A multi-phase sub-harmonic injection locking technique for bandwidth extension in silicon-based THz signal generation

This paper presents a multi-phase sub-harmonic injection locking technique to significantly extend the locking range of a multi-phase injection locking oscillator (ILO). Leveraging this technique, a scalable and cascadable “active frequency multiplier” chain architecture is proposed, which achieves THz signal generation from a low mm-wave frequency tone. We also propose a multi-ring topology to facilitate the design and the high-frequency routing. As a proof-of-concept, a cascaded 3-stage 3-phase 2nd-order sub-harmonic ILO chain is implemented in a SiGe BiCMOS process. It achieves 504 GHz signal generation from a 42 GHz tone with a 4.4% frequency tuning range, which is the largest tuning range among all the reported Si-based THz harmonic oscillator sources at the 0.5 THz band.