Interphase Twinscope Operation Manual page 75

ability for the array to concentrate its acoustic energy in
different directions depending on the different "phasing" of the
signals applied or received by each element. Depending on the
signal phasing to the array, acoustic beams can be directed in
an almost unlimited number of directions. For example, using
two 8 element phased arrays, the Twinscope is capable of
steering the acoustic beam in over 90 different angles in two
directions! Conventional fixed-beam technology would have
required the use of at least 180 transducer elements, each
pointed in a different direction. Such a transducer would be
much too costly and bulky to be of any practical use in the
marine market.
Since the acoustic beam in the phased array is steered
electronically, requiring no moving parts, it can be quickly and
reliably scanned and re-scanned over a large area. When
displayed, the changing information between subsequent scans
takes on an almost animated quality - showing, for example,
the movement of underwater fish or the constantly changing
bottom conditions.
In addition to its ability to electronically steer an acoustic
beam, the phased array has other advantages over fixed beam
technologies such as: allowing the user to adjust the transducer
beam width, to scan large areas limited only by the physics of
speed of sound through water (5,000 ft/sec.), and the ability to
provide nearly real-time or live-action underwater views.
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