Bandwidth-enhanced differential VCO and varactor-coupled quadrature VCO for mmWave applications

This paper presents a bandwidth-enhanced differential LC-Voltage Controlled Oscillator (LC-VCO) and varactor-coupled Quadrature VCO (QVCO) designed and simulated in high-performance SiGe HBTs of the GlobalFoundries (GFs) 130 nm SiGe BiCMOS8HP process for mmWave applications. Using the proposed varactor circuit, the designed VCO is operated in wideband and also the two-identical free-running differential VCOs (DVCOs) are coupled through the proposed varactor to oscillate in quadrature. The device sizes in the coupling network are properly set to achieve low I/Q errors. In addition, all the VCOs are designed in class-C to further improve their performances both in term of low power and low phase noise. The post-simulation results show that the differential oscillator is tunable from 20.3- to 31.3-GHz as the tuning voltage is varied from 0 to 1.2 V, while consuming only 10 mA from 1.2 V supply, presenting the best state-of-the-art figure-of-merit (FoMT) of −188 dBc/Hz. Similarly, the QVCO can cover 40.2% oscillation bandwidth around 25.5 GHz oscillating frequency which is significantly wider than other state-of-the-art VCOs operating at comparable frequencies.