A 30 GHz Class-C switchless dual-band two core VCO in 40-nm CMOS

This paper describes the design and the performance characteristics of a millimeter wave (mm-wave) two core switchless class-C VCO in 40nm CMOS technology. The frequency synthesis is accomplished by two VCOs, one operating in the low band of interest and the other at the high band. The appropriate band is selected by activating or deactivating the relevant VCO, resulting in a robust VCO structure characterized by the absence of switches in the signal path, thereby preserving overall performance. By this technique the final design achieves enhanced tuning range without sacrificing the performance regarding the phase noise. Both VCOs achieve continuous frequency tuning via a Metal-Oxide-Semiconductor (MOS) varactor, complemented by fine tuning through a capacitor bank. The low band VCO spans a range between 27.23 and 33.49 GHz and the high band VCO oscillates from 33.11 and 40.32 GHz. Consequently, the proposed design achieves a total tuning range of 38.75%. Simulated phase noise (PN) remains below -98.23 dBc/Hz at a 1 MHz frequency offset across all bands. The two VCOs are never simultaneously ON contributing to power conservation. The power of both VCOs reaches 8.1 mW from a 1.1 Volt supply. Simulated output power consistently exceeds -6 dBm across all frequency bands.