Built in self test transmitter phase calibration

An apparatus for calibrating a radio frequency, RF, transmitter, the apparatus comprising:

• a radio frequency phase rotator configured to be controlled by a digital-to-analog converter, DAC,;
• a saturation module positioned at a phase rotator output;
• a mixer configured to down convert an RF signal;
• an analog-to-digital-converter, ADC, configured to digitalize a baseband signal;
• an analyzer configured to apply an FFT algorithm to a baseband signal;
• and
• a digital compensation mechanism configured to perform digital predistortion on the RF signal.

A method for calibrating a phase rotator, the method comprising:

• identifying an impairment associated with a phase error of an RF signal;
• determining a spectral signature associated with the impairment;
• and
• in response to determining the spectral signature, compensating for the impairment based on the spectral signature, the compensating performed in a baseband using a cordic algorithm.