This paper considers an oscillator which tracks a frequency within some predetermined error. This oscillator has the advantages of a phase locked or frequency division system in that the ratio of input to output frequency remains fixed. However, the output does not remain in time phase with the input but rather drifts in and out of phase. The almost locked oscillator uses two binary counters, a memory register, and a high frequency oscillator. the amount of tracking error is determined by the ratio of the input frequency to the internal high frequency oscillator. The system is an open loop system and therefore is able to track the input cycle by cycle.
This paper costs $33 for non-members and is free for AES members and E-Library subscribers.