Method and device for measuring the frequency of a signal

1. A method for determining a frequency of a signal using a frequency measurement circuit, the method comprising, using the frequency measurement circuit:

a) counting a number of whole periods of the signal during a first period of a periodic reference signal;

b) repeating step a) for each period of the periodic reference signal until a first duration is equal to a first quantity of periods of the periodic reference signal;

c) determining a first average of the numbers of whole periods;

d) repeating at least one of steps a), b) and c) and at each repetition shifting a start of the counting of step a) by at least one period of the periodic reference signal;

e) determining a second average of the first averages; and

f) determining the frequency of the signal from the second average and the frequency of the periodic reference signal by multiplying the second average times the frequency of the periodic reference signal.

2. The method of claim 1 , wherein repeating at least one of steps a), b) and c) comprises repeating steps a), b) and c) in parallel.

3. The method of claim 1 , wherein steps a) to e) are implemented by applying the following formula:

M

⁢

⁢

2

=

1

R

*

(

∑

k

=

1

R

⁢

1

S

⁢

∑

i

=

k

k

+

S

-

1

⁢

C

i

)

wherein M 2 designates the second average, S corresponds to the first quantity of periods, R corresponds to a number of repetitions of steps during step d), and C i corresponds to the number of whole periods of the signal counted during a current period of the periodic reference signal.

4. The method of claim 1 , wherein the repetitions of steps a), b) and c) is equal to a second quantity of periods of the periodic reference signal reduced by the first quantity of periods.

5. The method of claim 4 , wherein the first quantity and the second quantity of periods are powers of two.

6. The method of claim 5 , wherein the first quantity of periods is equal to half the second quantity of periods.

7. The method of claim 6 , wherein steps a) to e) are implemented by applying the following formula:

M

⁢

⁢

2

=

1

P

-

S

*

1

S

*

(

∑

i

=

1

S

⁢

i

*

C

i

+

∑

i

=

S

+

1

P

-

1

⁢

(

P

-

i

)

*

C

i

)

wherein M 2 designates the second average, S corresponds to the first quantity of periods, P corresponds to the second quantity of periods and C i corresponds to the number of whole periods of the signal counted during a current period of the periodic reference signal.

8. The method of claim 5 , wherein the first quantity of periods is less than half the second quantity of periods.

9. The method of claim 8 , wherein steps a) to e) are implemented by applying the following formula:

M

⁢

⁢

2

=

1

P

-

S

*

1

S

*

(

∑

i

=

1

S

⁢

i

*

C

i

+

∑

i

=

S

+

1

P

-

S

⁢

S

*

C

i

+

∑

i

=

P

-

S

+

1

P

-

1

⁢

(

P

-

i

)

*

C

i

)

wherein M 2 designates the second average, S corresponds to the first quantity of periods, P corresponds to the second quantity of periods and C i corresponds to the number of whole periods of the signal counted during a current period of the periodic reference signal.

10. The method of claim 1 , wherein in steps b) and c) accounting for the numbers of whole periods of the signal already counted during the at least one preceding group of steps a) and b).

11. The method of claim 1 , wherein determining the second average comprises performing a bit shift on an accumulator value.

12. The method of claim 1 , wherein counting the number of whole periods comprises using a counter, the method further comprising, during step b), resetting the counter after each period of the periodic reference signal.

13. A method for determining a frequency of a signal using a frequency measurement circuit, the method comprising:

receiving the signal with a first input;

receiving a periodic reference signal with a second input;

counting, with a counter of the frequency measurement circuit, a number of whole periods of the signal to generate a period count during each period of the periodic reference signal for P −1 periods, wherein P is a positive integer;

resetting the counter after each period of the periodic reference signal;

incrementing by 1 a setpoint counter of the frequency measurement circuit after each period of the periodic reference signal until the setpoint counter reaches S, wherein S is a positive integer lower than P;

multiplying each period count with an output of the setpoint counter to generate respective counter values;

accumulating, with an accumulator of the frequency measurement circuit, the respective counter values; and

generating an average value by dividing the accumulated counter value by (P-S)*S, wherein the frequency of the signal is based on the average value.

14. The method of claim 13 , further comprising decrementing by 1 the setpoint counter a period after the setpoint counter reaches S.

15. The method of claim 13 , further comprising keeping the output of the setpoint counter at S for more than 1 period of the periodic reference signal.

16. The method of claim 13 , wherein S and P are powers of 2.

17. The method of claim 13 , wherein S is half of P.

18. The method of claim 13 , further comprising dividing the accumulated counter value by (P-S)*S by performing a shift operation on a register of the accumulator.

19. The method of claim 13 , wherein the first input is coupled to an output of a voltage controlled oscillator (VCO) of a phased-locked loop (PLL) and the second input is coupled to a reference input of the PLL.

20. The method of claim 1 , further comprising:

receiving the signal from a voltage controlled oscillator (VCO) of a phased-locked loop (PLL); and

receiving the periodic reference signal from the PLL.