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BASIC RF
Components
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OBJECTIVES:
Review the Basic Units, terminology
and RF components
Applications
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COURSE OUTLINE:
I. Basics of Telecom
a. Transmitter
b. Receiver
c. Information
II . Terms and Units
a. Relative and Absolute
i. Ratios
ii. Logarithmic
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b. Amplitude and Signal Level
i. Watt
ii. dBm
iii. 3 dB point
iv. Losses and Gains
v. C/I or S/Nc. Frequency
i. Hertz
ii.Center Frequency
iii. Bandwidth
d. SPECTRUM ANALYZER
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e. Newtons Law
III. RF Components
f. Law of Conservation of Energy
a. active
b. passive
c. basic RF Componentsi. antenna
1. types
2. practical requirements
3. diversity
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1. Low Pass Filter
2. High Pass Filter
3. Band Pass Filter
4. Band Stop/Notch Filter
iii. Amplifier
iv. Attenuator
ii. filter
vi. Coupler
vii. Splitter/Divider
v. Circulator
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viii. Resistive Load
ix. Cable
x. Connectors
xi. Leaky Cables
e. Complex RF Component
i. Combiner
ii. Duplexer
iii. Diplexer
- Nokia RF Components
AFE & RTC
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IV. Implementation
a. BTS
b. Repeaterc. DAS
V. Link Budget
VI. Practical Limitationa. Hopping
b. Losses
c. Size
d. Cost
e. O&M
f. Reliability
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I. Basic of Telecom
a. Transmitterthe equipment that generates andamplifies a RF carrier signal, modulating the
carrier signal with intelligence, and feeding the
modulated carrier to an antenna for radiation into
space as electromagnetic wave.
b. Receiveran equipment used for receiving
radio waves and converting them into the original
intelligence
c. Information/Intelligencethe actual message
that is being sent in a communication system.
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Hi! Good
Morningtoo.
Hi! Good
Morning.
Tx
Rx
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II. Terms and Units
a. Relative and Absolute
i. Ratiosunits which are in absolute form and
represent division of values. Ex. C/I, S/N, etc.
ii. Logarithmicunits which are converted into
its equivalent logarithmic values. Ex. decibel
b. Amplitude or Signal Level
i. Watts
- it is named after the Scottish inventor
James Watt
- the SI unit of electric power that inone second gives rise to energy to one joule.
- signifies the strength of the given signal
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Amplitude
Amplitudethe value of a varying signal at a specific period
in time
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ii. Decibela power measurement unit referred to another
unit.
dBmthe power level of a certain signal taking 1
milliwatt as the reference
iii. Losses and Gains -energies that are either
added/absorbed and subtracted/released in a system
iv. C/I or S/Nthe ratio of the desired signal to the
undesired signal or interference/noise
- this is a measure of the strength of a
signal compared to any unwanted
signal.
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c. Frequency - the number of complete cycle per unit of
time for a periodic quantity such as alternating current,
sound waves and radiowaves.
i. Hertzthe SI unit of frequency equal to cycle
per second
T
Frequency =1
Period ( T )
=Vel of PropagationFrequency
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v. 3 dB pointsHalf power points
- points on the waveform where of
the maximum signal is located
- this is the reference when we take the
bandwidth of a certain waveform
Max pt.
3dB pt
Bandwidth
amplitude
frequency
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ii. Center Frequency - the average frequency of the
emitted wave when modulated by a symmetrical signal
iii. Bandwidththe range of frequencies which havebeen specified as performance limits for a filter, amplifier
or attenuator, defined as the 3dB points at the high pass
and low pass ends of the frequency response curve
CF
Bandwidth
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Spectrum Analyzer - an instrument
that measures the amplitudes of the
components of a complex waveformthroughout the frequency range of the
waveform.
d. SPECTRUM ANALYZER
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Spectrum analyzer
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e. Newtons Laws
i. First LawLAW OF INERTIA
-
- there is no change in motion of a body
unless acted upon by a resultant force.
ii. Second LawLAW OF ACCELERATION
- a body being subject to a resultant force
experiences an acceleration in the direction of
the resultant force.
iii. Third LawLAW OF INTERACTION-for every force acted on a body there is a force
equal in magnitude but opposite in direction
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f. Law of Conservation of Energy
- this states that energy can neither be
created nor destroyed, instead it will
just transform from one form toanother.
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IV. RF COMPONENTS
a. Active - components that introduces
additional energy and reprocess the received
signal
b. Passivecomponents that do not introduce
any additional energy on the signal.
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c. Basic RF Components
i. ANTENNA - a device that radiates and receives
radio waves
- British term is AERIAL
- they transition point in the
communication chain, where the signal
changes from a wireline signal to a radio
wave propagating signal and vice versa.
Types
Omnidirectional antennas: radiate with the same intensity to
all directions (in azimuth)
Directional antennas: main radiation energy is concentrated
to certain directions
- sometimes called RADIATOR
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antennas
yagi
radiation pattern
pico
panel
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a. Practical Requirements
i. Number of Antenna - reduce the required
number of antenna relative to the number of
radios. One to one ratio of antenna to radio is
impractical.
ii. Antenna isolationthe separation
between two antennas that is usually
considered when employing a spacediversity technique. The distance should be
multiple of the half wavelength.
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Antenna Isolation: Vertical
K
A
The following is valid for 900 Mhz.,
1800,1900Mhz and co-located 900 + 1800/1900
Mhz.
Requirements: Tx -Rx and Rx- Tx: 30 dB
Pre-condition: No influence from tower
structures More than 2m bet Ant and tower.
( A in figure)
Vertical Separation: Tx - Rx and Rx - Tx
Minimum 0.2 m
( K in figure)
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Antenna Isolation: Horizontal
D
Requirements: Tx -Rx and Rx- Tx: 30 dB
Vertical Separation: See Table Below
Table: Horizontal Separation
Gain dBi 900 Mhz 1800/1900 900+1800/1900
10 5m 2.5 m 1m
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There is a need for receiver diversity in cellular systems
to improve the uplink.
Space Diversity
TX1/RXA TX1/RXA
BTS Equipment
Common
TX/RX
Antenna
dd
Horizontal Separation, dd
for diversity = 12-18 (wavelength)
for isolation = 30 dB = 2 (wavelength)
[antennas with 65 degrees beamwidth,
all gain values]
DIVERSITY
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Polarization Diversity using dual-polarized antennas
vertical + horizontal polarization +/- 45 degrees polarization
vertical
array
horizontal
array
antenna
housing
connectors
feeders
+45
degrees
- 45
degrees
DIVERSITY
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Polarization Diversity using dual-polarized antennas
1.5 dB downlink loss
TX1/RXA TX1/RXA
Required isolation >30 dB between
the two antenna parts...
DIVERSITY
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ii. Filters - a selective device that allows a
desired range of energy to pass throughand substantially attenuating all other
ranges.
- they are used to separate, combine orsuppress microwave frequencies.
- they are used to ensure that noharmonics are transmitted
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1. Low Pass Filtera filter that
attenuates frequencies higher than
the cut-off frequency
fcInput Output
Amplitude Amplitude
Frequency Frequency
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2. High Pass Filter -a filter
that permits frequencies
higher than the cut-offfrequency.
Amplitude Amplitude
Frequency Frequency
fcInput Output
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3. Band pass Filter - a filter that
accepts a band of
frequencies andconsiderably attenuates
higher and lower frequencies
than the desired band.
Amplitude Amplitude
Frequency Frequencyfc fc
Input Output
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4. Band stop/Notch Filter - a
filter that prohibits the
passage of a certain
band of frequencies and
allows other
frequencies.
Amplitude Amplitude
Frequency Frequencyfc fc
Input Output
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iii. Amplifier - a device that
increases the strength of a
signal without appreciably
altering its characteristic
waveform.
Input Output
Time
Amplitude
Time
Amplitude
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iv. Circulator - a waveguide component that has a number
of terminals so arranged that energy entering one terminal
is transmitted to the next in a particular direction. This canbe used as a duplexer
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v. Directional Coupler - a device that
couples a secondary system only to a
wave traveling in a particular
direction while completely ignoringthe wave traveling into the opposite
direction
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vi. Splitter/Divider - a device that has
the capability to distribute one input
signal to two or more outputwithout introducing distortion to the
signal.
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vii. Resistive Load - component that can absorb the
transmitted energy and behaves like an actual load such
as an antenna.
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attenuator
viii. Attenuator - a device that uses resistive
components to reduce the strength of a
signal without introducing considerable
distortion.
Time Time
Amplitude Amplitude
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ix. Isolator - allows a signal to pass through in one
direction and attenuates it in the other direction. This is
usually used to prevent a very high SWR.
Incident Wave
Reflected Wave
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ables
xi. Cables - a transmission linewhere energy can pass through
without considerable decrease
on the energy
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xii. Leaky Cables - a cable which has a leak where
energy escapes out continuously
d Complex RF Components
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i. Combiners are needed to enable more than
one transmitter to be connected to one
common transmitting antenna.In GSM, two different TX combiners can be
used -
FILTER COMBINER
HYBRID COMBINER
Transceiver 1
Transceiver 2
Transceiver 3
Transceiver 4
d. Complex RF Components
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NOKIA Combiners
AFE - Antenna Filter Extension Unit- can combine 2 TRX per AFE but 2 AFE canbe used for every sector, this configuration is
called Dual Duplex Operation
RTC - Remote Tune Combiner
- one RTC can combine up to 6 TRX
- this combiner can support both RF andBASEBAND Hopping
- can ONLY support BASEBAND Hopping
- sometimes called WIDEBAND Combiner
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REMOTE TUNE COMBINER
CombinerPart
TX1
TX2
TX3
TX4
Duplex
Filter ANTENNA
Test Out
Rx Out
D-bus In
D-bus out
POWER
CONTROLLER PART
Rx OutRx Out
Pf Pr M
Main Functional Part of the RTCA (900)
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ii. Duplexer - a switching device that permits
alternate use of the same antenna for both transmit
and receive.
Tx
Rx
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Tx Filter
Rx Filter LNA
Antenna
Rx
Tx
Duplexer Block Diagram
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iii. Diplexer - a coupling system that allows two
different transmitters to operate simultaneously
or separately from the same antenna.
Tx1
Tx 2
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Diplexer Block Diagram
Port 900
Port 1800
Dual Band
Antenna
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vi. RECEIVER MULTICOUPLER UNIT (RMU)
- amplifies the received signals and divides them to the
receivers (Rx) of the Transceiver units (TRXs).
RX 1
RX 3
RX 4
RX 5
RX 6
RX 2
Amplifier
ModuleTest
Module
RX
Filter
ANT
TEST
Main Functional Part of the RMUA (1800)
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IV. Implementation
a. BTSBase Transceiver Station
- this is the outer most part of the networkand it interfaces the mobile subscriber to
the network
MS BTSMSC
BSC
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Duplexer
Transceiver
Transceiver
Transceiver
Transceiver
Tx
Tx
Tx
Tx
Rx
Rx
Rx
Rx
RMU
Combiner
Antenna
Base Transceiver Station
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REPEATER
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BPF BPF
BPFBPF
BPF
BPF BSF
BSF
ATT
ATT
Downlink
Uplink
PSU AlarmsTo BTS To MS
PA
PA
LNA LNA
LNALNA
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V. Link Budget
- this is a calculation of the
signal strength seen at the receiver
considering the output power of the
transmitter and the possible gains and
losses that might be incurred within
the system.
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Downlink Link BudgetMobile sensitivity = Bts transmit power - Combiner loss -
duplexer loss - Cable/feeder loss + Bts antenna gain - Maximum
path loss - fading margin - Building/Car penetration loss - body
loss + Mobile antenna gain
Uplink Link BudgetBts sensitivity = Mobile transmit power + mobile antenna gain -
body loss - Maximum path loss - fading margin - building/car
penetration loss + Bts antenna gain + - Duplexer loss- cable/feeder loss + Low Noise Amplifier
Gi
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Mobile sensitivity = -104 {GSM} / -100 {DCS}
BTS sensitivity = -107 {GSM} / -104 {DCS}Sensitivity refers to the receivers ability to receive the weakest signal.
Combiner loss = 3 dB {Filter combiner} / 5 dB {Hybrid combiner}
Main Cable/Feeder cable = 1.2 dB loss per 100 ft
Jumper Cable = 2.1 dB loss per 100 ft
Connector loss = 0.1 dB
Lightning arrestor loss = 0.1 dB
Duplexer loss = 0.5 dB
BTS Antenna gain = 16 dBd / 18 dBi
Mobile Antenna gain = 0 dB
Given:
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Car penetration loss = 6 dB {ETSI}
Building penetration loss = 20 dB {dense urban}18 dB {urban}
12 dB {suburban}
Body Loss = 3 dB {ETSI} / 5 dB {Ericsson}
LNA Gain = 5 dB
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Down Link
MS Sensitivity = 43 dBm3 dB0.5 dB3 dB + 8 dB120 dB
- 6 dB3 dB + 0 dB
= - 84.5 dBm
* The received power is within the MS sensitivity
BTS Sensitivity = 30 dBm + 0 dB3 dB120 dB6 dB
+ 8 dB3 dB +5 dB0.5 dB
= - 89.5 dBm
* The received power is within the BTS sensitivity
MS Sensitivity = PobtsLcomb- LdupLcab+ GantLpathLcarLbody+ Gant
BTS Sensitivity = Poms+ GantLbodyLcarLpath+ GantLcabLdup+ LNA -Lcoupler
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AntennaNavigation
Trigger
Power level
Power Level Diagram
BTS
CombinerLoss
DuplexerLoss
CablesLoss
Antenna
Gain Path Loss
Car LossBody
Loss Mobile
Sensitivity
Pout
Antenna
Gain
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VI. Practical Limitation
a. Hopping - is a form of CDMA where a digitalcode is used to continually change the frequency
of the carrier.
b. Losses - this are the energy released within asystem which must be given due attention when
making a design to achieve the objective being
set.
c. Size - this must be considered when there is a
limitation in the space for the equipment
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d. Cost - good engineering is maximum performance
with minimum cost
e. O&M - maintenance of certain equipment must be
given utmost attention because this makes the
system perform well in the long run.
f. Reliability - a good design must have a reliability
of 99.99% to avoid any failure of service whenever
there is a breakdown of equipment and this can bemaintained by employing diversity techniques.