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1、CorrectingforDistortedAntennaPatternsinCODAROceanSurfaceMeasurementsDONALDE.BARRICK,MEMBER,IEEE,ANDBELINDAJ.LIPA(InvitedCommunication)Abstract-CODARsystemsemploycompactantennaelementssuchascrossspectraateachoftheantennaelements[l],[2].Fromelectricallysmall
2、loopsandmonopolestoextractbearinginformationinthesesolutions,estimatesofradialcurrentvelocityversusoceansurfaceobservations.Pastanalysismethodshaveassumedthatrangeandbearingareconstructed.Assumedintheuseofthesetheseelementpatternsareperfect,i.e.,cosineando
3、mnidirectional.closed-formsolutionsare:a)perfectomnidirectionalpatternsOperationsfrommetallicoffshoreplatformsusuallydistortthesepat-ternsbecauseofunavoidableobjectsintheirnearfield.Whensuchforeachofthemonopoleantennaelements,andb)nonoisedistortionsareigno
4、red,previousmethodsareshowntoproduce-35"addedtothereceivedsea-echosignalvoltages.In[5]itisrmsbearingerrors.Thereforeleast-squaresmethodsarepresentedandshownthatmutualinteractionamongthefourelements,demonstratedthatdealwithdifferentialelementpatterndistorti
5、ons.Itisneglectedintheclosed-formsolutions,Willproducesufficientshownhowtherequiredrelativepatternsareeasilymeasuredbyaboatpatterndistortiontocausebearingbiaseswiththissystem.circlingtheantenna,andthesepatternsarethenstoredaslook-uptablesintheleast-squares
6、inversionmethods.Relativepatterns(i.e.,oneAlthoughmutualinteractionamongelementsisnotaproblemelementpatterndividedbytheother),ratherthanabsolute,areallthatwiththecrossed-loopsystem[3],[4],recentoperationsfromarerequiredforextractionofsurfacecurrent,wavehei
7、ghtdirectionaloffshoreplatformshaveshownthatthemetallicstructurespectra,winddirection,anddriftingtransponderinformationwithbeneathandaroundtheantennacansignificantlydistorttheCODAR.patternsofthethreeelements.Hencetheassumptionthattheloopshavecosinepatterns
8、andthemonopolehasanomnidirec-I.INTRODUCTIONtionalpatternintheleast-squares[3]analysismethodsusedtoHECODARconceptembodiesallHFradarsystemsforextractdirectionalinformationmaynotbevalid.Furthermore,Tmeasuremento
