Quadrature delay locked loops

1. An apparatus comprising:

an oscillator circuitry configured to generate a clock signal;

a first delay circuitry coupled to the oscillator circuitry, the first delay circuitry configured to delay the clock signal from the oscillator circuitry according to a first control signal to generate a first delayed clock signal;

a second delay circuitry coupled to the oscillator circuitry, the second delay circuitry configured to delay the clock signal from the oscillator circuitry according to a second control signal to generate a second delayed clock signal, the first delayed clock signal and the second delayed clock signal having a substantially 90-degree phase difference with each other; and

a delay controller circuitry coupled to the first delay circuitry and the second delay circuitry, the delay controller circuitry and the first delay circuitry forming a first feedback loop, the delay controller circuitry and the second delay circuitry forming a second feedback loop, the delay controller circuitry configured to determine a difference between the first delayed clock signal and the second delayed clock signal and modify the first control signal and the second control signal according to the determined difference.

2. The apparatus of claim 1 ,

wherein the oscillator circuitry is further configured to generate an inverted clock signal having a substantially 180-degree phase difference with the clock signal,

wherein the first delay circuitry is configured to delay the inverted clock signal according to the first control signal to generate a third delayed clock signal, the first delayed clock signal and the third delayed clock signal having a substantially 180-degree phase difference with each other, and

wherein the second delay circuitry is configured to delay the inverted clock signal according to the second control signal to generate a fourth delayed clock signal, the second delayed clock signal and the fourth delayed clock signal having a substantially 180-degree phase difference with each other.

3. The apparatus of claim 1 , wherein the first delay circuitry and the second delay circuitry are configured to delay the clock signal by different delay amounts.

4. The apparatus of claim 1 , further comprising:

a fixed delay circuitry coupled between the oscillator circuitry and the second delay circuitry, the fixed delay circuitry configured to delay the clock signal by a predetermined amount.

5. The apparatus of claim 4 , wherein the first delay circuitry and the second delay circuitry have identical circuit components.

6. The apparatus of claim 4 , wherein the first delay circuitry is configured to delay the clock signal by a delay amount according to the first control signal, and the second delay circuitry is configured to delay the clock signal by the delay amount according to the second control signal.

7. The apparatus of claim 1 , wherein the first control signal and the second control signal are differential signals.

8. The apparatus of claim 1 , wherein the delay controller circuitry includes:

a downconverter circuitry coupled to the first delay circuitry and the second delay circuitry, the downconverter circuitry configured to downconvert the first delayed clock signal and the second delayed clock signal to obtain a first downconverted signal and a second downconverted signal, and

a filter circuitry coupled to the downconverter circuitry, the filter circuitry configured to:

filter spectral components above a predetermined frequency in the first downconverted signal to generate the first control signal, and

filter spectral components above the predetermined frequency in the second downconverted signal to generate the second control signal.

9. A method comprising:

generating, by an oscillator circuitry, a clock signal;

delaying, by a first delay circuitry coupled to the oscillator circuitry, the clock signal from the oscillator circuitry according to a first control signal to generate a first delayed clock signal;

delaying, by a second delay circuitry coupled to the oscillator circuitry, the clock signal according to a second control signal to generate a second delayed clock signal, the first delayed clock signal and the second delayed clock signal having a substantially 90-degree phase difference with each other;

determining, by a delay controller circuitry coupled to the first delay circuitry and the second delay circuitry, a difference between the first delayed clock signal and the second delayed clock signal; and

modifying, by the delay controller circuitry, the first control signal and the second control signal according to the determined difference.

10. The method of claim 9 , further comprising:

generating, by the oscillator circuitry, an inverted clock signal having a substantially 180-degree phase difference with the clock signal;

delaying, by the first delay circuitry, the inverted clock signal according to the first control signal to generate a third delayed clock signal, the first delayed clock signal and the third delayed clock signal having a substantially 180-degree phase difference with each other; and

delaying, by the second delay circuitry, the inverted clock signal according to the second control signal to generate a fourth delayed clock signal, the second delayed clock signal and the fourth delayed clock signal having a substantially 180-degree phase difference with each other.

11. The method of claim 9 , wherein the first delay circuitry and the second delay circuitry delay the clock signal by different delay amounts.

12. The method of claim 9 , further comprising:

delaying, by a fixed delay circuitry coupled between the oscillator circuitry and the second delay circuitry, the clock signal by a predetermined amount.

13. The method of claim 12 , further comprising:

delaying, by the second delay circuitry, a signal output from the fixed delay circuitry by an amount corresponding to the second control signal.

14. The method of claim 12 , wherein the first delay circuitry is configured to delay the clock signal by a delay amount corresponding to the first control signal, and the second delay circuitry is configured to delay the clock signal by the delay amount corresponding to the second control signal.

15. The method of claim 9 , wherein the first control signal and the second control signal are differential signals.

16. An apparatus comprising:

a first oscillator circuitry configured to generate a first clock signal;

a second oscillator circuitry coupled to the first oscillator circuitry, the second oscillator circuitry configured to generate a second clock signal;

a first delay circuitry coupled to the first oscillator circuitry, the first delay circuitry configured to delay the first clock signal from the first oscillator circuitry according to a first control signal to generate a first delayed clock signal;

a second delay circuitry coupled to the second oscillator circuitry, the second delay circuitry configured to delay the second clock signal from the second oscillator circuitry according to a second control signal to generate a second delayed clock signal, the first delayed clock signal and the second delayed clock signal having a substantially 90-degree phase difference with each other; and

a delay controller circuitry coupled to the first delay circuitry and the second delay circuitry, the delay controller circuitry configured to determine a difference between the first delayed clock signal and the second delayed clock signal and modify the first control signal and the second control signal according to the determined difference.

17. The apparatus of claim 16 ,

wherein the first oscillator circuitry is configured to generate a first inverted clock signal having a substantially 180-degree phase difference with the first clock signal,

wherein the first delay circuitry is configured to delay the first inverted clock signal according to the first control signal to generate a third delayed clock signal, the first delayed clock signal and the third delayed clock signal having a substantially 180-degree phase difference with each other,

wherein the second oscillator circuitry is configured to generate a second inverted clock signal having a substantially 180-degree phase difference with the second clock signal, and

wherein the second delay circuitry is configured to delay the second inverted clock signal according to the second control signal to generate a fourth delayed clock signal, the second delayed clock signal and the fourth delayed clock signal having a substantially 180-degree phase difference with each other.

18. The apparatus of claim 17 , wherein the first delay circuitry and the second delay circuitry have identical circuit components.

19. The apparatus of claim 17 , wherein the first delay circuitry is configured to delay the first clock signal by a delay amount according to the first control signal, and the second delay circuitry is configured to delay the second clock signal by the delay amount according to the second control signal.

20. The apparatus of claim 16 , wherein the delay controller circuitry includes:

a downconverter circuitry coupled to the first delay circuitry and the second delay circuitry, the downconverter circuitry configured to downconvert the first delayed clock signal and the second delayed clock signal to obtain a first downconverted signal and a second downconverted signal, and

a filter circuitry coupled to the downconverter circuitry, the filter circuitry configured to:

filter spectral components above a predetermined frequency in the first downconverted signal to generate the first control signal, and

filter spectral components above the predetermined frequency in the second downconverted signal to generate the second control signal.