Transcript New Simrad sonar SX90 Low frequency sonar Simrad Omni Sonars General advantages: • • • • • • • • Combination of horizontal and vertical beams Full roll and pitch stabilization as.

New Simrad sonar SX90
Low frequency sonar
Simrad Omni Sonars
General advantages:
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Combination of horizontal and vertical beams
Full roll and pitch stabilization as standard
Multiple frequency selection
Advanced Pulse Forms FM Hyperbolic, PSK...
Dual mode presentation
Easy to operate
Menu in your own language
Easy installation
SX90 System diagram
SX90 hull units
SX90 Hull Units
•Rugged high speed construction
(CD6350D)
•Wide range of hull units:
Hull Unit
SP90*
SP91
SP92
SP93
Stroke length
1,2 m
1,6 m
1,2 m
1,6 m
Max. speed
24 knots
20 knots
24 knots
20 knots
Trunk type
Simrad
Simrad
Furuno
Furuno
* Standard
•Selectable middle position
•Simple service and maintenance
SX90 Transceiver Unit
SX90 heat exchanger door
SX90 Specifications
The central frequency can vary from 20 to 30 kHz in 1 kHz step.
The beam-widths are:
Vertical normal: 11.4º at 20 kHz to 7.4º at 30 kHz
Vertical narrow: 10.9º at 20 kHz to 6.7º at 30 kHz
Horizontal receive: 13º at 20 kHz to 8.6º at 30 kHz
Source level in omni SL=218.7 dB re µPa at 1m at 26 kHz
Choice of vertical beamwidth, SP90 and SH80
• Selection of beamwidth to match conditions:
– For ranges where the main lobe does not touch the
surface or bottom, low sidelobes will be an advantage
– For ranges where the main lobe touches the surface or
bottom, most narrow main-lobe will be an advantage
Selection of vertical beamwidth
• The possibility for more narrow vertical
beamwidth gives:
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Less reverberation ”noise” from bottom and surface
Higher Source Level , appr. + 2 dB
Totally better range and more clean screen
Beamwidth vertically SX90: 7.8º narrow and 8.8º
normal at 28 kHz
– Beamwidth vertically SH80: 7.6º narrow and 9.5º
normal at 115 kHz
SX90 and SP70 10 ton herring depth 200m sand
40
SP70
SP90
SP90
35
30
Signal excess in dB
SP70
SX90 normal
SX90 narrow beam
25
20
15
10
5
0
200
400
600
800
1000
Range in meters
1200
1400
1600
1800
2000
SX90 tippet 180 degrees view
Tippet view SX90
The Doppler-effect’s influence on sonars
Radial component gives doppler
The vessel’s
Own doppler
is removed
Tangential does not give doppler
We see that the target’s radial component is the problem.
With several doppler channels we can measure this as an information.
In general the pulse length gives the doppler sensitivity:
dv = c/(2*f*T)
CW pulseform
CW means ”Continous Wave”,
It is a pulse of fixed frequency and a given length in time,
This is the normal pulse for all other sonars
For SX90 f=20-30 kHz og T=1-85 ms
Pros: Simple, good for large schools in deep water
Con: Low resolution and lots of reverberation in shallow waters,
sensitive to doppler
CW pulsform
1.000
0.800
0.600
0.400
0.200
0.000
-0.200
-0.400
-0.600
-0.800
-1.000
1
29
57
85 113 141 169 197 225 253 281 309 337 365 393 421 449 477 505 533 561 589
FM Hyperbolic
FM means Frequency Modulation, which mean that the
Frequency will vary in a hyperbolic way with time
Pros: High resolution in range with high energy and insensitive
to target doppler
Cons: Complicated, needs processing ”Matched filter”
Correlator, more complicated than PSK
Hyperbolic FM
frequency
Hyperbolic FM up
Hyperbolic FM down
time
Frequency versus time is hyperbolic
SX90 Pulseforms
• CW 1ms to 85 ms, resolution 0.75m to 64m
• Hyperbolic FM BW 500Hz 1ms to 85 ms,
resolution 1.5 m for all pulse-lengths, higher
resolution implemented later
• Future PSK resolution down to 15 cm
Ambiguity function CW
CW 40 ms
The Doppler-effect’s influence on sonars
In CW this means target speed tolerance versus pulselength:
T=1 ms dv= +-30 knots
T=10 ms dv= +-3 knots
T=60 ms dv= +-0.5 knot
A hyperbolic FM with bandwidth 500 Hz
T=40 ms dv= +- 5 knots
First fish on SX90 Oslo fjord