Digital pre-distortion technique using non-linear filters
AssigneeMicroelectronics Technology Inc.
InventorsKhiem V. Cai, David B. Rutan, Matthew S. Gorder, Don C. Devendorf
Life of this patent
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Abstract
A system, method and computer program product for stabilizing a coefficient set used by a digital predistortion (DPD) engine to apply pre-distortion to a transmit signal and cancel distortion generated by a distorting element or distorting system when transmitting the transmit signal, including obtaining an initial coefficient set; rotating the initial coefficient set to maintain a phase of fundamental components (w10(t), . . . , w1Q(t)) of the initial coefficient set a constant value; averaging the rotated coefficient set to obtain an averaged coefficient set; and applying the averaged coefficient set to the DPD engine.
Claims4
A computer-readable medium comprising program code for stabilizing a coefficient set used by a digital predistortion (DPD) engine to apply pre-distortion to a transmit signal and cancel distortion generated by a distorting element or distorting system when transmitting the transmit signal, the program code for causing performance of a method comprising:
- obtaining an initial coefficient set;
- rotating the initial coefficient set to maintain a phase of fundamental components (w10(t), . . . ,w1Q(t)) of the initial coefficient set as a constant value;
- averaging in the time domain the rotated coefficient set to obtain an averaged coefficient set;
- and
- applying the averaged coefficient set to the DPD engine,
- the initial coefficient set expressed as
- W
-
- (
- t
- )
- =
- [
- w
- 10
-
- (
- t
- )
- w
- 11
-
- (
- t
- )
- …
- w
- 1
-
- Q
-
- (
- t
- )
- w
- 20
-
- (
- t
- )
- w
- 21
-
- (
- t
- )
- …
- w
- 2
-
- Q
-
- (
- t
- )
- …
- …
- …
- …
- w
- k
-
-
- 0
-
- (
- t
- )
- w
- K
-
-
- 1
-
- (
- t
- )
- …
- w
- KQ
-
- (
- t
- )
- ]
- ,
- the program code further for causing performance of a method comprising:
- computing the phase of the fundamental components of the initial coefficient set as
- θ
- 1
-
- (
- t
- )
- =
- angle
- (
- ∑
- q
- =
- 0
- Q
-
-
- w
- 1
-
- q
-
- (
- t
- )
- )
- ,
- and
- ;
- computing the rotated coefficient set as
- W
- 2
-
- (
- t
- )
- =
- [
- w
- 10
-
- (
- t
- )
- w
- 11
-
- (
- t
- )
- …
- w
- 1
-
- Q
-
- (
- t
- )
- w
- 20
-
- (
- t
- )
- w
- 21
-
- (
- t
- )
- …
- w
- 2
-
- Q
-
- (
- t
- )
- …
- …
- …
- …
- w
- k
-
-
- 0
-
- (
- t
- )
- w
- K
-
-
- 1
-
- (
- t
- )
- …
- w
- KQ
-
- (
- t
- )
- ]
-
- ⅇ
- -
- j
-
- θ
- 1
-
- (
- t
- )
- .
A computer-readable medium comprising program code for generating a coefficient set with improved accuracy, the coefficient set used by a digital predistortion (DPD) engine to apply pre-distortion to a transmit signal and cancel distortion generated by a distorting element or distorting system when transmitting the transmit signal, the program code for causing performance of a method comprising:
- selecting samples from a pre-distorted transmit signal from the DPD engine exceeding a predetermined threshold;
- zeroing the selected samples from the transmit signal and the corresponding row of the “H”matrix of the distorting element or distorting system;
- and
- computing a coefficient set from the transmit signal and the delayed feedback signal with the selected samples removed,
- the pre-distorted transmit signal having samples S represented as S=[s(0)s(1)s(2)s(3) . . . s(U-1)]T, the program code further for causing performance of a method comprising:
- defining a soft factor vector as
- G=[g(0)g(1)g(2)g(3) . . . g(U−1)]T
- where
- g(i)=1 for |s(i)|<T2, g(i)=0 otherwise, and T2is the predetermined threshold:
- and
- if g(i) =0, zeroing an ith sample of S and zeroing an ith row of the H matrix.
Dependencies are inferred from the claim text.