Distortion-compensation device and distortion-compensation method
Disclosed is a distortion-compensation apparatus that can reduce the storage space for storing coefficients required for distortion-compensation calculation, and can accurately execute distortion compensation. Distortion-compensation apparatus ( 100 ) compensates for distortion of an output signal from a predetermined circuit by predistortion in which an input signal is preliminarily multiplied by a coefficient. First multiplication section ( 200 c ) of distortion-compensation apparatus ( 100 ) multiplies an input signal by a first coefficient selected from coefficient candidates in accordance with the input signal; second multiplication section ( 201 c 1 to 201 c m ) multiplies a delay signal of an input signal by a tap coefficient; and adding section ( 202 ) outputs a signal obtained by adding together an input signal multiplied by the compensation coefficient and the delay signal multiplied by the tap coefficient to the predetermined circuit.
1. A distortion-compensation apparatus comprising:
a first multiplication section that obtains a first multiplication signal by multiplying an input signal by a first pre-distortion coefficient selected from a plurality of first coefficient candidates in accordance with the input signal;
a second multiplication section that obtains a second multiplication signal by multiplying a delay signal of the input signal by a second pre-distortion coefficient;
an adding section that obtains an addition signal by adding the first multiplication signal and the second multiplication signal and outputs the addition signal to a predetermined circuit; and
an update-processing section that updates the first pre-distortion coefficient and the second pre-distortion coefficient by convergence calculation using an iteration scheme based on the input signal and the output signal outputted from the predetermined circuit, wherein,
the update-processing section updates the first pre-distortion coefficient, then updates the second pre-distortion coefficient, and after then updates both of the first updated pre-distortion coefficient and the second updated pre-distortion coefficient.
2. The distortion-compensation apparatus according to claim 1 , wherein when an absolute value of the second updated pre-distortion coefficient is smaller than a predetermined threshold, the update-processing section excludes the second updated pre-distortion coefficient from the convergence calculation.
3. The distortion-compensation apparatus according to claim 1 , wherein the iteration scheme is a Least Mean Square scheme.
4. A distortion-compensation method comprising:
obtaining a first multiplication signal by multiplying an input signal by a first pre-distortion coefficient selected from a plurality of first coefficient candidates in accordance with the input signal;
obtaining a second multiplication signal by multiplying a delay signal of the input signal by a second pre-distortion coefficient;
obtaining an addition signal by adding the first multiplication signal and the second multiplication signal;
outputting the addition signal to a predetermined circuit; and
updating the first pre-distortion coefficient, then updating the second pre-distortion coefficient, and after then updating both of the first updated pre-distortion coefficient and the second updated pre-distortion coefficient by convergence calculation using an iteration scheme based on the input signal and the output signal outputted from the predetermined circuit.