A 2.4 GHz fully integrated CMOS LC VCO

A fully integrated 2.4 GHz CMOS LC VCO is designed and fabricated in 0.35 μm BiCMOS process using PN varactor and planar spiral inductor. Trade offs for LC tank design as well as symmetry design considerations from schematic level to layout are presented. The VCO achieves a measured phase noise of -90 dBc/Hz at 100 KHz offset and -116 dBc/Hz at 2 MHz offset. The measured output frequency is from 2.2045 GHz to 2.4970 GHz, which corresponds to 290 MHz tuning range obtained by only tuning the PN varactor pairs. The VCO core draws 4 mA of current from the 3.3 V supply. The whole measurement is accomplished by using a FR-4 PCB test fixture.