Digital phase locked loop frequency estimation
A Digital Phase Locked Loop (DPLL), including a Time-to-Digital Converter (TDC) configured generate quantized phase values of a controlled oscillator signal; and a frequency estimation circuit configured to receive the quantized phase values, determine wraparound phase of the quantized phase values, and estimate a frequency based on the quantized phase values and the wraparound phase.
1. A Digital Phase Locked Loop (DPLL), comprising:
a Time-to-Digital Converter (TDC) configured to generate quantized phase values of a controlled oscillator signal; and
a frequency estimation circuit configured to receive the quantized phase values, determine a wraparound phase of the quantized phase values, and estimate a frequency based on the quantized phase values and the wraparound phase.
2. The DPLL of claim 1 , wherein the frequency estimation circuit comprises:
a phase determination circuit configured to determine an accumulation of the quantized phase values having the wraparound phase.
3. The DPLL of claim 1 , wherein the frequency estimation circuit comprises:
a wraparound phase determination circuit configured to determine the wraparound phase of the quantized phase values.
4. The DPLL of claim 3 , wherein the wraparound phase determination circuit comprises a decision circuit configured to determine the wraparound phase by comparing a difference between a current quantized phase value and a previous quantized phase value with an expected frequency.
5. The DPLL of claim 4 , wherein the decision circuit determines the wraparound phase in accordance with the following:
L
I
=
{
-
1
,
(
φ
k
-
φ
k
-
1
)
-
f
exp
<
-
P
/
2
0
,
else
1
,
(
φ
k
-
φ
k
-
1
)
-
f
exp
>
P
/
2
}
,
L
=
∑
l
=
1
k
L
l
,
where L is an accumulated number of phase wraparounds, φ k is the current quantized phase value, φ k-1 is the previous quantized phase value, f exp is the expected frequency, k is an index number of a phase value, and P is a threshold proportional to a period of the controlled oscillator signal.
6. The DPLL of claim 5 , wherein the frequency estimation circuit comprises:
an estimated frequency determination circuit configured to determine the estimated frequency by removing the wraparound phase from the quantized phase values.
7. The DPLL of claim 5 , wherein a value of the period used in the wraparound phase determination is an estimate of the period of the controlled oscillator signal.
8. The DPLL of claim 1 , wherein the estimated frequency is represented as follows:
{circumflex over (f)}=b 2 *y k =b 2 *{tilde over (y)} k +b 2 *( L k ·P ),
where {circumflex over (f)} is the estimated frequency, b 2 is a predetermined matrix, * is a multiplication operation of a vector by a vector, y k is a quantized phase value without the wraparound phase, {tilde over (y)} k is a quantized phase value with the wraparound phase, L k is an accumulated number of phase wraparounds, k is an index number of a phase value, and P is a threshold proportional to a period of the controlled oscillator signal.
9. The DPLL of claim 1 , wherein the frequency estimation circuit is configured to estimate the frequency on a quantized phase value-by-quantized phase value basis.
10. The DPLL of claim 1 , wherein the quantized phase values are in units relative to a period of the controlled oscillator signal.
11. A wireless communication device, comprising:
a baseband processor comprising the DPLL of claim 1 , or
a Radio Frequency (RF) front end comprising the DPLL of claim 1 .
12. A method of operating a Digital Phase Locked Loop (DPLL), comprising:
generating, by a Time-to-Digital Converter (TDC), quantized phase values of a controlled oscillator signal;
determining, by a frequency estimation circuit, a wraparound phase of the quantized phase values; and
least-squares estimating, by the frequency estimation circuit, a frequency based on the quantized phase values and the wraparound phase.
13. The method of claim 12 , wherein the least-squares estimating comprises:
determining, by a phase determination circuit, an accumulation of the quantized phase values having the wraparound phase.
14. The method of claim 12 , wherein the wraparound phase of the quantized phase values is determined by a wraparound phase determination circuit comprised within the frequency estimation circuit.
15. The method of claim 14 , wherein the wraparound phase is determined by a decision circuit comprised within the wraparound phase determination circuit, and by comparing a difference between a current quantized phase value and a previous quantized phase value with an expected frequency.
16. The method of claim 15 , wherein the decision circuit determines the wraparound phase is in accordance with the following:
L
I
=
{
-
1
,
(
φ
k
-
φ
k
-
1
)
-
f
exp
<
-
P
/
2
0
,
else
1
,
(
φ
k
-
φ
k
-
1
)
-
f
exp
>
P
/
2
}
,
L
=
∑
l
=
1
k
L
l
.
where L is an accumulated number of phase wraparounds, φ k is the current quantized phase value, φ k-1 is the previous quantized phase value, f exp is an expected frequency, k is an index number of a phase value, and P is a threshold proportional to a period of the controlled oscillator signal.
17. The method of claim 16 , wherein a value of the period used in the wraparound phase determination is an estimate of the period of the controlled oscillator signal.
18. The method of claim 12 , wherein the least-squares estimating comprises:
determining, by an estimated frequency determination circuit within the frequency estimation circuit, the estimated frequency by removing the wraparound phase from the quantized phase values.
19. The method of claim 12 , wherein the estimated frequency is represented as follows:
{circumflex over (f)}=b 2 *y k =b 2 *{tilde over (y)} k +b 2 *( L k ·P ),
where {circumflex over (f)} is the estimated frequency, b 2 is a predetermined matrix, * is a multiplication operation of a vector by a vector, y k is a quantized phase value without wraparound phase, {tilde over (y)} k is a quantized phase value with wraparound phase, L k is an accumulated number of phase wraparounds, k is an index number of a phase value, and P is a threshold proportional to a period of the controlled oscillator signal.
20. The method of claim 12 , wherein the least-squares frequency estimating comprises:
estimating the frequency on a quantized phase value-by-quantized phase value basis.
21. The method of claim 12 , wherein the quantized phase values are in units relative to a period of the controlled oscillator signal.