14 Jun
2004
14 Jun
'04
8:28 a.m.
On Mon, 2004-06-14 at 13:08, William Donzelli wrote:
Got my chronology wrong, thanks for the repair!
(They were also *analog* memories, not digital, and used no refresh, the
data being replaced every scan, so they were probably a lot easier to
implement than digital ones.)
They
originated in WWII radar, where they were used to remember the last
received signal pass, so they could detect differences with the current
signal pass, and cancel out stuff that didn't change.
Just post war, actually, at least in Allied radars. The Germans had some
sort of MTI technology in World War 2, but I don't know what they used. AN/APQ-15, a spoofer. It used an odd oil I have never
heard of before,
filled into a tank. A received pulse was amplified and sent to a
transducer in the tank. The (now) acoustic pulse would bounce around in a
semi-random pattern, and another transducer would pic up these echoes,
then retransmitted back to the offending radar. The idea was that one
AN/APQ-15 could "look" like a whole squadron of bombers, simulated in a
tank of oil.
Shows what you can do with a little ingenuity and (very) little
technology.