Everything you introduce between the clock source and the DW1000 is a potential source of error. This error can manifest itself in jitter, noise, and delay variation.
The Si5317, for example, has a phase noise rating of -106 dB/Hz at 1 KHz offset, the DW1000 specifies -132 dB/Hz at 1 KHz offset as the minimum spec. Now the Si5317 spec is at 622 MHz versus 38.4 MHz, but even considering that, the part doesn’t appear to meet the DW1000 datasheet target. This may manifest itself as error in your measurements.
You should also be aware that everything in the clock signal path can introduce delay variation with temperature. The Si5317 spec is 500 ps variation over its temperature range, which is 15 cm of error potentially introduced. Note that the Si5317 operates at significant power, so self heating will be present, meaning there is at least some sort of start up delay variation until thermal equilibrium is achieved. This means your system may have errors on startup until it has been operating for a while.
The temperature issue affects the cable. As temperature changes, the cable delay changes due to change in conductor spacing, change in insulation dielectric, and changes in length. These changes can be significant. Twisted pair cable seems more sensitive to this than good coax in our experience. Flexing of the cable also introduces delay changes as well.
I’ve observed a number of projects try to use a distributed clock and it has always been troublesome. Be very diligent in your design and be prepared to debug the clock stability. Trying to achieve picosecond level cable synchronization is quite hard.
The best way to distribute precise time to spatially separated nodes is by sending a UWB packet to all of them from a common source and then mathematically modeling the clock errors to the node’s local clocks. This method corrects for all sorts of errors a clock cable system can’t, including antenna delay variation with temperature. It does require the extra node to transmit periodic time packets, and it requires some mathematical coding to get right, so not a trivial exercise to accomplish.
Mike Ciholas, President, Ciholas, Inc
3700 Bell Road, Newburgh, IN 47630 USA
+1 812 962 9408