A Cryogenic Push-Pull Class-C Dual-Mode VCO with 72%-Tuning Range for Quantum Applications

This letter presents a cryogenic Class-C voltage-controlled oscillator (VCO) designed for quantum applications, capable of covering the 4-8 GHz frequency band. Leveraging the low phase noise characteristics of the Class-C VCO, an octave frequency tuning range is achieved using a dual-mode switch-inductor, eliminating the need for triple- or quad-mode inductors. To minimize power consumption, the design employs a current-reuse topology where the dual cores share the same bias current. Fabricated in TSMC 90nm CMOS technology, the proposed VCO achieves a 72% tuning range, making it the first VCO, to the best of our knowledge, to cover the entire 4-8 GHz band at 4K. Measured results show a phase noise of −115 dBc/Hz at 1 MHz offset, with a power consumption of 10 mW. The core area of the VCO is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.4 \times 0.65 \text{mm}^{2}$</tex>.