A Wideband VCO Using a Switchable Inductance Technique and Negative Gₘ Enhancement With Positive Feedback

In this letter, we propose a wideband voltage-controlled oscillator (VCO) that combines a switchable inductor technique and negative transconductance $(G_{m})$ enhancement with the positive feedback loop. To extend the tuning range (TR) and reduce the frequency overlapping region between two modes, a mathematical analysis for the optimization TR is proposed to resist the frequency gap caused by process variations and implement a wider TR by using the switchable inductor. Furthermore, to compensate for the loss of the switchable inductor, the source-coupled pair provides additional wideband – $G_{m}$ characteristics to improve the Q value of the entire LC tank across the TR, thereby cooperating with the switchable inductance technique to implement the better phase noise (PN) across all TR. The measured TR is 39.67%, spanning from 10.77 to 16.1 GHz. At 13.19 GHz, the measured PN is –138 dBc/Hz at a 10-MHz offset frequency. The proposed VCO consumes only 10.7 mW of the total DC power. Comparing the proposed VCO to existing designs, these results demonstrate that it has a wider TR, an improved PN, and a higher figure of merit (FoM).