Receivers and method with fast sampling phase and frequency acquisition
Fast sampling phase and frequency acquisition suitable for incorporation into various high bandwidth receivers and receiving methods. One illustrative integrated circuit receiver or “deserializer” design has: a clock circuit that provides a sample clock; an analog to digital converter that samples a receive signal in accordance with the sample clock to provide receive signal samples; and a clock recovery circuit. The clock recovery circuit includes: a phase and frequency acquisition module to determine and correct an initial frequency offset and an initial phase offset of the sample clock; and a feedback circuit to minimize timing error of the sample clock after the initial frequency offset and initial phase offset have been corrected.
1. A receiver comprising an integrated circuit having:
an analog to digital converter that samples a receive signal in accordance with a sample clock to provide a sampled receive signal; and
a clock recovery circuit that includes:
a phase and frequency acquisition module to determine and correct an initial frequency offset and an initial phase offset of the sample clock in part by:
obtaining a sampling clock phase estimate from each of multiple pairs of the receive signal samples during a preamble period; and
differencing the sampling clock phase estimates to determine the initial frequency offset; and
a feedback loop to minimize timing error of the sample clock after the initial frequency offset and the initial phase offset have been corrected.
2. The receiver of claim 1 , wherein the analog to digital converter is one of a set of analog to digital converters that sample the receive signal in response to staggered versions of the sample clock to provide a parallel set of sampled receive signals.
3. The receiver of claim 1 , wherein the integrated circuit includes an equalizer that converts the sampled receive signal into an equalized signal, and wherein the phase and frequency acquisition module uses the equalized signal to derive the initial frequency offset and the initial phase offset.
4. The receiver of claim 3 , wherein the phase and frequency acquisition module estimates a sampling clock phase using ratios of received signal sample pairs during a preamble period.
5. The receiver of claim 4 , wherein the sampling clock phase estimates are each calculated as an arctangent of one of said ratios.
6. The receiver of claim 1 , wherein the clock recovery circuit further includes a phase lock loop having an initial division ratio, the phase and frequency acquisition module being configured to correct the initial frequency offset by adjusting the initial division ratio.
7. The receiver of claim 1 , wherein the clock recovery circuit further includes a phase interpolator having an initial phase setting, the phase and frequency acquisition module being configured to correct the initial phase offset by adjusting the initial phase setting.
8. A method that comprises:
sampling a receive signal in response to a sample clock to provide receive signal samples, the sample clock having an initial frequency;
obtaining a sampling clock phase estimate from each of multiple pairs of the receive signal samples;
differencing the sampling clock phase estimates to determine an initial frequency offset; and
correcting a source of the sample clock to compensate for the initial frequency offset.
9. The method of claim 8 , further comprising:
combining at least some of the sampling clock phase estimates to obtain an initial phase offset; and
correcting a source of the sample clock to compensate for the initial phase offset.
10. The method of claim 9 , further comprising, after correcting the source of the sample clock to compensate for the initial frequency offset and the initial phase offset, enabling a clock recovery loop to minimize timing error.
11. The method of claim 8 , wherein said obtaining the sampling clock phase estimate includes equalizing each of the receive signal samples in the pair of receive signal samples.
12. The method of claim 8 , wherein said obtaining the sampling clock phase estimate is performed during a preamble period.
13. The method of claim 12 , wherein each sampling clock phase estimate is an arctangent of a ratio between the receive signal samples or between equalized versions of the receive signal samples.
14. A non-transitory information storage medium having a semiconductor intellectual property core to generate circuitry comprising:
a clock circuit configured to provides a sample clock;
an analog to digital converter configured to sample a receive signal in accordance with the sample clock to provide a sampled receive signal; and
a clock recovery circuit that includes:
a phase and frequency acquisition module configured to determine and correct an initial frequency offset and an initial phase offset of the sample clock in part by:
obtaining a sampling clock phase estimate from each of multiple pairs of the receive signal samples during a preamble period; and
differencing the sampling clock phase estimates to determine the initial frequency offset; and
a feedback circuit configured to minimize timing error of the sample clock after the initial frequency offset and initial phase offset have been corrected.
15. The non-transitory information storage medium of claim 14 , wherein the analog to digital converter is one of a set of analog to digital converters configured to sample the receive signal in response to staggered versions of the sample clock to provide a parallel set of sampled receive signals.
16. The non-transitory information storage medium of claim 14 , wherein the circuitry includes an equalizer configured to convert the sampled receive signal into an equalized signal, and wherein the phase and frequency acquisition module is configured to use the equalized signal to derive the initial frequency offset and the initial phase offset.
17. The non-transitory information storage medium of claim 16 , wherein the phase and frequency acquisition module is configured to estimate the sampling clock phase as an arctangent of a ratio between equalized signal samples during a preamble period.
18. The non-transitory information storage medium of claim 17 , wherein the phase and frequency acquisition module is configured to estimate the initial frequency offset based on differences between the sampling clock phase estimates.