2-9
When the transducer is moved across this pattern the elements measure the intensity along the
intersection of this map. Two sensors aligned with the motion may give the following result,
see figure below.
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40 60 80 100
120
s1
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s2
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Figure: two identical signals with delay caused by displacement between sensors.
A complex sensor as the CFT-780 Transducer will measure intensity along several
intersections of the map. The figure below shows the difference at 45º and a 90º relative to the
motion. The similarity decreases, and the signal time displacement decreases.
The ship moves the transducer during both transmit and receive. This will be seen as a doubled
speed of the speckle pattern during receive. The interference pattern will give signals with
100% modulation that are easy to detect. Side lobes give no false speed. The broad beam gives
always some signal component back, compared to doppler using a narrow beam which may be
missed if the ship is rolling. The interference pattern is also unaffected by salinity, temperature
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0 20 40 60 80 100 120
s1
n
s2
n
s3
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s4
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