Digital PLL With Hybrid Phase/Frequency Detector and Digital Noise Cancellation
First Claim
1. A phase locked-loop (PLL) comprising:
- a digitally controlled oscillator (DCO) configured to generate a DCO output frequency in response to a tuning input;
a frequency reference oscillator configured to generate a reference frequency input;
a mixed analog/digital signal Delta-Sigma (Δ
Σ
) Phase/Frequency Detector (Δ
Σ
PFD) configured to generate a digital output of frequency difference between the reference frequency input and the DCO frequency output;
an accumulator configured to generate digital phase and frequency error information by accumulating the Δ
Σ
PFD digital output combined with a digital indicator of a targeted output frequency for the DCO;
a loop filter following the accumulator and configured to tune phase/frequency of the DCO in response to digital phase and frequency error information;
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Abstract
Digital phase-locked loop (PLL) with dynamic hybrid (mixed analog/digital signal) delta-sigma (ΔΣ) phase/frequency detector (ΔΣ PFD). A hybrid 2nd-order ΔΣ PFD may be implemented based on a continuous-time 1st-order ΔΣ analog-to-digital converter (ADC) enhanced to 2nd-order via closed loop frequency detection. Fine resolution encoding of the ΔΣ PFD output facilitates true multi-bit phase/frequency error digitization with drastically reduced ΔΣ quantization noise. The implementation of low complexity ΔΣ PFD is assisted via digital requantization and adaptive noise cancellation. The PLL includes independent frequency-locking and phase-locking operational modes and all-digital control of a digitally controlled oscillator (DCO).
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Citations
20 Claims
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1. A phase locked-loop (PLL) comprising:
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a digitally controlled oscillator (DCO) configured to generate a DCO output frequency in response to a tuning input; a frequency reference oscillator configured to generate a reference frequency input; a mixed analog/digital signal Delta-Sigma (Δ
Σ
) Phase/Frequency Detector (Δ
Σ
PFD) configured to generate a digital output of frequency difference between the reference frequency input and the DCO frequency output;an accumulator configured to generate digital phase and frequency error information by accumulating the Δ
Σ
PFD digital output combined with a digital indicator of a targeted output frequency for the DCO;a loop filter following the accumulator and configured to tune phase/frequency of the DCO in response to digital phase and frequency error information; - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method comprising:
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performing phase/frequency detection with respect to a reference frequency and a feedback signal; generating a multiple bit error encoding of phase/frequency error responsive to the detection; receiving the multiple bit error encoding at a loop filter; and controlling a digitally controlled oscillator (DCO) with the loop filter to generate a reference frequency output. - View Dependent Claims (14, 15, 16, 17, 18)
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19. A phase locked loop (PLL) comprising:
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a reference frequency input; a phase and frequency detector charge-pump in communication with the reference frequency input; a delta sigma analog-to-digital converter (ADC) driven by the charge-pump, the ADC comprising a resolution mode input configured to selectively change the ADC between; a fine resolution mode providing a fine mode number of quantization levels for phase and frequency error; and a coarse resolution mode providing fewer quantization levels for the phase and frequency error than the fine mode number of quantization levels; a loop filter following the ADC and configured to accept the phase and frequency error and responsively drive a digitally controlled oscillator (DCO) that generates a reference frequency output; and a feedback path from the DCO to the charge-pump, the feedback path comprising a multi-modulus divider (MMD). - View Dependent Claims (20)
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Specification