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

• Published in: IEEE journal of solid-state circuits Vol. 38; no. 8; pp. 1333 - 1342
• Main Authors: Fong, N.H.W., Plouchart, J.-O., Zamdmer, N., Duixian Liu, Wagner, L.F., Plett, C., Tarr, N.G.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-08-2003; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Design methodology; Inductors; Integrated circuits; Local area networks; Methodology; Noise; Noise measurement; Phase measurement; Phase noise; Power dissipation; Tuning; Varactors; Voltage-controlled oscillators; Wideband; Wireless communication; Wireless LAN
• ISSN: 0018-9200; 1558-173X
• DOI: 10.1109/JSSC.2003.814440

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 for good phase noise performance; and 2) accumulation MOS (AMOS) varactors with C/sub max//C/sub min/ ratio of 6 to provide wide-band tuning capability at low-voltage supply. The adverse effect of AMOS varactors due to high sensitivity is 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 /spl plusmn/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 phase noise at 1-MHz offset is -124 dBc/Hz at the frequency of 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 feasibility of generating two local oscillator frequencies (2.4-GHz ISM and 5-GHz U-NII) for WLAN transceiver using a single VCO with only one monolithic inductor is demonstrated. The VCO is fabricated in a 0.13-/spl mu/m partially depleted silicon-on-insulator CMOS process.