DIGITAL TUNING OF CRYSTAL OSCILLATORS

摘要

Embodiments feature techniques and systems for digitally tuning a crystal oscillator circuit. In one aspect, embodiments feature a method for tuning a digitally tuned crystal oscillator circuit. The method involves receiving a multi-bit input signal into a digital modulator, modulating the multi-bit input signal with the digital modulator by oversampling or by noiseshaping and oversampling to produce a digitally-modulated output signal having a lower number of bits than the multi-bit input signal. The method also involves coupling a tuning capacitor with the crystal oscillator circuit, and coupling the digitally-modulated output signal from the digital modulator to the crystal oscillator circuit and the tuning capacitor. In some embodiments, the digital modulator can be a delta-sigma modulator, a noiseshaping modulator, a delta modulator, a pulse width modulator, a differential modulator, or a continuous-slope delta modulator.