A 20-GHz 1-V VCO with dual-transformer configuration and a pseudo-static divider on self-stabilized concept

A 20-GHz 1-V VCO with dual-transformer configuration and a self-stabilized pseudo-static frequency divider were developed using 0.18-μm SiGe BiCMOS technology. For the VCO, a combination of two types of transformers, which exhibit high-input impedance and capacitive-input impedance, contributes to the output of two sets of differential signals for mixers and the divider, maintaining both a wide frequency-tuning range and low-phase noise. The measured phase noise of the VCO at a 1-MHz offset frequency is -115 dBc/Hz with dissipating 7.5-mW DC power. The Figure of merit of the VCO is -197 dB, which is the best value among 20-GHz-class Si-based VCOs to our best knowledge. For the divider, a two-stage block configuration consisting of an inverter, a mixer, and a low-pass filter (LPF) contributes to enhancing the operation frequency range. The divider is designed to have high conversion gain at low frequency and small circuit delay at high frequency for wide operation range. The measured operation frequency of the divider is from 7 to 26 GHz while dissipating only 1.15-mW DC power and occupying small area of 0.004 mm². These excellent results indicate that the proposed techniques are very suitable for low-power transceivers of quasi-millimeter-wave wireless communication systems.