W-Band Switch-Less Reconfigurable-Push Dual-Band VCO Using Clover-Shaped Inductor and Robust Triple Cores for 6G Communications

This study proposes a switchless reconfigurable triple-push/push-push dual-band voltage-controlled oscillator (VCO) topology to design a ${W}$ -band metal-oxide-semiconductor (CMOS) for 6G communications. The proposed clover-shaped inductor consists of three branch inductors, where each node had a symmetrical layout, connecting to each another and to the output pad. This topology was demonstrated in a ${W}$ -band VCO using three cross-coupled cores with an ON/OFF-state control to achieve triple-push and push-push operations. An oscillating core based on a robust cross-coupled structure avoids the oscillation startup issue, while achieving a 120° phase offset through a vector-sum-based method. The measured center frequencies of the bands were 91.04 and 102.33 GHz, with the tuning ranges of 10.4% and 14.1%, respectively. The proposed VCO with an independent core ON/OFF-state control enables a low parasitic switchless frequency band shift, resulting in a superior tuning range compared with those of conventional dual-/single-band VCOs. The effectiveness of this approach was demonstrated through fabrication in a 28-nm CMOS process, with a best FOM $_{T}$ value of -178.6 dBc/Hz for the full band.