Pre-distortion and memory compensation apparatus

A pre-distortion apparatus for a power amplifier, the pre-distortion apparatus receiving an input signal and an output signal of the power amplifier, and providing a pre-distorted output signal, the pre-distortion apparatus comprising:

• an envelope detector which generates an envelope signal that is representative of an envelope of the input signal;
• a memory delay block which provides a delayed signal that is representative of the input signal delayed by a predetermined amount;
• error signal generating circuit that generates an error signal that is representative of a difference between the output signal of the power amplifier and the delayed signal;
• and
• a pre-distortion circuit comprising:
• first and second polynomial function generating circuits responsive to the error signal, each polynomial function generating circuit receiving the envelope signal to provide in-phase and quadrature gain signals each representing a polynomial function of the envelope signal;
• a quadrature-phase shifter receiving the input signal to provide in-phase and quadrature representations of the input signal;
• first and second variable gain amplifiers receiving the in-phase and the quadrature representations of the input signal and the in-phase and quadrature gain signals to provide gain modulated in-phase and quadrature output signals;
• and
• an summer summing the gain modulated in-phase and quadrature
• output signals to provide the pre-distorted output signal.