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Suppose, I have one Tx and one Rx physically separated by the long distance with clock signals CLK1 and CLK2 as shown in fig. (say both of 50MHz). enter image description here I wish to align them in phases. By that I mean, rising edge of CLK1 and rising edge of CLK2 should match at any instance of time. How to achieve it?

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  • \$\begingroup\$ Depends what you mean by "long distance". \$\endgroup\$ – Finbarr Mar 27 '18 at 13:19
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    \$\begingroup\$ Smells like an XY problem to me. \$\endgroup\$ – Andy aka Mar 27 '18 at 13:21
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    \$\begingroup\$ What accuracy are you looking for and for how long? Note that both clocks will drift with time and will not be equal in frequency so that their edges will never be in perfect alignment. \$\endgroup\$ – Barry Mar 27 '18 at 13:24
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    \$\begingroup\$ Why do they need to be aligned in phase, what are you actually trying to do? You don't need them both to be GPS synchronised for example if you are sending data from one to the other, the Rx clock can be derived from data embedded in the Tx stream. \$\endgroup\$ – Neil_UK Mar 27 '18 at 13:47
  • \$\begingroup\$ If it is digital data, NRZI encoding will keep Rx Tx aligned. \$\endgroup\$ – StainlessSteelRat Mar 27 '18 at 15:51
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An oscillator at each end that is phase locked to the WWV transmission on 10.0 MHz (as long as both sites can reliably receive that WWV transmission) would accomplish your need. If the two sites are not to far apart the carrier (with the side-bands filtered out) of an am radio between them can be used to provide the reference frequency for your clock frequency synthesizers. With more effort a GPS frequency standard or the carrier frequency of a (receivable by both sites) FM radio station could be used. These methods will result in two separate phase locked frequency standards.

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  • \$\begingroup\$ Something like WWV or conventional broadcast carrier will not actually synchronize them unless they are equidistant (in the applicable path of propagation) from the transmitter. \$\endgroup\$ – Chris Stratton Mar 31 '18 at 19:01
  • \$\begingroup\$ What you say is true if the same phased is necessary without any adjustment, but a small stable time delay to either clock signal is all that would be needed to control the precise relative phase of the two. This is commonly used for synchronous demodulation. (using a DM74LS221 ) \$\endgroup\$ – Ronald Youvan Apr 1 '18 at 17:56

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