Method and apparatus for reducing carrier leakage

An apparatus comprising:

• an in-phase signal amplifier having an in-phase baseband input and a quadrature signal amplifier having a quadrature baseband input;
• an in-phase current commutating mixer and a quadrature current commutating mixer connected to the in-phase signal amplifier and the quadrature signal amplifier, respectively, and the in-phase current commutating mixer and the quadrature current commutating mixer configured to be driven by an in-phase carrier signal and a quadrature carrier signal, respectively;
• a carrier leakage detector connected to an output of the in-phase current commutating mixer and connected to an output of the quadrature current commutating mixer, the carrier leakage detector configured to output an in-phase leakage level measurement based on a signal output of the in-phase current commutating mixer in the absence of an in-phase baseband signal at the in-phase baseband input and a quadrature leakage level measurement based on a signal output of the quadrature current commutating mixer in the absence of a quadrature baseband signal at the quadrature baseband input;
• a carrier-null offset signal generator connected to the carrier leakage detector configured to inject an in-phase carrier-null offset signal based on the in-phase leakage level measurement and to inject a quadrature carrier-null offset signal based on the quadrature leakage level measurement.

A method comprising:

• setting a baseband input signal level to a reference level at an input to an IQ amplifier;
• applying an IQ amplifier output to a carrier signal mixer input;
• obtaining a first measurement of a signal level of an output of the carrier signal mixer;
• and
• injecting a carrier-null offset signal to the IQ amplifier based on the first measurement.