Retriggered oscillator for jitter-free phase locked loop frequency synthesis

摘要

An embodiment of the present invention is a retriggered oscillator timebase including a phase lock loop controlled ring for direct retriggering by a reference oscillator. The ring has taps at various successive stages that are output to an on-the-fly selector 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 outputs are also used to drive two other retriggered rings 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 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 "t0fx " is equal to the reference frequency.