Calibration device for a phased locked loop synthesiser
View Patent ↗A calibration device for a phase locked loop arranged to generate an output frequency based upon a first frequency range of an input signal applied to a first input and a second frequency range of the input signal applied to a second input, the calibration phase locked loop synthesizer device comprising an estimator arranged to use a two dimensional estimation algorithm with a signal value indicative of a mismatch between the first input path and the second input path to determine an estimate of the mismatch to allow matching of the first input path and the second input path.
1. A calibration device for a phase locked loop arranged to generate an output frequency based upon a first frequency range of an input signal applied to a first input and a second frequency range of the input signal applied to a second input, the calibration device comprising an estimator arranged to use a two dimensional estimation algorithm with a signal value indicative of a mismatch between the first input path and the second input path to determine an estimate of the mismatch to allow matching of the first input path and the second input path, wherein:
one dimension of the two dimensional estimation algorithm is arranged to estimate a gain mismatch between the first input path and the second input path and the second dimension of the two dimensional estimation algorithm is arranged to estimate a time delay between the first input path and the second input path; and
the two dimensional estimation algorithm takes the form of:
[
k
^
h
(
n
+
1
)
τ
^
D
(
n
+
1
)
]
=
[
k
^
h
(
n
)
τ
^
D
(
n
)
]
+
[
μ
k
0
0
μ
τ
]
[
-
sin
{
ω
(
n
-
τ
^
D
(
n
)
-
τ
G
)
}
k
^
h
cos
{
ω
(
n
-
τ
^
D
(
n
)
-
τ
G
)
}
]
e
^
(
n
)
where:
ê(n) is a sampled tuning voltage,
τ G is the approximate group delay through the low port to the sampled, digitally processed tuning voltage,
ω is a test tone frequency,
μ τ and μ k are scalar constants that control calibration transients,
{circumflex over (τ)} D is the estimate of the high port delay and
{circumflex over (k)} h is the estimate of the high port gain.
2. A calibration device according to claim 1 , further comprising a detector arranged on the occurrence of a test tone being applied to the first input and the second input to generate a signal indicative of a mismatch between the first input path and the second input path.
3. A calibration device according to claim 2 , wherein the detector comprises a phase comparator for comparing a reference phase with a representation of an output phase to generate an output signal indicative of a mismatch between the first input path and the second input path and a loop filter for converting the phase comparator output to a tuning voltage that is utilized to provide a signal value indicative of a mismatch between the first input path and the second input path to the estimator.
4. A calibration device according to claim 1 , wherein the two dimensional estimation algorithm is a Least Mean Square algorithm based upon an instantaneous or stochastic gradient term.
5. A calibration device according to claim 4 , wherein the instantaneous or stochastic gradient term is:
∇
^
(
n
)
=
δⅇ
2
(
n
)
δ
Θ
^
(
n
)
=
δⅇ
2
(
n
)
δⅇ
(
n
)
δⅇ
(
n
)
δ
Θ
^
(
n
)
=
2
δⅇ
(
n
)
δ
Θ
^
(
n
)
ⅇ
(
n
)
where:
{circumflex over (Θ)}(n) is a vector of parameter estimates; and
e(n) is an instantaneous estimation error.
6. A calibration device according to claim 1 , wherein the phase locked loop comprises a loop filter for generating a tuning voltage that is utilized to provide a signal value indicative of a mismatch between the first input path and the second input path to the estimator.