METHOD AND DEVICE FOR INJECTION LOCKING OF VOLTAGE CONTROLLED OSCILLATORS USING DIRECT DIGITAL TUNING

摘要

The invention relates to the field of electronics and more particularly to t he tuning and injection locking of voltage controlled oscillators (VCOs). An improved injection locking circuit is provided which allows the VCO to injection lock with a smaller reference signal and therefore a smaller locki ng bandwidth (LBW). In order to allow the VCO to injection lock with a lower power reference signal, this invention includes a pre-tuning STEP to place t he VCO frequency such that the desired frequency is in the LBW. Tuning of the V CO is achieved using direct digital tuning that does not require an input reference. Injection locking is performed using a low frequency clock harmon ic as the reference signal. More specifically, tuning is accomplished by sub- sampling and digitizing the output signal of the VCO, determining the center frequency, and adjusting the VCO control voltage.