Fractional spur reduction technique using 45° phase dithering in phase interpolator based all‐digital phase‐locked loop.

A spur reduction technique in fractional‐N phase‐locked loops based on a current‐mode phase interpolator (CMPI) is presented by dithering input signals of the CMPI. CMPI shows deterministic phase error having symmetrical profile around 45° offset in each quadrant, and this non‐linear property leads to fractional spurs. The proposed 45° phase rotator with digital compensation reduces the fractional spur by 18.57 dB at most, and average improvement of fractional tones is 7.89 dB in 2 MHz frequency step measurement. [ABSTRACT FROM AUTHOR]