Continuous-time sigma-delta analog-to-digital converter with non-invasive filter(s) for immunity preservation against interferers

1. A continuous-time sigma-delta analog-to-digital converter for converting analog signals belonging to a chosen bandwidth into digital signals according to a signal transfer function, said converter comprising:

a signal path including at least one combiner adapted to combine analog signals to be converted with analog feedback signals,

at least one integrator adapted to integrate said combined analog signals, a quantizer adapted to convert said integrated signals into digital signals,

a feedback path comprising at least a digital-to-analog converter adapted to convert said digital signals outputted by said quantizer into analog feedback signals intended for said combiner, and

at least one non-invasive filter associated with said integrator, coupled in parallel to said signal path at a chosen location and arranged to introduce a notch into said signal transfer function by suppressing unwanted analog interference signals having a chosen frequency band that corresponds to said notch, and said feedback path comprises at least one analog weighting means adapted to convert said analog feedback signals into weighted analog feedback signals intended for said combiner.

2. The converter according to claim 1 , wherein said signal path comprises at least two different integrators coupled in series.

3. The converter according to claim 2 , wherein said signal path comprises five different integrators coupled in series.

4. The converter according to claim 3 , wherein said signal path comprises at least two combiners located in the signal path before two chosen different integrators respectively, and in that it comprises at least two local resonator feedback means coupled connected in parallel with said signal path and arranged to weight the analog signals outputted by two other chosen integrators with chosen coefficients to feed said combiners with weighted analog signals.

5. The converter according to claim 2 , further comprising at least one local resonator feedback means coupled in parallel with said signal path and arranged to weight the analog signals outputted by one chosen integrator with a chosen coefficient to feed a combiner located in the signal path before another integrator located before said chosen integrator with weighted analog signals.

6. The converter according to claim 2 , further comprising at least one weighted feedforward summation path coupled in parallel with said signal path and arranged to weight the analog signals outputted by at least one chosen integrator with a chosen coefficient to feed a combiner, located after said chosen integrator, with weighted analog signals.

7. The converter according to claim 6 , wherein said signal path further comprises another combiner located between the last integrator and said quantizer, and in that it comprises weighted feedforward summation paths coupled in parallel with said signal path and arranged to weight the analog signals outputted by each of said integrators except for the last one with differently chosen coefficients to feed said other combiner with weighted analog signals.

8. The converter according to claim 1 , characterized in that said signal path comprises at least two non-invasive filters associated to two different integrators respectively, coupled in parallel to said signal path at two chosen locations and arranged to suppress unwanted analog interference signals having two different chosen frequency bands.

9. The converter according to claim 1 , wherein each non-invasive filter is coupled to said signal path before the integrator it is associated to.

10. The converter according to claim 1 , wherein each non-invasive filter is coupled to said signal path after the integrator it is associated to.

11. The converter according to claim 1 , wherein each non-invasive filter comprises a resonator.

12. The converter according to claim 11 , wherein said resonator comprises first and second transconductances and a first capacitor coupled in series, a second capacitor coupled in parallel with said first transconductance, and a third transconductance coupled in parallel with said second transconductance.

13. The converter according to claim 1 , wherein said non-invasive filters are programmable.

14. The converter according to claim 1 , wherein said digital-to-analog converter and said quantizer are of the single-bit or multi-bit type.

15. An integrated circuit, comprising a converter according to claim 1 .

16. The integrated circuit according to claim 15 , comprising a baseband integrated circuit.

17. A receiving device, comprising an integrated circuit according to claim 15 .

18. A transceiver device, comprising a converter according to claim 1 .

19. Mobile radio communication equipment, comprising a converter according to claim 1 .

20. A continuous-time sigma-delta analog-to-digital converter for converting analog signals belonging to a chosen bandwidth into digital signals according to a signal transfer function, said converter comprising:

a signal path including at least one combiner adapted to combine analog signals to be converted with analog feedback signals,

at least one integrator adapted to integrate said combined analog signals, a quantizer adapted to convert said integrated signals into digital signals, and

a feedback path comprising at least a digital-to-analog converter adapted to convert said digital signals outputted by said quantizer into analog feedback signals intended for said combiner,

at least one non-invasive filter associated with said integrator, connected in parallel to said signal path at a chosen location and arranged to introduce a notch into said signal transfer function by suppressing unwanted analog interference signals having a chosen frequency band that corresponds to said notch,

said signal path comprising at least two different integrators connected in series, and

at least one local resonator feedback means connected in parallel with said signal path and arranged to weight the analog signals outputted by one chosen integrator with a chosen coefficient to feed a combiner located in the signal path before another integrator located before said chosen integrator with weighted analog signals.

21. A continuous-time sigma-delta analog-to-digital converter for converting analog signals belonging to a chosen bandwidth into digital signals according to a signal transfer function, said converter comprising:

a signal path including at least one combiner adapted to combine analog signals to be converted with analog feedback signals,

at least one integrator adapted to integrate said combined analog signals, a quantizer adapted to convert said integrated signals into digital signals, and

a feedback path comprising at least a digital-to-analog converter adapted to convert said digital signals outputted by said quantizer into analog feedback signals intended for said combiner,

at least one non-invasive filter associated with said integrator, connected in parallel to said signal path at a chosen location and arranged to introduce a notch into said signal transfer function by suppressing unwanted analog interference signals having a chosen frequency band that corresponds to said notch, and

said signal path comprises five different integrators connected in series and at least two combiners located in the signal path before two chosen different integrators respectively, and in that it comprises at least two local resonator feedback means connected in parallel with said signal path and arranged to weight the analog signals outputted by two other chosen integrators with chosen coefficients to feed said combiners with weighted analog signals.