8.4 An 83.3-to-104.7GHz Harmonic-Extraction VCO Incorporating Multi-Resonance, Multi-Core, and Multi-Mode (3M) Techniques Achieving -124dBc/Hz Absolute PN and 190.7dBc/Hz $\text{FoM}_{\mathrm{T}}$

The W-band offers a rich spectrum resource for thriving industries, such as automotive radar and satellite communications. Yet, developing a W-band voltage-controlled oscillator (VCO) simultaneously featuring a wide tuning range (TR) and low absolute phase noise (PN) is still challenging. The degraded quality factor (Q) of the switched-capacitor array (SCA) tightens the trade-off between TR and absolute PN at W-band oscillation frequency $(\mathrm{F}_{\text{OSC}})$ . The multi-resonant VCO [1] alleviates such trade-off by the 3 ^rd harmonic extraction. This act lowers $\mathrm{F}_{\text{OSC}}$ by 3×, and the created harmonic resonances can reshape the impulse sensitivity function (ISF), suppressing the circuit noise to PN upconversion. Yet, a single-core VCO has limited output power, and the achievable Q of the SCA under a single mode is low; both limit the improved absolute PN. Alternatively, the electrical-and-magnetic-coupling VCO in [2] nets 4 cores together and extends the number of modes from 2 to 4. Compared to every single core, the PN reduces by -6dB with the TR boosted by $\sim 4\times$ . Yet, the magnetic coupling between different cores hinders the usage of the multi-resonant tank in every single core for further PN improvement. The near-sinusoidal waveform is also suboptimal for harmonic extraction. For the VCO in [3] that realizes the coupling of 4 multi-resonant cores, there is only 1 operating mode. In summary, prior works did not explore concurrently a multi-resonant tank, the multi-mode, and the multi-core.