New Simrad sonar SX90 Low frequency sonar
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Transcript of New Simrad sonar SX90 Low frequency sonar
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New Simrad sonar SX90Low frequency sonar
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Simrad Omni Sonars
General advantages:• 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
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SX90 System diagram
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SX90 hull units
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SX90 Hull Units
•Rugged high speed construction
•Wide range of hull units:
•Selectable middle position
•Simple service and maintenance
Hull Unit Stroke length Max. speed Trunk type
SP90* 1,2 m 24 knots Simrad
SP91 1,6 m 20 knots Simrad
SP92 1,2 m 24 knots Furuno
SP93 1,6 m 20 knots Furuno * Standard
(CD
6350
D)
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SX90 Transceiver Unit
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SX90 heat exchanger door
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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
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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
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Selection of vertical beamwidth
• The possibility for more narrow vertical beamwidth gives:– 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
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SX90 and SP70 10 ton herring depth 200m sand
0 200 400 600 800 1000 1200 1400 1600 1800 20005
10
15
20
25
30
35
40
Range in meters
Sig
na
l e
xc
es
s i
n d
B
SP70
SP90
SP90
SP70 SX90 normal SX90 narrow beam
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SX90 tippet 180 degrees view
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Tippet view SX90
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The Doppler-effect’s influence on sonars
Radial component gives doppler
Tangential does not give doppler
The vessel’s Own doppleris removed
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)
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CW pulseformCW 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 msPros: Simple, good for large schools in deep waterCon: 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
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FM HyperbolicFM 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
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Hyperbolic FM
frequency
timeFrequency versus time is hyperbolic
Hyperbolic FM up
Hyperbolic FM down
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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
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CW 40 ms
Ambiguity function CW
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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
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First fish on SX90 Oslo fjord