Abstract: In an embodiment, an apparatus comprises an in-phase-quadrature (IQ) signal amplifier having an IQ baseband input, an IQ mixer input connected to the IQ signal amplifier, a carrier leakage detector connected to outputs of the IQ mixer, and a carrier-null offset signal generator connected to the carrier leakage detector. The IQ mixer is configured to be driven by an IQ carrier signal. The carrier leakage detector is configured to output an in-phase leakage level measurement and a quadrature leakage level measurement in the absence of an IQ baseband signal at the IQ baseband input. The carrier-null offset signal generator is configured to (i) inject an in-phase carrier-null offset signal based on the in-phase leakage level measurement and (ii) inject a quadrature carrier-null offset signal based on the quadrature leakage level measurement.

Abstract: In an embodiment, an apparatus comprises an in-phase-quadrature (IQ) signal amplifier having an IQ baseband input, an IQ mixer input connected to the IQ signal amplifier, a carrier leakage detector connected to outputs of the IQ mixer, and a carrier-null offset signal generator connected to the carrier leakage detector. The IQ mixer is configured to be driven by an IQ carrier signal. The carrier leakage detector is configured to output an in-phase leakage level measurement and a quadrature leakage level measurement in the absence of an IQ baseband signal at the IQ baseband input. The carrier-null offset signal generator is configured to (i) inject an in-phase carrier-null offset signal based on the in-phase leakage level measurement and (ii) inject a quadrature carrier-null offset signal based on the quadrature leakage level measurement.

Abstract: Improved carrier feed thru rejection is achieved for a linear amplifier in a transmitter. The DC training capabilities of a radio frequency mixer are used, not only to correct DC offset of the radio frequency mixer, but also to adjust the DC offset of any baseband circuit and filtering coupled to the radio frequency mixer. Output power adjustment is accomplished by adjusting a feedback attenuator in the feedback path of the radio frequency mixer. Constant loop gain is maintained by adjusting a forward attenuator in the forward path of the radio frequency mixer. The feedback and forward attenuators have a fine adjustment on the order of less than 5 dB.