Digital predistortion device and method
View Patent ↗The disclosure discloses a digital predistortion (DPD) device and method. The DPD device comprises a predistorter configured to obtain a predistortion component from a digital baseband signal using a predistortion parameter and output the predistortion component; and a weighting unit configured to: obtain one or more weighted predistortion components by applying the predistortion component to one or more weighting coefficients, and obtain one or more predistortion correction signals by combining the digital baseband signal and the one or more weighted predistortion components, wherein the one or more weighting coefficients are determined based on the digital baseband signal, the predistortion component, and a synthesized signal in a main lobe direction obtained by combining radio frequency signals from a beamforming array.
1. A digital predistortion (DPD) device, comprising:
a predistorter configured to obtain a predistortion component from a digital baseband signal using a predistortion parameter and output the predistortion component; and
a weighting unit configured to:
obtain one or more weighted predistortion components by applying the predistortion component to one or more weighting coefficients, and
obtain one or more predistortion correction signals by combining the digital baseband signal and the one or more weighted predistortion components,
wherein the one or more weighting coefficients are determined based on the digital baseband signal, the predistortion component, and a synthesized signal in a main lobe direction obtained by combining radio frequency signals from a beamforming array.
2. The DPD device of claim 1 , wherein the weighting unit comprises:
a post-weighting calculating unit configured to determine the one or more weighting coefficients based on the digital baseband signal, the predistortion component, and the synthesized signal,
at least one multiplier configured to obtain the one or more weighted predistortion components by multiplying the one or more weighting coefficients with the predistortion component, and
at least one adder configured to obtain the one or more predistortion correction signals by combining the digital baseband signal and the one or more weighted predistortion components.
3. The DPD device of claim 2 , wherein the post-weighting calculating unit is configured to:
select the one or more weighting coefficients based on a criterion of minimizing a maximum power value of a non-linear distortion component in other directions except the main lobe direction, or select the one or more weighting coefficients based on a criterion of minimizing a sum of power values of non-linear distortion components in all directions, or
select the one or more weighting coefficients based on a criterion of minimizing a power value of a non-linear distortion component in a fixed direction.
4. The DPD device of claim 1 , wherein the predistortion parameter is trained by a predistortion parameter training unit based on the digital baseband signal, the predistortion component and the synthesized signal, and the trained predistortion parameter is output by the predistortion parameter training unit to the predistorter.
5. The DPD device of claim 4 , wherein the synthesized signal is obtained by a multiplexer in a feedback channel by combining the radio frequency signals output by power amplifiers in the beamforming array and selecting one channel synthesized signal in the main lobe direction, and the synthesized signal is output to the predistortion parameter training unit and the post-weighting calculating unit.
6. The DPD device of claim 2 , wherein the post-weighting calculating unit, based on an output d(t) of the predistorter at time t, a weighting coefficient γ i of an i th channel, an analog beamforming coefficient ω i of the i th channel, and using a general memory polynomial model, obtains the synthesized signal of an array signal to be transmitted at an azimuth angle θ, which is
z
(
t
)
θ
=
∑
i
h
i
(
θ
)
ω
i
x
(
t
)
+
∑
i
h
i
(
θ
)
ω
i
(
z
i
(
t
)
-
x
(
t
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+
(
γ
i
-
1
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d
(
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wherein, I is a total number of channels, h(θ)=[h 1 (θ) . . . h I (θ)] T represents an array manifold of a transmitting antenna at the azimuth angle θ, and z i (t) is an output of the i th channel at the time t; the non-linear distortion in a direction of the azimuth angle θ is
z
N
L
(
t
)
θ
=
∑
i
h
i
(
θ
)
ω
i
(
z
i
(
t
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x
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1
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d
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{r i } in a non-linear distortion to meet τ i γ i =I.
7. A method for implementing the digital predistortion, the method comprises:
obtaining a predistortion component from a digital baseband signal using a predistortion parameter;
obtaining one or more weighted predistortion components by applying the predistortion component to one or more weighting coefficients; and
obtaining one or more predistortion correction signals by combining the digital baseband signal and the one or more weighted predistortion components,
wherein the one or more weighting coefficients are determined based on the digital baseband signal, the predistortion component, and a synthesized signal in a main lobe direction obtained by combining radio frequency signals from a beamforming array.
8. The method of claim 7 , wherein the one or more weighting coefficients is determined based on the digital baseband signal, the predistortion component, and the synthesized signal.
9. The method of claim 7 , wherein applying the predistortion component to the one or more weighting coefficients comprises multiplying the one or more weighting coefficients with the predistortion component.
10. The method of claim 7 , wherein the one or more weighting coefficients is selected based on one of a first criterion, a second criterion, and a third criterion,
wherein the first criterion is a criterion of minimizing a maximum power value of a non-linear distortion component in other directions except the main lobe direction,
wherein the second criterion is a criterion of minimizing a sum of power values of non-linear distortion components in all directions, and
wherein the third criterion is a criterion of minimizing a power value of a non-linear distortion component in a fixed direction.
11. The method of claim 7 , wherein the predistortion parameter is trained based on the digital baseband signal, the predistortion component and the synthesized signal.
12. The method of claim 11 , wherein the synthesized signal is obtained by combining the radio frequency signals output by power amplifiers in the beamforming array and selecting one channel synthesized signal in the main lobe direction.
13. The method of claim 7 , wherein, based on an output d(t) of a predistorter that obtains the predistortion component at time t, a weighting coefficient γ i of an i th channel, an analog beamforming coefficient ω i of the i th channel, and using a general memory polynomial model, the synthesized signal of an array signal to be transmitted at an azimuth angle θ is obtained as follows
z
(
t
)
θ
=
∑
i
h
i
(
θ
)
ω
i
x
(
t
)
+
∑
i
h
i
(
θ
)
ω
i
(
z
i
(
t
)
-
x
(
t
)
+
(
γ
i
-
1
)
d
(
t
)
)
wherein, I is a total number of channels, h(θ)=[h 1 (θ) . . . h I (θ)] T represents an array manifold of a transmitting antenna at the azimuth angle θ, and z i (t) is an output of the i th channel at the time t; the non-linear distortion in a direction of the azimuth angle θ is
z
N
L
(
t
)
θ
=
∑
i
h
i
(
θ
)
ω
i
(
z
i
(
t
)
-
x
(
t
)
+
(
γ
i
-
1
)
d
(
t
)
)
{r i } in a non-linear distortion to meet Σ i γ i =I.