-123.1 to -120.4 dBc/ Hz, Little-Phase-Noise Variation VCO over 8.9 to 11.2 GHz under Cryogenic Temperature Using Optimal Common-Mode Control for Quantum Computers

A technique called optimal common-mode control, which matches the second-harmonic frequency of a VCO to the resonator's common-mode resonant frequency across the entire frequency-tuning range and suppresses phase-noise variation, has been developed. The technique is especially useful for VCOs operating at cryogenic temperatures. Based on measurements of a prototype chip that employs this technique, the chip achieves low phase noise performance and small phase noise variation of -123.1 to -120.4 dBc/Hz over a frequency tuning range of 8.9 to 11.2 GHz. At present, the technique achieves the lowest variation in phase-noise among VCOs operating at cryogenic temperatures.