Publication Date: Feb,2018
Venue: ISSCC 2018 International Solid-State Circuits Conference - February 11-15, San Francisco
Domain: Information & Communication, Electronics & Photonics
The THz band has shown its unique characteristics and great potential in many applications. Harmonic oscillators are commonly used to generate THz signals; however, due to supply noise and ambient environment changes, free-running THz oscillators exhibit large spectral linewidth and frequency drift. As a result, frequency stabilization is required in many systems. Conventionally, PLLs are used for this purpose [1-3]; however, major challenges exist when frequency goes into THz band. Since the division ratio (N) is large in THz PLLs (103 to 104) and the reference phase noise is multiplied by N2 to the output, a high-quality off-chip crystal oscillator is needed to keep the noise contribution low enough. Moreover, the large N causes significant VCO-noise folding, potentially degrading the output in-band phase noise. Finally, injection-locking frequency dividers (ILFDs) in THz range provide insufficient locking range, which limits the achievable output frequency range. To boost the ILFD locking range, higher injection power or multiphase injection [1,4] is needed, which significantly increases the power consumption. In this paper, an entirely-on-chip frequency-stabilization feedback loop for mm-wave/THz sources is presented. The feedback loop eliminates the need for both frequency dividers and off-chip crystal oscillators, resulting in much lower cost and power consumption. To show the feasibility, a 301.7-to-331.8GHz source is designed in the STMicroelectronics 0.13μσι SiGe:C BiCMOS technology.