A 60-W/180-W Digitally Controlled Switched-Cap LC Oscillator for 900MHz/2.4GHz operation

An LC-tank oscillator for ultra-low-power narrow-band applications is designed using a switched capacitors tuning implementation in a 9-layer-metal 90 nm RF CMOS technology. The oscillator is targeted for 900 MHz and 2.4 GHz ISM bands operation with external inductors. The design resulted in a flexible and digitally controllable oscillator core that can be used with both external and planar integrated inductors. The presented VCO consumes 60 muW in the 900 MHz band and 180 muW in the 2.4 GHz band from a 1.2-V power supply. The best simulated phase noise at 1.5 MHz is -121 dBc/Hz and - 131.8 dBc/Hz in the 2.4 GHz band and in the 900 MHz band, respectively. A highlight of this design is the fact that an excellent Figure-of-Merit (ranging from -193 dB to -199 dB) is combined with a very large tuning range (>16% in both operational bands).