2.4 GHz CMOS quadrature voltage-controlled oscillator based on symmetrical spiral inductors and differential diodes

A voltage-controlled oscillator (VCO) which can generate 2.4 GHz quadrature local oscillating (LO) signals is reported. It combines a LC-VCO, realized by on-chip symmetrical spiral inductors and differential diodes, and a two-stage ring VCO. The principle of this VCO is demonstrated and further the phase noise is discussed in detail. The fabrication of prototype is demonstrated using 0.25 μm single-poly five-metal N-well salicide CMOS digital process. The reports show that the novel VCO can generate quadrature LO signals with a tuning range of more than 300 MHz as well as the phase noise - 104.33dBc/Hz at 600 KHz offset at 2.41 GHz (when measuring only one port of differential outputs). In addition, this VCO can work in low power supply voltage and dissipate low power, thus it can be used in many integrated transceivers.