ANTENG-CH2sal

ANTENG-CH2sal - Chapter 2 Fundamental Properties of...

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1 Chapter 2 Chapter 2 Fundamental Properties Fundamental Properties of Antennas of Antennas
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2 ± ± IEEE Standards IEEE Standards ± Definition of Terms for Antennas ± IEEE Standard 145-1983 ± IEEE Transactions on Antennas and Propagation Vol. AP-31, No. 6, Part II, Nov. 1983
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3 ± ± Radiation Pattern Radiation Pattern (or Antenna Pattern) (or Antenna Pattern) “The spatial distribution of a quantity which characterizes the electromagnetic field generated by an antenna.”
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4 ± ± Distribution can be a Distribution can be a ± Mathematical function ± Graphical representation ± Collection of experimental data points
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5 ± ± Quantity plotted can be a Quantity plotted can be a ± Power flux density W [W/m²] ± Radiation intensity U [W/sr] ± Field strength E [V/m] ± Directivity D
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6 ± Graph can be Graph can be ± Polar or rectangular
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7 ± Graph can be Graph can be ± Amplitude field | E | or power | E |² patterns (in linear scale) (in dB)
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8 ± ± Graph can be Graph can be ± 2-dimensional or 3-D most usually several 2-D “cuts” in principle planes
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9 ± ± Radiation pattern can be Radiation pattern can be ± Isotropic Equal radiation in all directions (not physically realizable, but valuable for comparison purposes) ± Directional Radiates (or receives) more effectively in some directions than in others ± Omni-directional nondirectional in azimuth, directional in elevation
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10 ± ± Principle patterns Principle patterns ± E -plane Plane defined by E -field and direction of maximum radiation ± H -plane Plane defined by H -field and direction of maximum radiation (usually coincide with principle planes of the coordinate system)
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11 Coordinate System Coordinate System Fig. 2.1 Coordinate system for antenna analysis.
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12 ± ± Radiation pattern lobes Radiation pattern lobes ± Major lobe (main beam) in direction of maximum radiation (may be more than one) ± Minor lobe - any lobe but a major one ± Side lobe - lobe adjacent to major one ± Back lobe – minor lobe in direction exactly opposite to major one
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13 ± ± Side lobe level or ratio (SLR) Side lobe level or ratio (SLR) ± (side lobe magnitude / major lobe magnitude) ± - 20 dB typical ± < -50 dB very difficult Plot routine included on CD for rectangular and polar graphs
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14 Polar Pattern Polar Pattern Fig. 2.3(a) Radiation lobes and beamwidths of an antenna pattern
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ANTENG-CH2sal - Chapter 2 Fundamental Properties of...

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