A Multi-Phase Sub-Harmonic Injection Locking Technique for Bandwidth Extension in Silicon-Based THz Signal Generation

Abstract

This paper presents a multi-phase sub-harmonic injection locking technique. This technique can significantly increase the locking range of a multi-phase injection locking oscillator compared to the conventional single-phase injection locking scheme. By application of this technique, a scalable “active frequency multiplier” chain architecture is proposed, which can generate THz signal from a low mm-wave frequency or RF reference source. We also propose a multi-ring system topology to implement this frequency multiplier scheme. As proof of concept, a cascaded 3-stage 3-phase 2nd-order sub-harmonic injection locking oscillator chain is implemented in the IBM9HP SiGe BiCMOS process with its $f_{\rm T}/f_{\max}$ of 300/350 GHz. The design achieves a maximum output power of $-$ 16.6 dBm at 498 GHz, a phase noise of $-$ 87 dBc/ Hz at 1 MHz offset, and a total 5.1% frequency tuning range from 485.1 GHz to 510.7 GHz, which is the largest frequency tuning range among all the reported silicon-based THz oscillator sources in the 0.5 THz band.