A sub-harmonic injection-locked oscillator with auto aligned multiple pulse injection

A sub-harmonic injection-locked oscillator with wide lock range is presented. In general, when the ratio between injection clock and output frequency is large, a lock range of sub-harmonic injection-locked oscillator becomes narrow, and the effect of phase noise suppression degrades. The proposed multiple pulse injection technique overcomes this problem by decreasing effective frequency ratio. For wideband use, the injection pulse generator incorporates a feedback loop to automatically adjusts the pulse interval. The proposed circuit is demonstrated using SiGe-BiCMOS process. The lock range of designed circuit is four times wider than that of conventional injection method. The fabricated IC achieved very low phase noise floor of -118.7 dBc/Hz at 8.0 GHz, which corresponds to the normalized noise floor of -236.8 dBc/Hz.