Sistem Komunikasi Bergerak 2

Modul : 05 PT3163 SISTEM KOMUNIKASI BERGERAK Antena pada Sistem Cellular Program Studi D3 Teknik Transmisi Jurusan Teknik Elektro – Institut Teknologi Telkom BANDUNG, 2008

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Macam-Macam Jenis Antena yang ada di BTS 1) Omnidirectional Rx Rx

2) Sectoring 120o

• Pada kondisi awal biasanya digunakan pola omnidirectional

Tx

( tergantung demand ). • Kegunaan dari pola Sectoring a. Menambah kapasitas b. Mengurangi interferensi

3) Sectoring 60o

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Bentuk Konfigurasi Sektor Sel

4 sector ( quad sector ) PT3163-SISKOMBER-MODUL:06

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

Bagaimana bentuk antena pada lokasi site ?

s it e 3 s e k t o r d e n g a n 7 a r r a y a n t e n a t ia p s e k to rn y a j a lu r t r a n s m is i g e lo m b a n g m ik r o m e n u j u BSC

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s in g le a n te n n a b a s e s t a t io n h o u s in g

Karakteristik Antena pada Sistem Selular Antena 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 λ ) • 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. PT3163-SISKOMBER-MODUL:06

Radio (Tx & Rx) System

Signal Source (Voice, data, etc)

• • • • • •

propagation Txer

PA

Rxer Tx filter

feedline

Signal Information

Rx filter Pre-Amp

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. PT3163-SISKOMBER-MODUL:06

Structure of Transmitter Connector Info Signal

BB Processing

Jumper Mod

PA

Depend on type of Mod used

• • •

Jumper

Cable

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 PT3163-SISKOMBER-MODUL:06

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 PT3163-SISKOMBER-MODUL:06

Reducing Cost with Combine Solution between AP and Antenna Indoor (Radio Interface)

Type A

Type B

With Amplifier PT3163-SISKOMBER-MODUL:06

Generic Structure of Rxer Antenna

Rxer

jumper PA

filter feedline

• •

1 2 . . . N

Multicoupler/ RF Distributor

IF

X

IF

Chanel Encoder

Data/ Signal

LO

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 PT3163-SISKOMBER-MODUL:06

Receiver Components • Antenna: to convert electromagnetic energy from atmosfer electric energy and transfer it to feed line • Feed line = Connector

Jumper

Cable

Jumper

 Jumper to ease maintenance and installation

• 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. PT3163-SISKOMBER-MODUL:06

Receiver Components • Multicoupler: - used for RF distribution - many signals/users can share the same receive antenna: signal 1:4 Splitter

RFin

#1 #2 #3 #4

1:4 Splitter 1:4 Splitter

# 13 # 14 # 15 # 16

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4 Basic Antenna System. λ/4 λ/2

Ground plane

G=2.14 dBi Ζ= 73 Ω

G=4 dBi Ζ= 36 Ω

a. Dipole

b. monopole λ

conductor

Feed point dielectric

λ/2 λ/2 Ground plane

c. Loop

d. Microstrip/ patch

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Base Station Antenna. • Use antenna with higher gain • Could be omnidirectional or sectoral depending on cell type • Collinear antenna:

λ

4

λ feeder

Omnidirectional Radiation Pattern

main lobe

2

S line

λ

boresight

2

(elevation) side lobe PT3163-SISKOMBER-MODUL:06

Base Station Antenna. •

Log periodic dipole array (LPDA) Transmission line

Dipoles

Directional Radiation Pattern

- very wide BW, with constant SWR - typical gain 10 dBi

•

Yagi antenna

main lobe

Reflector Driven element (dipole) Directors

- BW is smaller than LPDA - typical gain 12 – 14 dB

back lobe PT3163-SISKOMBER-MODUL:06

side lobe

main lobe

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 Amplitude Vmax

λ/2

Vmin

•

SWR = Vmax/Vmin, define the matching level between antenna and feeder line • Reflection coefficient:ρ

ρ=

SWR −1 SWR + 1

where ρ represent a percent of reflected power defined by: 2 2

( )

Re turn Loss = 10 log ρ

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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

G = µ .D

• •

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

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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: d

Rx2

h 835 d= x 11 f

Rx1 h

( feet )

where f is in MHz

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Antenna Installation d Tx

Rx2

Rx2

Tx

d

Rx1

a) Tower Rx1

b) Roof Top, Edge of Building

c) Roof Top

Rx1

sector 1 Rx2

Tx

d Rx1

d Tx

2

3

d) Wall Mounting PT3163-SISKOMBER-MODUL:06

φ Rx2

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. Table: Horizontal Antenna Tolerance Azimuth/Horizontal Pattern

Tolerance from Bore Sight

110O 92O 60O 40O

+/- 5.5o +/- 4.5o +/- 3.0o +/- 2.0o PT3163-SISKOMBER-MODUL:06

Antenna Isolation Tx

θ

x y

Tx

y Rx

Rx

a. vertical  y VI = 28 + 40 log  dB λ where y > λ

b) horizontal x HI = 22 + 20 log  dB λ  where x > 10λ

c. slant θ + HI dB o 90 where θ slant angle SI = (VI − HI )

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