A 10GHz 0.11μm CMOS varactor-less LC-VCO for multi-standard 802.11a/b/g WLAN using high resolution frequency calibration

A low phase noise LC oscillator for multi-band WLAN applications was realized in 0.11 mu m CMOS. The core VCO runs around 10GHz, while a divide by 2 or 4 was used to generate the quadrature LO signals with an I/Q phase error less than 0.3 degrees. The tuning gain was kept low by using a high resolution frequency calibration. To maximize the oscillating amplitude an NFET-only amplifier and dual MOS switches were used. A low process variation and high quality factor tuning capacitance was achieved by using only constant capacitors and variable resistor MOSFETs. A virtually constant VCO gain was achieved with several resistor-tuned capacitor cells connected in parallel and having their QV) comes uniformly distributed over the wide control voltage range. The VCO specifications include: <106dBc/Hz phase noise at 100KHz offset from the carrier, <5KHz 1/f(3) phase noise corner frequency, 6mA bias current from a 3.3V +/- 10 % supply voltage and 200x300um(2) die area.