IQ-modulator pre-distortion
View Patent ↗An IQ-modulator pre-distorter includes means for pre-distorting each IQ-vector by a 2-dimensional linear transformation that depends on the value of the IQ-vector to be pre-distorted. The transformation is based on polynomials in the I- and Q-components. In a preferred embodiment the transformation is based on a 2×2 dimensional lookup table matrix, the elements (T 11 , T 12 , T 21 , T 22 ) of which are sampled polynomials in the I- and Q-components of the IQ-vector.
1. An IQ-modulator pre-distortion method, said method comprising the step of pre-distorting each IQ-vector by a 2-dimensional linear transformation that depends on the value of the IQ-vector to be pre-distorted, wherein said transformation is based on polynomials in the I- and Q-components of said IQ-vector, wherein said transformation is based on a 2×2 dimensional lookup table matrix, the elements of which are sampled polynomials in the I- and Q-components of said IQ-vector, wherein one of the diagonal elements and one of the off-diagonal elements of said matrix depend on said I-component and the other diagonal element and the other off-diagonal element depend on said Q-component, and wherein said transformation is represented by the equation:
[
I
′
(
t
)
Q
′
(
t
)
]
=
[
T
11
(
I
(
t
)
)
T
12
(
Q
(
t
)
)
T
21
(
I
(
t
)
)
T
22
(
Q
(
t
)
)
]
[
I
(
t
)
Q
(
t
)
]
+
[
α
0
β
0
]
where
[
I
(
t
)
Q
(
t
)
]
is the IQ-vector to be pre-distorted,
[
T
11
(
I
(
t
)
)
T
12
(
Q
(
t
)
)
T
21
(
I
(
t
)
)
T
22
(
Q
(
t
)
)
]
is said matrix,
[
α
0
β
0
]
is an offset vector,
[
I
′
(
t
)
Q
′
(
t
)
]
is the pre-distorted vector, and
t is a variable representing time.
2. An IQ-modulator pre-distorter, comprising: means for pre-distorting each IQ-vector by a 2-dimensional linear transformation that depends on the value of the IQ-vector to be pre-distorted, wherein said transformation is based on polynomials in the I- and Q-components of said IQ-vector, wherein said transformation is based on a 2×2 dimensional lookup table matrix, the elements of which are sampled polynomials in the I- and Q-components of said IQ-vector, wherein one of the diagonal elements and one of the off-diagonal elements of said matrix depend on said I-component and the other diagonal element and the other off-diagonal element depend on said Q-component, and wherein said transformation is represented by the equation:
[
I
′
(
t
)
Q
′
(
t
)
]
=
[
T
11
(
I
(
t
)
)
T
12
(
Q
(
t
)
)
T
21
(
I
(
t
)
)
T
22
(
Q
(
t
)
)
]
[
I
(
t
)
Q
(
t
)
]
+
[
α
0
β
0
]
where
[
I
(
t
)
Q
(
t
)
]
is the IQ-vector to be pre-distorted,
[
T
11
(
I
(
t
)
)
T
12
(
Q
(
t
)
)
T
21
(
I
(
t
)
)
T
22
(
Q
(
t
)
)
]
said matrix,
[
α
0
β
0
]
is an offset vector,
[
I
′
(
t
)
Q
′
(
t
)
]
is the pre-distorted vector, and
t is a variable representing time, and
means for outputting each pre-distorted IQ vector.
3. A base station including an IQ-modulator pre-distorter, said pre-distorter comprising: means for pre-distorting each IQ-vector by a 2-dimensional linear transformation that depends on the value of the IQ-vector to be pre-distorted, wherein said transformation is based on polynomials in the I- and Q-components of said IQ-vector, wherein said transformation is based on a 2×2 dimensional lookup table matrix, the elements of which are sampled polynomials in the I- and Q-components of said IQ-vector, wherein one of the diagonal elements and one of the off-diagonal elements of said matrix depend on said I-component and the other diagonal element and the other off-diagonal element depend on said Q-component, and wherein said transformation is represented by the equation:
[
I
′
(
t
)
Q
′
(
t
)
]
=
[
T
11
(
I
(
t
)
)
T
12
(
Q
(
t
)
)
T
21
(
I
(
t
)
)
T
22
(
Q
(
t
)
)
]
[
I
(
t
)
Q
(
t
)
]
+
[
α
0
β
0
]
where
[
I
(
t
)
Q
(
t
)
]
is the IQ-vector to be pre-distorted,
[
T
11
(
I
(
t
)
)
T
12
(
Q
(
t
)
)
T
21
(
I
(
t
)
)
T
22
(
Q
(
t
)
)
]
said matrix,
[
α
0
β
0
]
is an offset vector,
[
I
′
(
t
)
Q
′
(
t
)
]
is the pre-distorted vector, and
t is a variable representing time, and
means for outputting each pre-distorted IQ vector.