第一章 航海雷达基本原理

MARINERADARANDARPAChapter1

BasicPrincipleofRadarChapter1 BasicPrincipleofRadarTheDevelopment&PrincipleofMarineRadarRadarConceptThedevelopmentofradartechniqueTheuseofradaratseaGeneralDescriptionTheprincipleofrangeandbearingmeasurementDisplaypresentationofabasicradarChapter1 BasicPrincipleofRadarRadarConceptGeneralConceptRadar——RadiodetectionandrangingFromthename:Tofindandmeasurethetargetsthatyouconcernaboutbywayofradiomagneticwave.Scientificdefinition:Radarisakindofelectronicsystemwhichcanbeusedtofindthetargetsandtomeasureordeterminatethetargetsinformation/databywayofthecharacteristicsofelectromagneticwave.Chapter1 BasicPrincipleofRadarThecharacteristicofelectromagneticwave:

î

í

ì

ReflactionFind:Reflect\Relay\RadiateTargets:Alltheobjectsthatcanbefoundbyradar.Targetsinformation/data:positionspeed,course,collisionavoidanceinformationconstantspeedstraightlineChapter1 BasicPrincipleofRadar雷达是一种主动遥感设备，它利用电磁波的二次辐射、转发或固有辐射来探测目标，并测定目标的空间坐标、速度及避碰参数的一个无线电技术范围。称为“雷达”。“二次辐射”：雷达发射电磁波到目标后、目标产生“二次辐射”，其中一小部分被雷达天线接收，称为目标回波,雷达收到回波便可发现目标。“转发”：来自应答器（Transponder），“识别器”，后者收到雷达信号后发射经过编码的“应答波”被雷达所接收，从而发现目标。“固有辐射”：来自具有固有辐射源的目标（如飞机、发动机、核爆炸、目标上无线电装置等）雷达接收目标的固有辐射波而发现目标。Chapter1 BasicPrincipleofRadar现代雷达与电子计算机、图象处理、数据处理、自动控制等技术结合，又具有自动信息处理功能及智能化显示终端，可自动、迅速、准确地完成测量、显示、控制和管理。Chapter1 BasicPrincipleofRadar1886-1888Hertz(Germany):realizedelectromagneticwaveoscillating,transmitting,receiving.1914(American):Echosounder－Proto-modelofradar.1922Marconi(Italy):Suggestedapracticableradarsystem.1930Blair:Pulseechomeasurement(range,direction)system－basicradar.Chapter1 BasicPrincipleofRadarRCACo.(American):Inventedairplane-carriedradar.(America):“NewYork”Cruiserequippedwithradar.AfterWWII:Asanavigationaidsdevelopedrapidly.China:Techniquemainlyfromdevelopedcountries.Modernradar/ARPA:Withcomputer,integratednavigationsystem(Loran,GPS,ECDIS,AIS),colourTVdisplayAutomaticbridgenavigationsystem.Chapter1 BasicPrincipleofRadarRadar/ARPA,ECDIS,GPS/DGPSanddataauto-pilotcombinedtogetherwillbefuturemajornavigationsystemChapter1 BasicPrincipleofRadar雷达发展历程模拟信号处理数字信息处理计算机信息处理Chapter1 BasicPrincipleofRadar模拟信号处理20世纪90年代前，雷达设备采用电子管或晶体管，发射功率较大，回波信号经接收系统实时处理，直接显示在径向圆周扫描显示器（平面位置显示器，PlanPositionIndicator-PPI）优点：技术成熟，具有良好的探测的分辨目标的能力，接收信噪比高，抗干扰能力强，故障率低，目标图像稳定清晰，操作简单方便，因而被称为驾驶员“眼睛”缺点：采用实时的模拟信号处理系统和径向圆周扫描显示器，荧光屏的显示亮度和对比度受到限制，无法实现彩色显示

Chapter1 BasicPrincipleofRadarChapter1 BasicPrincipleofRadar数字信号处理雷达设备进步采用数字处理技术采用高亮度光栅扫描显示（TV显示）实现ATT和ARPA功能Chapter1 BasicPrincipleofRadar计算机信息处理随着传感网技术、现代通信技术、信息处理技术和卫星定位技术的发展，雷达功能更加强大Chapter1 BasicPrincipleofRadarTheuseofradaratseaMarineradar:Centi-metricwavelengthpulsetransmittingnavigationalradarForourmajor:Theuseofradaratsea.Threemainapplications:ï

ï

ï

ï

ï

î

ï

ï

ï

ï

ï

í

ì

fixposition(2)

collisionanti-(1)

...course

velocity,bearing),direction(

distance,

targetsof

parameters

theMeasurevisibilityoflimitation

of

free(2)detection

range

long(1)

possible

asearly

as

targetsFind(3)

Navigatingtheship

GeneralDescriptionScandirectionRange:Echo(at10nm)Δt＝123.5μs

PeripheryofCRTOwnshipTargetIsland12nmTarget90°

245°

245EBL901802700BearingmarkerChartformRadarpictureFig.Range&bearingmeasurementSweepline(Length148.2μs

Equivalent12nmrange)Ring(6Total)HLIslandOwnshipRadarcannot“feel”thebacksideofatarget,therefortargetdistortionisinevitable.Chapter1 BasicPrincipleofRadarChapter1 BasicPrincipleofRadar雷达图像特点雷达图像不同于海图，也不同于日常生活中的视觉图像；雷达图像与设备自身性能、大气船舶条件、目标反射特性以及周围环境变化有关；雷达探测到的回波图像与真实目标相比，可能有较大的变形，表现在：P6Chapter1 BasicPrincipleofRadar1.RangemeasurementΔt:duringwhichradiowavetoandformthetarget,C:electromagneticwavetravelvelocityinfreespace.R=slantrange(antenna–aim)Chapter1 BasicPrincipleofRadarΔt:veryshot;beyondthecapabilityofanyconventionaltimemeasuringdevice;Electronicdevice——CRT.Averysmallspotoflight.Thespeedofthistravelcanbeaccuratelycontrolledatvalueswhichallowthespottotransitthescreeninaslittleasafewmicroseconds.Thetimetakenforthespottocrossthescreenisthesameasthetimetakenforaradarpulsetomakethetwo-wayjourneytoatargetatachosenrange.Chapter1 BasicPrincipleofRadarAnechoreturnfromatargetisusedtoproduceanincreaseinthebrillianceofthemovingspot.Whenthespothascompletedthetrace,thebrillianceisautomaticallyreducedtozeroandthespotfliesbacktotheorigintoawaittheincidenceofthenexttransmission.Chapter1 BasicPrincipleofRadarBearingmeasurementBywayofdirectional

antenna(Scanner,Aerial).Chapter1 BasicPrincipleofRadarChapter1 BasicPrincipleofRadarBearingmeasurementBywayofdirectionalantenna(Scanner,Aerial).Chapter1 BasicPrincipleofRadar1.2.2TheechoprincipleTheechoisneverasloudastheoriginalblast.Thechanceof