Its EASY to measure phase to a reasonable resolution at these frequencies, but again its a commercial thing, so I can't disclose any more of our methods. We don't actually use it for distance measurement, but it IS a standard technique in surveying systems.

The measurement relies on fairly coarse measurements at several different frequencies remember.

As for the pulse detection, its harder to extract the signal of the pulse in the presence of real noise.Modulated detection schemes are great, because you can use synchronous detection method, like phase sensitive detectors /Phase conscious rectification/ lock in amplification. You can extract the return from well BELOW the noise floor in the signal.

The ECL timers would have to be obscenely fast to get half ways decent resolution. As you point out 1 foot/ one nanosecond corresponds to a 1 Ghz clock !

Steve

Steve