microwave-chapter-2

POLITEKNIK SULTAN MIZAN ZAINAL ABIDIN
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EP604 Microwave Communication System

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CHAPTER 2
SPACE AND EARTH SATELLITE
EN. MUHAMMAD RIDZUAN BIN IDRIS
EN. MOHD MARAMUZAFAR BIN MOHAMAD
Semester December Session 2012/2013

POLITEKNIK SULTAN MIZAN ZAINAL ABIDIN 3/20
•2.1.1 Draw the block diagram of satellite subsystem.
•2.1.2 Explain the satellite subsystem.
2.1 Understand Satellite Subsystem
•2.2.1 Explain types of satellite:
•a. Active.
•b. Passive
•2.2.2 Describe satellite transponder.
•2.2.3 Draw the transponder block diagram.
•2.2.4 Identify satellite system links:
•a. Up-link.
•b. Down-link.
•c. Cross-link.
•2.2.5 Define foot print.
•2.2.6 Explain radiation patterns:
•a. Spot
•b. Zonal
•c. Hemispherical
•d. Earth
2.2 Understand satellite communication concepts.
Space and Earth Satellite
EP604 MICROWAVE COMMUNICATION SYSTEM

POLITEKNIK SULTAN MIZAN ZAINAL ABIDIN 4/20
•2.3.1 Explain types of earth station:
•a. Transmit only
•b. Receive only
•c. Transmit and received
•2.3.2 Sketch the block diagram of the earth station:
•a. Earth station transmitter
•b. Earth station receiver
2.3 Understand types of earth station
•2.4.1 Determine the frequency band for satellite range.
•2.4.2 Describe the channelization method.
•2.4.3 List the advantages and disadvantages between C- band, Ku-band and Ka-band.
2.4 Understand satellite frequency band

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2.1 Understand Satellite Subsystem

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Irrespective of the intended application, be it a
communications satellite or a weather satellite or even an
Earth observation satellite, different subsystems comprising a
typical satellite include the following:
1. Mechanical structure
2. Propulsion
3. Thermal control
4. Power supply
5. Tracking, telemetry and command
6. Attitude and orbit control
7. Payload
8. Antennas
SATELLITE SUBSYSTEM

7/20POLITEKNIK SULTAN MIZAN ZAINAL ABIDIN
Satellite Anatomy
SATELLITE SUBSYSTEM

SATELLITE SUBSYSTEM
Subsystem Description
1. Mechanical structure The structural subsystem provides the framework for mounting other subsystems of the satellite and
also an interface between the satellite and the launch vehicle.
2. Propulsion The propulsion subsystem is used to provide the thrusts required to impart the necessary velocity
changes to execute all the manoeuvres during the lifetime of the satellite. This would include major
manoeuvres required to move the satellite from its transfer orbit to the geostationary orbit in the case
of geostationary satellites and also the smaller manoeuvres needed throughout the lifespan of the
satellite, such as those required for station keeping.
3. Thermal control The thermal control subsystem is essential to maintain the satellite platform within its operating
temperature limits for the type of equipment on board the satellite. It also ensures a reasonable
temperature distribution throughout the satellite structure, which is essential to retain dimensional
stability and maintain the alignment of certain critical equipments.
4. Power supply The primary function of the power supply subsystem is to collect the solar energy, transform it to
electrical power with the help of arrays of solar cells and distribute electrical power to other
components and subsystems of the satellite. In addition, the satellite also has batteries, which provide
standby electrical power during eclipse periods, during other emergency situations and also during the
launch phase of the satellite when the solar arrays are not yet functional.
5. Tracking, telemetry and
command
The telemetry, tracking and command (IT &C) subsystem monitors and controls the satellite right
from the lift-off stage to the end of its operational life in space. The tracking part of the subsystem
determines the position of the spacecraft and follows its travel using angle, range and velocity
information. The telemetry part gathers information on the health of various subsystems of the
satellite, encodes this information and then transmits it. The command element receives and executes
remote control commands to effect changes to the platform functions, configuration, position and
velocity.

SATELLITE SUBSYSTEM
Subsystem Description
6. The attitude and orbit control It controls the orbital path, which is required to ensure that the satellite is in the correct location in
space to provide the intended services. It also provides attitude control, which is essential to prevent
the satellite from tumbling in space and also to ensure that the antennae remain pointed at a fixed
point on the Earth's surface.
7. The payload part of the satellite that carries the desired instrumentation required for performing its intended
function and is therefore the most important subsystem of any satellite. The nature of the payload on
any satellite depends upon its mission. The basic payload in the case of a communication satellite is
the transponder, which acts as a receiver, amplifier and transmitter. In the case of a weather
forecasting satellite, a radiometer is the most important payload. High resolution cameras,
multispectral scanners and thematic mappers are the main payloads on board a remote sensing
satellite. Scientific satellites have a variety of payloads depending upon the mission. These include
telescopes, spectrographs, plasma detectors, magnetometers, spectrometers and so on
8. Antennas used for both receiving signals from ground stations as well as for transmitting signals towards them.
There are a variety of antennas available for use on board a satellite. The final choice depends mainly
upon the frequency of operation and required gain. Typical antenna types used on satellites include
horn antennas, centre-fed and offset-fed parabolic reflectors and lens antennas.

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2.2 Satellite Communication Concepts

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•Satellite -as the space segment and composed of three separate units(fuel system, the
satellite and telemetry controls, and the transponder)
• Transponder- includes the receiving antenna to pick-up signals from the ground station, a
broad band receiver, an input multiplexer, and a frequency converter which is used to reroute
the received signals through a high powered amplifier for downlink. Primary role of a satellite
is to reflect electronic signals.
•Example-1)telecom satellite-the primary task is to receive signals from a ground station and
send them down to another ground station located a considerable distance away from the
first. This relay action can be two-way, as in the case of a long distance phone call.
•2)television broadcasts-the ground station's uplink is then downlinked over a wide region, so
that it may be received by many different customers possessing compatible equipment. Still
another use for satellites is observation, wherein the satellite is equipped with cameras or
various sensors, and it merely downlinks any information it picks up from its vantagepoint.
Satellite Communication Concepts

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•Passive satellites are relay stations in space. It simply reflects light or radio waves
transmitted from one ground terminal to another without amplification or
retransmission.
•The principle of communication by passive satellite is based on the properties of
scattering of electromagnetic waves from different surface areas. Thus an
electromagnetic wave incident on a passive satellite is scattered back towards the
earth and a receiving station can receive the scattered wave.
Passive Satellite
What is
Passive
Satellite?

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The disadvantages of passive satellites for communications are:
•Earth Stations required high power (10 kW) to transmit signals strong
enough to produce an adequate return echo.
•Large Earth Stations with tracking facilities were expensive.
•Communications via the Moon is limited by simultaneous visibility of the
Moon by both the transmit and the receive stations along with the larger
distance required to be covered compared to that of closer to earth
satellite.
•A global system would have required a large number of passive satellites
accessed randomly by different users.
•Control of satellites not possible from ground.
Passive Satellite

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•It is a functioning satellite that receives and transmits or retransmits radio
communication signals to or from a base station.
•They have more complicated structures having a processing equipment called
Transponder which is very vital for functioning of the satellite. These transponders
serve dual-purpose i.e. provides amplification of the incoming and performs the
frequency translation of the incoming signal to avoid interference between the
incoming and outgoing signals.
Active Satellite
What is
Active
Satellite?

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In active satellites, which amplify and retransmit the signal from the earth
have several advantages over the passive satellites. The advantages of
active satellites are:
•Require lower power earth station
•Less costly
•Not open to random use
•Directly controlled by operators from ground.
Disadvantages of active satellites are:
•Disruption of service due to failure of electronics components on-
board the satellites
•Requirement of on-board power supply
•Requirement of larger and powerful rockets to launch heavier
satellites in orbit
Active Satellite

Satellite Transponder
Block Diagram

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•The circuitry in the satellite that acts as the receiver, frequency
changer, and transmitter is called a transponder.
•This basically consists of a low noise amplifier, a frequency changer
consisting a mixer and local oscillator, and then a high power
amplifier.
•The filter on the input is used to make sure that any out of band
signals such as the transponder output are reduced to acceptable
levels so that the amplifier is not overloaded. Similarly the output
from the amplifiers is filtered to make sure that spurious signals are
reduced to acceptable levels.
•In view of the fact that the receiver and transmitter are operating at
the same time and in close proximity, care has to be taken in the
design of the satellite that the transmitter does not interfere with
the receiver.
Satellite Transponder

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•The communication going from a satellite to ground is called downlink, and when it is going
from ground to a satellite it is called uplink. When an uplink is being received by the spacecraft
at the same time a downlink is being received by Earth, the communication is called two-way.
If there is only an uplink happening, this communication is called upload. If there is only a
downlink happening, the communication is called one-way.
•Some companies sell uplink and downlink services to television stations, corporations, and to
other telecommunication carriers. A company can specialize in providing uplinks, downlinks, or
both.
Introduction to Microwave Communication System
Uplink and Downlink
What is uplink
and downlink?
Satellite Path
Uplink Downlink
Earth
Station
User

Cross Link
What is Cross Link?
Earth
Station
User

Footprint
What is Footprint?
An example of an
elliptical footprint
with a reception
area of Germany,
Austria and
Switzerland. The
ellipses indicate the
necessary antenna
diameter for
receiving in cm.
•The footprint of a communications satellite is the ground area that its
transponders offer coverage, and determines the satellite dish diameter required to
receive each transponder's signal. There is usually a different map for
each transponder (or group of transponders) as each may be aimed to cover
different areas of the ground.
•Footprint maps usually show either the estimated minimum satellite dish
diameter required or the signal strength in each area measured in dBW.

Radiation Pattern
Satellite coverage by four types of beam:
• the global/earth beam, which covers roughly one-third of the globe;
-the beamwidth of a satellite antenna to provide coverage of the visible Earth will
depend on satellite altitude.
- Ground station antennas used as a hub to anchor satellite services will typically
comprise highgain reflector antennas at microwave frequencies.
• the hemispherical beam, which covers roughly one-sixth of the disk;
-for applications where the user is mobile (for example, in a car, train or boat)
• the zonal beam, which covers a large landmass like Europe;
• the spot beam, which covers a ‘specific geographical area’.
-that is beams that are smaller than those that cover the visible Earth – are typically
used to provide services requiring higher power/sensitivity
- typically provided using high-gain reflector antennas

Earth Station
What is Earth
Station?
•The earth station is the link between the terrestrial data sources and the remote
satellite resource.
•Its most familiar component is the earth station antenna, which can be tens of
meters in diameter or a small portable dish. In addition, there are numerous, less
obvious devices in the chain of devices that transmit or receive the signal.

Earth Station
Transmitter?
The primary component within the section of a satellite system is the earth station
transmitter. A typical earth station transmitter consists of an IF(Intermediate
frequency) modulator, an IF to RF microwave up-converter, a high power amplifier
(HPA).The IF modulator converts the input baseband signals to either an FM, a PSK
or a QAM modulated intermediate frequency. The up-converter (mixer and BPF)
converts the IF to an appropriate RF carrier frequency. The HPA provides adequate
input sensitivity and output power to propagate the signal to the satellite
transponder. The HPA’s commonly used are klystrons and TNT’s.

Earth Station
Receiver?
An earth station receiver includes an input BPF(band pass filter), an LNA(low noise
amplifier) and an RF to IF down converter. The BPF limits the input noise power to
the LNA. The LNA is a highly sensitive, low noise device. The RF-to-IF down
converter is a mixer, BPF combination which converts the received RF signal to an IF
frequency. The most common frequencies used for satellite communications are
6/4 and 14/12 GHz bands. The first number indicates the uplink (earthstation-to-
transponder) frequency and the second number is downlink (transponder-to-
earthstation) frequency. Since C band is most widely used, this band is becoming
overcrowded. A typical C band transponder can carry 12 channels, each with a
bandwidth of 36 MHz.

Earth Station
Transmitter
and Receiver?
A transponder is a part of a satellite, which is a combination of transmitter and
receiver. The main function of transponder is frequency translation and
amplification. Based on the frequency translation process, there are three basic
transponder configurations. These are single conversion transponder, double
conversion transponder and regenerative transponder. The uplink signal is received
by the receiving antenna. The received signal is first band limited by Band Pass Filter
(BPF), then it is routed to Low Noise Amplifier (LNA). The amplified signal is then
frequency translated by a mixer and an oscillator. Here only the frequency is
translated from high-band up-link frequency to the low-band down link frequency.
The mixer output (down link signal) is then applied to BPF then it is amplified by a
High Power Amplifier (HPA). This down link signal is then transmitted to receiver
earth station through a high power transmitting antenna.

Frequency Band
Frequency band?
The frequency of operation is perhaps the major determining factor in the design
and performance of a satellite communications link. The wavelength of the free
space path signal is the principal parameter that determines the interaction effects
of the atmosphere, and the resulting link path degradations. Also, the satellite
systems designer must operate within the constraints of international and domestic
regulations related to choice of operating free space path frequency.
Two different methods of designation have come into common use to deﬁne radio
frequency bands.
•Letter band designations
•Nominal wavelength

Channelization Method
Common Channelization Method
•Frequency division multiple access (FDMA), based on frequency-division multiplex (FDM)
•Wavelength division multiple access (WDMA)
•Orthogonal frequency division multiple access (OFDMA), based on Orthogonal
frequency-division multiplexing (OFDM)
•Single-carrier FDMA (SC-FDMA), a.k.a. linearly-precoded OFDMA (LP-OFDMA), based on
single-carrier frequency-domain-equalization (SC-FDE).
•Time-division multiple access (TDMA), based on time-division multiplex (TDM)
•Multi-Frequency Time Division Multiple Access (MF-TDMA)
•Code division multiple access (CDMA), a.k.a. Spread spectrum multiple access (SSMA)
•Direct-sequence CDMA (DS-CDMA), based on Direct-sequence spread spectrum (DSSS)
•Frequency-hopping CDMA (FH-CDMA), based on Frequency-hopping spread
spectrum (FHSS)
•Orthogonal frequency-hopping multiple access (OFHMA)
•Multi-carrier code division multiple access (MC-CDMA)
•Space division multiple access (SDMA)

Frequency Band
Letter band designations Nominal wavelength

Frequency Band
Band Description Advantages Disvantages
C The C band is a name given to certain portions of
the electromagnetic spectrum, including
wavelengths of microwaves that are used for long-
distance radio telecommunications. The IEEE C-
band is a portion of the electromagnetic spectrum
in the microwave range of frequencies ranging
from 4.0 to 8.0 gigahertz (GHz)
-Less disturbance from heavy
rain fade
-Cheaper Bandwith
-Needs a larger satellite dish
(diameters of minimum 2-
3m)
-Powerful (=expensive) RF
unit
-More expensive hardware
-Possible Interference from
microwave links
Ku The Ku-band frequency range is allocated to be
exclusively used by satellite communication
systems, thereby eliminating the problem of
interference with microwave systems. Due to
higher power levels at new satellites Ku-band
allows for significantly smaller earth station
antennas and RF units to be installed at the VSAT
location.
-No interference from
microwave links and other
technologies
-Operates with a smaller
satellite dish (diameters
from 0.9m) -> cheaper and
more easy installation
-Needs less power ->
cheaper RF unit
-More expensive capacity
-Sensitive to heavy rain fade
(significant attenuation of
the signal) / possibly can be
managed by appropriate
dish size or transmitter
power.
Ka The Ka band is a portion of the K band of the
microwave band of the electromagnetic spectrum.
Ka band in future will allow a broader application
field in the V-SAT Industry. At the moment only
very few capacity possibilities are available in Ka
Band.
- Generally higher frequency
- Smaller dish
- Generally lower latency
- Less Expensive Equipment
-Uses Spot Beam Technology
- More susceptible to rain
fade

REFERENCE
• Donald G. Dudley, 2000 Foundations for Microwave Engineering, A JOHN WILEY &
SONS, INC. PUBLICATION
•Stanford Park Division Uses for the Microwave Spectrum
•David M. Pozar , 2005, Microwave Engineering, John Wiley & Sons,Inc
•Slide: SATELLITE COMMUNICATION SYSTEMS
•Anil K. Maini and Varsha Agrawal, 2007 Satellite Technology: Principle and
Application
•Dennis Roddy, 2006, Satellite Communications, The McGraw-Hill Companies, Inc.
•http://en.wikipedia.org/wiki/Channel_access_method#Fundamental_types_of_ch
annel_access_schemes

THANK YOU
EP604 Microwave Communication System
INTRODUCTION TO MICROWAVE COMMUNICATION SYSTEM

microwave-chapter-2

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