Ultra-low-power injection locked oscillator for IQ clock generation

1. An injection locked oscillator (ILO) circuit, comprising:

a first clock injection stage to receive a first input clock signal having a first frequency and to generate a first injection signal based on the first input clock signal, the first clock injection stage including a first programmable inverter in series with a first self-biased inverter;

a second clock injection stage to receive a second input clock signal having the first frequency and to generate a second injection signal based on the second input clock signal, the second clock injection stage including a second programmable inverter in series with a second self-biased inverter; and

a phase locked loop (PLL) stage to receive the first injection signal and the second injection signal and to generate an output clock signal based at least in part on the first frequency, the phase locked loop stage including a multi-stage ring oscillator configured to generate the output clock signal based at least in part on the first injection signal and the second injection signal.

2. The ILO circuit of claim 1 , wherein the PLL stage further includes a pair of dummy buffers for balancing loading of an oscillator tank of the multi-stage ring oscillator, the pair of dummy buffers comprising:

a first dummy buffer coupled to a first output of a first stage of the multi-stage ring oscillator; and

a second dummy buffer coupled to a second output of the first stage of the multi-stage ring oscillator.

3. The ILO circuit of claim 1 , wherein the multi-stage ring oscillator further comprises a plurality of non-cross-coupled inverters and a plurality of cross-coupled programmable inverters.

4. The ILO circuit of claim 1 , wherein the PLL stage is further configured to receive a control voltage input for controlling an oscillation frequency of the PLL stage.

5. The ILO circuit of claim 4 , further comprising a coarse frequency tracking circuit to compare the first frequency with the oscillation frequency of the PLL stage and to determine a coarse control voltage for controlling the oscillation frequency of the PLL stage, wherein the coarse control voltage is configured to reduce a difference between the oscillation frequency of the PLL stage and the first frequency.

6. The ILO circuit of claim 5 , wherein the clock output signal comprises a plurality of delayed clock signals; and

wherein the ILO circuit further comprises a fine quadrature locked loop (QLL) stage, comprising:

a quadrature phase detector (QPD) circuit to receive the plurality of delayed clock signals and to determine a fine control voltage for controlling the oscillation frequency of the PLL stage, wherein the fine control voltage is based on the plurality of delayed clock signals and configured to reduce a difference between the oscillation frequency of the PLL stage and the first frequency.

7. The ILO circuit of claim 6 , wherein the PLL stage is selectively coupled to receive the coarse control voltage or the fine control voltage as the control voltage input based on the difference between the first frequency and the oscillation frequency of the PLL stage.

8. The ILO circuit of claim 6 , wherein the plurality of delayed clock signals comprises eight delayed clock signals, each of the eight delayed clock signals delayed in phase by an integer multiple of 45 degrees.

9. The ILO circuit of claim 6 , wherein the fine QLL stage further comprises a voltage regulator to suppress a supply noise in the control voltage input.

10. The ILO circuit of claim 6 , wherein the fine QLL stage is configured to reduce the difference between the oscillation frequency of the PLL stage and the first frequency to within a locking range of the ILO circuit.

11. A method for operating an injection locked oscillator (ILO) circuit, comprising:

providing a first input clock signal, having a first frequency, to a first clock injection stage including a first programmable inverter in series with a first self-biased inverter, and generating a first injection signal using the first clock injection stage;

providing a second input clock signal, having the first frequency, to a second clock injection stage including a second programmable inverter coupled to a second self-biased inverter, and generating a second injection signal using the second clock injection stage;

providing the first injection signal and the second injection signal to a phase locked loop (PLL) stage configured to generate an output clock signal based at least in part on the first frequency, the PLL stage comprising a multi-stage ring oscillator.

12. The method of claim 11 , wherein the PLL stage further comprises a pair of dummy buffers for balancing loading of an oscillator tank of the multi-stage ring oscillator.

13. The method of claim 11 , wherein the multi-stage ring oscillator further comprises a plurality of non-cross-coupled inverters and a plurality of cross-coupled programmable inverters.

14. The method of claim 11 , wherein the phase locked loop stage further comprises a control input to receive a control voltage for controlling an oscillation frequency of the PLL stage.

15. The method of claim 14 , further comprising:

comparing the first frequency with the oscillation frequency of the PLL stage; and

generating a coarse control voltage for coupling to the control input based on the comparing, the coarse control voltage to reduce a difference between the oscillation frequency of the PLL stage and the first frequency.

16. The method of claim 15 , further comprising:

generating a plurality of delayed clock signals, by delaying the output clock signal by a plurality of phases; and

determining, using a quadrature phase detector (QPD) circuit, a fine control voltage for controlling the oscillation frequency of the PLL stage, wherein the fine control voltage is based on the plurality of delayed clock signals to reduce a difference between the oscillation frequency of the PLL stage and the first frequency.

17. The method of claim 16 , further comprising selectively coupling the PLL stage to receive either the coarse control voltage or the fine control voltage as the control input based on the difference between the first frequency and the oscillation frequency of the PLL stage.

18. The method of claim 16 , wherein the plurality of delayed clock signals comprises eight delayed clock signals, each of the eight delayed clock signals delayed in phase by an integer multiple of 45 degrees.

19. The method of claim 16 , further comprising reducing, using a voltage regulator, a supply noise in the control voltage.

20. An injection locked oscillator (ILO) circuit, comprising:

means for providing a first input clock signal, having a first frequency, to a first clock injection stage including a first programmable inverter in series with a first self-biased inverter, and generating a first injection signal based on the first input clock signal;

means for providing a second input clock signal, having the first frequency, to a second clock injection stage including a second programmable inverter in series with a second self-biased inverter, and generating a second injection signal based on the second input clock signal;

means for providing the first injection signal and the second injection signal to a phase locked loop (PLL) stage configured to generate an output clock signal based at least in part on the first frequency, the PLL stage comprising a multi-stage ring oscillator.