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Wave Polarization, Polarimetric SAR, and Polarimetric Scattering Models

다음은 PACRIM Training Course (Workshop) 의 강의 Note 중에서 1.1 Wave Properties 만을 발췌한 것으로 , 전파의 성질을 이해하는데 도움이 될 것입니다 . Wave Polarization, Polarimetric SAR, and Polarimetric Scattering Models. Yisok Oh Dept. of Radio Engineering, Hong-Ik University.

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Wave Polarization, Polarimetric SAR, and Polarimetric Scattering Models

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  1. 다음은 PACRIM Training Course (Workshop) 의 강의 Note 중에서 1.1 Wave Properties 만을 발췌한 것으로, 전파의 성질을 이해하는데 도움이 될 것입니다. Wave Polarization, Polarimetric SAR, and Polarimetric Scattering Models Yisok Oh Dept. of Radio Engineering, Hong-Ik University Seoul National University, February 16-19, 2000

  2. Contents • Wave Polarization • 1.1 Wave Properties • 1.2 Polarization Synthesis • Polarimetric Radar System • 2.1 A Scatterometer System • 2.2 NASA/JPL POLSAR System • Polarimetric Scattering Models • 3.1 Surface Scattering • 3.2 Volume Scattering

  3. 1.1 Wave Properties -. What is the “Field”? -. Waves : Electromagnetic Waves by Maxwell -. Planewave Propagation in free space -. Polarization : Basic concepts -. Microwave Generation : DC to AC -. Microwave Guidance by Waveguides/ Trans. lines -. Microwave Radiation by Antennas -. EM Wave Reflection from infinite planes -. Microwave Scattering from -. Point Targets -. Distributed Targets

  4. Electromagnetic Fields Fields: Spatial distribution of a physical quantity. Electromagnetic Fields Static Fields Dynamic Fields : DC : AC No time-variation Time-varying Fields Separation of Electric Field and Magnetic Field Co-existence of Electric and Magnetic fields

  5. + - V E d Conducting Plates Assuming infinite plates, Electrostatic Fields E : Electric Field (showing flux lines) Direction of E : From + charges to - charges

  6. Assuming an infinite current line, Magnetostatic Fields I I : Current H : Magnetic Field (showing flux line) H voltage Electric Fields IEEE Emblem current Magnetic Fields Direction of H : Right-hand rule,

  7. Dynamic (Time-Varying) Fields Maxwell’s Equations Electromotive Force (Voltage Source) Displacement Current Conduction Current Time-varying Electric Field E(r,t) Time-varying Magnetic Field H(r,t)

  8. Waves Consider Water wave in a pond. Cut water surface at once (t=t0) with Kwan-Woo’s Sword (청룡언월도) and look Log the height of Fishing Buoy (x=x0) as a time function Wave Height Wave Height X (Spatial Displacement) t (Time) Even though the wave comes toward me, the water doesn’t !

  9. Time z, distance Electromagnetic (EM) Waves An Example of an EM wave: Magnitude (source, distance, etc.) Sinusoidal Wave Time Variation Z-directed propagation Vector (Polarization)

  10. = constant Same Phase Phase Velocity Assume these circles are surfing boards. Phase velocity = velocity of the equi-phase point Poynting Vector: : Real Power Flow (Magnitude and Direction)

  11. (Maxwell Equation) Time variation Time-Harmonic Fields Time-harmonic Assumption: (Phasor form) z : wave prop. direction

  12. Approximate Planewave in the Far-zone x Ex z Hy y Z-directed propagating Linear polarized (x-direction) Wave Planewave Propagation Planewave: wavefront is plane Spherical wave near an antenna

  13. Polarization : shape of the locus of the E vector tip at a given point in space as a function of time. Polarization Conditions Examples Linear Circular Elliptical Other Cases

  14. Find polarization of the wave, Ey 1 2 Ex Linear pol. with Exercise (determination of polarization) Find instantaneous electric field: Plot electric field: Determine polarization

  15. = Rotation Angle = Ellipticity Angle Polarization Ellipse Lin. Pol. Circular Pol.

  16. Wave direction Thumb Electric Field Other fingers of left hand Various Polarization States Left Circular pol.

  17. Microwave Generation Oscillators Tubes Solid State Klystron TWT Magnetron Gunn Diode MESFET HEMT, etc. Light, Cheap High Power A MESFET Oscillator: Instability Microwave (A.C.) Resonator Amplifying D.C. Power

  18. H E direction Microwave Guidance Waveguides Two Conductors Single Conductor No Conductor Coaxial Cable Two-wire Microstrip Rectangular, Circular Waveguides Dielectric Waveguide (Optical fibers) TE, TM waves TEM wave (Transverse ElectroMagnetic) A Coaxial Cable :

  19. Microwave Radiation Dipole Antenna : Transmission Line (Wave guider) Radiator (Discontinuity) * Current : temporal Variation of charges

  20. Electric Field Lines Microstrip Antenna Coaxial Cable Antennas Wire Antenna Aperture Antenna Reflector Antenna Printed Antenna

  21. EM Wave Reflection z z Infinite plane x x Perpendicular Polarization ParallelPolarization Electric field is perpendicular to the incidence plane Electric field is parallel to the incidence plane Horizontal Polarization Vertical Polarization Electric field is horizontal to Earth surface Magnetic field is horizontal to Earth surface

  22. : Radar Cross Section : Scattering Coefficient Microwave Scattering Radar System Radar System Point Target Distributed Target where

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