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New Simrad sonar SX90 Low frequency sonar

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 selectio n Advanced Pulse Forms FM Hyperbolic, PSK... Dual mode presentation Easy to operate

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New Simrad sonar SX90 Low frequency sonar

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  1. New Simrad sonar SX90Low frequency sonar

  2. 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

  3. SX90 System diagram

  4. SX90 hull units

  5. SX90 Hull Units • Rugged high speed construction • Wide range of hull units: • Selectable middle position • Simple service and maintenance

  6. SX90 Transceiver Unit

  7. SX90 heat exchanger door

  8. 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

  9. 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

  10. 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

  11. SX90 and SP70 10 ton herring depth 200m sand SP70 SX90 normal SX90 narrow beam

  12. SX90 tippet 180 degrees view

  13. Tippet view SX90

  14. 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)

  15. 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

  16. 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

  17. Hyperbolic FM frequency Hyperbolic FM up Hyperbolic FM down time Frequency versus time is hyperbolic

  18. 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

  19. Ambiguity function CW CW 40 ms

  20. 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

  21. First fish on SX90 Oslo fjord

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