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 0.0108 mm(2) due to lack of inductors. The frequency is tunable from 28.36 to 31.96 GHz, and the single-sideband phase noise is -85.33 dBc/Hz at 1-MHz offset from 31.96 GHz. 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.