30-GHz Low-Phase-Noise Scalable Multicore Class-F Voltage-Controlled Oscillators Using Coupled-Line-Based Synchronization Topology

In this letter, low-phase-nose multicore class-F voltage-controlled oscillators (VCOs) using coupled-lined-based synchronization topology are proposed. Compared to traditional resistance-coupled multicore VCOs, the proposed coupled-line-based topology improves the $Q$ of the small inductors in the millimeter-wave frequency range. Mode ambiguity is eliminated for a robust oscillation startup. Quad-core and oct-core VCO prototypes are designed and implemented in 65-nm CMOS process, which exhibit a measured frequency tuning range of 20.5% centered at 31.32 GHz. The quad-core VCO has a measured phase noise (PN) of -134.33 dBc/Hz and a corresponding FoM of 191.32 dBc/Hz at 10-MHz offset from 28.28 GHz. The oct-core VCO has a measured PN of -137.23 dBc/Hz and a corresponding FoM of 191.08 dBc/Hz at 10-MHz offset from 28.16 GHz.