ANTENG Ch15SAL032006

ANTENG Ch15SAL032006 - 1 Chapter 15 Chapter 15 Reflector...

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Unformatted text preview: 1 Chapter 15 Chapter 15 Reflector Reflector Antennas Antennas ECE 5318/6352 ECE 5318/6352 Antenna Engineering Antenna Engineering Dr. Stuart Long Dr. Stuart Long 2 ¡ GEOMETRICAL CONFIGURATIONS GEOMETRICAL CONFIGURATIONS ¡ large flat sheet large flat sheet ¡ corner reflector corner reflector ¡ small flat sheet small flat sheet ¡ parabolic reflector parabolic reflector (wide freq. range) (narrow freq. range) 3 ¡ FLAT REFLECTOR FLAT REFLECTOR image driven element d ¡ Image Theory Analysis Image Theory Analysis Source polarization and spacing used to control radiating properties 4 ¡ FLAT REFLECTOR FLAT REFLECTOR ¡ Gain relative to a Gain relative to a λ / 2 dipole in free space dipole in free space losses decrease gain at small spacing larger spacing – less gain – more bandwidth .5 λ λ d/ λ G imperfect conductors 1 2 5 ¡ CORNER REFLECTOR CORNER REFLECTOR ¡ Electrostatic Imaging Electrostatic Imaging n for D 180 = α , , 3 #1 4 # 2 3 images in phase in phase but negative φ 1 2 3 4 ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ≈ φ λ π φ λ π φ sin 2 cos cos 2 cos d d E 6 ¡ CORNER REFLECTOR CORNER REFLECTOR (CONT) (CONT) ¡ Gain Gain region w/ gain < 0 dB ⇒ main lobe in another direction 7 ¡ CORNER REFLECTOR CORNER REFLECTOR (CONT) (CONT) if spacing gets too large, multilobe patterns in real plane d = 0.5 λ d = 1.5 λ d = 1.0 λ G = 3.1 G = 3.8 G = 4.4 ¡ Multilobes Multilobes 8 ¡ CORNER REFLECTOR CORNER REFLECTOR (CONT) (CONT) ¡ Multilobes Multilobes appear when...
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ANTENG Ch15SAL032006 - 1 Chapter 15 Chapter 15 Reflector...

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