BASIC RF Components

OBJECTIVES:

Review the Basic Units, terminology and RF components

Applications

COURSE OUTLINE:

I. Basics of Telecom

a. Transmitter

b. Receiver

c. Information

II . Terms and Unitsa. Relative and Absolute

i. Ratios

ii. Logarithmic

b. Amplitude and Signal Level

i. Watt

ii. dBm

iii. 3 dB point

iv. Losses and Gains

v. C/I or S/N

c. Frequency

i. Hertz

ii.Center Frequency

iii. Bandwidth

d. SPECTRUM ANALYZER

e. Newton’s Law

III. RF Components

f. Law of Conservation of Energy

a. activeb. passive

c. basic RF Components

i. antenna1. types2. practical requirements

3. diversity

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

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

IV. Implementationa. BTS

b. Repeater

c. DAS

V. Link Budget

VI. Practical Limitation

a. Hopping

b. Losses

c. Size

d. Cost

e. O&M

f. Reliability

I. Basic of Telecom

a. Transmitter – the equipment that generates and amplifies 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. Receiver – an equipment used for receiving radio waves and converting them into the original intelligence

c. Information/Intelligence – the actual message that is being sent in a communication system.

Hi! Good Morning too.

Hi! Good Morning.

Tx

Rx

II. Terms and Units

a. Relative and Absolute

i. Ratios – units which are in absolute form and represent division of values. Ex. C/I, S/N, etc.

ii. Logarithmic – units 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 in one second gives rise to energy to one joule.

- signifies the strength of the given signal

Amplitude

Amplitude – the value of a varying signal at a specific period in time

ii. Decibel – a power measurement unit referred to another unit.

dBm – the 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/N – the 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.

c. Frequency - the number of complete cycle per unit of time for a periodic quantity such as alternating current, sound waves and radiowaves.  i. Hertz – the SI unit of frequency equal to cycle

per second

T

Frequency = 1

Period ( T )

=

Vel of PropagationFrequency

v. 3 dB points – Half power points

- points on the waveform where ½ 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

ii. Center Frequency - the average frequency of the emitted wave when modulated by a symmetrical signal

iii. Bandwidth – the range of frequencies which have been 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

Spectrum Analyzer - an instrument that measures the amplitudes of the components of a complex waveform throughout the frequency range of the waveform.

d. SPECTRUM ANALYZER

Spectrum analyzer

e. Newton’s Laws

i. First Law – LAW OF INERTIA

-        

- there is no change in motion of a body unless acted upon by a resultant force.

ii. Second Law – LAW OF ACCELERATION

- a body being subject to a resultant force experiences an acceleration in the direction of the resultant force.

iii. Third Law – LAW OF INTERACTION

- for every force acted on a body there is a force equal in magnitude but opposite in direction

f. Law of Conservation of Energy

- this states that energy can neither be created nor destroyed, instead it will just transform from one form to another.

IV. RF COMPONENTS

a. Active - components that introduces additional energy and reprocess the received signal

b. Passive – components that do not introduce any additional energy on the signal.

c. Basic RF Componentsi. 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

antennas

yagi

radiation pattern

pico

panel

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 isolation – the separation between two antennas that is usually considered when employing a space diversity technique. The distance should be multiple of the half wavelength.

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)

Antenna Isolation: Horizontal

D

Requirements: Tx -Rx and Rx- Tx: 30 dB

Vertical Separation: See Table Below

Table: Horizontal Separation

Gain dBi 900 Mhz 1800/1900900+1800/1900

<10 3m 1.5m 1m

>10 5m 2.5 m 1m

There is a need for receiver diversity in cellular systemsto improve the uplink.

Space Diversity

TX1/RXA TX1/RXA

BTS Equipment

CommonTX/RXAntenna

dd

Horizontal Separation, dd

for diversity = 12-18 (wavelength)

for isolation = 30 dB = 2 (wavelength)[antennas with 65 degrees beamwidth,all gain values]

DIVERSITY

Polarization Diversity using dual-polarized antennas

vertical + horizontal polarization +/- 45 degrees polarization

verticalarray

horizontalarray

antennahousing

connectors

feeders

+45degrees

- 45degrees

DIVERSITY

Polarization Diversity using dual-polarized antennas

1.5 dB downlink loss

TX1/RXA TX1/RXA

Required isolation >30 dB betweenthe two antenna parts...

DIVERSITY

ii. Filters - a selective device that allows a desired range of energy to pass through and substantially attenuating all other ranges.

- they are used to separate, combine or suppress microwave frequencies.

- they are used to ensure that no harmonics are transmitted

1. Low Pass Filter – a filter that attenuates frequencies higher than the cut-off frequency

fcInput Output

Amplitude Amplitude

Frequency Frequency

2. High Pass Filter -a filter that permits frequencies higher than the cut-off frequency.

Amplitude Amplitude

Frequency Frequencyfc

Input Output

3. Band pass Filter - a filter that accepts a band of frequencies and considerably attenuates higher and lower frequencies than the desired band.

Amplitude Amplitude

Frequency Frequencyfc fc

Input Output

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

iii. Amplifier - a device that increases the strength of a signal without appreciably altering its characteristic waveform.

Input Output

Time

Amplitude

Time

Amplitude

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 can be used as a duplexer

v. Directional Coupler - a device that couples a secondary system only to a wave traveling in a particular direction while completely ignoring the wave traveling into the opposite direction

vi. Splitter/Divider - a device that has the capability to distribute one input signal to two or more output without introducing distortion to the signal.

vii. Resistive Load - component that can absorb the transmitted energy and behaves like an actual load such as an antenna.

attenuator

viii. Attenuator - a device that uses resistive components to reduce the strength of a signal without introducing considerable distortion.

Time Time

Amplitude Amplitude

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

Connectors

x. Connectors - device that joins two or more circuit

Cables

xi. Cables - a transmission line where energy can pass through without considerable decrease on the energy

xii. Leaky Cables - a cable which has a leak where energy escapes out continuously

i. Combiners are needed to enable more thanone transmitter to be connected to onecommon transmitting antenna.

In GSM, two different TX combiners can beused -

• FILTER COMBINER• HYBRID COMBINER

Transceiver 1

Transceiver 2

Transceiver 3

Transceiver 4

d. Complex RF Components

NOKIA Combiners

AFE - Antenna Filter Extension Unit - can combine 2 TRX per AFE but 2 AFE can be 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 and BASEBAND Hopping

- can ONLY support BASEBAND Hopping

- sometimes called WIDEBAND Combiner

Tx outΣ50 Ωtermination

Isolator

Isolator

Tx 1

Tx 2

Wideband Combiner Block Diagram (AFE)

Remote Tune Combiner Block Diagram

REMOTE TUNE COMBINER

Combiner Part

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)

ii. Duplexer - a switching device that permits alternate use of the same antenna for both transmit and receive.

TxRx

Tx Filter

Rx Filter LNA

Antenna

Rx

Tx

Duplexer Block Diagram

iii. Diplexer - a coupling system that allows two different transmitters to operate simultaneously or separately from the same antenna.

Tx1

Tx 2

Diplexer Block Diagram

Port 900

Port 1800

Dual BandAntenna

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 Module

Test Module

RX Filter

ANT

TEST

Main Functional Part of the RMUA (1800)

IV. Implementationa. BTS – Base Transceiver Station

- this is the outer most part of the network and it interfaces the mobile subscriber to the network

MS BTSMSC

BSC

Duplexer

Transceiver

Transceiver

Transceiver

Transceiver

Tx

Tx

Tx

Tx

Rx

Rx

Rx

Rx

RMU

Combiner

Antenna

Base Transceiver Station

b. Repeater - an amplifier that processes weak signals and retransmits stronger signal without reshaping their waveform

BPF BPF

BPFBPF

BPF

BPF BSF

BSF

ATT

ATT

Downlink

Uplink

PSU AlarmsTo BTS To MS

PA

PA

LNA LNA

LNALNA

REPEATER

D.A.S.

Splitter/divider

Splitter/divider

amplifier

c. DAS – Distributed Antenna System- a system employed wherein several antennas can be used to cover several areas with only one transmitter

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.

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

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 ftJumper Cable = 2.1 dB loss per 100 ft Connector loss = 0.1 dBLightning arrestor loss = 0.1 dB

Duplexer loss = 0.5 dBBTS Antenna gain = 16 dBd / 18 dBiMobile Antenna gain = 0 dB

Given:

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

Down Link

MS Sensitivity = 43 dBm – 3 dB – 0.5 dB – 3 dB + 8 dB – 120 dB - 6 dB – 3 dB + 0 dB

= - 84.5 dBm

* The received power is within the MS sensitivity

BTS Sensitivity = 30 dBm + 0 dB – 3 dB – 120 dB – 6 dB + 8 dB – 3 dB +5 dB – 0.5 dB

= - 89.5 dBm

* The received power is within the BTS sensitivity

MS Sensitivity = Pobts – Lcomb - Ldup – Lcab + Gant – Lpath – Lcar – Lbody + Gant

BTS Sensitivity = Poms + Gant – Lbody – Lcar – Lpath+ Gant – Lcab – Ldup+ LNA -Lcoupler

AntennaNavigation

Trigger

Power level

Power Level Diagram

BTS

Combiner Loss

Duplexer Loss

Cables Loss

Antenna Gain Path Loss

Car Loss Body Loss Mobile

Sensitivity

Pout

Antenna Gain

VI. Practical Limitation

a. Hopping - is a form of CDMA where a digital code is used to continually change the frequency of the carrier.

b. Losses - this are the energy released within a system 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

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 be maintained by employing diversity techniques.