A 5 GHz fully integrated VCO in a SiGe bipolar technology

A fully integrated voltage controlled oscillator operating at 5 GHz is presented. The circuit is designed in a SiGe bipolar technology employing three metal layers. The design is based on a fully integrated LC tank using square spiral inductors. The simulated phase noise is -101.4 dBc/Hz at 100 kHz offset. The effect of bias current on phase noise is also examined. It is shown that an optimum bias current exists, that minimizes phase noise in bipolar cross-coupled differential pair VCOs.