On-Chip Localized Surface Plasmon Resonator for 127 GHz Compact CMOS Oscillator

An on-chip localized surface plasmon resonator (LSPR) and its frequency tuning method are proposed to realize a compact 127 GHz oscillator in 40 nm CMOS process. Conventional LSPRs generate dipole mode (m = 2) instead of monopole mode (m = 1). In addition, these LSPRs are bulky and difficult to be directly integrated with differential circuits. This letter proposes an on-chip LSPR to halve its electric size by adding a slit on the metallic ring of LSPR. The slit also facilitates the integration of varactors and differential output buffer simultaneously. Moreover, two inward poles on inner radius of LSPR are directly connected with switched capacitor (SC) and cross-coupled pair. To experimentally validate the proposed on-chip LSPR structure, a LSPR-based 127 GHz oscillator is designed and measured. Benefiting from the deep sub-wavelength size of LSPR and full integration with active circuits, the LSPR-based oscillator achieves a FoMA of 196.3 dBc/Hz. To the best of the authors’ knowledge, this is the first on-chip LSPR for CMOS oscillator.