New Simrad sonar SX90 Low 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

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 SX90 normal SX90 narrow beam

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

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