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Simrad EY 500
* The normalized echo length must be less than the max echo length
parameter (default 1.8).
* The correction value returned by the gain correction model must not exceed
the max gain compensation parameter (default 4 dB). Narrow beamwidth for
small targets is obtained by using smaller max. gain compensation and
should be considered when TS detection is poor.
* Average electrical phase jitter between samples inside an echo pulse must
not exceed the max phase deviation parameter (default 2 phase steps) where
max phase deviation is set in units of phase steps (64 phase steps = 180
electrical degrees). In a noisy environment or when the targets are small, the
max. gain compensation and TS minimum values should be carefully
optimized to suit the current situation.
The transmitted signal is characterized by a square-like envelope with zero rise
and decay times. However, on its way the signal passes through filters in the
transmitter and receiver and twice through the transducer which has a
bandpass-like response. The shape of the received signal is therefore different
from the transmitted one in the sense that the rise and decay times are no
longer zero and the peak amplitude is slightly reduced as shown in figure 5.
The EY 500 corrects for these effects by
* including a small peak amplitude correction factor in the algorithm for point
backscattering strength.
* using the effective pulse length rather than the transmitted pulse length in
the algorithm for volume backscattering strength.
16
8 IMPULSE RESPONSE
Transmitted envelope
Figure 5 Signal envelopes.
Received envelope
(CD471)
P3403E/A
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