Wide tuning range LC VCO with parallel coupled negative gm cells

To minimise phase noise degradation with a wide tuning range, the proposed LC voltage controlled oscillator incorporates parallel coupled negative transconductance (g_m) cells. Phase noise for wide tuning range VCOs suffers from degradation of quality factor of tank inductors or tank capacitors due to their parasitic resistance. The proposed parallel coupled negative g_m cells provide additional current to compensate for the loss of phase noise. The measured results show a tuning range of 25.4% and a phase noise of - 116.7 dBc/Hz at 1 MHz offset frequency at 5.87 GHz with power consumption of 1.4 mW. The figure-of-merit with the fractional tuning range of the VCO was - 199.9 dBc/Hz, which is the best among the latest state-of-the-art wide tuning range CMOS LC VCOs.