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:
receiving four quadrature signals at a fundamental frequency;
supplying the four quadrature signals at the fundamental frequency to a fully differential coupled oscillator comprising a predetermined number of sub-oscillator slices, wherein each sub-oscillator slice comprises two pairs of series-connected cross-coupled forwarding inverters;
adjusting a phase of the four quadrature signals at the fundamental frequency by respectively applying the four quadrature signals at the fundamental frequency to current injection inverters connected to inputs of the two pairs of series-connected cross-coupled forwarding inverters; and
outputting phase adjusted multiphase clock signals based on the four quadrature signals at the fundamental frequency.
2. The method of claim 1 , further comprising adjusting a frequency of the four quadrature signals at the fundamental frequency.
3. The method of claim 1 , wherein the fully differential coupled oscillator comprises sixteen sub-oscillator slices.
4. The method of claim 3 , wherein the fully differential coupled oscillator comprises 64 current injection inverters.
5. The method of claim 1 , further comprising supplying the phase adjusted multiphase clock signals to a multilane transceiver.
6. The method of claim 5 , further comprising supplying the phase adjusted multiphase clock signals to respective analog to digital converters of the multilane transceiver.
7. The method of claim 1 , further comprising receiving a control word and applying the four quadrature signals at the fundamental frequency to the current injection inverters based on the control word.
8. The method of claim 7 , further comprising generating the control word based on feedback received from a multilane optical receiver.
9. The method of claim 8 , wherein the feedback received from the multilane optical receiver is received from an equalizer of the multilane optical receiver.
10. The method of claim 1 , further comprising buffering the phase adjusted multiphase clock signals.
11. An apparatus comprising:
a fully differential coupled oscillator comprising a predetermined number of sub-oscillator slices, wherein each sub-oscillator slice comprises two pairs of series-connected cross-coupled forwarding inverters; and
current injection inverters respectively connected to inputs of the two pairs of series-connected cross-coupled forwarding inverters.
12. The apparatus of claim 11 , further configured to apply four quadrature signals at a fundamental frequency to selected ones of the current injection inverters to adjust a phase of the four quadrature signals at the fundamental frequency.
13. The apparatus of claim 12 , wherein phase adjusted multiphase clock signals are output based on the four quadrature signals at the fundamental frequency.
14. The apparatus of claim 13 , further configured to supply the phase adjusted multiphase clock signals to a multilane transceiver.
15. The apparatus of claim 14 , further configured to supply the phase adjusted multiphase clock signals to respective analog to digital converters of the multilane transceiver.
16. An apparatus comprising:
a first pair of forwarding inverters;
a second pair of forwarding inverters connected in series with the first pair of forwarding inverters; and
two pairs of oppositely-oriented cross-coupling inverters respectively connecting outputs of the first pair of forwarding inverters to outputs of the second pair of forwarding inverters.
17. The apparatus of claim 16 , further comprising current injection inverters respectively connected to inputs of the first pair of forwarding inverters and to inputs of the second pair of forwarding inverters.
18. The apparatus of claim 17 , further configured to apply four quadrature signals at a fundamental frequency to selected ones of the current injection inverters to adjust a phase of the four quadrature signals at the fundamental frequency.
19. The apparatus of claim 18 , wherein phase adjusted multiphase clock signals are output based on the four quadrature signals at the fundamental frequency.
20. The apparatus of claim 19 , further configured to supply the phase adjusted multiphase clock signals to a multilane transceiver.