TACTICALAIRNAVIGATION(TACAN)我TCTCLRNV我GTION(TCN)

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1、CHAPTER2TACTICALAIRNAVIGATION(TACAN)INTRODUCTION(2)usethebearinganddistancefromaspecificbeacontofixhisorhergeographiclocation.BeforewebegindiscussingTACAN,youneedtorecallthedefinitionofthepolar-coordinatesystem.TACANPRINCIPLESThepolar-coordinatesystemisa

2、geometricsystemusedtolocatepointsonaplane.Inelectronics,itisThedistancemeasuringconceptusedinTACANusuallyusedforplottingantennadirectionalpatterns.equipmentisanoutgrowthofradar-rangingtechniques.Radar-rangingdeterminesdistancebyTACANisapolar-coordinatety

3、peradioair-measuringtheround-triptraveltimeofpulsedrfnavigationsystemthatprovidesanaircrewwithenergy.Thereturnsignal(echo)oftheradiateddistanceinformation,fromdistancemeasuringenergydependsonthenaturalreflectionoftheradioequipment(DME),andbearing(azimuth

4、)waves.However,TACANbeacon-transpondersinformation.Thisinformation,asshowninfigure2-generateartificialrepliesinsteadofdependingon1,isusuallyprovidedbytwometers.Onemeternaturalreflection.indicates,innauticalmiles,thedistanceoftheaircraftfromthesurfacebeac

5、on.TheothermeterindicatesNowlookatfigure2-2.Theairborneequipmentthedirectionofflight,indegrees-of-bearing,tothegeneratestimedinterrogationpulsepairsthatthegeographiclocationofthesurfacebeacon.ByusingsurfaceTACANsystemreceivesanddecodes.AftertheTACANequip

6、mentinstalledintheaircraftanda50-µsecdelay,thetransponderrespondswithaTACANgroundequipmentinstalledaboardareply.TheairborneDMEthenconvertstheround-particularsurfaceshiporshorestation,apilotcantriptimetodistancefromtheTACANfacility.Theobtainbearingtoanddi

7、stancefromthatlocation.Hefrequencyandidentificationcodeprovidetheorshecantheneither:geographiclocationofthetransmittingbeacon.(1)flydirectlytothatparticularlocation,orTACANPULSEPAIRSTACANtranspondersusetwin-pulsedecoderstopassonlythosepulsepairswiththepr

8、operspacing.Thepurposeofthistwin-pulsetechniqueistoincreasetheaveragepowerradiatedandtoreducethepossibilityoffalsesignalinterference.Afterthereceiverdecodesaninterrogation,theencodergeneratesthenecessarypulsepairrequiredfo