A 40nm wideband direct-conversion transmitter with sub-sampling-based output power, LO feedthrough and I/Q imbalance calibration

The integration of analog/RF circuits with the digital part in an SoC enables the use of inexpensive DSP power to calibrate non-idealities. Digitally-assisted RF allows for more power and area-efficient systems that achieve good performance over process, temperature and supply (PVT) variations. This paper presents a calibration scheme that uses the available DSP power to perform the transmitter image, local oscillator feed-through (LOFT) and output power calibration by sub-sampling the transmitter spectrum. The system achieves an IR of 55dBc, a 40dBc LOF and a ±0.6dB gain accuracy up to a 1.6GHz LO frequency.