Dynamic multiphase injection-locked phase rotator for electro-optical transceiver
Presented herein are methodologies for generating clock signals for transceivers that rely on frequency and phase error correction functions. The methodology includes generating a differential clock signal at a fundamental frequency, generating, based on the differential clock signal and using a multiphase generator, four quadrature signals at the fundamental frequency, supplying the four quadrature signals to an injection-locked phase rotator, and outputting, from the injection-locked phase rotator, a phase adjusted multiphase clock signal based on the four quadrature signals.
1. A method comprising:
generating a differential clock signal at a fundamental frequency;
generating, based on the differential clock signal and using a multiphase generator, four quadrature signals at the fundamental frequency;
supplying the four quadrature signals to an injection-locked phase rotator; and
outputting, from the injection-locked phase rotator, a phase adjusted multiphase clock signal based on the four quadrature signals.
2. The method of claim 1 , further comprising setting the fundamental frequency to a sub-rate of a data rate of data to be decoded, wherein the sub-rate is one of a half-rate, a quarter-rate, or an eighth-rate.
3. The method of claim 1 , wherein the multiphase generator is one of an injection-locked multiphase generator or a quadrature delay-locked loop.
4. The method of claim 1 , wherein the phase adjusted multiphase clock signal comprises one of 2, 4 or 8 phases.
5. The method of claim 1 , further comprising supplying the phase adjusted multiphase clock signal to analog-to-digital converters, respectively.
6. The method of claim 1 , further comprising adjusting a frequency of the phase adjusted multiphase clock signal using the injection-locked phase rotator.
7. The method of claim 1 , wherein the injection-locked phase rotator is a fully differential coupled oscillator.
8. The method of claim 7 , wherein the fully differential coupled oscillator comprises a predetermined number of sub-oscillator slices.
9. The method of claim 8 , wherein each of the sub-oscillator slices comprises two pairs of series-connected cross-coupled forwarding inverters.
10. The method of claim 9 , wherein each of the sub-oscillator slices comprises current injection inverters respectively connected to inputs of the series-connected cross-coupled forwarding inverters.
11. The method of claim 1 , further comprising generating, with clock-data recovery logic, a control word and supplying the control word to the injection-locked phase rotator to adjust a phase of the phase adjusted multiphase clock signal.
12. The method of claim 1 , further comprising applying fractional injection to the injection-locked phase rotator to achieve additional fine phase resolution.
13. An apparatus comprising:
a differential clock signal generator configured to generate a differential clock signal at a fundamental frequency;
a multiphase generator configured to generate four quadrature signals at the fundamental frequency based on the differential clock signal; and
an injection-locked phase rotator configured to receive the four quadrature signals and to output a phase adjusted multiphase clock signal based on the four quadrature signals.
14. The apparatus of claim 13 , wherein the fundamental frequency is set to a sub-rate of a data rate of data to be decoded, wherein the sub-rate is one of a half-rate, a quarter-rate, or an eighth-rate.
15. The apparatus of claim 13 , wherein the multiphase generator is one of an injection-locked multiphase generator or a quadrature delay-locked loop.
16. The apparatus of claim 13 , wherein the phase adjusted multiphase clock signal comprises one of 2, 4 or 8 phases.
17. The apparatus of claim 13 , wherein the injection-locked phase rotator is a fully differential coupled oscillator.
18. The apparatus of claim 17 , wherein the fully differential coupled oscillator comprises a predetermined number of sub-oscillator slices.
19. The apparatus of claim 18 , wherein each sub-oscillator slice comprises two pairs of series-connected cross-coupled forwarding inverters.
20. A non-transitory computer readable storage media encoded with instructions that, when executed by a processor, cause the processor to:
generate a differential clock signal at a fundamental frequency;
generate, based on the differential clock signal and using a multiphase generator, four quadrature signals at the fundamental frequency;
supply the four quadrature signals to an injection-locked phase rotator; and
output, from the injection-locked phase rotator, a phase adjusted multiphase clock signal based on the four quadrature signals.