A low-noise K-band class-C VCO for E-band 5G backhaul systems in 55nm BiCMOS technology

Next-generation 5G communication systems require adaptive high-order modulations to increase spectral efficiency. To limit EVM, very low phase noise levels are required — i.e. less than −117dBc/Hz at 1MHz offset for 64QAM at f=20GHz. In this paper, the design and measurements of a low-noise K-Band VCO are presented. The challenges of achieving such a low phase noise are discussed in detail, with particular emphasis on the minimization of L/Q, inductor versus quality factor ratio. Prototypes have been realized in a 55nm BiCMOS technology. Operated at 2.5V supply with the largest amplitude allowed by reliability constraints, measurements show a phase noise as low as −119dBc/Hz at 1MHz from a 20GHz carrier offset with a tuning range (TR) of 19% and FoM=−187dBc/Hz. Power consumption is 56mW. To the best of authors' knowledge, the presented VCO shows the lowest reported phase noise among state-of-the-art BiCMOS VCOs with TR>10%.