Multi-loop .SIGMA. .DELTA. analog to digital converter
First Claim
1. A sigma-delta analog-to-digital converter comprising:
- a plurality of loops coupled in cascade, wherein each loop is implemented with multi-sampling circuitry, said multi-sampling circuitry configured to implement filter functions and to sample a respective loop input signal at multiple phases of a clock signal;
at least one feed-forward gain element, one gain element coupled between each pair of sequential loops; and
a noise cancellation logic coupled to each of said plurality of loop, said noise cancellation logic providing a converter output.
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Abstract
A bandpass ΣΔ DC utilizing either a single-loop or a MASH architecture wherein the resonators are implemented as either a delay cell resonator, a delay cell based resonator, a Forward-Euler resonator, or a two-path interleaved resonator. The resonator can be synthesized with analog circuit techniques such as active-RC, gm-C, MOSFET-C, switched capacitor, or switched current. The switched capacitor or switched current circuits can be designed using single-sampling, double-sampling, or multi-sampling circuits. The non-stringent requirement of a ΣΔ ADC using switched capacitor circuits allows the ADC to be implemented in a CMOS process to minimize cost and reduce power consumption. Double-sampling circuits provide improved matching and improved tolerance to sampling clock jitter. In particular, a bandpass MASH 4-4 ΣΔ ADC provides a simulated signal-to-noise ratio of 85 dB at an oversampling ratio of 32 for a CDMA application. The bandpass ΣΔ ADC can also be used in conjunction with undersampling to provide a frequency downconversion.
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Citations
40 Claims
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1. A sigma-delta analog-to-digital converter comprising:
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a plurality of loops coupled in cascade, wherein each loop is implemented with multi-sampling circuitry, said multi-sampling circuitry configured to implement filter functions and to sample a respective loop input signal at multiple phases of a clock signal; at least one feed-forward gain element, one gain element coupled between each pair of sequential loops; and a noise cancellation logic coupled to each of said plurality of loop, said noise cancellation logic providing a converter output. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A sigma-delta analog-to-digital converter comprising:
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a plurality of loops coupled in cascade, each loop including at least one delay circuit, wherein each delay circuit comprises an amplifier and two or more signal paths, each signal path comprising; a first switch; a capacitor coupled to said first switch; a second switch coupled to said capacitor and an AC ground; a third switch coupled to said first switch and an output of said amplifier; and a fourth switch coupled to said second switch and an input of said amplifier; wherein each signal path in a particular delay circuit is clocked by a set of clock signals having clock phases unique from those of other signal paths in the particular delay circuit.
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18. A sigma-delta analog-to-digital converter comprising:
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a plurality of loops coupled in cascade, each loop including at least one delay cell and summer circuit, wherein each delay cell and summer circuit comprises an amplifier and two or more signal paths, each signal path comprising; a first switch; a first capacitor coupled to said first switch; a second switch coupled to said first capacitor and said AC ground; a third switch coupled to said first switch and said output of said loop in which said delay cell and summer circuit reside; a second capacitor coupled to said first capacitor; a fourth switch coupled to said second switch and an inverting input of said amplifier; a fifth switch coupled to said second capacitor and said n-inverting output of said amplifier; and a sixth switch coupled to said second capacitor and an inverting output of said amplifier within said delay circuit of said resonator section. - View Dependent Claims (19, 20, 21, 22, 23)
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24. A sigma-delta analog-to-digital converter comprising:
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a plurality of loops coupled in cascade, wherein each loop includes a quantizer implemented with two comparators, wherein one comparator is clocked by a switching clock having a first phase and another comparator is clocked by a switching clock having a second phase, and wherein said comparators provide differential outputs; at least one feed-forward gain element, one gain element coupled between each pair of sequential loops; and a noise cancellation logic coupled to each of said plurality of loop, said noise cancellation logic providing a converter output. - View Dependent Claims (28, 29, 30, 31, 33)
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25. A bandpass sigma-delta analog-to-digital converter comprising:
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two or more loops coupled in cascade, each loop including a plurality of discrete delay elements; a feed-forward gain element, one gain element coupled between each pair of adjacent loops; and a noise cancellation logic coupled to each loop, said noise cancellation logic providing a converter output.
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26. A sigma-delta analog-to-digital converter comprising:
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two or more loops coupled in cascade; and at least one feed-forward gain element, one feed-forward gain element coupled between each pair of sequential loops, wherein a bias current of at least one of said two or more loops can be adjusted based on a required dynamic range. - View Dependent Claims (32)
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27. A sigma-delta analog-to-digital converter comprising:
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two or more loops coupled in cascade; and at least one feed-forward gain element, one feed-forward gain element coupled between each pair of sequential loops, wherein at least one of said two or more loops can be disabled based on a required dynamic range.
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34. A bandpass sigma-delta analog-to-digital converter comprising:
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two or more loops coupled in cascade, wherein each loop is implemented with two or more interleaved high-pass signal paths; and a feed-forward gain element, one feed-forward gain element coupled between each pair of sequential loops. - View Dependent Claims (35, 36, 37)
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38. A sigma-delta analog-to-digital converter comprising:
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a plurality of loops coupled in cascade, each loop including at least one filter section, wherein each filter section is implemented with multi-sampling circuitry that samples a respective filter input signal at multiple phases of a clock signal; and at least one feed-forward gain element, one gain element coupled between each pair of sequential loops. - View Dependent Claims (39, 40)
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Specification