An Inverse Class-F VCO with Reduced Third Harmonic Detriment Using a High Fundamental and Second Harmonic Q-Factor Resonator Achieving a 198.9dBc/Hz Peak FoM

This paper presents a novel topology to design the inverse-class-F voltage-controlled oscillator (VCO). The proposed architecture employs a distributed dual-mode resonator (DMR) as the LC tank to replace the transformer (xfmr)-based tank in the conventional class-F-1 VCOs. The proposed DMR can achieve high Q-factors at both the fundamental and 2nd harmonic frequencies by avoiding magnetic flux cancellation that is inevitable for the xfmr-based counterpart. Using this DMR to construct a class-F-1 VCO, the ratio of 2nd harmonic to fundamental components in the output oscillation is considerably large. This results in a sufficiently wide duration of impulse sensitivity function (ISF)~0 within the output waveform period to suppress noise to PN conversion without introducing excessive drain to gate gain. In the class-F-1 VCOs, the misaligned third harmonics in the oscillating signal deteriorates the ISF. Thanks to the DMR’s dual high-Q characteristics, the proposed VCO considerably reduces the detrimental 3rd harmonic components, further optimizing PN. The fabricated VCO prototype demonstrates a frequency tuning range (FTR) from 9.37 GHz to 10.86 GHz, with a best-in-class phase noise (PN) of -143 dBc/Hz at a 10 MHz offset, corresponding to a peak figure of merit (FoM) of 198.9 dBc/Hz.