Post on 14-Nov-2014
PT3163-SISKOMBER-MODUL:06
Modul : 05
PT3163SISTEM KOMUNIKASI BERGERAK
Antena pada Sistem Cellular
Program Studi D3 Teknik TransmisiJurusan Teknik Elektro – Institut Teknologi Telkom
BANDUNG, 2008
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Macam-Macam Jenis Antena yang ada di BTS
1) Omnidirectional
Tx
Rx Rx
2) Sectoring 120o
3) Sectoring 60o
Pada kondisi awal biasanya digunakan pola omnidirectional ( tergantung demand ).
Kegunaan dari pola Sectoring a. Menambah
kapasitasb. Mengurangi
interferensi
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Bentuk Konfigurasi Sektor Sel
4 sector ( quad sector )
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RBS / BTS = Radio Base Station / Base Transceiver Station= Merupakan perangkat transceiver yang berhubungan dari / ke
pelanggan (Interface / repeater antara MS dan MSC) .= Elemen-elemen RBS :
Transceiver Control Unit / BSC / Base Station Controller Antena Data terminal
singleantenna
base stationhousingjalur transm isi
gelom bangm ikro m enujuBSC
site 3 sektor dengan 7array antena tiapsektornya
Bagaimana bentuk antena pada lokasi site ?
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Karakteristik Antena pada Sistem SelularAntena pada BTS, mempunyai karakteristik :• Pola radiasi yang diinginkan mempunyai pola radiasi horizontal
ke segala arah, tetapi tidak mempunyai pola radiasi ke atas (vertical plane)
• Banyak digunakan antena dipole ( terutama dipole ½ )• Mempunyai daya pancar yang cukup tinggi.
Antena pada MS, mempunyai karakteristik :• Antena MS harus mempunyai pola radiasi kesegala arah
(omnidirectional).• Berdimensi kecil sehingga memungkinkan diletakkan dibody
handset.• Mempunyai daya pancar yang rendah.
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Radio (Tx & Rx) System
• Signal Source: Informasi & Baseband Processing.• Tx-er: Modulator, Channel Encoder, Interleaver, etc.• PA: Power Amplifier.• Feedline: Cable, Connector and Jumper.• Pre-Amp: LNA.• Rx-er: Demodulator, Channel Decoder, De-Interleaver, etc.
RxerPASignalInformation
Txer
SignalSource(Voice, data, etc)
propagation
feedlineTx filter Rx filter Pre-Amp
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Structure of Transmitter
• BB Processing: to process analog signal into digital signal & other processing• Mod: translate from BB freq. To RF freq depend on type of cellular system
being used e.g. G-MSK modulator for GSM.• Power Amp:
- Class A: high linearity- Class B: greater output power more efficient than Class A, but less linear- Class AB: combined adv. of class A & B become widely used in wireless.- Class C: more power efficient widely used in wireless
BBProcessing
Mod PAInfoSignal
Jumper
Jumper
Cable
Connector
Depend ontype of Mod used
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Transmitting Combiners• Allows multiple transmitters to feed
single antenna, providing– Minimum power loss from transmitter
to antenna– Maximum isolation between
transmitters• Combiner types
– Tuned• low insertion loss ~1-3 dB• transmitter frequencies must be
significantly separated– Hybrid
• insertion loss -3 dB per stage• no restriction on transmitter
• frequencies– Linear amplifier– Linearity and intermodulation are
major design and operation issues
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Reducing Cost with Combine Solution between AP and Antenna Indoor (Radio Interface)
Type AType B
With Amplifier
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Generic Structure of Rxer
• Block diagram of Rxer varies depend on type of modulation, encoder, and/ or base band processing.
• Parameters to be considered are:- frequency range- dynamic range- sensitivity- distortion- noise- tuning speed
12...
N
ChanelEncoder
PAData/Signal
filter
jumper
Multicoupler/RF Distributor
X IF
LOfeedline
Antenna
IF
Rxer
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• Antenna: to convert electromagnetic energy from atmosfer electric energy and transfer it to feed line
• Feed line
Receiver Components
Jumper Cable Jumper
• Filter & Pre-Amplifier:- Filter: to pass the wanted signal & attenuated the
interference designed to work according to the intended bands- Pre-Amplifier is used to increased S/N of received
signals.
= Connector
Jumper to ease maintenance and installation
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Receiver Components
• Multicoupler:- used for RF distribution- many signals/users can share the same receive antenna:
1 : 4Splitter
1 : 4Splitter
# 1
# 2
# 3
# 4
1 : 4Splitter
# 13
# 14
# 15
# 16
RFin
signal
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4 Basic Antenna System.
G=2.14 dBi
a. Dipole
G=4 dBi
b. monopole
Ground plane
c. Loop
Ground plane
conductorFeed point
d. Microstrip/ patch
dielectric
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Base Station Antenna.• Use antenna with higher gain• Could be omnidirectional or sectoral depending on cell type• Collinear antenna:
S
2
2
4
feeder
line
OmnidirectionalRadiationPattern
boresight
main lobe
side lobe(elevation)
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• Log periodic dipole array (LPDA)
Base Station Antenna.
DipolesTransmissionline
- BW is smaller than LPDA- typical gain 12 – 14 dB
Reflector Driven element (dipole)Directors
• Yagi antenna
Directional RadiationPattern
main lobe
main lobeside lobeback lobe
- very wide BW, with constant SWR- typical gain 10 dBi
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Antenna Downtilt
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Vertical Depression Angles
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Types Of Downtilt
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Antenna Downtilt: Reduce Interference
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Antenna Downtilt: Avoid Overshoot
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SWR of Antenna
• SWR = Vmax/Vmin, define the matching level between antenna and feeder line
• Reflection coefficient:
1
1
SWR
SWR2
2log10Re Lossturn
where represent a percent of reflected power defined by:
Amplitude
Vmax
Vmin
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Performance Criteria of Antenna• Antenna Pattern, defined at azimuth and elevation orientation
either omni or bidirectional antenna• Main Lobe & Side Lobe, the lower side lobe the better resistance to
interference• Input Impedance, usually complex matching input ipedance and
feeder line impedance is very critical to have maximum power transfer from feeder to antenna
• Beamwidth, usually defined as angular separation where there is 3 dB reduction from bore-sight
• Directivity & Gain, is ratio of radiation intensity at wanted direction and coverage radiation intensity over all direction
• Bandwidth, define operating range of antenna, limited by SWR. A typical BW is for SWR 1:1.2 at the band edge.
• Polarization, defined by orientation of
E
DG .
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Performance Criteria of Antenna
• Front to Back Ratio, is ratio between main lobe & back lobe, very impotant for directional antenna.
• Spatial diversity:
Rx2 Rx1
h
d
)(835
11feet
fx
hd
where f is in MHz
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Antenna Installation
a) Tower
Tx
Rx1Rx2
d
b) Roof Top, Edge of Buildingc) Roof Top
d
Rx1
Rx2Tx
d
Rx1
Rx2Tx
d) Wall Mounting
sector 1 Rx1
Rx2
Tx2
3
d
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Antenna Installation Tolerance• Apply to physical oriented & plumbness of its installation• For omnidirectional antenna, it is unnecessary. But for directi-
onal antenna it is very critical• Usually taken +/- 5% from antenna horizontal/azimuth pattern.
Azimuth/Horizontal Pattern Tolerance from Bore Sight
110O +/- 5.5o
92O +/- 4.5o
60O +/- 3.0o
40O +/- 2.0o
Table: Horizontal Antenna Tolerance
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Antenna Isolation
a. vertical
y
Tx
Rx
ywhere
dBy
VI log4028
c. slant
y
angleslantwhere
dBHIHIVISIo
90
Tx Rx
x
b) horizontal
10
log2022
xwhere
dBx
HI