Adaptive predistortion for a transmit system

A method of processing an input signal to produce a system output signal, the method comprising:

• a) receiving said input signal and accessing an entry in a lookup table;
• b) applying a deliberate predistortion to said input signal to result in a predistorted signal, said deliberate predistortion being based on said entry;
• c) decomposing said predistorted signal into at least two component signals;
• d) combining said at least two component signals to produce said system output signal;
• e) adjusting said deliberate predistortion based on said system output signal;
• and
• f) updating at least one entry in said table.

An adaptive predistortion subsystem for use with a signal processing system which produces a system output signal, the predistortion subsystem comprising:

• determining means for determining a deliberate predistortion to be applied to an input signal, said determining means comprising
• a lookup table having entries, said entries being used to determine said deliberate predistortion and
• an interpolating means for determining values not found in said lookup table;
• adjustment means for applying said deliberate predistortion to said input signal;
• and
• update means for periodically updating said determining means based on characteristics of said system output signal.

A system for processing an input signal, the system comprising:

• an adaptive predistortion subsystem for receiving said input signal and for producing a predistorted signal by applying a deliberate predistortion to said input signal, wherein said deliberate predistortion includes phase distortions which adjust a phase of said input signal;
• and
• a signal processing subsystem receiving and processing said predistorted signal and producing a system output signal,
• wherein
• said adaptive predistortion subsystem distorts said Input signal to compensate for distortions in said system output signal;
• said signal processing subsystem decomposes said predistorted signal into separate components, each of said separate components being processed separately;
• said processing subsystem combines said components after processing to produce said system output signal;
• and
• said deliberate predistortion applied to said input signal by said adaptive predistortion subsystem to produce said predistorted signal is adjusted based on said system output signal.