PH0101 Unit 2 Lecture ykkgg

7/26/2019 PH0101 Unit 2 Lecture ykkgg

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PH0101 Unit 2 Lecture 6 1

PH0101 Unit 2 Lecture 6

KlystOcil

Refle

Traveg ave Tue

Biological effect of microwaves


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Klystron Oscillator

A klystron is a vacuum tube that can beused either as a generator or as anamli!ier o! o"er# at micro"ave

!re$uencies%


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&"o cavity Klystron Amli!ier


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PH0101 Unit 2 Lecture 6 !

Alications

As o"er outut tubes

1" in UH# T$ transmitters

2" in tro%os%&ere scatter transmitters" satellite communication groun' station

!" ra'ar transmitters

As o"er oscillator() * )0 +H,-. if use'as a /lystron oscillator


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PH0101 Unit 2 Lecture 6 )

'e!le( Klystrons

T&e refle /lystron &as een t&e mostuse' source of microwave %ower in

laoratory a%%lications"


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)onstruction

refle /lystron consists of an electron gun. a cavity wit& a%air of gri's an' a re%eller %late as s&own in t&e aove'iagram"

3n t&is /lystron. a single %air of gri's 'oes t&e functions ofot& t&e unc&er an' t&e catc&er gri's"

T&e main 'ifference etween two cavity refle /lystronam%lifier an' refle /lystron is t&at t&e out%ut cavity is

omitte' in refle /lystron an' t&e re%eller or reflectorelectro'e. %lace' a very s&ort 'istance from t&e singlecavity. re%laces t&e collector electro'e"


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*orking

T&e cat&o'e emits electrons w&ic& are accelerate'forwar' y an accelerating gri' wit& a %ositive voltage on itan' focuse' into a narrow eam"

T&e electrons %ass t&roug& t&e cavity an' un'ergo

velocity mo'ulation. w&ic& %ro'uces electron unc&ingan' t&e eam is re%elle' ac/ y a re%eller %late /e%t at anegative %otential wit& res%ect to t&e cat&o'e"

On return. t&e electron eam once again enters t&e samegri's w&ic& act as a unc&er. t&ery t&e same %air of gri's

acts simultaneously as a unc&er for t&e forwar' movingelectron an' as a catc&er for t&e returning eam"


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'e!le( Klystron oscillator


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*orking

T&e fee'ac/ necessary for electrical oscillations is'evelo%e' y reflecting t&e electron eam. t&e velocitymo'ulate' electron eam 'oes not actually reac& t&ere%eller %late. ut is re%elle' ac/ y t&e negative voltage"

T&e %oint at w&ic& t&e electron eam is turne' ac/ cane varie' y a'7usting t&e re%eller voltage" T&us t&e re%eller voltage is so a'7uste' t&at com%lete

unc&ing of t&e electrons ta/es %lace at t&e catc&er gri's.t&e 'istance etween t&e re%eller an' t&e cavity is c&osen

suc& t&at t&e re%eller electron unc&es will reac& t&ecavity at %ro%er time to e in sync&roni,ation"

8ue to t&is. t&ey 'eliver energy to t&e cavity. t&e result ist&e oscillation at t&e cavity %ro'ucing R# fre9uency"


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Per!ormance )haracteristics1" #re9uency: ! * 200 +H,

2" Power: 1 m; * 2") ;

" T&eoretical efficiency : 22"45

at 10 m;


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Alications

T&e refle /lystrons are use' in

1" Ra'ar receivers2" Local oscillator in microwave receivers

" >ignal source in microwave generator of

variale fre9uency

!" Portale microwave lin/s

)" Pum% oscillator in %arametric am%lifier


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&raveling *ave &ube

Traveling ;ave Tue (T;T- is t&e most versatile

microwave R# %ower am%lifiers"

T&e main virtue of t&e T;T is its etremely wi'e

an' wi't& of o%eration"


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+asic structure o! a

&raveling *ave &ube ,&*&-


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PH0101 Unit 2 Lecture 6 1!

+asic structure

T&e asic structure of a T;T consists of a cat&o'e an'filament &eater %an ano'e t&at is iase' %ositively toaccelerate t&e electron eam forwar' an' to focus it into anarrow eam"

T&e electrons are attracte' y a %ositive %late calle' t&ecollector. w&ic& &as given a &ig& 'c voltage"

T&e lengt& of t&e tue is usually many wavelengt&s at t&eo%erating fre9uency"

>urroun'ing t&e tue are eit&er %ermanent magnets orelectromagnets t&at /ee% t&e electrons tig&tly focuse' intoa narrow eam"


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PH0101 Unit 2 Lecture 6 1)

.eatures T&e uni9ue feature of t&e T;T is a &eli or coil t&at

surroun's t&e lengt& of t&e tue an' t&e electron eam%asses t&roug& t&e centre or ais of t&e &eli"

T&e microwave signal to e am%lifie' is a%%lie' to t&e

en' of t&e &eli near t&e cat&o'e an' t&e out%ut ista/en from t&e en' of t&e &eli near t&e collector"

T&e %ur%ose of t&e &eli is to %rovi'e %at& for R#signal"

T&e %ro%agation of t&e R# signal along t&e &eli isma'e a%%roimately e9ual to t&e velocity of t&e electroneam from t&e cat&o'e to t&e collector


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.unctioning

T&e %assage of t&e microwave signal 'own t&e&eli %ro'uces electric an' magnetic fiel's t&atwill interact wit& t&e electron eam"

T&e electromagnetic fiel' %ro'uce' y t&e &elicauses t&e electrons to e s%ee'e' u% an'slowe' 'own. t&is %ro'uces velocity mo'ulationof t&e eam w&ic& %ro'uces 'ensity mo'ulation"

8ensity mo'ulation causes unc&es of electronsto grou% toget&er one wavelengt& a%art an'"t&ese unc& of electrons travel 'own t&e lengt&of t&e tue towar' t&e collector"


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.unctioning

T&e electron unc&es in'uce voltages into t&e

&eli w&ic& reinforce t&e voltage alrea'y %resent

t&ere" 8ue to t&at t&e strengt& of t&eelectromagnetic fiel' on t&e &eli increases as t&e

wave travels 'own t&e tue towar's t&e collector"

t t&e en' of t&e &eli. t&e signal is consi'eraly

am%lifie'" ?oaial cale or wavegui'e structures

are use' to etract t&e energy from t&e &eli"


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Advantages

1" T;T &as etremely wi'e an'wi't&" Hence. it

can e ma'e to am%lify signals from UH# to

&un're's of giga&ert,"

2" @ost of t&e T;TAs &ave a fre9uency range of

a%%roimately 2:1 in t&e 'esire' segment of t&e

microwave region to e am%lifie'"

" T&e T;TAs can e use' in ot& continuous an'%ulse' mo'es of o%eration wit& %ower levels u%

to several t&ousan's watts"


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Per!ormance characteristics

1" #re9uency of o%eration: 0") +H, * ) +H,

2" Power out%uts:

) m; (10 * !0 +H, * low %ower T;T-

2)0 /; (?;- at +H, (&ig& %ower T;T- 10 @; (%ulse'- at +H,

" fficiency :) * 20 < ( 0 < wit& 'e%resse'

collector-


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Alications o! &*&

1" Low noise R# am%lifier in roa' an' microwavereceivers"

2" Re%eater am%lifier in wi'e an' communication lin/san' long 'istance tele%&ony"

" 8ue to long tue life ()0.000 &ours against Ct& forot&er ty%es-. T;T is %ower out%ut tue incommunication satellite"

!" ?ontinuous wave &ig& %ower T;TAs are use' intro%oscatter lin/s ('ue to larger %ower an' largeran'wi't&s-"

)" Use' in ir orne an' s&i% orne %ulse' &ig& %owerra'ars"


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+iological e!!ects o! micro"aves

lectromagnetic ra'iation in t&e 1 mm to 1 m

wavelengt& range (00 @H, to 00 +&,- is

referre' to as microwave ra'iation" %art of w&ic& is /nown as ra'iofre9uency (R#-

ra'iation. w&ic& covers 0") @H, to 00 +H,

range an' is consi'ere' in t&e contet of

a'verse iological effects"


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/oniing and non ioniing radiations

o! electromagnetic energy


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/oniing radiation

3oni,ation is a %rocess y w&ic& electrons arestri%%e' from atoms an' molecules an' t&is can%ro'uce molecular c&anges t&at can lea' to'amage in iological tissue. inclu'ing effects on8D. t&e genetic material"

T&is %rocess re9uires interaction wit& &ig& levelsof electromagnetic energy to ioni,e iologicalmaterial. t&is inclu'e E=ra'iation an' gammara'iation"

T&e energy levels associate' wit& R# an'microwave ra'iations are not great enoug& tocause t&e ioni,ation of atoms an' molecules.t&erefore. it is a ty%e of non=ioni,ing ra'iation"


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PH0101 Unit 2 Lecture 6 2!

on ioniing radiation

@icrowave energy is non=ioni,ingelectromagnetic ra'iation" 3oni,ing ra'iation messes u% molecules. non=

ioni,ing ra'iation merely &eats t&em"

3n general. it 'oes not &ave sufficient energy to/ic/ an electron off an atom t&us %ro'ucingc&arge' %article in a o'y an' cause iological'amage"

T&e only %roven &armful effect from e%osure to

microwave (or R#- ra'iation is t&ermal"R# ra'iation can enter 'ee% into t&e o'y an'

&eat &uman organs"


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PH0101 Unit 2 Lecture 6 2)

3!!ect o! micro"aves in human body

T&e loo' vessels are 'ilating an' t&e loo' flow

increases sustantially as t&e t&ermoregulatory

mec&anism is activate' in or'er to /ee% t&e o'ytem%erature constant"

;it& rising o'y tem%erature t&e metaolic rate rises.

w&ic& may lea' to >tress='a%tation=#atigue>yn'rome"


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3!!ects roduced by the electromagnetic

"aves at di!!erent !re$uency levelove 10 +H, ( cm wavelengt& or less- &eating

occurs mainly in t&e outer s/in surface"#rom +H, to 10 +H, (10 cm to cm- t&e

%enetration is 'ee%er an' &eating &ig&er "#rom 1)0 @H, to aout 1 +H, (200 cm to 2) cm

wavelengt&-. %enetration is even 'ee%er an'ecause of &ig& asor%tion. 'ee% o'y &eatingcan occur"

ny %art of t&e o'y t&at cannot 'issi%ate &eatefficiently or is &eat sensitive may e 'amage' ymicrowave ra'iation of sufficient %ower"


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4easurement o! 4icro"ave e(osure T&e microwave energy e%osure is measure' in terms of

>R (>%ecific sor%tion Rate- or P8 (Power 8ensity-" >R is t&e energy w&ic& is asore' in a unit of mass or

volume of t&e o'y %er unit time" T&e stan'ar's t&at limit microwave e%osure were set at

0"! ;F/g >R for occu%ational an' 0"05;FKg for %ulice%osure"

T&e averaging time for 'etermination of >R was 6minutes" Power 'ensity is t&e energy asore' %er unitarea in unit time" T&e &ig& %ower microwaves 'efinitelycause some a'verse effects in t&e &uman system


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3!!ects o! 4icro"ave energyPo"er

level,m* 5cm2-

Longterm e!!ecton human body

'emarks

0"01 Dot&ing

0"1 Dot&ing

1 Dot&ing) Dot&ing cce%te' stan'ar' for microwave

oven lea/age

10 Dot&ing cce%te' stan'ar' for maimumcontinuous e%osure to ra'iate'

emissions (cell %&ones. etc"-0 Gou can feel &eat

100 ?ataracts can e%ro'uce'

>ummer sunlig&t is at t&is level

1000 Pain is in'uce'


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What do Microwave Ovens, Cell Phones and

Cordless Phones have in common?They all emit... Dangerous MicrowaveRadiation!The GOOD NEWSis... with Microwave radiation

you can... Boil water Cook meat Fry eggs

7o you kno" 8OU' +rain can be .'/37999


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T&e +A7 3*:is"""

wit& @icrowave ra'iation you can"""

#ry Gour Brain

Gour &ea' an' rain &eat u% significantly w&en you tal/

on your cell %&one or cor'less %&one"


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Want proof?

After 15 minutes of using a cell phone, the orange, red and pink show

significant, dangerous HEAT.Most heat is generated in your ear canal,

which is directly connected to YOUR RA!"


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!ter "# minutes o! using a cell $hone WITH the BIOPRO

Harmonization Chip applied to it, the green and blue colorsshow cool tissue.

%our head&s tem$erature remains normal, $roviding you with the$rotection you deserve.


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PH0101 Unit 2 Lecture 6 !

#roof enough?

$ome scientists estimate that you are now e%posed daily to

1&& million times the electromagnetic fre'uency (Micro

wa)e* radiation of your grandparents+$o+

AVOID FREQUET U!E OF

"E## $HOE!%%%


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PH0101 Unit 2 Lecture 6 )

Have a nice day.

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PH0101 Unit 2 Lecture ykkgg