Matakuliah : H0122 / Dasar Telekomunikasi
Tahun
: 2008
Propagasi Gelombang
Pertemuan 8
Learning Outcomes
Mahasiswa dapat menjelaskan berbagai cara sinyal
berpropagasi pada atmosfir dan ruang hampa serta
fungsi antena.
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Outline Materi
• Pengertian Propagasi gelombang
• Polarisasi
• Jenis Antena
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Wave Propagation
• Once a radio signal has been radiated by an antenna, it travels or
propagates through space and ultimately reaches the receiving antenna.
• The energy level of the signal decreases rapidly with distance from the
transmitting antenna.
• The electromagnetic wave is affected by objects that it encounters
along the way such as trees, buildings, and other large structures.
• The path that an electromagnetic signal takes to a receiving antenna
depends upon many factors, including the frequency of the signal,
atmospheric conditions, and time of day.
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Characteristics Waves
 Radio waves act much like light waves.
 Light waves can be reflected, refracted, diffracted, and focused by
other objects.
 The focusing of waves by antennas to make them more
concentrated in a desired direction is comparable to a lens focusing
light waves into a narrower beam.
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Radio Waves Types
Radio-Wave Propagation Through Space
• The three basic paths that a radio signal can take through space
are:
• Ground wave
• Sky wave
• Space wave
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Ground Wave
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Line of Sight
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Sky Wave
Use the ionospheres layers to reflect the signal back to
earth
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Antena
• Fungsi antena
Meradiasikan energi ke sekeliling (untuk transmisi) atau
menangkap energi dari sekeliling (untuk penerimaan)
• Prinsip Antenna Reciprocity
Suatu antena dirancang untuk mengirim dan dapat dipakai untuk
menerima
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Antenna Parameters
• Radiation field pattern
• Gain
• Lobes
• Beamwidth
• Directivity
• Radiation angle
• Bandwidth
• Polarization
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Dipole
• Formed by spreading the conductors of the two-wire transmission
line out into a straight line.
• Impedance is purely resistive at 73 Ω
• Also called as Hertz Antenna
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Folded Dipole
• Bandwidth is about 10% greater than the open dipole
• The folded dipole impedance is 292 Ω
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Multiple Element
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•
•
•
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Array Antenna
Log Periodic Antenna
Phased Array Antenna
Slot Antenna
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Array
• To shape the radiation pattern of the antenna field to focus it more sharply and
thus increase the apparent power or gain in a specific direction
• Three basic elements : the active, powered, or driven element plus the director,
and the reflector
• Yagi-Uda array is a single driven element which has enough capability and
flexibility
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Summary
• Telah dipelajari karakteristik propagasi gelombang.
• Telah dipelajari berbagai jenis antenna.
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