A 5.8-GHz VCO with Precision Gain Control

In this paper, we present a fully integrated 5.8-GHz LC voltage controlled oscillator (VCO) featuring over 300MHz tuning range while retaining the VCO gain (K
_VCO
) to as low as 45MHz/V A modified frequency-tuning topology employing accumulation-mode MOS varactors (AMOS) with virtual ground node bandswitching was adopted to set the appropriate operating frequency and to program K
_VCO
to a necessary minimum. Realized in 0.13μm CMOS technology, the VCO obtains an adjustable gain ranging from 45MHz/V to 106MHz/V in 20MHz/V-step. With mimimum K
_VCO
, phase noise improves by 6dB and goes down to -115dBc/Hz at 1MHz offset away from 5.98GHz carrier while dissipating merely 12.5mW dc power.