Compensation technique for the nonlinear behavior of digitally-controlled oscillator (DCO) gain

1. A method for controlling a digitally controlled oscillator (DCO), the method comprising:

generating a first normalized tuning word (NTW) corresponding to a first channel of a plurality of channels;

generating a plurality of normalizing gain multipliers, including a first normalizing gain multiplier X, using a multiplexer, based on a reference frequency f R and a nonlinear function of frequency of a digitally controlled oscillator or an estimate of the nonlinear function of frequency, at a first frequency corresponding to the first channel;

multiplying the first NTW by the first normalizing gain multiplier X to obtain a first oscillator tuning word (OTW); and

inputting the first OTW to the DCO to cause the DCO to hop to the first channel.

2. The method of claim 1 , wherein the reference frequency f R is the frequency of a second channel of the plurality of channels.

3. The method of claim 2 , wherein the second channel is a central channel of the plurality of channels.

4. The method of claim 1 , further comprising:

generating a second NTW corresponding to a first channel of the plurality of channels;

wherein said generating a plurality of normalizing gain multipliers includes generating a second normalizing gain multiplier X based on the nonlinear function of frequency at a second frequency corresponding to a second channel or based on an estimate of the nonlinear function of frequency at the second frequency;

multiplying the second NTW by the second normalizing gain multiplier X to obtain a second OTW; and

inputting the second OTW to the DCO to cause the DCO to hop to the second channel.

5. The method of claim 1 , wherein at least part of the method is performed in an all-digital phase locked loop (ADPLL).

6. The method of claim 1 , wherein the first normalizing gain multiplier X is based on a linear interpolation of the nonlinear function of frequency at the first frequency.

7. The method of claim 6 , wherein the interpolation is based on a center point of the nonlinear function of frequency.

8. The method of claim 6 , wherein the nonlinear function of frequency is a cubic function of frequency.

9. The method of claim 6 , wherein the interpolation is based on:

y

=

y

0

+

dy

0

df

⁢

(

f

-

f

0

)

=

y

0

⁡

(

1

-

3

⁢

f

-

f

0

f

0

)

in which y corresponds to a change in DCO gain variation, f 0 corresponds to a frequency at which the DCO gain variation is 100%, and y 0 corresponds to the value of the change in DCO gain variation at which the gain variation is 100%.

10. A system for controlling a digitally controlled oscillator, the system comprising:

a phase-locked loop (PLL) configured to generate a plurality of normalized tuning words, each NTW corresponding to a respective channel of a plurality of channels;

a digitally controlled oscillator (DCO) having a gain that is a nonlinear function of frequency;

a multiplexer configured to generate a plurality of normalizing gain multipliers X, each normalizing gain multiplier X being based on a reference frequency f R and the nonlinear function of frequency, or an estimate of the nonlinear function of frequency, at a respective frequency of a channel of the plurality of channels; and

an arithmetic module configured to generate a plurality of oscillator tuning words (OTWs) based on a respective NTW and a respective normalizing gain multiplier X,

wherein the DCO hops among the plurality of channels based on respective OTWs of the plurality of OTWs.

11. The system of claim 10 , wherein the PLL comprises an all-digital PLL.

12. The system of claim 10 , wherein at least one of the multiplexer and the arithmetic module are provided as part of a normalized DCO comprising the DCO.

13. The system of claim 10 , wherein each normalizing gain multiplier X is based on a linear interpolation of the nonlinear function of frequency.

14. The system of claim 13 , wherein the interpolation is based on a center point of the nonlinear function of frequency.

15. The system of claim 13 , wherein the nonlinear function of frequency is a cubic function of frequency.

16. The system of claim 13 , wherein the interpolation is based on:

y

=

y

0

+

dy

0

df

⁢

(

f

-

f

0

)

=

y

0

⁡

(

1

-

3

⁢

f

-

f

0

f

0

)

in which y corresponds to a change in DCO gain variation, f 0 corresponds to a frequency at which the DCO gain variation is 100%, and y 0 corresponds to the value of the change in DCO gain variation at which the gain variation is 100%.

17. The system of claim 10 , wherein the reference frequency f R is the frequency of a second channel of the plurality of channels.

18. A normalized digitally controlled oscillator (nDCO), comprising:

a digitally controlled oscillator (DCO) having a gain that is a nonlinear function of frequency;

a multiplexer configured to generate a plurality of normalizing gain multipliers, each normalizing gain multiplier based on a reference frequency f R and the nonlinear function of frequency, or an estimate of the nonlinear function of frequency, at a respective frequency of a plurality of frequencies; and

an arithmetic module configured to generate a respective oscillator tuning word (OTW) based on each normalizing gain multiplier,

the DCO generating a respective frequency based on each OTW.

19. The DCO of claim 18 , wherein each normalizing gain multiplier is based on a linear interpolation of the nonlinear function of frequency.

20. The nDCO of claim 19 , wherein the linear interpolation is based on a center point of a frequency range.