A very low phase noise SiGe VCO at X-band frequencies

The design and measurement of a voltage controlled oscillator (VCO) at 9 GHz are described in this paper. The design of the oscillator is based on a reflection-type configuration using a packaged SiGe transistor (Siemens BFP 540F). The oscillation frequency is determined by a microstrip resonator integrated on a duroid substrate and tuned by a GaAs varactor diode (M/A-COM ML46580). A 150 MHz tuning range is obtained with an output power varying from 0 to 5 dBm. The phase noise is below -92 dBc/Hz at 100 kHz offset over the whole tuning bandwidth. This is, to our knowledge, one of the best phase noise performances from a SiGe VCO using a plastic packaged device at X-band frequencies.