Patent attributes
A predistorter (26) comprises an array (44) of band pass filters (46 to 52) which divide an input signal into components. Each of the components is manipulated using coefficients retrieved from respective look-up tables (54 to 60). The amplitude of each component is used to retrieve a coefficient from its respective look-up table. The amplitude of each component is then multiplied with its respective retrieved coefficient to generate a predistorted amplitude for that component. The predistorted amplitudes are summed (at 80) to produce a predistorted input signal. The predistortion of the input signal is arranged to counter the distortion characteristic of a signal handling element (such as non-linear power amplifier 22 in FIG. 1) to which the predistorted input signal is subsequently supplied. The coefficients in the look-up tables (54 to 60) can be adapted using feed back from the output of the signal handling means (FIG. 5). Fast Fourier transformation and inverse fast Fourier transformation can be used in place of band pass filter array (44) and combiner (80), respectively (FIG. 4).
