雷达系统分析2

1Chapter2:Ourgoal:•RadarTransmitters•RadarReceivers•RadarAntennas•PropagationofRadarWaves•RadarEquation22.1RadarTransmitters2.1.1Transmitter()345•12346•CAF(Magnetron)“”Doppler;(CFA:Crossed-FieldAmplifier)(2565)(716dB)CFATWT7(Klystron)()3GHz:(TWT:TravelingWaveTube):TWT45dBCFA8••(a)(b)9(a)(b)10123456112.1.211000MHz1000MHz2ptpavrtrtavfpTppττ==DrerefTTT=123=45f013fmdBHzfm1HzBHz-80dBdB/Hzlg10lg10)(BBfLm∆∆••−=146.7.8.MTBF;MTTR9.10.:152.2RadarReceivers2.2.11——“”231617+•+I,Q•+182.2.21.2.3.4.5.6.7.191.(1)——¾kk=1.3810-23J/KRBnT17T=T0=290KPf=4kTR=“”nnnBfpkTRBu)(42==20¾Z=R+jxZL=Z*=Rjx•TBRERRESSSa4222==nnSkTRBuE42=→nnkTBRuN==42021¾TATA=0.876TA'+36(K)TA‘¾P(f)=Pn0(f)BnBn“”“”H2(f0)f0nAAnABRkTu42=)f(df|)f(H|)f(df)f(0202000HPPBnnn∫∫∞∞==22¾•“”•SNRiSNR0∆N:iiNSNS//00=iiNSNS//00FaiiiiGNNNSNSSNRSNR0000==iaSSG0=NGBkTNGNNanai∆+=∆+=0010≥∆+=anGBkTNF123•F•T0=290KFF•FdBF(dB)=10lgF(dB)•F24¾TANA=kTABn∆NRATe,∆N=kTeBnGaTe—“”“”290k)1F()1F(11000×−=−=⇒+=+=TTTTGBkTGBkTFeeanane25¾F2F1F4F3G1=1/Ln()G2=GRFG3=1/Lc()G4=GIFF1=LnF2=FRFF3=LcNRF4=FIF(/)n1212131210111−−++−+−+=nnGGGFGGFGFFFLL262.Simin==⇒=0000000000NSFBkTNSFNSNSNSFniiiiMFBkTNSFBkTSnni00min0000min)(==M—•F0SNRsatmaxMM3dBfr•M=1—“”•1mW00minFBkTSni=(dBmW)10(w)lg10(dBmW)3minminiiSS•=27•-90~-110dBmWkT0=1.3810-23290=410-21Si,min=-114dB+10lgBn(MHz)+10lgF0F0=6dB,Bn=1.8MHzSi,min=-105.4dBmW:10-6~10-7vAiSRSEimin2min=283.AGC•D=10lg(dB)•AGCmin,iS29K52013003002400((dB)-125-615(dB)777278[80](dB)888378[80]MHz20010022(dB)575578[80]301AGC•(“”)(AGC)312(IAGC)••(EC):nECinIi=(5~20)•32333(STC)“”“(STC)”PimRPim=K·R-aKaa=2.7~4.7344.1BRIBoptfzBRI=Bopt+fzfzfz=2fε0.1MHz~0.5MHzBV≥Bopt/22B0BVB0=2~5/τ355.366.123AFC377.1,..,..,.,382.3Antennas2.3.1FunctionsoftheRadarAntenna•Actsasthetransducerbetweenpropagationinspaceandguided-wavepropagationinthetransmissionlines.•Concentratestheradiatedenergyindirectionoftarget(asmeasuredbytheantennagain)•Collectstheechoenergyscatteredbacktotheradarfromatarget(asmeasuredbytheantennaeffectiveaperture).•Measurestheangleofarrivalofthereceivedechosignalsoastoprovidethelocationofatargetinazimuth,elevation,orboth.•Actsasaspatialfiltertoseparate(resolve)targetsintheangle(spatial)domain,andrejectsundesiredsignalsfromdirectionsotherthanthemainbeam.•Providesthedesiredvolumetriccoverageoftheradar.•Establishesthetimebetweenradarobservationsofatarget(revisittime).392.3.2ApertureAntennasElectricfields:Magneticfields:yayxaxaaEaEEˆ),(ˆ),(),(ζξζξζξ+=rηζξζξζξyaxxayaaEaEHˆ),(ˆ),(),(+−=r40)]sincos(cos)sincos[(4000φφθφφπθxyyxrjkggZffrejkE−++⋅=−)]sincos()sincos([cos4000φφφφθπφyxxyrjkggZffrejkE−++⋅=−λππ2airorspacefreefor377or120)(mediumtheof)impedance(intrinsic00=Ω=Ω=kZ)','(''),','('''ˆ'ˆ00yxedydxyxedydxaArjkaArjkHgEfrr∫∫∫∫∆⋅∆⋅==rinrunitvecto,cosˆsinsinˆcossinˆˆθφθφθzyxr++=directions)(alongvectorsbaseunitare)ˆ,ˆ,ˆ(,'ˆ'ˆ'ˆ'x,y,zzyxzzyyxx++=r41axwayaywaxEHEHγγ+=−=,admittancewave=wγxwyywxfgfgγγ+=−=,)cos1()sincos(4000θγφφπθwyxrjkZffrejkE+++⋅=−)(cos)sincos(4000wxyrjkZffrejkEγθφφπφ++−⋅=−)','('']cos')sin'cos'([sin0yxEedydxfayaxAzyxjkyx∫∫∆++=θφφθ42•RectangularAperturewithuniformilluminationX=-a/2toa/2;y=-b/2tob/2spacefreein,/100Zw==γγ⋅+=+=∫∫−−φθλπφθλπθθφθφθsinsinsinccossinsinc)cos1('')cos1(2/2/sinsin'2/2/cossin'00baabEedyedxEfayaxbbyjkaaxjkayaxyxplaneforthe,planeforthe,,sinsinc)(:functionpatternantennay-zbx-zaddF==θλπθzxay43L,2,1,)12(2sin)21(sind1-=+=+=nndnnλθπθλπ44•Beamwidth:Thesolidangleofcoverage:707.021)2sin(sinc)(===BdFθλπθ21!312=+−Lu326.1)211(6)2sin(=−==Bduθλπ1,844.0)422.0(sin21≈=−dddBλλλθ)()844.0(844.0844.022abbaBBBλλλφθ=⋅==Ω45•Power•PowerdensitydP/dAatθ=0°forEθandEφ)(2),(2202abEyxEdxdyPaaAwaγγ==∫∫∆spacefreein,377/1/11-00Ω===Zwγγo0at),(==θabEfayaxyx))((2)(22power)radiatedtotalthe(2202020abEEabEAEPPayaxaaTa+==∆==γγγ)]sincosRe(2sin||cos|[|4422*2222200200φφφφπγγθθθyxyxpeakffffrkEdAdP++===)]sincosRe(2cos||sin|[|4422*2222200200φφφφπγγθφφyxyxpeakffffrkEdAdP−+===]|||[|)()(2]|||[|)(2222202220ayaxyxpeakEEabrffrdAdP+⋅=+⋅=λγλγ46eTpeakAabPdAdPrG2224)(4)/(4λπλππ===•Ae=∆Aforilluminatedapertureforanyshape,where∆Aistheactualphysicalaperturearea•Ae=abforilluminatedrectangularaperture=πρ2forilluminatedcircularapertureofradiusρ47CircularAperturewithuniformillumination'sin'ˆ'cos'ˆ'φρφρyx+=r)'cos(sin')'sinsin'cos(cossin''ˆ000φφθρφφφφθρ−+⋅=jkjkrjkeeer48Electricfields:zero-orderBesselfunctionofthefirstkindwithargumentAφφφφπρρπφρρρφφθρπρφφθρρπ−=⋅=⋅=∫∫∫∫−''',''21''2)','('''''cossin'200)'cos(sin'0200000jkaajkeddeddEEfφπφπcos20021)(jAedAJ∫=L+−==⋅=∫422)(,sin)sin()(2)()sin(2231000012000sin02000xxxJkkJkxxJdxkkaθρθρπρθπθρEf1sinif,16)sin(1sin)sin(0020000001+−=θρθρθρθρkkkkJL492116)sin(1200=−θρk1if,378.1689.0sin208.1sin22112sin210101===−=−−−DDDBλλλπρλπρλθdiameteraperturetheisD202244=⋅==λππρλπλπDAGe50NonuniformApertureDistributions2|'|,2|'|;|'|21)','(00byaxaxEyxEayaxayax≤≤−=200sinsin4sincsinsin2sinc2=φθφθakbkabfyx2sin2sinc)(=θλπθaFL,3,2,1,)(1lg40)(21=+=nnAdBnπL,3,2,1),(sin221