Design of wide-band CMOS VCO for multiband wireless LAN applications

In this paper, a general design, methodology of low-voltage wide-band voltage-controlled oscillator (VCO) suitable for wireless, LAN (WLAN) application is described. The applications of high-quality passives for the resonator are. introduced: 1) a single-loop horseshoe inductor with Q > 20 between 2 and 5 GHz [1] for good phase noise performance; and 2) accumulation MOS (AMOS), varactors with C-max/C-min ratio of ning capability At low-voltage supply. 6 [2] to provide wide-band tuning capability at low voltage supply. adverse effect of AMOS varactors due to high sensitivity is A examined. Amendment using bandswitching topology is suggested, and a phase noise improvement of 7 dB is measured to prove. the concept. The measured VCO, operates on a 1-V supply with a wide tuning range of 58.7 % between 3.0 and 5.6 GHz when tuned between +/-0.7 V. The phase noise is -120 dBc/Hz at 3.0 GHz, And -114.5 dBc/Hz at 5.6 GHz, with the nominal power dissipation between 2 and 3 mW Across the whole tuning range. The best 124 dBc/Hz at the frequency, of phase noise at 1-MHz offset is 3 GHz, a supply voltage of 1.4 V, and,power dissipation of 8.4 mW. When the supply is reduced to 0.83 V, the VCO dissipates less than 1 mW at 5.6 GHz. Using this design methodology, the A feasibility of generating two local oscillator frequencies (2.4-GHZ ISM and 5-GHz U-NII) for WLAN tranceiver using a single VCO with only one monolithic inductor is demonstrated. The VCO is fabricated in a 0.13-mum, partially depleted, silicon-on-insulator CMOS process.