Kongsberg Simrad SN90 Reference Manual page 621

between the samples in the echo are measured. If the angle is too large, the echoes
are deleted.
If the angle at a given range is too large, this indicates multiple targets.
Maximum Gain Compensation
This setting applies to both CW and FM operation.
Not all single targets are located in the centre of the beam. Targets located off
centre will offer weaker echoes due to the beam properties. The SN90 system
automatically compensates for this using a mathematical model, and you can
manually control the effect of this algorithm by defining a maximum gain value.
Using the 3 dB setting all echoes from within the nominal beam width of the
transducer will be accepted. By reducing the value, you will only accept echoes
that appear closer to the centre of the beam. Reducing the value of this parameter
will effectively narrow the beam opening angles for single target detections, but
will normally improve the accuracy of the target strength values for the detected
single targets.
Minimum Echo Spacing
This setting only applies to CW operation.
This parameter defines the minimum distance between two single echoes when
you are using CW pulses. If they are too close, the echoes are skipped.
The distance is defined as a relation to the length of the transmitted signal.
Selecting 1 means that the minimum spacing corresponds to the physical distance
covered by the transmit pulse. Increasing the value will require the targets to be
further separated, but can improve the accuracy of the target strength values.
Tip
Overlapping targets will not be identified with this function. Use the
,
Length Maximum Echo Length
Distance Before Target
These settings only apply to FM operation.
The
Distance Before Target
spacing before and after one target to the end and beginning of the next target. This
is the same functionality as the
but the algorithms are very different.
They also define the range of target samples which are used for Fourier
transformation to create the target strength frequency response (the curve in the
TS(f) information pane) and the target position phase values.
Increasing the distance values will require the targets to be further separated, but
can increase the frequency resolution for the target strength frequency response
(in the TS(f) information pane).
381294/E
and
Maximum CW Phase Deviation
/
Distance After Target
and
Distance After Target
Minimum Echo Spacing
Functions and dialog boxes
Minimum Echo
to handle these.
settings define the required
function for CW operations,
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