–123.1 to –121.4-dBc/Hz, Little-Phase-Noise-Variation VCO over 8.9 to 11.2 GHz under Cryogenic Temperature Using Optimal Common-Mode Control

A technique called optimal common-mode control, which matches the second harmonic frequency of a VCO to the common-mode resonant frequency of a resonator over an entire oscillation frequency range, and suppresses phase noise variation, has been developed. The technique is especially useful for VCOs operating under cryogenic temperatures. From the results of measurement with a prototype chip using the technique, the technique achieved a low phase noise performance, and little phase noise variation, from −123.1 to −121.4 $\mathrm{dBc} / \mathrm{Hz}$ over an entire oscillation frequency range of 8.9 to 11.2 GHz. At present, the technique leads to the lowest variation in phase noise in VCOs operating under cryogenic temperatures.