Adaptive digital pre-distortion system
First Claim
1. An electronic circuit, for amplifying an input signal, x0, comprising:
- a clipping unit for generating a signal, x, having a reduced peak-to-average power ratio by clipping the input signal x0′
;
a pre-distorter for generating a pre-distorted signal, ξ
, defined by an pre-distortion algorithm which is based on an amplifier model function A;
a representation unit for representing the amplifier model function, A, either in terms of coefficients of polynomials, or as look-up tables;
a non-linear processing unit, like a power amplifier, for generating a processed signal, z, like an amplified pre-distorted signal;
a time delay unit for compensating a processing time for the pre-distorted signal ξ
generating a delayed pre-distorted signal ξ
′
;
a time delay cascade for delaying the pre-distorted signal, ξ
′
, at integer sample clocks 1,2, . . . , n generating delayed signals
ξ
−
1′
,ξ
−
2′
, . . . ,ξ
−
n′
and an adaptation unit for learning the amplifier model function A using the processed signal, z, and the delayed signals
ξ
,ξ
−
1′
,ξ
−
2′
, . . . ,ξ
−
n′
such that a measure for non-linearity Ln is minimized.
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Accused Products
Abstract
An adaptive Digital Pre-distortion System and a method for correcting especially power amplifier memory effects. In particular, the invention relates to an electronic circuit, for amplifying an input signal, comprising: a clipping unit for generating a signal, having a reduced peak-to-average power ratio by clipping the input signal; a pre-distorter for generating a pre-distorted signal, defined by an pre-distortion algorithm which is based on the amplifier model function; a representation unit for representing the amplifier model function; a non-linear processing unit, in particular a power amplifier, for generating a processed signal, in particular by amplifying said received pre-distorted signal; a time delay unit for compensating the processing time for the pre-distorted signal generating the delayed pre-distorted signal; and a time delay cascade for delaying the said delayed pre-distorted signal, at the integer sample clocks generating the signals.
62 Citations
6 Claims
-
1. An electronic circuit, for amplifying an input signal, x0, comprising:
-
a clipping unit for generating a signal, x, having a reduced peak-to-average power ratio by clipping the input signal x0′
;a pre-distorter for generating a pre-distorted signal, ξ
, defined by an pre-distortion algorithm which is based on an amplifier model function A;a representation unit for representing the amplifier model function, A, either in terms of coefficients of polynomials, or as look-up tables; a non-linear processing unit, like a power amplifier, for generating a processed signal, z, like an amplified pre-distorted signal; a time delay unit for compensating a processing time for the pre-distorted signal ξ
generating a delayed pre-distorted signal ξ
′
;a time delay cascade for delaying the pre-distorted signal, ξ
′
, at integer sample clocks 1,2, . . . , n generating delayed signals
ξ
−
1′
,ξ
−
2′
, . . . ,ξ
−
n′and an adaptation unit for learning the amplifier model function A using the processed signal, z, and the delayed signals
ξ
,ξ
−
1′
,ξ
−
2′
, . . . ,ξ
−
n′such that a measure for non-linearity Ln is minimized.
-
-
2. A method for predistortion with an electronic circuit, for amplifying an input signal, x0, comprising:
-
a clipping unit for generating a signal, x, having a reduced peak-to-average power ratio by clipping the input signal x0′
;a pre-distorter for generating a pre-distorted signal, ξ
, defined by an pre-distortion algorithm which is based on an amplifier model function A;a representation unit for representing the amplifier model function, A, either in terms of coefficients of polynomials, or as look-up tables; a non-linear processing unit, like a power amplifier, for generating a processed signal, z, like an amplified pre-distorted signal; a time delay unit for compensating a processing time for the pre-distorted signal ξ
generating a delayed pre-distorted signal ξ
′
;a time delay cascade for delaying the pre-distorted signal, ξ
′
, at integer sample clocks 1, 2, . . . , n generating delayed signals
ξ
−
1′
,ξ
−
2′
, . . . ,ξ
−
n′and an adaptation unit for learning the amplifier model function A using the processed signal, z, and the delayed signals
ξ
,ξ
−
1′
,ξ
−
2′
, . . . ,ξ
−
n′such that a measure for non-linearity Ln is minimized wherein a complex digital amplifier output signal from a feedback, path can be described as a function having a multiplicative and additive terms, where
K=max(K1,K2), K1=0,1, . . . , K2=1,2, . . .- View Dependent Claims (3, 4, 5)
and the measure for the non-linearity Ln has the limit
Ln→
0.
-
-
4. The method for predistortion according to claim 3, characterized in that for each given clipped sample
xna constant
C(xn;- ξ
n−
1,ξ
n−
2, . . . ,ξ
n−
k)is calculated according to equation , where
yfbis a constant feedback gain.
- ξ
-
5. Method for predistortion according to claim 3 characterized in that for each given clipped sample
xna predistorted sample
ξ-
n
is calculated iteratively according to equation
-
n
-
6. A wireless communication system comprising a power amplifier, characterized by further comprising an electronic circuit, for amplifying an input signal, x0, comprising:
-
a clipping unit for generating a signal, x, having a reduced peak-to-average power ratio by clipping the input signal x0′
;a pre-distorter for generating a pre-distorted signal, ξ
, defined by an pre-distortion algorithm which is based on an amplifier model function A;a representation unit for representing the amplifier model function, A, either in terms of coefficients of polynomials, or as look-up tables; a non-linear processing unit, like a power amplifier, for generating a processed signal, z, like an amplified pre-distorted signal; a time delay unit for compensating a processing time for the pre-distorted signal ξ
generating a delayed pre-distorted signal ξ
′
;a time delay cascade for delaying the pre-distorted signal, ξ
′
, at integer sample clocks 1, 2, . . . , n generating delayed signals
ξ
−
1′
,ξ
−
2′
, . . . ,ξ
−
n′and an adaptation unit for learning the amplifier model function A using the processed signal, z, and the delayed signals
ξ
,ξ
−
1′
,ξ
−
2′
, . . . ,ξ
−
n′such that a measure for non-linearity Ln is minimized.
-
Specification