| 摘要 |
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 ). |
