A Low Close-In Phase Noise Class-C Differential Clapp VCO Topology in 180 nm Si-Ge HBT Technology

This paper reports a new improved Clapp VCO topology designed in 180 nm Si-Ge HBT technology for operations around 5 GHz. The designed topology uses a series-tuned resonator, a back-to-back series varactor configuration for tuning the output frequency and a filtering tail current designed for shunting to ground the second harmonic noise component. At the supply voltage of 3.3V, and across Process, Voltage and Temperature (PVT), the resulting VCO exhibits a very low phase noise (-113 dBc/Hz at 100 kHz offset from the carrier frequency), a high tuning range (25%), a power consumption of 6 mW and a Tuning Range based Figure Of Merit (FOM) equal to 211 dB, classifying itself as a challenging VCO and suggesting the opportunity to be considered for further investigations and implementations in Si-Ge HBT Technology.