A 42/84-GHz Multi-Ring Rotary Traveling-Wave Oscillator

A multi-ring rotary traveling-wave oscillator (RTWO) is presented. The oscillation frequency of the main RTWO ring is designed for 42-GHz with 2-GHz tunability. Multiphase signals generated in the main RTWO ring drive doubler circuits to generate second harmonic signals. The transformer used in each doubler circuit produces differential signals that are injected into the outer ring. Differential signals in the secondary terminals of the transformers are combined by coupled co-planar strip-line to support traveling-wave in the second ring. Bi-CMOS 0.13-μm technology is used to design and implement the multiring RTWO circuit. The chip area is about 0.78-mm by 0.75mm. Total power consumption is 68-mW. SiGe HBT has been preferred over nMOS transistors to implement the gain stages, frequency doublers and the buffer circuits due to high f
_T
and f
_max
of the SiGe HBTs. The measured frequency of oscillation is 42.24-GHz and 84.48-GHz with 5.6% tuning range and measured phase noise at the main RTWO ring is -97.5 dBc/Hz at 10 MHz.