8.1 An 11.5-to-14.3GHz 192.8dBc/Hz FoM at 1MHz Offset Dual-Core Enhanced Class-F VCO with Common-Mode-Noise Self-Cancellation and Isolation Technique

The current 5G and future 6G high-speed mobile-Internet era puts forward stricter requirements on the power consumption, silicon area, and phase noise specifications for local oscillators (LOs) in mobile and portable devices, especially in battery-powered mobile phones, notebook computers, and unmanned aerial vehicles (UAVs) used for mobile base stations. Over the past few decades, intensive research to improve the power efficiency of RF and millimeter-wave oscillators while maintaining required phase-noise characteristic has been carried out. As represented in Fig. 8.1.1, the authors in [1] reported a BiCMOS series-resonance VCO with the lowest phase noise among silicon-based oscillators identified in [1] at the cost of high power consumption (600mW), which is not feasible for energy-efficient applications. In addition to the series resonance technique, the commonly used method to reduce the phase noise is to introduce a high resistance at the second harmonic frequency. However, the head filter in [2] that generates the high resistance occupies additional area and cannot prevent noise current injection at the GND. Although separate filters are added at the VDD and GND, as reported in [3], the noise current passing through the head common-mode inductance is coupled in the same phase to the noise current of the bottom inductance, which increases the total injected noise to some extent. To solve the problem of the additional area for the common-mode resonator, the authors in [4] merged the common-mode filter with the differential-mode resonator at the cost of the reduced switching speed of the gate and worsened phase noise and the ability to cut off the noise-injection path from the VDD coupled to the gate. In order to overcome the above-mentioned issues, a 11.5-to-14.3GHz dual-core Class-F VCO with common-mode-noise self-cancellation and isolation technique is proposed in this paper. Without occupying additional area, the injection noise of the VDD and the GND is cancelled inherently at the same time, and the noise path from the drain to gate is isolated. The measurement results indicate that the proposed common-mode-noise self-cancellation and isolation VCO achieves -119.2dBc/Hz phase noise at 1MHz offset from a carrier of 11.8GHz, which translates to an FoM of 192.8dBc/Hz. The reported FoM is competitive among VCOs operating in a nearby frequency range.