A micromachine-based RF low-noise voltage-controlled oscillator

A voltage-controlled oscillator (VCO) employs an aluminum micromachined variable capacitor for frequency tuning. Unlike conventional varactor diodes, the capacitor is fabricated on a silicon substrate and thus amenable to monolithic integration with a standard IC process. Experimental capacitors achieve a 16% tuning range with a nominal capacitance value of 2 pF and a quality factor above 60 at 1 GHz. A prototype VCO exhibits -107 dBc/Hz phase-noise at 100 kHz offset frequency from the carrier. The center frequency of 714 MHz and 14 MHz tuning range are limited by the test setup.