EE 529 Remote Sensing Techniques. Review

Transcription

1 59 Rmo Snsing Tchniqus Rviw

2 Oulin Annna array Annna paramrs RCS Polariaion Signals CFT DFT

3 Array Annna Shor Dipol l <<λ Far fild of annna r >>λ r, R[ r ω ] r H φ ηk Ilsin 4πr η µ - Prmiiviy ε - Prmabiliy kr η µ ε

4 Array Array Annna Annna S S r r r r Il k kr π η 4 sin 4 sin r Il k kr π η 4 sin r Il k kr π η d/ d/

5 Far Fild Approimaion r kr ηk Ilsin 4πr kr ηk Ilsin 4πr S d/ d/ S r r ηk Ilsin r r r d k r sin 4πr r r sin ηk Ilsin d k r+ sin 4πr r r + d d sin

6 Far Fild Approimaion Far Fild Approimaion sin d sin d + + sin sin d d T sin cos d T Array Facor Toal fild Fild du o a singl lmn a origin Array Facor r Il k kr π η 4 sin r Il k d r k π η 4 sin sin r Il k d r k π η 4 sin sin +

7 Far Fild Approimaion Far Fild Approimaion S S r d d r r 3 r N S S N sin sin sin N k kd kd n T AF AF N n kd n sin ψ AF sin sin ψ ψ ψ ψ ψ ψ ψ ψ ψ ψ ψ N N N N N N

8 Far Fild Approimaion r N AF N sin ψ ψ sin S N r 3 T AF S d r N ma S d S r AF n N sin ψ ψ N sin

9 Annna Paramrs Radiaion bamwidh Firs-Null Bamwidh Half-Powr Bamwidh Main lob Sidlobs

10 Annna Paramrs Powr radiaion parn G sin N sin N kd kd sin sin Nd L G 3.5 db db λ L Radians db

11 Annna Paramrs W L λ db Radians L λ φdb Radians W Sidlobs Main lob

12 Annna Paramrs Powr dnsiy: Avrag radiad powr P d PT 4πr Radiaing ransmiing powr Radiaion innsiy U D T 4 π r P P d Dirciviy: Raio of maimum powr dnsiy o avrag powr dnsiy in all dircions from an idal sourc 4πr P P T d,ma

13 Annna Paramrs Gain U ma G U rf 4π G φ 3dB 3dB ffciv ara and annna gain Maimum radiaion innsiy of a rfrnc annna L W λ db Radians L A LW G 4 πa λ λ φdb Radians W Sidlobs Main lob

14 RCS RCS: Srngh of cho in rcivd signal P σ r P di P dr Pr 4πR Incidn powr dnsiy Powr dnsiy a rcivr Rflcd powr from obc σ 4πR P P dr di RCS 4πR lim R P P dr di σ, φ ;, φ i i r r 4πR Pdr R, r, φr P, φ di i i Approima RCS Prdicion Mhods: GO, PO, GTD, PTD, MC

15 RCS Dc obc largr han is wavlngh, dpndn on viwing angl, frquncy and polariaion Scaring Mari S S S XX YX S S XY YY r r y S y Incidn fild Backscard fild σ σ XX YX σ σ XY YY S S XX S XY 4πR YX S YY

16 Polariaion Polariaion ] R[, ω + + cos cos, y y k k δ ω δ ω k $ $y, $ y, + + cos cos,, y y y k k δ ω δ ω

17 $y $ Linar Polariaion, $y, $ $ δ δ y δ +, y α an cos ω k + δ y y α α π / -polarid y-polarid

18 $y $ Circular Polariaion, $y, $ π δ δ δ y + + kπ, y y, y $ α, ± ω k + δ

19 llipical llipical Polariaion Polariaion $y $, δ δ sin, cos,,, + y y y y $ $y y, $ TH RAL LCTRIC FILD VCTOR MOVS IN TIM ALONG AN LLIPS Wih: y δ δ δ,

20 llipical Polariaion $y, oy o τ $ CIRCULAR τ : LLIPTICITY ANGL o oy LLIPTIC π τ 4 o oy

21 llipical Polariaion $y $y, $ τ A φ φ $ A : WAV AMPLITUD φ : ORINTATION ANGL π π φ τ : LLIPTICITY ANGL π τ 4

22 RCS and Polariaion HH+VV HV HH-VV

23 Coninuous Signals Coninuous Signal Coninuous in im Coninuous rang of ampliud valus sinπf

24 Coninuous Signals Dla or Impuls funcion Propris: δ for f δ d f δ d f δ d f f f τ δ τ dτ

25 Coninuous Signals Linar Convoluion Calculaion of oupu y of a sysm o inpu h y τ h τ dτ h h τ τ dτ Lngh of N Lngh of h N Lngh of y N +N -. 3,,, h y

26 Coninuous Signals Fourir Transform Givs h frquncy conns of a signal X ω ω d π π π X ω ω dω δ πδ ω

27 Som usful rlaions: ω ω X ω ω ω X ω ω X X ω ω π X X ω X m m ω ω ω for ohrwis m π sinω Coninuous Coninuous Signals Signals

28 Discr Signals Sampling Thorm s δ nt s n X s ω X ω nωs T s n To prvn aliasing, sampling frquncy mus b grar han wic h highs frquncy prsn in a signal ωs ω ma

29 Discr Signals Discr-im Signal.8.6 n.4. Quanid in im Quanid ampliud valus :/4:-/4; sin*pi**; sm,'.' n n sinπfns

30 Discr Signals Discr-im Signal n n n n sinπfns n n sinπfns + πm sinπ f + kfs ns

31 Discr Fourir Transform Discr Signals Priodic signal X m N n n N ω m n N m mωs N πnm / N X m πmn / N Ampliud :.:-.; ap**pi*5*; plo,rala Ampliud f smabsffa,. Fas Fourir Transform - im saving compuaion chniqu of h Discr Fourir Transform

32 Discr Signals Linar Convoluion m y n h m n m Circular Convoluion y n N m h m n m N y n ω ω ω n X H dω π y n N N k X k H k πkn / N Lngh of n N Lngh of hn N Lngh of yn N +N - Lngh of n N Lngh of hn N Lngh of yn N Circular convoluion lads o aliasd oupu unlss N is chosn corrcly, i.. N +N - This can b carrid ou by ro padding boh n and hn

33 Discr Signals Linar Convoluion [ ]; [ - -]; conv, Circular Convoluion iffff.*ff iffff,5.*ff, iffff,6.*ff, iffff,7.*ff,

34 Discr Signals Ampliud Ampliud n Ampliud Ampliud n a ros,; a: ; sma,'.' b ros,; b ; smb,'.' smabsiffffa.*ffb,'.' c p-**pi*9*[:]/; smabsiffffa.*c,'.' n n