8-GHz CMOS quadrature VCO using transformer-based LC tank

A fully integrated quadrature VCO at 8 GHz is presented. The VCO is implemented using a transformer-based LC tank in 0.18 /spl mu/m CMOS technology, in which two VCOs are coupled to generate I-Q signals. The VCO is realized employing the drain-gate transformer feedback configuration proposed here. This makes use of the quality factor enhancement in the resonator using a transformer and the deep switching-off technique by controlling gate bias. By turning off switching transistors of the differential VCO core deeply, the phase noise performance is improved more than 10 dB. The measured phase noise values are -110 and -117 dBc/HZ at the offset frequencies of 600 kHz and 1 MHz respectively. The tuning range of 250 MHz is achieved with the control voltage from 0 to 1 V. The VCO draws 8 mA in two differential core circuits from 3 V supply. When the bias voltage goes down to 2.5 V, the phase noise decrease only 2 dB compared to that of 3 V bias. The VCO performances are compared with previously reported quadrature Si VCOs in 5/spl sim/12 GHz frequency range.

[1]  Gabriel M. Rebeiz,et al.  A low-noise transformer-based 1.7 GHz CMOS VCO , 2002, 2002 IEEE International Solid-State Circuits Conference. Digest of Technical Papers (Cat. No.02CH37315).

[2]  D. Kasperkovitz,et al.  A 9.8-11.5 GHz quadrature ring oscillator for optical receivers , 2001, Proceedings of the IEEE 2001 Custom Integrated Circuits Conference (Cat. No.01CH37169).

[3]  Hyunchol Shin,et al.  A 1.8-V 6/9-GHz switchable dual-band quadrature LC VCO in SiGe BiCMOS technology , 2002, 2002 IEEE Radio Frequency Integrated Circuits (RFIC) Symposium. Digest of Papers (Cat. No.02CH37280).

[4]  D. Kasperkovitz,et al.  Analysis and design of an optimally coupled 5-GHz quadrature LC oscillator , 2002, IEEE J. Solid State Circuits.

[5]  M. Steyaert,et al.  A 1.57 GHz fully integrated very low phase noise quadrature VCO , 2001, 2001 Symposium on VLSI Circuits. Digest of Technical Papers (IEEE Cat. No.01CH37185).

[6]  Ting-Ping Liu,et al.  1.5 V 10-12.5 GHz integrated CMOS oscillators , 1999 .

[7]  E. Klumperink,et al.  Intrinsic 1/f device noise reduction and its effect on phase noise in CMOS ring oscillators , 1999, IEEE J. Solid State Circuits.