Specifications

SimradSH90

Whenthebeamstabilizerisactivated,bothhorizontaland

verticalbeamswillbestabilizedelectronicallyforrollandpitch

movementsupto±20degrees.Thebeamdirectionwillthen

changecontinuouslyaccordingtothevessel’smovements,and

secureanoptimalcontactwiththetargetseveninroughseas.

Figure7Stabilisationsystem

Reception

Agreatefforthasbeenmadetoreduceunwantednoisetogeta

cleanandstableechopresentation.Toachievethisgoalthesonar

receiverhasthefollowinglteringpossibilities:

•FMCorrelationlter

•AGC(AutomaticGainControl)

•RCG(ReverberationControlledGain)

•Ping-to-pinglter

•TVG(TimeV ariableGain)

•Noiselter

FMCorrelationlter

TheFM(frequencymodulation)isasweepinfrequencies.

Thereceiverltersoutthosesignalsthatarethesameasthe

transmitted.Thisprovidesalteringeffect,whichefciently

reducesinterference,noiseandreverberation.Inadditionto

givingacleanandstableechopresentation,thiswillnormally

alsoincreasethesonar’sdetectionrange.Theadvantageof

theFMcorrelationlteristhatitretainsthehighresolutionin

rangewithlongpulselengthsandhighenergy,andthatitisnot

sensitivetomovingtargets.

AGC(AutomaticGainControl)

TheAGC(AutomaticGainControl)sensestheecholevelin

severaldirections,andusethisasabasisforadjustingallthe

receiverbeams.TheAGCwillthusprovideautomaticscaling

ofthedatainordertomaintainproperdynamicrangebasedon

allechovalues

Thestrengthoftheltercanbeselectedinthemenu.

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