A push-push VCO with 13.9-GHz wide tuning range using loop-ground transmission line for full-band 60-GHz transceiver

A 59-GHz push-push voltage-controlled oscillator (VCO)-based on 0.18-μm SiGe BiCMOS technologyfor a full-band 60-GHz transceiver was developed. The VCO uses a loop-ground transmission line (LG-TML) composed of λ _fo/ 2 signal lines (half wavelength at fundamental frequency) and λ _2fo/4 secondary lines (quarter wavelength at second harmonic frequency). The LG-TML makes it possible to output both a large signal at second harmonic frequency and an adequate signal at the fundamental frequency for driving a prescalar, while it prevents the Miller effect of the HBTs in the VCO from increasing and negative conductance from being reduced. As a result, the VCO achieves high output power of +1.5 dBm, while maintaining wide tuning range of 13.9 GHz (26% of the center oscillation frequency). Moreover, it exhibits a low phase noise of -108 dBc/Hz at a 1-MHz offset frequency and achieves a state-of-the-art figure of merit (FOM _T) of -189.6 dB.