Analog-to-digital converter and method
An analogue-to-digital converter (ADC), comprising: an adaptive whitening filter configured to filter an analogue input signal and output a whitened analogue input signal; a first converter configured to receive said whitened analogue input signal and output a whitened digital signal; a controller configured to adapt the whitening filter based on the received analogue input signal.
1. An analogue-to-digital converter (ADC), comprising:
an adaptive whitening filter configured to filter an analogue input signal and output a whitened analogue input signal;
a first converter configured to receive said whitened analogue input signal and output a whitened digital signal;
an adaptive de-whitening filter configured to filter the whitened digital signal and output a de-whitened digital output signal, the de-whitening filter being substantially inverse to the whitening filter; and
a controller configured to adapt the whitening filter and the de-whitening filter based on the analogue input signal.
2. The ADC of claim 1 , wherein the whitening filter is one of:
a) a shelving filter;
b) a bandpass filter;
c) a high pass filter; and
d) a differentiator.
3. The ADC of claim 1 , wherein the controller is configured to adapt the whitening filter based on the whitened digital signal.
4. The ADC of claim 1 , wherein the controller is further configured to adapt the first converter based on the analogue input signal.
5. The ADC of claim 4 , wherein the controller is configured to adapt the first converter based on the whitened digital signal.
6. The ADC of claim 4 , wherein the first converter is a sigma-delta ADC and wherein adapting of the first converter comprises one or more of:
a) changing an order of the ADC;
b) changing an over sample ratio of the ADC;
c) changing a bias current of one or more circuits in the ADC;
d) changing a number of bits in a quantizer of the ADC; and
e) switching between a high-performance integrator and a low-performance integrator.
7. The ADC of claim 1 , wherein adapting the whitening filter comprises selectively bypassing the whitening filter.
8. The ADC of claim 7 , further comprising a second converter configured to receive said analogue input signal and output a secondary digital signal to the controller, wherein the controller is configured to selectively bypass the whitening filter based on the secondary digital signal.
9. The ADC of claim 7 , wherein the controller is configured to selectively bypass the whitening filter in response to detecting that the analogue input signal exceeds a clipping threshold.
10. An electronic device comprising an ADC as claimed in claim 1 .
11. A method of analogue-to-digital conversion, comprising:
whitening an analogue input signal with a whitening filter to generate a whitened analogue input signal;
converting the whitened analogue input signal with a first converter to generate a whitened digital signal; and
filtering the whitened digital signal and outputting a de-whitened digital output signal, with an adaptive de-whitening filter, the de-whitening filter being substantially inverse to the whitening filter; and
adapting the whitening filter and the de-whitening filter based on the analogue input signal.
12. The method of claim 11 , wherein the whitening filter is one of:
a) a shelving filter;
b) a bandpass filter;
c) a high pass filter; and
d) a differentiator.
13. The method of claim 11 , wherein the de-whitening filter is adapted based on the whitened digital signal.
14. The method of claim 11 , further comprising adapting the first converter based on the received analogue input signal.
15. The method of claim 14 , wherein the first converter is adapted based on the whitened digital signal.
16. The method of claim 14 , wherein the first converter is a sigma-delta ADC and wherein adapting of the first converter comprises one or more of:
a) changing an order of the ADC;
b) changing an over sample ratio of the ADC;
c) changing a bias current of one or more circuits in the ADC;
d) changing a number of bits in a quantizer of the ADC.
17. The method of claim 11 , wherein adapting the whitening filter comprises selectively bypassing the whitening filter, the method further comprising converting with a second converter the analogue input signal to generate a secondary digital signal, wherein the whitening filter is selectively bypassed based on the secondary digital signal.
18. The method of claim 17 , wherein the whitening filter is selectively bypassed in response to detecting that the analogue input signal exceeds a clipping threshold.
19. The ADC of claim 1 , wherein the controller is configured to adapt the
whitening filter based on the de-whitened digital output signal.
20. The ADC of claim 1 , wherein the controller is configured to adapt the first converter based on the analogue input signal and the de-whitened digital output signal.
21. The method of claim 11 , the de-whitening filter is adapted based on the de-whitened digital output signal.
22. The method of 11 , further comprising adapting the first converter based on the analogue input signal and the de-whitened digital output signal.