Adaptive digital predistortion for power amplifiers with real time modeling of memoryless complex gains

An adaptive device for predistorting a signal to be transmitted, supplied by a signal source to an input of a power amplifier having an output for delivering an amplified output signal, comprising:

• predistorter means comprising predistortion amplitude and phase look-up table means interposed between the signal source and the input of the power amplifier for amplitude and phase predistorting the signal to be transmitted;
• means for producing a first feedback signal in response to the predistorted signal from the predistorter means;
• means for producing a second feedback signal in response to the amplified output signal from the power amplifier;
• delay means for eliminating any time lag between the first and second feedback signals;
• means for modeling the power amplifier in response to the first and second feedback signals;
• and
• means for updating the predistortion amplitude and phase look-up table means in response to said modeling of the power amplifier.

An adaptive device for predistorting a signal to be transmitted, supplied by a signal source to an input of a power amplifier having an output for delivering an amplified output signal, comprising:

• predistorter means comprising predistortion amplitude and phase look-up table means interposed between the signal source and the input of the power amplifier for amplitude and phase predistorting the signal to be transmitted;
• means for producing a first feedback signal in response to the predistorted signal from the predistorter means;
• means for producing a second feedback signal in response to the amplified output signal from the power amplifier;
• delay means for eliminating any time lag between the first and second feedback signals;
• and
• means for updating the predistortion amplitude and phase look-up table means in response to the first and second feedback signals;
• wherein the predistortion amplitude and phase look-up table means comprises, in cascade, a one-dimensional predistortion amplitude look-up table and a one-dimensional predistortion phase look-up table;
• wherein said signal to be transmitted comprises an amplitude component and a phase component;
• and
• wherein said predistorter means comprises:
• said one-dimensional predistortion amplitude look-up table for producing a predistorted amplitude in response to the amplitude component of the signal to be transmitted;
• said one-dimensional predistortion phase look-up table for producing a predistorted phase in response to the predistorted amplitude;
• and
• means for combining the phase component of the signal to be transmitted, the predistorted amplitude and the predistorted phase into said predistorted signal.