Techniques for In-band Phase Noise Suppression in Re-circulating DLLs

This paper presents a re-circulating delay-locked loop @LL) with various innovations to improve in-band phase noise suppression. The voltage-controlled oscillator @’CO) and bias circuitry incorporate circuit-level techniques that reduce l/f noise through switched biasing. The phase realignment theory presented in [I] is applied to optimize the VCO so as to maximize the phase noise suppression achieved by periodically switching in a clean reference pulse, and it is further applied to optimize the loop filter. Theoretical predictions are verified through a 100 MHz prototype IC fabricated in a 0.18 p~ CMOS process.