Adaptive digital predistortion method and apparatus for wireless transmitter
First Claim
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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Abstract
An adaptive digital predistortion apparatus and method for transmitting broadband digital signals from a wireless transmitter to a transmitting channel are provided. In the adaptive digital predistortion process, a non-linearity conversion opposite to the transmitting channel characteristic is performed by a digital predistorter for input baseband signals. The predistorted signals are amplified by a power amplifier via an up conversion channel. A part of the signals outputted from the power amplifier are fed back to an adaptive controller via a coupler. The feedback signals are processed by the adaptive controller to obtain out-of-band emission energy of the feedback signals. Using the out-of-band emission energy as a target function, the predistortion parameters are updated by employing a multi-parameter optimum seeking module. Accordingly, broadband signals to be transmitted are predistorted by the digital predistortion system to cancel out the non-linear characteristic of the transmitting channels, and to suppress the out-of-band emission energy of the outputting signals. Meanwhile, by using a multi-parameter optimization seeking module, the predistortion parameters are adjusted adaptively by the digital predistortion system based on the slow variation of non-linearity of the transmitting channels.
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Citations
6 Claims
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1. An adaptive digital predistortion apparatus for transmitting broadband digital signals from a wireless transmitter to a transmitting channel, comprising:
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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. - View Dependent Claims (2)
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3. An adaptive digital predistortion method for transmitting broadband digital signals from a wireless transmitter to a transmitting channel, comprising the steps of:
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a) performing a non-linearity conversion opposite to non-linearity characteristic of the transmitting channel by a digital predistorter for the broadband digital signals, the digital predistorter having a set of predistortion parameters;
b) amplifying predistorted signals by a power amplifier via an up conversion channel;
c) feeding back a part of amplified signals outputted from the power amplifier to an adaptive controller via a coupler;
d) processing the feedback signals by the adaptive controller to obtain out-of-band emission energy of the feedback signals; and
e) updating the predistortion parameters by employing a multi-parameter optimum seeking module using the out-of-band emission energy as a target function. - View Dependent Claims (4, 5, 6)
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Specification