microwave_chapter_1_.pptx

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POLITEKNIK SULTAN MIZAN ZAINAL ABIDIN1/20

EP604 Microwave Communication System


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CHAPTER 1INTRODUCTION TO MICROWAVE COMMUNICATION SYSTEM

EN. MUHAMMAD RIDZUAN BIN IDRIS

EN. MOHD MARAMUZAFAR BIN MOHAMAD

Semester December Session 2012/2013

POLITEKNIK SULTAN MIZAN ZAINAL ABIDIN


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1.1.1 History of microwave communication system. 1.1.2 Satellite. 1.1.3 Evolution of satellites technology. 1.1.4 Features of typical satellite .

1.1 Introduction to Microwave Communication System

1.2.1 Define circular and elliptical orbits. 1.2.2 Sketch the circular and elliptical satellite orbits. 1.2.3 Explain :

a. Circular orbit: i. LEO ii. MEO iii. GEO

b. Elliptical orbit 1.2.4 Explain satellite orbital patterns:

a. Polar b. Inclined c. Equatorial

1.2 Satellite Orbits

Introduction to Microwave Communication System

EP604 MICROWAVE COMMUNICATION SYSTEMINTRODUCTION TO MICROWAVE COMMUNICATION SYSTEM


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1.1 Introduction to Microwave Communication System


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Radio astronomy

RadarNavigation

Communication

A microwave is used to describe electromagnetic waves with wavelengths ranging

from 1 cm to 1 m corresponding frequency range is 300 MHz up to 30 GHz for 1-cm-wavelength waves.




Application

MICROWAVE COMMUNICATION SYSTEM


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Developed over 100 years ago (World War II) In 1945, Michael Faraday Studied the effect ofelectromagnetic field on the propagation of light throughglass. The foundations of modern electromagnetic theory were

formulated in 1873 by James Clerk Maxwell Heinrich Hertz, a German professor of physics and a giftedexperimentalist who also understood the theory published byMaxwell, carried out a set of experiments during the period1887-1891 that completely validated Maxwell's theory ofelectromagnetic waves. In 1895, Guglielmo Marconi succeeded radio signal over adistance 1mile and can transmitted the signal 3000mile in1901.




HISTORY MICROWAVE COMMUNICATION SYSTEM


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HISTORY MICROWAVE COMMUNICATION SYSTEM

Original apparatus used by Hertz for his electromagnetic experiments.


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The word satellite originated from the Latin word Satellit - meaning an attendant, one who is constantly hovering around & attending to a master or big man. Satellite is simply any body that moves around another (usually much larger) onein a mathematically predictable path called an orbit . A communication satellite is a microwave repeater station in space that is used for

telecommunication , radio and television signals. The first man made satellite with radio transmitter was in 1957. There are about 750 satellite in the space , most of them are used forcommunication .




DEFINE SATELLITE

Whatexactly is a

satellite?


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Two Stations on Earth want to communicate through radio broadcast but are toofar away to use conventional means. The two stations can use a satellite as a relaystation for their communication. One Earth Station transmits the signals to the satellite. Up link frequency is thefrequency at which Ground Station is communicating with Satellite. The satellite Transponder converts the signal and sends it down to the secondearth station. This frequency is called a Downlink.




DEFINE SATELLITE

How dosatellite work?

Satellite Path Uplink Downlink

EarthStation

User
http://localhost/var/www/apps/conversion/tmp/video/GOOD%20Satellites.flvhttp://localhost/var/www/apps/conversion/tmp/video/GOOD%20Satellites.flvhttp://localhost/var/www/apps/conversion/tmp/video/GOOD%20Satellites.flvhttp://localhost/var/www/apps/conversion/tmp/video/GOOD%20Satellites.flvhttp://localhost/var/www/apps/conversion/tmp/video/GOOD%20Satellites.flvhttp://localhost/var/www/apps/conversion/tmp/video/GOOD%20Satellites.flvhttp://localhost/var/www/apps/conversion/tmp/video/GOOD%20Satellites.flvhttp://localhost/var/www/apps/conversion/tmp/video/GOOD%20Satellites.flvhttp://localhost/var/www/apps/conversion/tmp/video/GOOD%20Satellites.flvhttp://localhost/var/www/apps/conversion/tmp/video/GOOD%20Satellites.flvhttp://localhost/var/www/apps/conversion/tmp/video/GOOD%20Satellites.flvhttp://localhost/var/www/apps/conversion/tmp/video/GOOD%20Satellites.flvhttp://localhost/var/www/apps/conversion/tmp/video/GOOD%20Satellites.flv


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Advantages of satellite over terrestrial communication:

*The coverage area of a satellite greatly exceeds that of aterrestrial system.*Transmission cost of a satellite is independent of thedistance from the center of the coverage area.

* Satellite to Satellite communication is very precise .* Higher Bandwidths are available for use.

Disadvantages of satellites: * Launching satellites into orbit is costly .* Satellite bandwidth is gradually becoming used up .*There is a larger propagation delay in satellitecommunication than in terrestrial communication.




DEFINE SATELLITE


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DEFINE SATELLITEApplication


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1. Era of Hot Air Balloons and Sounding Rockets2. Launch of Early Artificial Satellites3. Satellites for Communications, Meteorology and Scientific Exploration - Early

Developments.4. Nongeosynchronous Communication Satellites: Telstar and Relay Programmer5. International Communication Satellite Systems6. Domestic Communication Satellite Systems7. Satellites for other Applications also make Rapid Progress




Evolution of satellites technology

1 2 6 7


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TYPES OF SATELLITES


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TYPES OF SATELLITES

Satellite Used Features Orbit Communicati

ons

Audio, video, data

transmission

Dishes to capture radio

waves; large solar panelsto power soundamplifiers

Geosynchronous (circle

once every 24 hours), 22,300miles above Earth's Equator.

EarthObservationSatellites

Photographing theEarth to observechanges such asearthquakes,drought and formineral

prospecting.

Barrel-shaped design tohouse mirrors, camera.

Low-flying polar orbit at 90to 300 miles above Earth.

WeatherSatellites

Photographingchanges in cloudformations,weather patterns.

Similar in design to Earthobservation satellites.

Low-flying polar orbiterscircle every two hours at300-600 miles above Earth.High-flying geostationaryorbit at 22,300 miles.

Navigationsatellites

Global PositioningSystems by pilots,boaters, etc.

GlobalStar TrackingSystems.

GPS satellites orbit at lowaltitude (90-300 mi.).

MilitarySatellites

Analyzing globaltroop and weaponmovement;communication.

Military satellite designsare top-secret.

Both low-flying orbit forobservation and geosynchhigh orbit (22,300 miles) forGPS monitoring satellites.

SpecialSatellites

Space observationand habitation.

The Mir Space Station;Hubble Telescope;Magellan Venus orbiter;Mariner 9 Mars Orbiter.

Space stations orbit at lowaltitude (90-300 mi.); deepspace probes travel anelliptical orbit.


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1.2 Satellite Orbits


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Satellites move in a path around the Earth called an orbit. Every satellite must have an orbital path and the type of path it takes isdetermined by the physics involved A satellites orbit works because of a balance between two forces . The orbit is a

combination of the satellites velocity the speed it is travelling in a straight line and the force of the Earths gravitational pull on the satellite. Basically, gravity keeps the satellites velocity from sending the satellite flying outin a straight line away from the Earth, and the satellites velocity keeps the force ofgravity from pulling the satellite back to Earth.




What issatelliteorbits?

SATELLITE ORBITS


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Though no orbit is perfectly circular, the general name for any orbit that is nothighly elliptical (egg-shaped) is circular. Circular orbits have an eccentricity of 0 .There are several types of circular orbits and they include:

geostationary polar

sun-synchronous Equatorial Satellite orbits are also classified based on their heights above the earth:

GEOLEOMEO




What isCircularorbits?

CIRCULAR AND ELLIPTICAL ORBITS.


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An elliptical orbit @ eccentric orbit-in the shape of an ellipse . satellite's velocity changes depending on where it is in its orbital path. When the satellite is in the part of its orbit closest to the Earth , it moves fasterbecause the Earth's gravitational pull is stronger . An elliptical orbit can be useful to a communications satellite because it allows thesatellite to travel over a specific region for a long portion of its orbit, and it is onlyout of contact with that region for a short time when it is zipping quickly around theother side of the Earth.




What iselliptical

orbits?

CIRCULAR AND ELLIPTICAL ORBITS.


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CIRCULAR ORBITS


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35,786 km above the earths surface along the equator. same speed as the earth rotates-the same position relative to the surface of earth.Advantages

A GEO satellites distance from earth gives it a large coverage area, almost afourth of the earths surface. GEO satellites have a 24 hour view of a particular area. These factors make it ideal for satellite broadcast and other multipointapplications Minimal Doppler shift




What isGEO?

GEO


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ranging from 500 to 1,500 km above the surface. LEO satellites dont stay in fixed position relative to the surface, and are onlyvisible for 15 to 20 minutes each pass. A network of LEO satellites is necessary for LEO satellites to be useful




What isLEO?

Low Earth Orbit (LEO)


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The Iridium system has 66 satellites in six LEO orbits, each at an altitude of 750 km.Iridium is designed to provide direct worldwide voice and data communicationusing handheld terminals, a service similar to cellular telephony but on a globalscaleAdvantages

proximity to earth compared to a GEO satellite gives it a better signal strengthand less of a time delay- better for point to point communication.

smaller area of coverage is less of a waste of bandwidth .Disadvantages A network of LEO satellites is needed, which can be costlyLEO satellites have to compensate for Doppler shifts cause by their relativemovement.*Atmospheric drag effects LEO satellites, causing gradual orbital deterioration




Low Earth Orbit (LEO)


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between 8,000 km and 18,000 km above the earths surface. MEO satellites are similar to LEO satellites in functionality . MEO satellites are visible for much longer periods of time than LEO satellites,usually between 2 to 8 hours. MEO satellites have a larger coverage area than LEO satellites.Advantage

A MEO satellites longer duration of visibility and wider footprint meansfewer satellites are needed in a MEO network than a LEO network.Disadvantage

A MEO satellites distance gives it a longer time delay and weaker signal thana LEO satellite, though not as bad as a GEO satellite.




What isMEO?

Medium Earth Orbit (MEO)


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SATELLITE ORBITAL PATTERNS

Classification of orbits:


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A satellite in equatorial orbit flies along the line of the Earth's equator . To get intoequatorial orbit, a satellite must be launched from a place on Earth close to theequator. NASA often launches satellites aboard an Ariane rocket into equatorial

orbit from French Guyana. Equatorial orbits can be useful for satellites observing tropical weather patterns , asthey can monitor cloud conditions around the globe. Equatorial orbits are usuallymedium or low orbits .




Equatorial



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A satellite is said to occupy an inclined orbit around the Earth if the orbit exhibitsan angle other than zero degrees with the equatorial plane. This angle is called theorbit's inclination. A planet is said to have an inclined orbit around the Sun if it hasan angle other than zero to the plane of the ecliptic.




Inclined



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1.3 Orbital Determination


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velocity which is give to an artificial earth's satellite a few hundred kilometersabove the earth's surface so that it may start revolving round the earth. A satellite in orbit moves faster when it is close to the planet or other body that itorbits, and slower when it is farther away.

A satellite in circular orbit has a constant speed which depends only on the massof the planet and the distance between the satellite and the center of the planet.




OrbitalVelocity?

ORBITAL VELOCITY


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ORBITAL VELOCITY


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LOOK ANGLE



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LOOK ANGLE



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LOOK ANGLE


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With spin stabilization, the entire spacecraft rotates around its own vertical axis,spinning like a top. This keeps the spacecraft's orientation in space under control. The spinning spacecraft resists perturbing forces. Designers of early satellites used spin-stabilization for their satellites, which mostoften have a cylinder shape and rotate at one revolution every second. The advantage of spin stabilization is that it is a very simple way to keep thespacecraft pointed in a certain direction. A disadvantage of this stabilization is that the satellite cannot use large solararrays to obtain power from the Sun. Thus, it requires large amounts of batterypower. Another disadvantage of spin stabilization is that the instruments or antennasalso must perform despin maneuvers so that antennas or optical instrumentspoint at their desired targets.




Spin Stability?

STABILIZATION OF SATELLITE IN THE ORBIT



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With three-axis stabilization, satellites have small spinning wheels , called reactionwheels or momentum wheels, that rotate so as to keep the satellite in the desiredorientation in relation to the Earth and the Sun.

If satellite sensors detect that the satellite is moving away from the properorientation, the spinning wheels speed up or slow down to return the satellite toits correct position. Some spacecraft may also use small propulsion-system thrusters to continuallynudge the spacecraft back and forth to keep it within a range of allowed positions. An advantage of 3-axis stabilization is that optical instruments and antennas can

point at desired targets without having to perform despin maneuvers




Three axisStability?

STABILIZATION OF SATELLITE IN THE ORBIT

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1.4 Geostationary Satellite



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A geostationary orbit is a special case of a geosynchronous orbit. A satellite is in a geostationary orbit when it appears stationary from the point ofview of an observer on the Earth's surface. This can only occur when:

The orbit is geosynchronous

The orbit is a circle The orbit lies in the plane of the Earth's equator Thus, a geosynchronous satellite will be geostationary only with the additionalrestrictions of it being in a circular orbit situated over the equator. satellite velocity in this orbit is 3075 m/s.




What isGeostationarySatellite ?

GEOSTATIONARY SATELLITE



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ORBITAL VELOCITY EXAMPLE Operate in the 2.0 GHz to 18 GHz range When the inclination and eccentricity of the orbit is zero, the satellite appears tobe stationary to an observer from ground.Applications:

Telecommunication systemsRadioData Transmission systems

ADVANTAGES OF GEOSTATIONARY ORBITS Make repeated observations over a given area (constant view area).Get high temporal resolution data. GOES E and W can give you a temporalresolution of 1 minute!! Hence, GOES E and W can effectively monitor the severeweather environment and track severe storms and hurricanes in real time.DISADVANTAGES OF GEOSTATIONARY ORBITS

Due to the high orbit, the spatial resolution of the data is not as great as for thepolar orbiting satellites. Poor spatial resolution in the polar regions (parallax).



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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 andApplication Matt Kragen, Rancho Buena Vista High School, Vista, California, How SatellitesChanged the World, http://historyday.crf-usa.org/2702/index.htm , 11/25/2012 Produced by Galactics. Last updated on: 8 August 1997.http://www.satellites.spacesim.org/english/credits/imagecre.html Dennis Roddy, 2006, Satellite Communications, The McGraw-Hill Companies, Inc.

Lyndon State College Atmospheric Sciences,http://apollo.lsc.vsc.edu/classes/remote/lecture_notes/satellite/platforms/geo_adv _disadv.html

http://www.physicsclassroom.com/class/circles/u6l4c.cf Dharma Raj Cheruku 2009, Satellite Communication, I. K. International Pvt Ltd

http://historyday.crf-usa.org/2702/index.htmhttp://www.satellites.spacesim.org/english/credits/imagecre.htmlhttp://apollo.lsc.vsc.edu/classes/remote/lecture_notes/satellite/platforms/geo_adv_disadv.htmlhttp://apollo.lsc.vsc.edu/classes/remote/lecture_notes/satellite/platforms/geo_adv_disadv.htmlhttp://www.physicsclassroom.com/class/circles/u6l4c.cfhttp://www.physicsclassroom.com/class/circles/u6l4c.cfhttp://apollo.lsc.vsc.edu/classes/remote/lecture_notes/satellite/platforms/geo_adv_disadv.htmlhttp://apollo.lsc.vsc.edu/classes/remote/lecture_notes/satellite/platforms/geo_adv_disadv.htmlhttp://www.satellites.spacesim.org/english/credits/imagecre.htmlhttp://historyday.crf-usa.org/2702/index.htmhttp://historyday.crf-usa.org/2702/index.htmhttp://historyday.crf-usa.org/2702/index.htm


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