A Novel Transformer Based Current Reused VCO/ILFD With Variable Dividing Ratio

A novel, current reused, voltage-controlled oscillator (VCO) and injection-locked frequency divider (ILFD) with variable dividing ratio is presented and implemented in UMC 0.18 triple-well CMOS process. The proposed architecture allows compact and low power solution to be attained by the stacking of a ring-type ILFD and a transformer based VCO. The LC VCO provides the wideband differential output and the two-stage ring oscillator generates the quadrature output with selectable division ratios. Experimental results show an output frequency range from 0.58 to 3.11 GHz and a phase noise level of -112.5 dBc/Hz at 1 MHz offset from carrier (5.72 GHz). This chip occupies a core area of 0.5 × 0.3 mm² and consumes 4.7 mA from a 1.8 V power supply.