An FBAR Driven −261dB FOM Fractional-N PLL

A 1mW −261dB FOM PLL with 91fs jitter is presented that combines a low-noise, high-frequency FBAR reference with the unity-gain harmonic-mixing (HM) PLL to minimize reference noise gain and avoid entirely the amplification of sigma-delta modulator quantization noise and fractional spurs, which, in turn, allows for a substantially larger loop bandwidth to suppress the VCO noise and speed settling.