PH0101 Unit 2 Legncture 6

8/18/2019 PH0101 Unit 2 Legncture 6

1/35

PH0101 Unit 2 Lecture 6 1

PH0101 Unit 2 Lecture 6

KlystOscillor

Refle

Traveling Wave Tube

Biological effect of icro!aves


2/35


3/35

PH0101 Unit 2 Lecture 6 "

&"o cavity Klystron Amli!ier


4/35

PH0101 Unit 2 Lecture 6 #

Alications

As o"er outut tubes

1$ in UH% T& transitters

2$ in tro'os'(ere scatter transitters"$ satellite counication groun) station

#$ ra)ar transitters

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


5/35

PH0101 Unit 2 Lecture 6 +

'e!le( Klystrons

T(e refle lystron (as been t(e ostuse) source of icro!ave 'o!er in

laboratory a''lications$


6/35


)onstruction

3 refle lystron consists of an electron gun a cavity !it( a'air of gri)s an) a re'eller 'late as s(o!n in t(e above)iagra$

4n t(is lystron a single 'air of gri)s )oes t(e functions ofbot( t(e bunc(er an) t(e catc(er gri)s$

T(e ain )ifference bet!een t!o cavity refle lystrona'lifier an) refle lystron is t(at t(e out'ut cavity is

oitte) in refle lystron an) t(e re'eller or reflectorelectro)e 'lace) a very s(ort )istance fro t(e singlecavity re'laces t(e collector electro)e$


7/35


*orking

T(e cat(o)e eits electrons !(ic( are accelerate)for!ar) by an accelerating gri) !it( a 'ositive voltage on itan) focuse) into a narro! bea$

T(e electrons 'ass t(roug( t(e cavity an) un)ergo

velocity o)ulation !(ic( 'ro)uces electron bunc(ingan) t(e bea is re'elle) bac by a re'eller 'late e't at anegative 'otential !it( res'ect to t(e cat(o)e$

On return t(e electron bea once again enters t(e saegri)s !(ic( act as a bunc(er t(erby t(e sae 'air of gri)s

acts siultaneously as a bunc(er for t(e for!ar) ovingelectron an) as a catc(er for t(e returning bea$


8/35

PH0101 Unit 2 Lecture 6

'e!le( Klystron oscillator


9/35


*orking

T(e fee)bac necessary for electrical oscillations is)evelo'e) by reflecting t(e electron bea t(e velocityo)ulate) electron bea )oes not actually reac( t(ere'eller 'late but is re'elle) bac by t(e negative voltage$

T(e 'oint at !(ic( t(e electron bea is turne) bac canbe varie) by a)8usting t(e re'eller voltage$ T(us t(e re'eller voltage is so a)8uste) t(at co'lete

bunc(ing of t(e electrons taes 'lace at t(e catc(er gri)st(e )istance bet!een t(e re'eller an) t(e cavity is c(osen

suc( t(at t(e re'eller electron bunc(es !ill reac( t(ecavity at 'ro'er tie to be in sync(roni.ation$

9ue to t(is t(ey )eliver energy to t(e cavity t(e result ist(e oscillation at t(e cavity 'ro)ucing R% fre:uency$


10/35


Per!ormance )haracteristics1$ %re:uency; # , 200 -H.

2$ Po!er; 1 W , 2$+ W

"$ T(eoretical efficiency ; 22$5 <#$ Practical efficiency ; 10 < = 20 <

+$ Tuning range ; + -H. at 2 W , "0 -H.

at 10 W


11/35


Alications

T(e refle lystrons are use) in

1$ Ra)ar receivers2$ Local oscillator in icro!ave receivers

"$ >ignal source in icro!ave generator of

variable fre:uency

#$ Portable icro!ave lins

+$ Pu' oscillator in 'araetric a'lifier


12/35


&raveling *ave &ube

Traveling Wave Tube *TWT/ is t(e ost versatile

icro!ave R% 'o!er a'lifiers$

T(e ain virtue of t(e TWT is its etreely !i)e

ban) !i)t( of o'eration$


13/35

PH0101 Unit 2 Lecture 6 1"

+asic structure o! a

&raveling *ave &ube ,&*&-


14/35

PH0101 Unit 2 Lecture 6 1#

+asic structure

T(e basic structure of a TWT consists of a cat(o)e an)filaent (eater 'an ano)e t(at is biase) 'ositively toaccelerate t(e electron bea for!ar) an) to focus it into anarro! bea$

T(e electrons are attracte) by a 'ositive 'late calle) t(ecollector !(ic( (as given a (ig( )c voltage$

T(e lengt( of t(e tube is usually any !avelengt(s at t(eo'erating fre:uency$

>urroun)ing t(e tube are eit(er 'eranent agnets orelectroagnets t(at ee' t(e electrons tig(tly focuse) intoa narro! bea$


15/35

PH0101 Unit 2 Lecture 6 1+

.eatures T(e uni:ue feature of t(e TWT is a (eli or coil t(at

surroun)s t(e lengt( of t(e tube an) t(e electron bea'asses t(roug( t(e centre or ais of t(e (eli$

T(e icro!ave signal to be a'lifie) is a''lie) to t(e

en) of t(e (eli near t(e cat(o)e an) t(e out'ut istaen fro 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 isa)e a''roiately e:ual to t(e velocity of t(e electronbea fro t(e cat(o)e to t(e collector


16/35


.unctioning

T(e 'assage of t(e icro!ave signal )o!n t(e(eli 'ro)uces electric an) agnetic fiel)s t(at!ill interact !it( t(e electron bea$

T(e electroagnetic fiel) 'ro)uce) by t(e (elicauses t(e electrons to be s'ee)e) u' an)slo!e) )o!n t(is 'ro)uces velocity o)ulationof t(e bea !(ic( 'ro)uces )ensity o)ulation$

9ensity o)ulation causes bunc(es of electronsto grou' toget(er one !avelengt( a'art an)$t(ese bunc( of electrons travel )o!n t(e lengt(of t(e tube to!ar) t(e collector$


17/35


.unctioning

T(e electron bunc(es in)uce voltages into t(e

(eli !(ic( reinforce t(e voltage alrea)y 'resent

t(ere$ 9ue to t(at t(e strengt( of t(eelectroagnetic fiel) on t(e (eli increases as t(e

!ave travels )o!n t(e tube to!ar)s t(e collector$

3t t(e en) of t(e (eli t(e signal is consi)erably

a'lifie)$ ?oaial cable or !avegui)e structures

are use) to etract t(e energy fro t(e (eli$


18/35


Advantages

1$ TWT (as etreely !i)e ban)!i)t($ Hence it

can be a)e to a'lify signals fro UH% to

(un)re)s of giga(ert.$

2$ @ost of t(e TWTAs (ave a fre:uency range of

a''roiately 2;1 in t(e )esire) segent of t(e

icro!ave region to be a'lifie)$

"$ T(e TWTAs can be use) in bot( continuous an)'ulse) o)es of o'eration !it( 'o!er levels u'

to several t(ousan)s !atts$


19/35


Per!ormance characteristics

1$ %re:uency of o'eration ; 0$+ -H. , 7+ -H.

2$ Po!er out'uts;

+ W *10 , #0 -H. , lo! 'o!er TWT/

2+0 W *?W/ at " -H. *(ig( 'o!er TWT/ 10 @W *'ulse)/ at " -H.

"$ fficiency ; + , 20 < * "0 < !it( )e'resse)

collector/


20/35


Alications o! &*&

1$ Lo! noise R% a'lifier in broa) ban) icro!avereceivers$

2$ Re'eater a'lifier in !i)e ban) counication linsan) long )istance tele'(ony$

"$ 9ue to long tube life *+0000 (ours against Ct( forot(er ty'es/ TWT is 'o!er out'ut tube incounication satellite$

#$ ?ontinuous !ave (ig( 'o!er TWTAs are use) intro'oscatter lins *)ue to larger 'o!er an) largerban)!i)t(s/$

+$ Use) in 3ir borne an) s(i' borne 'ulse) (ig( 'o!erra)ars$


21/35


22/35


/oniing and non ioniing radiations

o! electromagnetic energy


23/35

PH0101 Unit 2 Lecture 6 2"

/oniing radiation

4oni.ation is a 'rocess by !(ic( electrons arestri''e) fro atos an) olecules an) t(is can'ro)uce olecular c(anges t(at can lea) to)aage in biological tissue inclu)ing effects on9D3 t(e genetic aterial$

T(is 'rocess re:uires interaction !it( (ig( levelsof electroagnetic energy to ioni.e biologicalaterial t(is inclu)e E=ra)iation an) gaara)iation$

T(e energy levels associate) !it( R% an)icro!ave ra)iations are not great enoug( tocause t(e ioni.ation of atos an) oleculest(erefore it is a ty'e of non=ioni.ing ra)iation$


24/35

PH0101 Unit 2 Lecture 6 2#

on ioniing radiation

@icro!ave energy is non=ioni.ingelectroagnetic ra)iation$ 4oni.ing ra)iation esses u' olecules non=

ioni.ing ra)iation erely (eats t(e$

4n general it )oes not (ave sufficient energy toic an electron off an ato t(us 'ro)ucingc(arge) 'article in a bo)y an) cause biological)aage$

T(e only 'roven (arful effect fro e'osure to

icro!ave *or R%/ ra)iation is t(eral$R% ra)iation can enter )ee' into t(e bo)y an)

(eat (uan organs$


25/35

PH0101 Unit 2 Lecture 6 2+

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

T(e bloo) vessels are )ilating an) t(e bloo) flo!

increases substantially as t(e t(eroregulatory

ec(anis is activate) in or)er to ee' t(e bo)yte'erature constant$

Wit( rising bo)y te'erature t(e etabolic rate rises

!(ic( ay lea) to >tress=3)a'tation=%atigue>yn)roe$


26/35


3!!ects roduced by the electromagnetic

"aves at di!!erent !re$uency level 3bove 10 -H. *" c !avelengt( or less/ (eating

occurs ainly in t(e outer sin surface$%ro " -H. to 10 -H. *10 c to " c/ t(e

'enetration is )ee'er an) (eating (ig(er $%ro 1+0 @H. to about 1 -H. *200 c to 2+ c

!avelengt(/ 'enetration is even )ee'er an)because of (ig( absor'tion )ee' bo)y (eatingcan occur$

3ny 'art of t(e bo)y t(at cannot )issi'ate (eatefficiently or is (eat sensitive ay be )aage) byicro!ave ra)iation of sufficient 'o!er$


27/35


4easurement o! 4icro"ave e(osure T(e icro!ave energy e'osure is easure) in ters of

>3R *>'ecific 3bsor'tion Rate/ or P9 *Po!er 9ensity/$ >3R is t(e energy !(ic( is absorbe) in a unit of ass or

volue of t(e bo)y 'er unit tie$ T(e stan)ar)s t(at liit icro!ave e'osure !ere set at

0$# WFg >3R for occu'ational an) 0$0WFKg for 'ublice'osure$

T(e averaging tie for )eterination of >3R !as 6inutes$ Po!er )ensity is t(e energy absorbe) 'er unitarea in unit tie$ T(e (ig( 'o!er icro!aves )efinitelycause soe a)verse effects in t(e (uan syste


28/35


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 3cce'te) stan)ar) for icro!ave

oven leaage

10 Dot(ing 3cce'te) stan)ar) for aiucontinuous e'osure to ra)iate)

eissions *cell '(ones etc$/"0 Gou can feel (eat

100 ?ataracts can be'ro)uce)

>uer sunlig(t is at t(is level

1000 Pain is in)uce)


29/35


What do Microwave Ovens, Cell Phones and

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

you can...• Boil water• Cook meat• Fry eggs

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


30/35

PH0101 Unit 2 Lecture 6 "0

T(e +A7 3*: is$$$

!it( @icro!ave ra)iation you can$$$

%ry Gour Brain

Gour (ea) an) brain (eat u' significantly !(en you tal

on your cell '(one or cor)less '(one$


31/35


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!"


32/35


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

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

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


33/35

PH0101 Unit 2 Lecture 6 ""


34/35

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!%%%


35/35

PH0101 Unit 2 Lecture 6 "+

Have a nice day.

Documents

PH0101 Unit 2 Legncture 6