A temperature-compensated low-noise digitally-controlled crystal oscillator for multi-standard applications

This paper presents an integrated 26-MHz digitally-controlled crystal oscillator (DCXO) with temperature compensation function for multi-standard cellular applications, that achieves a phase noise of -154 and -159 dBc/Hz at 10 kHz and 100 kHz offset, respectively. The frequency instability over temperature is compensated by built-in temperature sensor and compensating capacitor. The frequency instability from -10 to 55 degC is about +/- 1 ppm. The AFC frequency tuning is done by a digitally-controlled metal-oxide-metal capacitor array that is 13-bit thermometer decoded. The DCXO is implemented in a 0.13-mum CMOS technology.