A Low-Noise RF Voltage-Controlled Oscillator Using On-Chip High-Q Three-Dimensional Coil Inductor and Micromachined Variable Capacitor

A RF voltage-controlled oscillator (VCO) employs an onchip, high-Q, three-dimensional (3-D) coil inductor and micromachined variable capacitor for frequency tuning. Unlike conventional spiral inductors, the 3-D inductor minimizes the substrate loss and achieves a record Q of 30 at 1 GHz. The micromachined variable capacitor achieves a 15% tuning range with a nominal 2pF capacitance and a Q value above 60 at 1 GHz. Both passive components are fabricated on silicon substrates and thus amenable to monolithic integration with standard IC processes. The prototype VCO exhibits a phase-noise of 136 dBcMz at 3 MHz offset frequency from the carrier, suitable for most wireless communication applications, in particular GSM [l]. The VCO is tunable from 8.55 MHz to 863 MHz under 3V, limited by the test setup.