An inductorless Ka-band SiGe HBT ring oscillator

An inductorless Ka-band silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) ring oscillator is presented. The Ka-band operation is achieved with the addition of a cross-coupled pair to the simple differential inverting amplifier of a single-stage ring oscillator. Implemented with 120-GHz SiGe HBTs, the circuit occupies an extremely compact active area of only 0.0108mm² due to lack of inductors. The frequency is tunable from 28.36 to 31.96GHz, and the single-sideband phase noise is -85.33 dBc/Hz at 1-MHz offset from 31.96GHz. Operating on a -3-V supply, the total power consumption is 87 mW. The resulting oscillator figure-of-merit is -156 dBc/Hz. To our knowledge, this oscillator achieves the best figure-of-merit while occupying the least active area, when compared with other state-of-the-art inductorless ring oscillators operating over a similar frequency range.