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Adaptive digital predistortion method and apparatus for wireless transmitter

  • US 20030104794A1
  • Filed: 01/13/2003
  • Published: 06/05/2003
  • Est. Priority Date: 07/20/2000
  • Status: Active Grant
First Claim
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1. An adaptive digital predistortion apparatus for transmitting broadband digital signals from a wireless transmitter to a transmitting channel, comprising:

  • a modulator for modulating broadband digital signals;

    a predistorter coupled to the modulator for receiving and predistorting modulated signals;

    a digital to analogue (D/A) converter coupled to the predistorter for receiving and converting predistorted signals from the predistorter;

    an up converter coupled to the D/A converter for receiving and converting converted signals from the D/A converter;

    a power amplifier coupled to the up converter for receiving and amplifying up converted signals from the up converter;

    an antenna coupled to the power amplifier for receiving and transmitting amplified signals from the power amplifier;

    a down converter coupled to the power amplifier for receiving and feeding back a part of the amplified signals from the power amplifier;

    a local oscillator coupled between the up converter and the down converter for providing oscillation signals to the up converter and the down converter;

    an analogue to digital (A/D) converter coupled to the down converter for receiving and converting converted feedback signals from the down converter;

    a predistortion parameter adaptive controller coupled to the A/D converter and to the predistorter for receiving the converted feedback signals from the A/D converter and adaptively adjusted predistortion parameters of the predistorter and sending the adjusted predistortion parameters to the predistorter;

    wherein the broadband digital signals to be transmitted are input to the digital predistorter and processed by the digital predistorter, then converted by the D/A converter and the up converter, then amplified by the power amplifier and transmitted by the antenna; and

    meanwhile, a part of the amplified signals outputted from the power amplifier are fed back to a feedback loop, in which the feedback signals are down converted by the down converter and converted by the A/D converter, and processed by the predistortion parameter adaptive controller;

    wherein out-of-band energy emission of the feedback signals are used as a target function, and the predistortion parameters are adjusted adaptively by employing a multi-parameter optimization process to allow the transmitting channel to maintain a linear transfer characteristic.

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