A VCO With Extra Cross-Coupling Path

Authors：Wan, Cao; Xu, Taotao; Yi, Xiang; Xue, Quan^*

Source：IEEE Microwave and Wireless Components Letters, 2021, 31(10): 1130-1133.

DOI：10.1109/LMWC.2021.3102028

• Extra cross-coupling path
• low power
• negative G(m)
• phase noise (PN)
• startup time

This letter presents a voltage-controlled oscillator (VCO) with an extra cross-coupling path realized by a novel transformer-based resonator. The extra cross-coupling can enhance the negative G(m) and loop gain of the cross-coupled pair. The triode time of the active device during the oscillation will be reduced, resulting in better phase noise (PN) and shorter startup time than the conventional LC-VCO. Fabricated in a CMOS 65-nm process, the proposed VCO consumes 0.9 mW average dc power under a voltage supply of 0.38 V. The 1-MHz offset PN can reach -107.15 dBc/Hz at 8.38 GHz, and the corresponding figure of merit (FoM) is -186.75 dBc/Hz. The VCO's bandwidth is 34.1% ranging from 6.26 to 8.84 GHz, which corresponds an FoM(T) of -197.41 dBc/Hz. Thanks to the compact layout of the transformer, the VCO occupies only 0.055 mm(2) core area, resulting in a -199.35 dBc/Hz FoM(A).