| 摘要 |
An adaptive predistortion circuit for a digital transmission system includes a predistortion circuit (521, 522, 523) for predistorting the input data before they pass through a modulator (56) and then through an amplifier (57), and an adaptation circuit (611, 612, 613) for continuously adapting the predistortion circuit to the stream of input data in response to a demodulation of the stream of transmitted data. The predistortion circuit further includes an encoder (51) which, on a first path, in response to digital data ak, generates digital data bk which leave a first predistortion circuit (521) in a predistorted manner in-phase with the symbol clock, on a second path, digital data ck which leave a second distortion circuit (522) in a predistorted manner phase-shifted by T/3 relative to the symbol clock and on a third path, digital data dk which leave a third predistortion circuit (523) in a predistorted manner phase-shifted by 2T/3 relative to the symbol clock. The signals bk, c k and dk are obtained by means of a polynomial encoding. The encoding may be performed by shift registers (621 . . . 62I) addressing a memory (63) or, by a transversal filter (711, 712, 713). It may also be obtained by means of an analog transmission filter (81) followed by samplers (811, 822, 823).
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