A 0.6V quadrature VCO with optimized capacitive coupling for phase noise reduction

This paper presents a 0.6V quadrature voltage-controlled oscillator (QVCO) with a novel capacitive coupling technique, which is employed not only for quadrature signal coupling, but also for noise reduction. As a result, the proposed QVCO can even achieve 3 to 5dB lower phase noise than a single-phase VCO of the same kind. Optimized capacitive coupling combined with inductive enhance-swing technique enables low-power consumption and low phase noise simultaneously. The QVCO achieves a measured phase noise of -132.3dBc/Hz @ 3MHz offset with a center frequency of 5.6GHz and consumes 4.2mW from a 0.6V supply. This performance corresponds to a Figure-of-Merit (FoM) of 191.5dB. The QVCO RFIC is implemented in a 0.13 μm CMOS technology with core area of 0.6×0.8mm².