Method and apparatus for a cartesian error feedback circuit to correct distortion within a power amplifier

A circuit comprising;

• a pair of input signal ports, each input signal port for receiving an input signal component, the two input signal components comprising a transmit signal according to a predetermined standard;
• an output port, the output port for receiving a primary output signal;
• a microwave processor, the microwave processor electrically coupled to the pair of input signal ports and output port, the microwave processor for processing the input signal components to provide the output signal, the microwave processor comprising;
• a control signal port, the control signal port for receiving a control signal;
• an input coupler for each input signal component, each input coupler for dividing the input signal component into a primary input signal component and a secondary input signal component;
• a vector modulator, the vector modulator operating according to the standard and for up-converting and combining the two input signal components to form an RF signal in dependence upon at least a first oscillator signal;
• an amplifier, the amplifier for amplifying at least the RF signal and providing an output signal, the output signal being a combination of an amplified replica of the RF signal and distortion generated by the amplifier;
• an output coupler, the output coupler for dividing the output signal into the primary output signal and a secondary output signal, the output coupler having a main port electrically coupled to at least the output port, the main port for providing the primary output signal, and a tap port, the tap port for providing the secondary output signal;
• providing a vector demodulator, the vector demodulator operating according to the standard, the vector modulator for receiving and down-converting the secondary output signal and providing two secondary output signal components in dependence upon at least a second oscillator signal;
• a first summation circuit for each secondary input signal component, the first summation circuit for subtractively combining the secondary input signal component and respective secondary output signal component to provide an error feedback signal component;
• and
• a second summation circuit for each primary input signal component, the second summation circuit for combining the primary input signal component and respective error feedback signal component to form one of the input signal components;
• and,
• a controller, the controller comprising a control port, the control port electrically coupled to the control signal port, the control port for providing the control signal, the controller generating the control signal at least in dependence upon a measure of the error feedback signal components.