A 900 MHz frequency synthesizer with integrated LC voltage-controlled oscillator

Integration of general-purpose frequency synthesizers usually requires a BiCMOS process and necessitates a compromise between the level of integration and performance. Frequency synthesizers with extensive channel programming flexibility and low phase noise typically require external voltage-controlled oscillators (VCOs) while highly-integrated synthesizers utilizing on-chip VCOs tend to exhibit degraded phase-noise performance. The frequency synthesizer presented here features low reference spurs and low phase-noise and is fully-integrated with the exception of an external crystal and an RC loop-filter. It uses a 25 GHz f/sub /spl tau// silicon bipolar process and is for 900 MHz ISM band applications and operates over a supply voltage range of 2.7 V to 5.0 V. The integration level is achieved by a simplified pulse-swallow architecture that provides 41 channels with a 600 kHz spacing and requires a 6 bit programming word.