2.4 GHz CMOS VCO with multiple tuning inputs

A fully integrated 2.4 GHz inductance-capacitance (LC)-tuned complementary metal-oxide-semiconductor (CMOS) voltage-controlled oscillator (VCO) with multiple tuning inputs is presented. The frequency tuning is achieved by use of four parallel, inversion mode NMOS varactors, each with its individual control electrode. It is demonstrated how the use of some of the inputs for coarse tuning can be used to keep down the VCO gain while still covering a wide frequency band. This could be useful as a means of reducing the sensitivity to noise.