Wireless communication unit and linearised transmitter circuit therefor

A linearised transmitter integrated circuit comprising:

• a linearised transmitter for transmitting a linearised radio signal, and
• a forward path comprising quadrature circuits for routing a signal to be transmitted and for operable coupling to a power amplifier for transmitting a linearised radio signal;
• a feedback loop, operably coupled to the forward path and for operable coupling to an output of a power amplifier, wherein the feedback loop comprises a loop adjustment function, and quadrature circuits;
• and
• a processor, operably coupled to the feedback loop for applying a first training signal to a first quadrature circuit loop in the linear transmitter integrated circuit to be routed through the forward path, power amplifier and feedback path to determine at least one first parameter setting of the loop adjustment function,
• wherein said processor applies a second training signal to a second quadrature circuit loop in the linear transmitter integrated circuit to determine at least one second parameter setting of the loop adjustment function;
• and
• wherein said first and second training signals are applied by the processor while the first and second quadrature circuit loops are open.

A method of training a linearised transmitter having a forward path, a power amplifier and a feedback loop comprising a loop adjustment function, wherein the forward path and feedback loop comprise quadrature circuits, the method comprising the steps of:

• applying a first training signal to be routed through a first quadrature circuit loop of the forward path, power amplifier and feedback path, wherein said first training signal is applied while the first quadrature circuit loop is open;
• and
• determining at least one first parameter setting for the loop adjustment function based on the first training signal,
• applying a second training signal to a second quadrature circuit loop of the forward path, power amplifier and feedback path, wherein said second training signal is applied while the second quadrature circuit loop is open;
• and
• determining at least one second parameter setting for the loop adjustment function based on the second training signal.