A Dual Band CMOS Class F VCO at mmWave Frequencies

Abstract

With growing demand for 5G applications, there is huge amount of interest for communication systems operating at 5G frequencies. An integral part of these systems is a Voltage Controlled Oscillator (VCO). RF signals need to be modulated on-to a carrier frequency for wireless communication. A VCO are used to generate the carrier frequency signal. Communication standards dictate the Phase Noise requirement of the oscillator based on the number of channels in the band. Class F VCOs are known to provide 3dB better Phase Noise than traditional Class B VCOs. Current work explores this benefit at mmWave frequencies. This work proposes a Class F dual band VCO with active switching capability, centered around the two mmWave bands at 22 and 35GHz. A Class B VCO is also designed for similar frequency bands, to validate the FoM improvement of a Class F design. Both the VCOs are designed using Global Foundaries 22nm FDSOI process. The Class F VCO achieves a tuning range of 22% and 14% in the 22 and 35GHz bands, and phase noise 1MHz is less than -112dBc/Hz and -103dBc/Hz in the low and high bands, respectively. The Oscillator consumes 17mW at 0.8V supply. In comparison, the Class B Oscillator provides FoM of 190dB and 185dB while the Class F design gives FoM less than -192dB and -190dB in 22 and 35GHz bands respectively, suggesting that the Class F design gives superior performance.