Crystal Drift Compensation in a Mobile Phone

We propose a novel method of performing frequency synchronization of local oscillator in a mobile phone to a stable reference of the base station. A free-running crystal oscillator (XO) is used instead of an expensive voltage-controlled or digitally-controlled XO. The frequency drift of the crystal is adjusted in the digital domain of the frequency synthesizer's frequency command word. The proposed techniques have been successfully implemented in a single-chip GSM transceiver realized in 90 nm CMOS