Injection-locked frequency divider

Patent Granted A free-running oscillator which has a small amount of a higher-frequency signal fed to it will tend to oscillate in step with the input signal. Such frequency dividers were essential in the development of television. It operates similarly to an injection locked oscillator. In an injection locked frequency divider, the frequency of the input signal is a multiple (or fraction) of the free-running frequency of the oscillator. While these frequency dividers tend to be lower power than broadband static (or flip-flop based) frequency dividers, the drawback is their low locking range. The ILFD locking range is inversely proportional to the quality factor (Q) of the oscillator tank. In integrated circuit designs, this makes an ILFD sensitive to process variations. Care must be taken to ensure the tuning range of the driving circuit (for example, a voltage-controlled oscillator) must fall within the input locking range of the ILFD.