A Micromachined RF Low Phase Noise Voltage-Controlled Oscillator For Wireless Communications

An RF low phase noise voltage-controlled oscillator is implemented with micromachined IC-compatible variable capacitors and three-dimensional coil inductor. Unlike conventional on-chip passive devices, the micromachined variable capacitors achieve a high-Q value above 60 at 1 GHz with a 15% tuning range for a nominal 2 pF capacitance with 3 V tuning voltage. Three-dimensional inductors minimize the substrate loss and achieve a Q of 30 at 1 GHz with a 4.8 nH inductance. Both passive components are fabricated on silicon substrates and thus amenable to monolithic integration with standard IC process. The prototype VCO exhibits −136 dBc/Hz phase noise at 3 MHz offset frequency from the carrier, suitable for most wireless communication applications, in particular GSM. The VCO is tunable from 855 Mhz to 863 MHz, limited by the test set-up. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 285–300, 2001.