A fully-integrated 0.13/spl mu/m CMOS low-IF DBS satellite tuner using a ring oscillator based frequency synthesizer

The first low-IF fully-integrated tuner for DBS satellite TV applications was realized in 0.13 mum CMOS. A wideband ring oscillator based frequency synthesizer having a large frequency step was used to down-convert a cluster of channels to a coarsely defined low-IF frequency, while the second down-conversion to baseband was performed in the digital domain. Eliminating the oscillator inductors has reduced the parasitic magnetic coupling, allowing a single-chip integration of the sensitive tuner and the noisy digital demodulator. A significant die area reduction was achieved by using a single oscillator to cover the entire satellite TV spectrum, while a noise attenuator was cascaded with the PLL loop filter to reduce the equivalent tuning gain