yagi-udaantenna-17012207345564644136.ppt

Yagi Uda Antenna

1. PRESENTED BY
DEEKSHA SHREE N

2. CONTENT
INDRODUCTION
PRINCIPLE
CONSTRUCTION
WORKING.
PICTURE OF ANTENNA.
ADVANTAGES
DISADVANTAGES.
INTRODUCTION.
APPLICATIONS.

3. INTRODUCTION
TheYagi-UdaantennaorYagiAntennaisoneofthemostbrilliantantennadesigns.Itis
simpletoconstructandhasahighgaintypicallygreaterthan10dB.
TheYagi-UdaantennastypicallyoperateintheHFtoUHFbands(about3MHzto3GHz)
andCovers40to60Km.
ADirectionalAntennaSystemConsistingofanarrayofCoupledParallelDipoles.Thisis
commonlyknownasYagi-udaorSimplyYagiAntenna.
Yagi-udaAntennaisfamiliarastheCommonestkindOfTerrestrialTVAntennato
befoundontheRooftopsofhouses.

5. PRINCIPLE
•YAGI-UDAANTENNAISANELECTROMAGNETICDEVICETHAT
COLLECTSRADIOWAVES.
•ANANTENNATUNEDTOAPARTICULARFREQUENCYWILLRESONATE
TOARADIOSIGNALOFTHESAMEFREQUENCY

6. CONSTRUCTION
THERE ARE THREE TYPES OF ELEMENTS :
THE REFLECTOR (R)
THE DRIVEN ELEMENT (D)
THE DIRECTORS (DI)

7. CONSTRUCTION
DRIVEN ELEMENT :
•THEDRIVENELEMENTOFAYAGIISTHEFEEDPOINTWHERETHEFEEDLINE
ISATTACHEDFROMTHETRANSMITTERTOTHEYAGITOPERFORMTHE
TRANSFEROFPOWERFROMTHETRANSMITTERTOTHEANTENNA.
•A DIPOLE DRIVEN ELEMENT WILL BE "RESONANT" WHEN ITS ELECTRICAL
LENGTHIS 1/2 OF THE WAVELENGTH OF THE FREQUENCY APPLIED TO ITS
FEED POINT.
•THE FEED POINT IN THE PICTURE ABOVE IS ON THE CENTER OF THE DRIVEN
ELEMENT.

8. CONSTRUCTION
DIRECTOR :
•THEDIRECTORISTHESHORTESTOFTHEPARASITICELEMENTSANDTHISENDOF
THEYAGIISAIMEDATTHERECEIVINGSTATION.ITISRESONANTSLIGHTLYHIGHER
INFREQUENCYTHANTHEDRIVENELEMENT,ANDITSLENGTHWILLBEABOUT5%
SHORTER,PROGRESSIVELYTHANTHEDRIVENELEMENT.
•THEDIRECTORSLENGTHSCANVARY,DEPENDINGUPONTHEDIRECTORSPACING,
THENUMBEROFDIRECTORSUSEDINTHEANTENNA,THEDESIREDPATTERN,
PATTERNBANDWIDTHANDELEMENTDIAMETER.
•THEAMOUNTOFGAINISDIRECTLYPROPORTIONALTOTHELENGTHOFTHE
ANTENNAARRAYANDNOTBYTHENUMBEROFDIRECTORSUSED.

9. CONSTRUCTION
REFLECTOR
•THEREFLECTORISTHEELEMENTTHATISPLACEDATTHEREAROFTHEDRIVEN
ELEMENT(THEDIPOLE).
•IT'SRESONANTFREQUENCYISLOWER,ANDITSLENGTHISAPPROXIMATELY5%
LONGERTHANTHEDRIVENELEMENT.IT'SLENGTHWILLVARYDEPENDINGONTHE
SPACINGANDTHEELEMENTDIAMETER
•THE SPACING OF THE REFLECTOR WILL BE BETWEEN .1 WAVELENGTH AND .25
WAVELENGTH. IT'S SPACING WILL DEPEND UPON THE GAIN, BANDWIDTH, F/B
RATIO, AND SIDE LOBE PATTERN REQUIREMENTS OF THE FINAL ANTENNA DESIGN.

10. WORKING
•REFLECTORHEREDERIVESIT’SMAINPOWERFROMADRIVER,IT
REDUCESTHESIGNALSTRENGTHINIT’SOWNDIRECTIONANDTHUS
REFLECTESTHERADIATIONTOWARDESTHEDRIVERAND
DIRECTORS.
•THEDRIVENELEMENTISWHERETHESIGNALISINTERCPETEDBYTHE
RECEIVINGEQUIPMENTANDHASTHECABLEATTACHEDTHATTAKES
THERECEVIEDSIGNALTOTHERECEIVER
•THERADIATORANDDRIVERCANBEPLACEDMORECLOSERTO
INCREASETHERADIATIONLENGTHTOWARDSTHEDIRECTORS.

11. WAVELENGTH = 3*10^8
FERQUENCY(MHZ)
TO DETERMINE THE WAVE-LENGTH OF A RADIO STATION WITH
A FREQUENCY OF 92.1 MHZ , SIMPLY DIVIDE THE SPEED OF
LIGHT ( 300,000,000 METERS PER SECOND) BY 92,100,000
CYCLES PER SECOND.
THE SECONDS CANCELS OUT IN THE FORMULA WITH THE
WAVE-LENGTH ENDING UP AT 3.26 METERS. IN OTHER WORDS
THE WAVES PASSING YOU BUY RIGHT NOW FROM A RADIO
STATION TRANSMITTING AT 92.1 MHZ ARE 3.26 METERS LONG.

12. FIVE ELEMENT YAGI-UDA
REFLECTOR
DRIVER

13. RADIATION PATTERN FORMED
BY THE DIRECTIONAL ANTENNA
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14. RADIATION PATTERN FORMED
BY THE DIRECTIONAL ANTENNA
THEANTENNAEXHIBITSADIRECTIONALPATTERNCONSISTINGOFA
MAINFORWARDLOBEANDANUMBEROFSPURIOUSSIDELOBES.
THEMAINONEOFTHESEISTHEREVERSELOBECAUSEDBY
RADIATIONINTHEDIRECTIONOFTHEREFLECTOR.
THEANTENNACANBEOPTIMISEDTOEITHERREDUCETHISOR
PRODUCETHEMAXIMUMLEVELOFFORWARDGAIN.
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15. PICTURE OF ANTENNA
ELEVEN ELEMENT’S OF YAGI-UDA ANTENNA
FORWARD
DIRECTION

16. PICTURE OF ANTENNA FOR TV
SIGNAL RECEPTION
TheYagiantennaisaparticularlyusefulformofRFantennadesign.
ItiswidelyusedinapplicationswhereanRFantennadesignis
requiredtoprovidegainanddirectivity.Inthiswaytheoptimum
transmissionandreceptionconditionscanbeobtained.

17. PICTURE OF ANTENNA IN RADAR
Radar using group of Yagi-antenna with antenna gainG = 69

18. ADVANTAGES
IT HAS A MODERATE GAIN OF ABOUT 7 (DB).
IT IS A DIRECTIONAL ANTENNA.
CAN BE USED AT HIGH FREQUENCY.
ADJUSTABLE FROM TO BACK RATIO.

19. DISADVANTAGES
THE GAIN IS NOT VERY HIGH.
NEEDS A LARGE NUMBER OF ELEMENTS TO BE USED.

20. APPLICATIONS
Yagi-udaantennaisaunidirectionalantenna.Usedfor
televisionrecivers.Theyprovidebettertunningbecause
oflargebandwidthandhasdecentgain.