Satellite Slides by Sir Haleem Junejo(Microwave & Satellite Communication)

8/3/2019 Satellite Slides by Sir Haleem Junejo(Microwave & Satellite Communication)

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Engineer Muhammad Haleem JunejoB.E( Electronics), MSc (Satellite Communication Engineering),CCNAMPEC

[email protected]

Microwave & Satellite

Communication



Introduction



Satellite Communications

Introduction & Systems Overview



•Resources

–FrequenciesVhfL bandS band

C bandKu bandKa bandQ/V bands

–OrbitsGEOHEOLEO

MEO



-Radio Regulations-

Why radio regulations?•Radio regulations rule the assignment and use of frequencies so as to

AVOID causing HARMFUL INTERFERENCE from one communicationsystem to another.•Two important aspects are to be considered:

–Allocation of frequency bands to the various services (WARC) –Standards for performance and compatible inter working of radiosystems (CCIR).•Space radio communication services are:

–Fixed satellite service

–Mobile satellite service –Broadcasting satellite service –Earth exploration satellite service –Space research service –Radio determination satellite service –

Amateur satellite service –Inter-satellite service



Major system trends in Satellite Communications

•Fixed service –Telephony growing slowly –Video distribution, moderately

–VSATs slowly –IP for back haul increasing and interest inbroadband•Broadcast service

–Growing fast digital TV services-interactive –Radio, multicast and multimedia content•Mobile services

–Growing moderately for vehicles—reqt for broader

bandwidth



The International Telecommunication Union (ITU)



Communication Fundamentals



Interference considerations in satellite systems

Limited orbits & spectrum resources forceclose satellite spacing & sharing of spectrum

with other services (e.g. radio relay links).

Need to take account of interference, to &

from other satellite systems, existing &

planned.

Need to take account of interference, to &

from other services, existing & planned. Need to efficiently use resources so that

others can operate at future dates using some

of the remaining resources.



Interference considerations

1.Terrestrial systems (restrictive if exclusive

bands not used).

2. Interference with same satellite network.

3. Interference with other satellite networks.



Link Performance Interference



Evolution of SatelliteCommunications



1945 Arthur C Clarke

1956 First transatlantic telephone cable

1962 Telstar

1964 Intelsat founded1965 Early bird

1969 Intelsat completes global system

1976 Marisats launched

1977 Eutelsat created

1979 Inmarsat created

1982 Inmarsat starts operations

1983 EutelsatF1 launched

development of commercial satellite communication



development of commercial satellite communication

1984 PanAmSat founded

1985 SES Astrain corporated1987 Iridium conceived

1988 First transatlantic fiber cable

1988 First PanAmSat launch

1989 First SES Astra launch1995 PanAmSat completes global system

1998 Iridium service launch

2001 Intelsat & Eutelsat privatisations

2002 SDR operation US –

SIRIUS/XM

2004 DMB in Japan/Korea

2005 INTELSAT PANAMSAT Merger

2006 SES/New Skies merger – one manufacturer in Europe!

HYLAS new UK o erator launched



Evolution of Satellite Communications



I4 Wid b



I4 Wide-beam coverage



I4-Narrow-beam



Orbit Options



Satellite Communications

Systems Architecture



Ground Segment Functions

Track satellite motion with antenna system Boot Telemetry signal with high gain antenna Process, record and analyse Telemetry data Transmit commands to satellite using high power -

unblock able' uplink signal Provide Ranging data Perform scheduled operations Maintain communications with spacecraft under all

possible circumstances Data Distribution Satellite Health data to Satellite Control Centre Experimental data to user groups/investigators Alarm/Alert warning messages



Single Ground Station Model



Ground Station Components



Typical Ground Station

MCC – plansand operates

the entire

space mission

SOCC – satellite

bus and

communication

systems

POCC – onboard

payload

instruments



Location of Ground Segment The number and location of TT&C stations will vary

according to the orbit and mission Geo-stationary Orbit Once on station only one TT&C facility, which may also be the

Satellite Control Centre (SCC) is required in satellite servicearea e.g. ASTRA/SES Luxembourg EUTELSAT Paris

Large organizations with multiple service areas INTELSAT,INMARSAT maintain remote or multiple TT&C facilities

Deep Space Network A network of very large installations (often multiple antennas)

maintained in varying longitudes to provide near continuous

coverage of the plane of the solar system. – The system is US led and maintained by NASA/JPL locations

Australia,Mexico,Hawaii ESOC - network controlled from Darmstadt Jet Propulsion Laboratory

National Aeronautics and Space Administration

Locations of STDN Stations

http://www.jpl.nasa.gov/

http://www.jpl.nasa.gov/



Locations of STDN Stations STDN - NASA’s Satellite Tracking and Data Network

Earth Station Technology




-Earth Station Architecture




Earth Station Architecture



Space Segment



Space Segment Functions

Maintain Earth coverage for antenna low gain omni directional antennas

high gain directional antennas for stabilizedplatform

Receive commands from authorized sources

Transmit spacecraft Telemetry and status

Receive ranging signals and retransmit in

coherent mode Maintain communications with Earth

stations under all possible circumstances

Transmit payload data



Satellite Subsystems

• Communications Payload• –Antennas• –Repeater

• Bus• –Structure• –Electrical power subsystem

• –Satellite attitude control subsystem• –Propulsion subsystem• –Thermal control subsystem

• –Telemetry, tracking and command (TTC)

Attit d /O bit C t l



Attitude/Orbit Control Satellites experience external forces which can disturb

orbits and attitude

Compensation uses rocket propulsion (jets)

Disturbing torques? –solar pressure and magneticdisturbances

Techniques used -Spin stabilization (old INTELSAT‘s)

Three axis momentum (momentum wheels)(most modern/satellites)

Gravity gradient (SSTL/Orbcom) Reaction controlMagnetic control Solar sailing (EurostarSeries)

St t l



Structural

Spacecraft frame and skeleton

Mechanical support and rigidity

shock loads

Rigours of launch (vibration table)Temperature cycling.

Radiation fields –vacuum.

Minimum mass and cost.Pyrotechnics –deployments.

Tracking Telemetry and command



Tracking, Telemetry and command

(TT&C)

Transmits/receives house keeping data to/from satellite

allowing ranging, Doppler, tracking and commands from

ground control

Measures temperature, pressure, voltages, currents,

GPS, etc.

Formats data – command and data handling (C&DH)

Dedicated TTC transponder

Commands to initiate mode changes, turn on/off

equipment, fire thrusters, etc.

P S l



Power Supply

Solar photovoltaic cells –Si & GaAs –sized toproduce average power requirements –10-25%efficient –lifetime degradation due to spaceradiation. BOL and EOL power

Batteries (clinical) –eclipse and peak powerrequirements Nicad Lithi-ion

Regulation and conditioning (need to survivemillions of charge/discharges and distribution tovarious parts of the bus).

Th l



Thermal

On earth –Radiation/conduction/convectionIn space -only radiation

Objects > 273K radiate heat energy

Thermal control is achieved by using externalsurface properties together with heaters,thermostats, heat pipes and interface fillers

Sun shields, black paint, heat shields etc.



Propulsion

Need thrusters to create momentum –propellants

Cold gas –precise, low thrust, simple

Liquid propellant -Hydrogen, hydrogen peroxide

-Higher thrust –more complex

Bipropellants -Liquid hydrogen, oxygen etc-very high thrust –complex and expensive

-high mass propellant

Electric Propulsion -electrostatic –electro –thermal-ion engines



Access Schemes in Satellite Networks



Satellite Network organisation



Satellite Network organisation

Satellite Networks



Satellite Networks

Fixed and Demand Assignment

Satellite Networks



Satellite Networks

Fixed and Demand Assignment

Basic multiple access techniques



Basic multiple access techniquesFREQUENCY DIVISION MULTIPLE ACCESS

(FDMA)




Basic multiple access techniquesTime Division Multiple Access (TDMA)




Basic multiple access techniquesCode Division Multiple Access (CDMA)



Various layers of multiple access

FDMA (1 carrier per link)



FDMA (1 carrier per link)

FDMA(1 carrier per station)



FDMA(1 carrier per station)

FDMA throughput



FDMA throughput

FDMA S



FDMA Summary

Access Channel: give frequency band

Advantages

Use of existing hardware to a greater extent than other techniques Network timing not required

Disadvantages

As the number of accesses increases, intermodulation noise reduces

the usable repeater output power (TWT back-off). Hence there is a lossof capacity relative to single carrier/transponder capacity

The frequency allocation may be difficult to modify Uplink power coordination is required



TDMA Satellite System

• In a TDMA system, each earth station transmitstraffic bursts, synchronized so that they occupyASSIGNED NON-OVERLAPPING time slots. Timeslots are organized within a periodic structurecalled TIME FRAME.

• A burst is received by all stations in the downlinkbeam and any station can extract its traffic from

any of the bursts• a BURST = link from one station to several

stations (TDMA=one-link-per-station scheme)



TDMA Satellite System

Principles of Time Division Multiple



Principles of Time Division MultipleAccess (TDMA)

TDMA throughput



TDMA throughput

TDMA summary



Access Channel: given time slot within time frame

Advantages

Digital signaling provides easy interfacing with developing digitalnetworks on ground

Digital circuitry has decreasing cost Higher throughput compared to FDMA when number of accesses is

large

Disadvantages

Stations transmit high bit rate bursts, requiring large peak power

Network control is required Generation and distribution of burst time plans to all traffic stations Protocols to establish how stations enter the network Provision of redundant reference stations with automatic switchover to

control the traffic stations Means for monitoring the network



CDMA Spread spectrum communications

Direct sequence systems



Direct sequence systems



-power spectrum of data and of spread signal-

CDMA



Frequency hopping systems

Multiple access



pComparison of multiple access techniques

Advantages/disadvantages



g g

Random Access Schemes (1)



( )

FDMA/TDMA/CDMA fixed access have

been designed for circuit/stream traffic

Bursty data traffic –e.g. packets-moreefficiently dealt with via random access

schemes

In random access there is no permanent

assignments –resource is allocated when

needed on a random basis

R d A S h (1) td



Random Access Schemes (1) ctd

In random access or contention methods, no station is superior to another station and none is assigned the

control over another. No station permits, or does not

permit, another station to send. At each instance, a

station that has data to send uses a procedure defined by the protocol to make a decision on whether or not to

send.




Simplest system is ALOHA –transmit packets andif collide, retransmit with random time difference.

Performance via ‗throughput versus delay‘

Throughput = N λL/R –N= no transmissions

–λ= packet generation rate (S-1)

–L= packet length (bits) –R= transmission bit rate (bits/s)

ALOHA doesn‘t need synchronization

Maximum throughput 18%

Frames in a pure ALOHA



a es a pu e O

network




SLOTTED-ALOHA confinestransmission to slot boundariesand needs time synchronization

Maximum throughput isincreased to 36%

As system rapidly becomesunstable as collisions build up,usual to operate below maxima

Frames in a slotted ALOHA network



Frames in a slotted ALOHA network

R d A S h (4)




For variable length messages need toemploy more complex scheme e.g.

slotted reject ALOHA

Use multi-packet message and onlyre-transmit sub-packets that collide

Increases throughput (≈0.37)independent of message length





Slotted Reject-Aloha

Comparison of random access



p

Summary



Summary

Select RA scheme for traffic type and

delay/throughput (α number of tx’s)

Take care to achieve stability

ALOHA: short bursty traffic

S-ALOHA: short bursty traffic –better

throughputS-R.ALOHA: variable length messages

DA-TDMA: stream or file transfers

VSATs



VSATs

Why VSAT? –advantages and disadvantages

Structure of VSAT networks -star/mesh

Traffic types and their description

Choice and comparison of multiple accesssystems

Capacity and throughput analysis -protocolsand network interfaces

VSAT system design drivers Regulatory and licensing aspects.

Genesis of VSATs: WHAT IS A VSAT?



Genesis of VSATs: WHAT IS A VSAT?

VSAT is an acronym for Very Small Aperture Terminal.

It is a small satellite terminal that can be used for one-way and/or interactive communications.

ETSI (the European Telecommunications StandardsInstitute) define, in brief, a VSAT as a one or two-wayterminal used in a star, mesh or point to point network.

Antenna size is restricted to being less than or equal to1.8 m at Ka band, 3.8 m at Ku band and 7.8 m at C band

Genesis of VSATs: ETSI VSAT Ku-Band



Frequency Bands

The VSATs are operating in one or more frequencyranges in part of the following bands allocated:-

exclusively to the Fixed Satellite Services (FSS):

14,00 GHz to 14,25 GHz (earth-to-space); 12,50 GHz to 12,75 GHz (space-to-earth).

or in the shared parts of the following bands,

allocated to the FSS and Fixed Services (FS): 14,25 GHz to 14,50 GHz (earth-to-space);

10,70 GHz to 11,70 GHz (space-to-earth).

Genesis of VSATs



Ge es s o S s VSATs were first employed for data distribution to a

large number of locations.

They provided a means to avoid the highly regulated(monopoly based) communications infrastructure as wellas the associated high charges for such networks (alsoknown as ‗by-pass‘).

Most early use was in private networks.

VSAT networks first appeared in the early 1980‘s whenEquatorial Communications, a start-up company launchedby Ed Parker and Dean Mack in a warehouse near PaloAlto, initiated the first use of really small dish antennas forreceive-only applications.

Data distributors like ―wire services‖ were quick tojump to using the technology to economically distributeinformation to thousands of receive only VSAT‘s.

Genesis of VSATs: WHY USE A VSAT?



Genesis of VSATs: WHY USE A VSAT?

Genesis of VSAT Systems



Early Equatorial Communications Inc.VSAT (CDMA)



VSAT (CDMA)

Mid 1980sC-Band

2 way

Current day outdoor unit



Genesis of VSAT Systems: Hardware



SATELLITE SERVICE EVOLUTION



VSAT evolution

More than 30,000 Equatorial C-band (4/6 GHz)60 cm antenna systems were sold in the early1980s.

Equatorial later developed a C-band (4/6 GHz)2 way system using 1m x 0.5 m antennas andsold about 10,000 units in 1984-85.

2005 around 1.4 million VSAT terminal in useglobally.



VSAT Network Topologies

Star –employs a large hub Large antenna hub enables

small VSAT with low powerVSAT transmitter

Typical of networks in the

1980s and 1990sMesh –VSAT to VSAT

Need higher VSAT andsatellietransmit powers buteliminates double delay

Typical of networks in thelast 5 years




p g

VSAT Network Topologies: TCP/IP



VSAT Network Topologies: Extensionwith Wireless Distribution



with Wireless Distribution

SAMPLE OF VSAT USERS (1984-1994)



SAMPLE OF VSAT USERS (1995-1999)



Geographic location of VSAT terminals



Internet Protocol (IP) over Satellite



( )

TCP/IP consists of TCP -Transmission Control Protocol and IP -Internet Protocol which form a protocol stack.

TCP/IP is primarily oriented mostly to terrestrial based networks, whenSatellite Internet access and VSAT systems are yet to be utilized commercially.Despite significant optimizations and enhancements proposed over the manyyears, TCP/IP operation has not changed significantly since RFC 793,

published in 1981.

Applying standard TCP/IP to Satellite Internet access circuits leads to theunder-utilization of the link and degraded performance.

There is the issue of round trip latency due to the fact that geostationary

satellites are 30,000 km above the earth surface: it takes approximately half asecond for the signal to travel from the user to the satellite and back to thehub.

Additionally, there is a packet loss possible due to the error rate of the link.

Internet Protocol (IP) over Satellite



There are a number of solutions available in order toovercome TCP/IP performance degradation.

Usually, these solutions are named TCP accelerators andPerformance Enhancing Proxies (PEP).

TCP accelerators use various techniques to substituteTCP/IP with a protocol set which is more optimized for SatelliteInternet access.

Most of solutions use UDP as the primitive IP packetstransport while speed and window size negotiations are done

inside the TCP accelerator protocol.

Most of the TCP accelerators also bundle a number of wellknown techniques in order to improve the performance of theSatellite Internet circuit. These techniques usually include DNScaching, HTTP pre-fetching and on-the-fly traffic compression.

ACCESS TECHNIQUES



FDMA -Frequency Division Multiple Access TDMA -Time Division Multiple Access CDMA -Code Division Multiple Access

MF-TDMA -Multi-Frequency Time Division Multiple Acces

DAMA with SCPC –Demand Assigned Multiple Access with Single Channel Per Carrier

DAMA with MF-TDMA

–Demand Assigned Multiple Access with Multi-Frequency Time Division Multiple Access

PCMA -Paired Carrier Multiple Access

Optimizing the Access System



Different VSAT platforms use various technologies in order

to access the satellite radio space segment and share it amongmultiple subscribers.

Many of sharing techniques are based on TDMA technology.

The concept of sharing the satellite space segment amongmultiple subscribers is based on allocating a group of users

the same transmit and/or receive frequencies and dividing itinto many timeslots.

Simple approaches allow users to transmit randomly,decreasing the overall performance of the network down toalmost 15-20% while more complex concepts dedicatetimeslots to every subscriber, raising the performance to near80%.

Multiple Access Schemes



TDMA► Packet-based

► Star and mesh Topology► Large volume (1000s) for Star► Small volume (10s to 100s) for Mesh► Efficient for random/Bursty Traffic and Bandwidth on Demand

SCPC-DAMA

► Circuit switched► Star and Mesh topology► Small to medium volume (10s to 100s)► Efficient for dedicated/continuous data transfers

SPREAD SPECTRUM (CDMA)► Packet-based► Star topology► Large volume (1000s)► Efficient for random /bursty Traffic•

Single Channel per carrier (SCPC)A



Access.

Multi-Frequency TDMA (MF-TDMA)



q y ( )

The conventional TDMA uses only one frequency andall Earth stations transmit and receive on a singlefrequency, whatever the destination of the bursts is.

Therefore, it does not provide power efficiency and thesatellite link speed is limited.

To solve this inefficiency, the MF-TDMA was proposed.The MF-TDMA reduces satellite antenna sizes andtransmission power, and increases satellite networkbandwidth.

Most of the future broadband satellite networks will useMF-TDMA or MF-TDMA-like schemes.

DAMA with MF-TDMA



In order to achieve a greater efficiency in broadbandsatellite networks, the DAMA scheme can be used with

other access schemes such as MF-TDMA.

By exchanging signaling packets, the process of call

setup involves the negotiation among the Earth station anda master control station (MCS) which controls the satellitenetwork.

The signaling packets are transmitted in the

synchronization area which is a fixed portion in the MF-TDMA frame.

Once the connection is established, a certain amount ofmemory and bandwidth is allocated to the new connection.

MF-TDMA



MF-TDMA



Paired Carrier Multiple Access



Bandwidth saving is by the overlaying of the twochannels

No power is saved as we still need to transmitboth carriers across the transponder

We can re-use up to twice the availablebandwidth limited by

►The point where we have bandwidth and power parityon the Transponder

►A need for asymmetry of the two carriers

Available from ViaSat, HNS, TranscendentTechnologies (DoubleTalk)

Standards



In the early years of VSATs the lack of compliance toany specific standards and the shortage of agreed

standards were significant impediments to thedevelopment of a thriving VSAT market.

In the early 1990s there were some 27 vendors offeringVSAT products with around 20 different interfaces, service

quality levels and network management approaches. Looseassociation with protocols such as X25.

On the other hand, Standards Bodies were not veryinterested in spending resources to develop standards if

the market was not mature and significant.

In the late 1990s the market had matured sufficiently forthe open standards to be developed ( the need forproprietary systems to protect high investment values had

diminished).

STANDARDISATION OF SATELLITETERMINALS IN ETSI



TERMINALS IN ETSI

The relevant standardization body for Standards fallingunder

the scope of the R&TTE Directive is the EuropeanTelecommunications Standards Institute (ETSI), which isresponsible for all telecommunication-related standards.

The focal point for all satellite-related activities within ETSIis

the Technical Committee for Satellite Earth Stations andSystems(TC-SES).

ETSI publishes DVB standards within its range of standardsand reports.

DVB



The Digital Video Broadcasting Project(DVB) is an industry-led consortium of over270 broadcasters, manufacturers, networkoperators, software developers, regulatorybodies and others in over 35 countries

committed to designing global standards forthe global delivery of digital television anddata services.

Services using DVB standards areavailable on every continent with more than

120 million DVB receivers deployed. DVB publishes it standards via ETSI.

www.dvb.org

DVB Return Channel via Satellite (DVB-RCS)



• In 1995 SES/Astra began working with various

industry bodies (ETSI, DAVICS, DVB and others)to establish a standards-based return channeldesign for the DVB system (DVB-RCS).

• DVB-RCS was adopted as a standard by ETSIduring mid-2000 joining a range of DVB standardswhich include return channels for wireless, cableand other media.

• DVB-RCS offers high bandwidth on the forwardand return links -with a 45 Mbps outbound channeland an inbound channel of 2 Mbps working with amultiple-frequency TDMA access scheme.

Political Aspects



The USA led the way in competition policies for thetelecommunications industry during the late 1970s andearly 1980s.

Restrictive legislation was reduced and regulation

minimized with market forces encouraged. This resulted in an expansion of telecommunicationservice companies and associated growth ofentrepreneurial developments and products.

VSAT systems owe a great deal to these developments

as a catalyst to their market places. The UK followed by Western Europe lagged but were

not far behind.

Political Aspects



Elsewhere in the world, politics have molded the shape of VSAT

services in many countries.

Competition in domestic services is one thing, but manygovernments maintained their monopoly on international services.

1994 saw Europe in the interim stages of liberalization and this was

only really completed by 2000.

During the early 1990s, Latin America was probably exhibiting thefastest rates of deregulation. Services were relatively free in Chile,Argentina, Colombia, Ecuador, Venezuela and Mexico.

Africa has been hard for a number of reasons, but now many of thekey economies in the region have liberalized, the market has begun tolook more attractive and some limited regional services are possible.

Political Aspects



Difficult economic conditions and the swift market correction whichtook place in early 2001 left many operators and system vendors in aprecarious position.

Manufacturers and operators went searching for customers able topay a commercial rate for a service and found them in the SMEsegment.

Broadband access services targeted at enterprises -as opposed toenterprise networks which also connected IP services -finally becamea reality and Europe in particular saw wholesalers begin to developprogrammers for value added resellers in order to address smallercustomer sales.

As the major markets of Asia and Latin America struggled, Africasuddenly assumed the role of golden opportunity and a gold rushensued and, mostly, still remains.

Political Aspects



Where VSAT platforms have moved on is in the

integration of products around a core IP-centricdesign.

Having established IP as the primary elementof the system architecture, all of the vendors have

gone on to build router capabilities into theirsystems as an inherent part of their feature set. Various features have been added -

acceleration, QoS, classes of service, encryption,web page acceleration and, in some instances,support for VoIP.

With increased processing power VoIPimplementations have grown beyond the clumsyservices of a few years ago and are now hard to

distinguish from a toll-quality terrestrial line

Political Aspects



Nearly all VSAT systems are now based on IP,with a very broad spectrum of applications. At December 2004, the total number of VSAT

terminals ordered stood at over 1 million withnearly 650,000 sites in service.

Annual VSAT service revenues were $3.88billion, with TDMA & DAMA hardware revenues at$746.9 million

Some political will is being expended to

identify if Satellite Broadband can close the socalled ‗Digital Divide‘, but the key questions arewill funding be assured and the market not beeradicated in terms of timescales and competition.



Communications PayloadEngineering

Constraints on the Communications PayloadDesign



Design Constraints from the Platform

Accommodation - Physical size, must fit on spacecraft platform, compatibility withlaunch vehicle fairing

Thermal Dissipation - Limited ability of spacecraft to radiate heat, radiator area Mass

- Launcher capability and spacecraft platform set absolute limit - Payload Mass Contends with: - Life (Mass of station keeping fuel) - Cost (Launch cost) - Payload Power ( Mass of the Power Sub-system)

Available Electrical Power - Mass and accommodation of power sub-system Temperature Control - Comms. performance versus mass and power consumption of

thermal control hardware Electromagnetic Compatibility with the Platform




Design

Constraints from the Environment

Received Earth Noise - Sets lower limit to the communications payload system noise

temperature

- Typically 100 to 300 Kelvin depending on frequency and

location viewed on the Earth Ionising Radiation

- Materials and active electronics must survive for the designedlifetime

Vacuum

- No convective heat transfer

- Multipaction Breakdown

- Air to vacuum frequency shift for vacuum cavity filters




es g

Communications Payload Function



Communications Payload



Essential Communication Payload Functions



Satellite Communication Frequencies



Key Communications Requirements



A Satellite Antenna



Antenna Types and Functions



Typical Spacecraft Antennas



Satellite Antenna - Side deployed



Typical Repeater Functions



Receive and filter uplink signals

Provide minimum C/No degradation

Provide variable high gain amplification

Down convert Frequency for re-transmission

Filter high power downlink signal and re-transmit

Provide high reliability in functionality

Beam-to-beam interconnectivity Functional re-configurability

Beam forming

Why High Reliability?



Quality of the Receive System – G/T



Noise Temperature



E.I.R.P



Payload Configurations - Basic Elements



Why Filter?



Why Chanalised Amplification?



Payload Configurations - Channelisation



Input De-Multiplexer – (IMUX)



Payload Equipment - Input Multiplexers



Choice of HPA



Dual Travelling Wave Tube Amplifier(TWTA)



Payload Configurations – Trends



On-board Processing – Why?



On-board Processing – Why Not?



Transparent Or Regenerative



Typical Digital Processor Architecture



Inmarsat 4



Payload Equipment - Receivers



Payload Equipment – Multi-Chip Module(MCM) Technology



Payload Equipment – Integrated Down converterHi-Modular Microwave Hybrid Technology (Hi-MMHT)



Payload Equipment - Channel Amplifier



Payload Equipment - Frequency Generator



INMARSAT 4 Digital Signal Processor



Anechoic Chamber

• An anechoic chamber is a shielded room designed



An anechoic chamber is a shielded room designed

to attenuate waves. Anechoic chambers wereoriginally used in the context of acoustic (sound)echoes caused by reflections from the internalsurfaces of the room, but more recently anechoicchambers have been used to provide a shieldedenvironment for radio frequency (RF) andmicrowaves. An RF anechoic chamber is designedto suppress the electromagnetic wave analogy ofechoes: reflected electromagnetic waves, from theinternal surfaces. Both types of chamber areconstructed with echo suppression features andwith effective isolation from the acoustic or RFnoise present in the external environment.

Astra In Anechoic Chamber

http://en.wikipedia.org/wiki/Acoustics

http://en.wikipedia.org/wiki/Sound

http://en.wikipedia.org/wiki/Reflection

http://en.wikipedia.org/wiki/Radio_frequency

http://en.wikipedia.org/wiki/Electromagnetic_radiation

http://en.wikipedia.org/wiki/Reflection_(physics)

http://en.wikipedia.org/wiki/Noise

http://en.wikipedia.org/wiki/Natural_environment

http://en.wikipedia.org/wiki/Natural_environment

http://en.wikipedia.org/wiki/Noise

http://en.wikipedia.org/wiki/Reflection_(physics)

http://en.wikipedia.org/wiki/Electromagnetic_radiation

http://en.wikipedia.org/wiki/Radio_frequency

http://en.wikipedia.org/wiki/Reflection

http://en.wikipedia.org/wiki/Sound

http://en.wikipedia.org/wiki/Acoustics



Astra Repeater in Assembly andIntegration



Typical Repeater Panel Layout



Astra Repeater Panels



Future Trends



Future Trends – Next GenerationGeneric Flexible Payloads



An introduction to Inmarsat



http://www.arianescup2007astrium.com/images/Inmarsat_logo.jpg

Satellite Slides by Sir Haleem Junejo(Microwave & Satellite Communication)

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Transcript of Satellite Slides by Sir Haleem Junejo(Microwave & Satellite Communication)