US 12,451,893 B2
Stable scalable digital frequency reference
Brent Carlson, Penticton (CA)
Assigned to NATIONAL RESEARCH COUNCIL OF CANADA, Ottawa (CA)
Filed by National Research Council of Canada, Ottawa (CA)
Filed on Feb. 2, 2024, as Appl. No. 18/431,019.
Application 18/431,019 is a division of application No. 17/776,322, granted, now 12,334,940, previously published as PCT/CA2020/051560, filed on Nov. 13, 2020.
Claims priority of provisional application 62/934,864, filed on Nov. 13, 2019.
Prior Publication US 2024/0204787 A1, Jun. 20, 2024
Int. Cl. H03L 7/099 (2006.01); H03L 7/14 (2006.01); H03L 7/24 (2006.01)
CPC H03L 7/0991 (2013.01) [H03L 7/141 (2013.01); H03L 7/24 (2013.01)] 11 Claims
OG exemplary drawing
 
1. A system for implementing a scalable stable digital frequency reference, the system comprising:
a plurality of independent crystal oscillator circuitry coupled to each other, each of the plurality of independent crystal oscillator circuitry comprising:
(a) an independent crystal oscillator;
(b) a direct digital synthesizer having a first input from the independent crystal oscillator and second input comprising a phase increment clock source cycle to align all direct digital synthesizers in frequency;
(c) a phase sampler for sampling an output phase of each direct digital synthesizer into a common synchronous clock domain;
(d) a sin/cos look-up table stored in a computer-readable medium, wherein the sin/cos look-up table generates a precision digital complex tone based on output of the phase sampler;
a collective coherent vector sum module for combining the precision digital complex tone in-phase to other precision digital complex tone for each of the other direct digital synthesizer to generate a collective coherent vector sum;
a phase management block wherein each of the plurality of independent crystal oscillator circuitry compares its own sin/cos vector with the collective coherent vector sum to determine requisite phase and frequency corrections of its own direct digital synthesizer; and
a conditioner for conditioning the collective coherent vector sum and outputting the scalable stable digital frequency reference.