frequency independent antenna log periodic antennas self-complementary: when metal is replaced by...
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Frequency Independent Antenna โข Log Periodic Antennas
๐
๐0
๐ผ๐ฝ
๐ 1
๐ 2
๐1๐2
Self-complementary:When metal is replaced by air and vice versa, the resultant antenna is identical to the original one ๐ฝ=45 ยฐ
๐ผ=135 ยฐTeeth width and gap equalized:
๐=๐๐
๐ ๐
=๐ ๐+1
๐๐
=โ๐
Frequency Independent Antenna โข Log Periodic Dipole Array (N elements)
๐ผ ๐ฟ1
๐ ๐+1
๐ ๐
๐๐
๐=๐ ๐+1
๐ ๐
=๐ฟ๐+1
๐ฟ๐
<1
๐=๐๐
2๐ฟ๐
๐ฟ1
๐ 1
=๐ฟ2
๐ 2
=โฆ=๐ฟ๐
๐ ๐
๐๐=๐ ๐โ๐ ๐+1
ยฟ (1โ๐)๐ ๐
tan๐ผ2
=๐ฟ๐
2๐ ๐
๐=1โ๐
4 tan๐ผ2
๐ฟ1โ๐๐ฟ
2๐ฟ๐ โ
๐๐
2
Frequency Independent Antenna โข Log Periodic Dipole Array (N elements)
๐ผ ๐ฟ1
๐ ๐+1
๐ ๐
๐๐
Frequency Independent Antenna โข LPDA Design Example
Gain contour๐ =54 216 MHz
Gain
๐=0.822๐=0.149
๐ฟ1=ฮป๐ฟ2
=5.562
=2.78m
๐ฟ๐=ฮป๐2
=1.3892
=0.694m
Frequency Independent Antenna โข LPDA Design Example
๐ =54 216 MHzGain
๐=0.822๐=0.149
๐ฟ1=2.78 m
2.78 0.828
2.29 0.682
1.88 0.560
1.54 0.459
1.27 0.378
1.04 0.310
0.858 0.256
0.705 0.210
0.579 N/A๐๐=2๐ ๐ฟ๐=0.298๐ฟ๐
๐ฟ๐=0.694 m
Frequency Independent Antenna โข LPDA Design Example II
๐ =200 600 MHzGain
๐=0.917๐=0.169
๐ฟ1=ฮป๐ฟ2
=1.52
=0.75 m
๐ฟ๐=ฮป๐2
=0.52
=0.25 m
Yagi-Uda Antennaโข Computer program (Prof. Balanis)
โข N = 15โข Number of directors = 13โข Number of reflectors = 1โข Length of reflector = 0.5 โข Length of driven element = 0.47 โข Length of directors = 0.406 โข Spacing between reflector and driven element = 0.25 โข Spacing between directors = 0.34 โข Radius of wires = 0.003
Yagi-Uda Antennaโข Computer program (Prof. Balanis)
โข E-plane pattern (red)โข H-plane pattern (blue)โข HPBW: 26.48 (E), 27.37(H)โข Directivity: 14.8 dB