Continuous gain calibration of an FM-radio transmitter based on an all-digital PLL

This paper describes a continuous technique to control and calibrate the digitally controlled oscillator (DCO) frequency slope gain of an all-digital phase-locked loop (ADPLL) based frequency modulation (FM) radio transmitter. The transmitter uses the FM baseband data during transmission and evaluates the resolving phase error to compensate voltage and temperature variations. The technique provides good convergence and an adjustment of the gain factor after a voltage or temperature variation in milliseconds. The technique is very important in continuously transmitting applications for future mobile devices and allows a deep-submicrometer complementary metal oxide semiconductor (CMOS) system-on-a-chip (SoC) realization at low power and space costs.