Adaptive predistortion circuit for a digital transmission system

Details Adaptive predistortion circuit for a digital transmission system Adaptive predistortion circuit for a digital transmission system

1990-01-09

1992-04-21

Olms, Douglas W.

Pulse or digital communications

Repeaters

Testing

332123, 332124, 332159, 332160, 455126, H04L 2549, H04L 2503

Patent

active

051075202

ABSTRACT:
An adaptive predistortion circuit for a digital transmission system includes a predistortion circuit (52.sub.1, 52.sub.2, 52.sub.3) for predistorting the input data before they pass through a modulator (56) and then through an amplifier (57), and an adaptation circuit (61.sub.1, 61.sub.2, 61.sub.3) 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 a.sub.k, generates digital data b.sub.k which leave a first predistortion circuit (52.sub.1) in a predistorted manner in-phase with the symbol clock, on a second path, digital data c.sub.k which leave a second distortion circuit (52.sub.2) in a predistorted manner phase-shifted by T/3 relative to the symbol clock and on a third path, digital data d.sub.k which leave a third predistortion circuit (52.sub.3) in a predistorted manner phase-shifted by 2T/3 relative to the symbol clock. The signals b.sub.k, c.sub. k and d.sub.k are obtained by means of a polynomial encoding. The encoding may be performed by shift registers (62.sub.1 . . . 62.sub.I) addressing a memory (63) or, by a transversal filter (71.sub.1, 71.sub.2, 71.sub.3). It may also be obtained by means of an analog transmission filter (81) followed by samplers (81.sub.1, 82.sub.2, 82.sub.3).

REFERENCES:
patent: 4412337 (1983-10-01), Bickley et al.
patent: 4639938 (1987-01-01), Kennett
patent: 4750192 (1988-06-01), Dzung
patent: 4890300 (1989-12-01), Andrews

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