A J Gasiewski remote sensing course notes lecture10 PDF
Preview A J Gasiewski remote sensing course notes lecture10
ECEN 5254 Remote Sensing Signals and Systems Professor Albin J. Gasiewski Lecture #10 – February 16, 2012 ECOT 246 303-492-9688 (O) [email protected] CCllasses: EECCCCSS 11BB1144 TTRR 99:3300-1100:4455 AAMM 1 ECEN 5254 Remote Sensing Signals & Systems Spring 2012 University of Colorado at Boulder Administration • Readingg: – Ulaby et al., Chapter 6 – RRSSSSSS sslliiddeess • HW #2 due Tuesday Feb 21 COB • HHWW ##33 ttoo bbee ppoosstteedd oonn DD22LL TTueessddaay FFeebb 21 COB 2 ECEN 5254 Remote Sensing Signals & Systems Spring 2012 University of Colorado at Boulder Last Lecture • Fourier transform relationship • Circular appertures,, Bessel functions • Aperture field autocorrelation •• RReefflleeccttoorr aanntteennnnaass • Phase uncertainty & Ruze’ equation 3 ECEN 5254 Remote Sensing Signals & Systems Spring 2012 University of Colorado at Boulder Today’s Lecture • AAppeerrttuurree pphhaassee uunncceerrttaaiinnttyy • Antenna pattern convolution • NNyquiistt spattiiall samplliing • Fresnel approximation • Thin lens transformation • FFTT pprrooppeerrttyy ooff lleennsseess • Human eye 5 ECEN 5254 Remote Sensing Signals & Systems Spring 2012 University of Colorado at Boulder Surface Error Characterization = surface profile error = 00 ((zzeerroo mmeeaann)) x Correlation function: z ff = focal lenggth oo Actual y σ = RMS surface profile profile rroouugghhnneessss ((ssuurrffaaccee eerrrroorr SSTTDD)) IIddeall reflector l = surface error transverse profile correlation lenggth (assume l » λ – not restrictive) 7 Effect of Surface Errors on Gain Ideal pattern reduced Ideal ppattern convolved overall by factor of (Ruze): with blurring function: This is the Kirchoff factor Convolution moves energy for rough surface reflection. from main lobe into near PPeakk gaiin GG andd bbeam effffiiciiency siiddellobbes. AAngullar wiiddthh o η are reduced by this factor. depends on corr. length l. b 8 Gain Redistribution Due to Blurring GG mo G so Original Gain Pattern (narrow main beam) 9 Gain Redistribution Due to Blurring GG mo ~ G =G m mo ** G so Blurring Function ((uunniittaarryy)) Original Gain Pattern (narrow main beam) 10 Gain Redistribution Due to Blurring ~~ GG GG =GG mo ~ m mo G =G m mo G n ** G G =G so s so Blurring Function ((uunniittaarryy)) Blurred Gain Pattern Original Gain Pattern (narrow main beam) 11 Gain Redistribution: Circular Aperture ~ ~ ηη ==00.9988 EExxaammppllee:: DD==3300 mm, ff ==1100 GGHHzz, qquuaaddrraattiicc ttaappeerr ((ηη ==00.7755, )) :: a b 12
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