Orthogonal Basis Function Set for Digital Predistorter
AssigneeTelefonaktiebolaget L M Ericsson (publ)
InventorChunlong Bai
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Abstract
A predistorter applies a distortion function to an input signal to predistort the input signal. The output of the distortion function is modeled as the sum of the output signals from the orthogonal basis functions weighted by corresponding weighting coefficients. Techniques are described for orthogonalizing the basis function output signals depending on the distribution of the input signal.
Claims14
A method of compensating for distortion of an input signal by an electronic device that operates on the input signal to produce an output signal, said method comprising:
- computing a set of model coefficients for a two-dimensional lattice prediction model of a basis function set from a set of input signal samples over a predetermined sampling interval, wherein the lattice prediction model represents basis functions in a predistorter basis function set as different combinations of power basis functions;
- determining, from said set of model coefficients, a corresponding set of predistorter connection coefficients for combining power basis function output signals from the power basis functions to generate basis function output signals;
- computing a set of power basis function output signals from an input signal and the set of power basis functions;
- applying the set of predistorter connection coefficients to the power basis function output signals to produce a set of basis function output signals;
- and
- combining the basis function output signals to produce a predistorted input signal from the input signal.
The method of clam 1 wherein computing a set of power basis function output signals comprises computing, for each of a plurality of sampling time instances, a set of basis function output signals from a single input signal sample and the set of power basis functions.
A circuit for compensating an input signal for distortion introduced by an electronic device operating on an input signal to produce an output signal, said circuit comprising:
- a basis function modeling circuit configured to:
- compute a set of model coefficients for a two-dimensional lattice prediction model of a basis function set from a set of input signal samples over a predetermined sampling interval, wherein the lattice prediction model represents basis functions in a predistorter basis function set as different combinations of power basis functions in a set of power basis functions;
- determine, from said set of model coefficients, a corresponding set of predistorter connection coefficients for combining power basis function output signals from the power basis functions to generate basis function output signals;
- a predistorter configured to:
- compute a set of power basis function output signals from an input signal and the set of power basis functions;
- apply the set of predistorter connection coefficients to the power basis function output signals to produce a set of basis function output signals;
- and
- combine the basis function output signals to produce a predistorted input signal from the input signal.
Dependencies are inferred from the claim text.