interference cancellation loop comprises a cascaded arrangement of at least two feedback branches, each feedback branch comprising a digital filter and a digital-to-analog converter.

7. The analog-to-digital converter according to claim 1, wherein the interference cancellation loop comprises a digital replica of a signal transfer function of the sigma-delta modulator, wherein the digital replica is configured to receive the filtered digital feedback signal or a derived filtered signal, and provide an estimated response of the sigma-delta modulator in response to the digital filtered feedback signal or the derived filtered signal, wherein the estimated response is combined with the digital modulator output signal or a derived modulator output signal to provide an output signal of the analog-to-digital converter.

8. The analog-to-digital converter according to claim 7, wherein the interference cancellation loop comprises a further digital replica of the signal transfer function of the sigma-delta modulator and a further digital filter, wherein the further digital replica and the further filter are arranged in a cascaded arrangement with the digital replica and the digital filter so that a further estimated response provided by the further digital replica is combined with the digital modulator output signal to provide the derived filtered signal for the digital filter, and that a further digital filtered signal provided by the further digital filter is combined with the digital filtered signal to provide the cancellation signal.

9. The analog-to-digital converter according to claim 1, wherein the digital filter is an adaptive filter.

10. The analog-to-digital converter according to claim 1, wherein the interference cancellation loop is substantially linear between an output of the sigma-delta modulator and an input of the digital-to-analog converter.

11. An apparatus, comprising:

a baseband processor;

an antenna port; and

an analog-to-digital converter configured to convert an input signal, the analog-to-digital converter being coupled to the baseband processor and the antenna port, and comprising;

a sigma-delta modulator configured to receive an analog modulator input signal and provide a digital modulator output signal; and

an interference cancellation loop, comprising;

a digital filter configured to amplify the digital modulator output signal in a frequency band, attenuate the digital modulator output signal outside the frequency band and a transition band surrounding the frequency band, and provide a filtered digital feedback signal;

a digital-to-analog converter configured to convert the filtered digital feedback signal to a cancellation signal; and

a signal combiner configured to combine the analog modulator input signal with the cancellation signal resulting in the analog modulator input signal, in order to at least partially cancel interference signal portions within the analog modulator input signal.

12. A signal processor, comprising

a forward signal processing path comprising a sigma-delta modulator;

and

a feedback signal processing path comprising a digital controller configured to condition a modulator output signal from the sigma-delta modulator and feed a resulting cancellation signal to an input of the forward signal processing path for selective cancellation of signal portions of an input signal of the signal processor, wherein the digital controller is configured to emphasize an out-of-band frequency range so that feeding the resulting cancellation signal to the input of the forward signal processing path reduces out-of-band signal portions within the out-of-band frequency range of the input signal of the signal processor.

13. The signal processor according to claim 12, wherein the sigma-delta modulator is configured to receive an analog modulator input signal and wherein the modulator output signal is a digital signal.

14. The signal processor according to claim 12, wherein the digital controller comprises a digital resonator.

15. The signal processor according to claim 12, wherein the feedback signal processing path further comprises a digital noise shaper.

16. The signal processor according to claim 12, wherein the digital controller comprises a digital noise shaper.

17. The signal processor according to claim 12, wherein the feedback signal processing path comprises a cascaded arrangement of at least two feedback branches, each feedback branch comprising a digital controller.

18. The signal processor according to claim 12, wherein the feedback signal processing path comprises a replica of a signal transfer function of the forward signal processing path, wherein the digital replica is configured to receive a controller output signal from the digital controller, or a signal derived from the controller output signal, and provide an estimated response of the forward signal processing path in response to the controller output signal, wherein the estimated response is combined with a forward path output signal provided by the forward signal path to provide an output signal of the signal processor.

19. The signal processor according to claim 18, wherein the feedback signal processing path comprises a further digital replica of the signal transfer function of the forward signal processing path and a further digital controller, wherein the further digital replica and the further digital controller are arranged in a cascaded arrangement with the digital replica and the digital controller so that a further estimated response provided by the further digital replica is combined with forward path output signal to provide the signal derived from the controller output signal to the digital controller, and that a further controller output signal provided by the further digital controller is combined with the controller output signal to provide the cancellation signal.

20. The signal processor according to claim 12, wherein the digital controller comprises an adaptive controller.

21. An apparatus, comprising:

a baseband processor;

an antenna port; and

a signal processor coupled to the baseband processor and the antenna port, and comprising;

a forward signal processing path comprising a sigma-delta modulator; and

a feedback signal processing path comprising a digital controller configured to condition a modulator output signal and feed a resulting cancellation signal to an input of the forward signal processing path for selective cancellation of signal portions of an input signal of the signal processor, wherein the digital controller is configured to emphasize an out-of-band frequency range so that feeding the resulting cancellation signal to the input of the forward signal processing path reduces out-of-band signal portions within the out-of-band frequency range of the input signal of the signal processor.

22. An analog-to-digital converter for converting an input signal, the analog-to-digital converter comprising:

means for combining the input signal with a cancellation signal and for providing a corresponding modulator input signal;

means for sigma-delta modulating the modulator input signal and for providing a sigma-delta modulated signal;

means for filtering the sigma-delta modulated signal in a frequency band and for attenuating the sigma-delta modulated signal outside the frequency band and a transition band surrounding the frequency band to obtain a filtered sigma-delta modulated signal; and

means for digital-to-analog converting the filtered sigma-delta modulated signal to obtain the cancellation signal.

23. A method for analog-to-digital conversion, comprising:

receiving an analog modulator input signal;

combining the analog modulator input signal with a cancellation signal, resulting in an analog modulator input signal;

sigma-delta modulating the analog modulator input signal, resulting in a digital modulator output signal;

providing an output signal of the method for analog-to-digital conversion based on the digital modulator output signal;

filtering the digital modulator output signal or a derived digital modulator output signal within a passband frequency range; and

digital-to-analog converting a filtered signal resulting in the cancellation signal, the filtered signal based on the filtering, so that the cancellation signal cancels, at least partially, interference signal portions of the analog modulator input signal that are in the passband frequency range.

24. The method according to claim 23, wherein the passband comprises, overlaps, or is within a frequency range of an expected interference signal.

25. The method according to claim 23, wherein filtering attenuates the digital modulator output signal in an in-band frequency range of the input signal and relatively amplifies the digital modulator output signal in an out-of-band frequency range of the input signal.

26. The method according to claim 23, further comprising:

digitally noise shaping the digital modulator output signal or the filtered signal.

27. The method according to claim 23, further comprising:

digitally estimating, using a digital replica of a signal transfer function of the action of sigma-delta modulating, a response of the action of sigma-delta modulating to a digital representation of the cancellation signal; and

combining the estimated response with the modulator output signal to obtain the output signal of the method of analog-to-digital conversion.

28. A method for processing an input signal, the method comprising:

sigma-delta modulating a modulator input signal, resulting in a modulator output signal;

conditioning the modulator output signal by emphasizing the modulator output signal in an out-of-band frequency range, to obtain a cancellation signal; and

feeding the cancellation signal back to an input of the action of sigma-delta modulating to be combined with the modulator input signal, thereby reducing out-of-band signal portions within the out-of-band frequency range of the input signal of the method for signal processing.