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How are antenna arrays synchronized for direction finding/localisation?

For example, if the processing unit is located closer to one antenna then another, it will see the signal from the closer antenna first even if it hits them at the same time(voltage propagation speed within the line is at most the speed of light if not significantly less). How is this dealt with? Do you take into account the antenna transmission line lengths and attempt to fix it in software?

Alternatively, suppose you have two receivers each collecting data at their specific antenna locations - how can you synchronize the timing between them? Even if they are locally synchronized then moved, oscillator drift will cause timing mismatches. How is this problem solved?

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Absolutely, that delay difference has to be compensated for in some way. This is usually done by matching the feed line lengths to all of the antennas so they are identical to within some precision. Depending on what the antennas are connected to, it may also be possible to compensate for the delay somewhere else.

As far as time synchronisation of separate receivers, this is usually done by locking them on to some sort of common time and frequency reference signal, such as GPS or perhaps a higher resolution frequency standard transfer system.

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  • \$\begingroup\$ Ok that makes sense, in the case of synchronization of two different receivers - I don't understand how any RF signal would work since it will still experience RF delay associated with the speed of light. Basically I want to measure the time difference between when it takes two separate receivers to receive an RF signal but unless the receivers are synced I don't see how. \$\endgroup\$
    – FourierFlux
    May 18, 2018 at 6:56
  • \$\begingroup\$ @FourierFlux you have to sync the receivers. \$\endgroup\$
    – user253751
    May 18, 2018 at 8:10
  • \$\begingroup\$ Well, part of the synchronization technique is dealing with/compensating for time of flight delays in distributing the timing information. With something like GPS, this is done automatically and is essentially a byproduct of the location computation, and the accuracy is necessarily very good, within a few nanoseconds even for receivers that are very far apart. \$\endgroup\$
    – alex.forencich
    May 18, 2018 at 16:14

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