New Simrad sonar SX90Low frequency sonar

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

SX90 System diagram

SX90 hull units

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

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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:– 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

0 200 400 600 800 1000 1200 1400 1600 1800 20005

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Range in meters

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SP70

SP90

SP90

SP70 SX90 normal SX90 narrow beam

SX90 tippet 180 degrees view

Tippet view SX90

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)

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

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

Hyperbolic FM

frequency

timeFrequency versus time is hyperbolic

Hyperbolic FM up

Hyperbolic FM down

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

CW 40 ms

Ambiguity function CW

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