Digital memory-based predistortion technique

A method for reducing the memoryless and memory effects in the amplitude and the phase of an output signal of a power amplifier, the output signal obtained by predistorting an input signal to get a predistorted signal and passing the predistorted signal through the power amplifier, the method comprising:

• a. determining an amplitude memory signal using a memory-based AM/AM model and a memoryless AM/AM model, the amplitude memory signal representing the memory effects in the amplitude of the output signal;
• b. subtracting the amplitude memory signal from the input signal to get an amplitude memory-subtracted signal;
• and
• c. performing memoryless amplitude predistortion on the amplitude memory-subtracted signal using a memoryless amplitude predistortion model to get an amplitude-predistorted signal, the memoryless amplitude predistortion being performed to reduce the memoryless effects in the amplitude of the output signal.

A method for reducing the memoryless and memory effects in the amplitude and the phase of an output signal of a power amplifier, the output signal obtained by predistorting an input signal to get a predistorted signal and passing the predistorted signal through the power amplifier, the method comprising:

• a. determining an amplitude memory signal using a memory-based AM/AM model and a memoryless AM/AM model, the amplitude memory signal representing the memory effects in the amplitude of the output signal;
• b. subtracting the amplitude memory signal from the input signal to get an amplitude memory-subtracted signal;
• c. performing memoryless amplitude predistortion on the amplitude memory-subtracted signal using a memoryless amplitude predistortion model to get an amplitude-predistorted signal, the memoryless amplitude predistortion being performed to reduce the memoryless effects in the amplitude of the output signal;
• d. performing memory-based phase predistortion on the amplitude-predistorted signal using a memory-based phase predistortion model to get a phase predistorted signal, the memory-based phase predistortion being performed to reduce the memoryless and memory effects in the phase of the output signal;
• and
• e. applying an input correction filter model to the phase predistorted signal, the input correction filter model representing the inverse model of the linear response of the power amplifier.

A system for reducing memoryless and memory effects in the amplitude and the phase of an output signal of a power amplifier, the output signal obtained by predistorting an input signal to get a predistorted signal and passing the predistorted signal through the power amplifier, the system comprising:

• a. a predistortion parameter analyzer, the predistortion parameter analyzer determining the AM/AM characteristics of the power amplifier, the AM/PM characteristics of the power amplifier and computing models required for predistortion using the input signal and the output signal;
• b. an amplitude memory subtracted signal calculator, the amplitude memory subtracted signal calculator determining an amplitude memory signal, the amplitude memory signal representing the memory effects in the amplitude of the output signal, and subtracting the amplitude memory signal from the input signal, the amplitude memory subtracted signal calculator comprising:
• i. a memoryless AM/AM block, the memoryless AM/AM block representing the memoryless effects in the amplitude of the output signal;
• ii. a memory-based AM/AM block, the memory-based AM/AM block representing the memoryless effects and the memory effects in the amplitude of the output signal;
• iii. a first subtracting module, the first subtracting module subtracting the output of the memoryless AM/AM block from the output of the memory-based AM/AM block to obtain the amplitude memory signal;
• and
• iv. a second subtracting module, the second subtracting module subtracting the output of the first subtracting module from the input signal to obtain an amplitude memory subtracted signal;
• c. a memoryless amplitude predistortion block, the memoryless amplitude predistortion block performing memoryless amplitude predistortion on the amplitude memory subtracted signal;
• d. a memory-based phase predistortion block, the memory-based phase predistortion block performing memory-based phase predistortion on the output of the memoryless amplitude predistortion block;
• and
• e. an input correction filter, the input correction filter implementing the inverse model of the linear response of the power amplifier on the output of the memory-based phase predistortion block.

A system for reducing memoryless and memory effects in the amplitude and the phase of an output signal of a power amplifier, the output signal obtained by predistorting an input signal to get a predistorted signal and passing the predistorted signal through the power amplifier, the system comprising:

• a. a predistortion parameter analyzer, the predistortion parameter analyzer determining the AM/AM characteristics of the power amplifier, the AM/PM characteristics of the power amplifier and computing models required for predistortion using the input signal and the output signal;
• b. an amplitude memory subtracted signal calculator, the amplitude memory subtracted signal calculator determining an amplitude memory signal, the amplitude memory signal representing the memory effects in the amplitude of the output signal, and subtracting the amplitude memory signal from the input signal, the amplitude memory subtracted signal calculator comprising:
• i. a memoryless AM/AM block, the memoryless AM/AM block introducing the memoryless effects in the amplitude of the output signal;
• ii. a memory-based AM/AM block, the memory-based AM/AM block representing the memoryless effects and the memory effects in the amplitude of the output signal;
• iii. a first subtracting module, the first subtracting module subtracting the output of the memoryless AM/AM block from the output of the memory-based AM/AM block to obtain the amplitude memory signal;
• and
• iv. a second subtracting module, the second subtracting module subtracting the output of the first subtracting module from the input signal to obtain an amplitude memory subtracted signal;
• c. a memoryless amplitude predistortion block, the memoryless amplitude predistortion block performing memoryless amplitude predistortion on the amplitude memory subtracted signal;
• and
• d. a memory-based phase predistortion block, the memory-based phase predistortion block performing memory-based phase predistortion on the output of the memoryless amplitude predistortion block.