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As a missile approaches a target, the radar-controlled fuse that tells it
when to explode can be confused by objects near the target. But a military
patent just published has a solution. A proximity fuse filed by Licentia Patent
of Frankfurt (GB 2 336 196) has a radar transmitter and receiver in the tip
which analyses the Doppler shift in reflections from the target. To avoid
“clutter” echoes from the ground, the fuse is pre-programmed with a reference
library of the steady reflection characteristics of dry sand, moist soil,
vegetation and water. So a Doppler-shifted echo then stands out from the clutter
and primes the fuse.