Digital correction of spurious tones caused by a phase detector of a hybrid analog-digital delta-sigma modulator based fractional-N phase locked loop
First Claim
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1. A dual-path, hybrid analog-digital delta-sigma modulator (DSM) based fractional-N phase-lock-loop (PLL) comprising:
- an integral path for providing an integral path control signal, the integral path implemented in the digital domain, the integral path including an integral path phase detector;
a proportional path for providing a proportional path control signal, wherein the proportional path control signal and the integral path control signal are combined to produce a combined control signal; and
a feed-forward error correction signal generator for attenuating in-band spurs generated by quantization of a phase detector error output from the integral path phase detector, the feed-forward error correction signal generator configured to;
generate a representative signal of the instantaneous phase detector error output from the integral path phase detector by accumulating a DSM noise code sequence;
truncate the representative signal to replicate non-linearity of the integral path phase detector; and
subtract the truncated representative signal from an output of the integral path phase detector.
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Abstract
A hybrid analog-digital, dual path, delta-sigma modulator (DSM) based fractional-N phase-lock-loop (PLL) that includes an integral path and a proportional path is provided. The integral path is implemented in the digital domain. The proportional path may be implemented in either the digital or analog domain. A feed-forward error correction signal generator is used to generate a feed-forward signal for attenuating in-band spurs generated by the quantization error of the integral path phase detector.
28 Citations
21 Claims
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1. A dual-path, hybrid analog-digital delta-sigma modulator (DSM) based fractional-N phase-lock-loop (PLL) comprising:
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an integral path for providing an integral path control signal, the integral path implemented in the digital domain, the integral path including an integral path phase detector; a proportional path for providing a proportional path control signal, wherein the proportional path control signal and the integral path control signal are combined to produce a combined control signal; and a feed-forward error correction signal generator for attenuating in-band spurs generated by quantization of a phase detector error output from the integral path phase detector, the feed-forward error correction signal generator configured to; generate a representative signal of the instantaneous phase detector error output from the integral path phase detector by accumulating a DSM noise code sequence; truncate the representative signal to replicate non-linearity of the integral path phase detector; and subtract the truncated representative signal from an output of the integral path phase detector. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of correcting spurious tones in a dual-path, hybrid analog-digital delta-sigma modulator (DSM) based fractional-N phase-lock-loop (PLL), the PLL including an integral path implemented in the digital domain, a proportional path, and a DSM, the integral path including an integral path phase detector, the method comprising:
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generating a representative signal of the instantaneous phase detector error output from the integral path phase detector by accumulating a DSM noise code sequence; truncating the representative signal to replicate non-linearity of the integral path phase detector; and subtracting the truncated representative signal from an output of the phase detector.
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12. A dual-path, hybrid analog-digital delta-sigma modulator (DSM) based fractional-N phase-lock-loop (PLL) comprising:
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an integral path for providing an integral path control signal, the integral path implemented in the digital domain, the integral path including an integral path phase detector; a proportional path for providing a proportional path control signal, wherein the proportional path control signal and the integral path control signal are combined to produce a combined control signal; a feed-forward error correction signal generator for generating a feed-forward signal for attenuating in-band spurs generated by quantization of a phase detector error output from the integral path phase detector; a delta sigma modulator (DSM) coupled to the feed-forward error correction signal generator; and a fractional divider in a feedback path of the fractional-N PLL, the fractional divider having an input for receiving a control signal from the delta sigma modulator, wherein the feed-forward error correction signal generator generates the feed forward correction signal according to the equation; - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21)
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Specification