RETRIGGERED OSCILLATOR FOR JITTER-FREE PHASE LOCKED LOOP FREQUENCY SYNTHESIS

摘要

A retriggered oscillator time base including a phase lock loop controlled ring (54) for direct retriggering by a reference oscillator (52). The ring (54) has taps (55) at various successive stages that are outputs to an on-the-fly selector (58) that can add any ten-bit value to a current-tap selection to enable a next-tap selection. Such on-the-fly addition can increase the period of a signal each cycle and thereby divide the reference frequency. Ring's outputs (55) are also used to drive two other retriggered rings (72, 74) for a plurality of NANO timing generators. The use of two rings allows retriggering of one of the rings before the other has completed a whole one-shot cycle. An on-the-fly selector (76) subtracts a value from a present NANO select to a next NANO select to convert back the timebase to the fixed reference frequency for phase and frequency comparison. The subtraction acts as a frequency multiplication whose output Tofx is equal to the reference frequency.