That's cool. Why could'nt you do that acoustically?

> they linearly
slewed the transmitter frequency at a given rate and then heterodyned
the current  tx  signal with the reflected signal. The difference in
frequency between tx and rx signals gave the time delay and hence
distance... If you use phase comparisons on tx and
rx rather than just frequency you can deal with slower to much slower
slew rates.

Jack
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