microwave chapter 2

POLITEKNIK SULTAN MIZAN ZAINAL ABIDIN1/20

EP604 Microwave Communication System

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CHAPTER 2SPACE AND EARTH SATELLITE

EN. MUHAMMAD RIDZUAN BIN IDRISEN. MOHD MARAMUZAFAR BIN MOHAMAD

Semester December Session 2012/2013

POLITEKNIK SULTAN MIZAN ZAINAL ABIDIN

POLITEKNIK SULTAN MIZAN ZAINAL ABIDIN 3/20

• Background of study• Problem statement• Objective of study• Scope of study

1. Introduction

• Previous of Endau Rompin Water Quality• Summary

2. Literature Review

• Overall research methodology• Research design principles• Experimental design and variables• Research procedures• Instrumentation

3. Experimental Setup

• WQI• Water Quality

4. Results & Discussions

Space and Earth Satellite

EP604 MICROWAVE COMMUNICATION SYSTEMSPACE AND EARTH SATELLITE

POLITEKNIK SULTAN MIZAN ZAINAL ABIDIN 4/20

2.3 Understand types of earth station

• 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

2.4 Understand satellite frequency band

• 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.



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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



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Satellite AnatomySatellite Anatomy

SATELLITE SUBSYSTEM




SATELLITE SUBSYSTEMSubsystem Description1. 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 Description6. 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.

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 typicallyused 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)


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

http://en.wikipedia.org/wiki/Frequency-division_multiplex

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

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

http://en.wikipedia.org/wiki/Orthogonal_frequency-division_multiplexing

http://en.wikipedia.org/wiki/Single-carrier_FDMA

http://en.wikipedia.org/wiki/Time-division_multiple_access

http://en.wikipedia.org/wiki/Time-division_multiplex

http://en.wikipedia.org/w/index.php?title=Multi-Frequency_Time_Division_Multiple_Access&action=edit&redlink=1

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

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

http://en.wikipedia.org/wiki/Direct-sequence_CDMA

http://en.wikipedia.org/wiki/Direct-sequence_spread_spectrum

http://en.wikipedia.org/wiki/Frequency-hopping_CDMA

http://en.wikipedia.org/wiki/Frequency-hopping_spread_spectrum

http://en.wikipedia.org/w/index.php?title=Orthogonal_frequency-hopping_multiple_access&action=edit&redlink=1

http://en.wikipedia.org/wiki/Multi-carrier_code_division_multiple_access

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



Frequency Band

Letter band designations Nominal wavelength




Frequency Band

Band Description Advantages DisvantagesC 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_channel_access_schemes


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

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

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EP604 Microwave Communication System

POLITEKNIK SULTAN MIZAN ZAINAL ABIDINEP604 MICROWAVE COMMUNICATION SYSTEM

INTRODUCTION TO MICROWAVE COMMUNICATION SYSTEM

microwave chapter 2

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