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8/3/2019 Chuong 1 Gioi Thieu Ve Anten 3
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K THUT ANTEN
TRUYN SNG
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TI LIU THAM KHO
1. TRUYN SNG V ANTEN L TIN THNG, TRN VN S
2. L THUYT V K THUT ANTEN PHAN ANH
3. ANTENNA THEORY ANALYSIS AND DESIGNCONSTANTINE A.BALANIS
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Phn 1 Anten
Chng 1 Gii Thiu V Anten
Chng 2 Cc c Tnh Ca Anten
Chng 3 L Thuyt Anten
Chng 4 H Thng Bc X Chng 5 Cc Loi Anten
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Phn 2 Truyn Sng
Chng 6 Truyn Sng Trn ng Dy dn
Chng 7 Truyn Sng Qua ng dn Sng
Chng 8 Truyn Sng V Tuyn
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Phn 1 Anten
Chng 1 Gii Thiu V Anten
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I. GII THIU LCH S PHT TRIN CA ANTEN
nh ngha Anten:
Anten l thit b dng bc x v (hoc) thu nhn nng lng in t.Anten l thit b dng truyn nng lung in t gia my pht v mythu m khng cn phng tin truyn dn tp trung.
Lch s pht trin ca anten: 1886 Heinrich Hertz (c) kim tra s tn ti ca sng in t. ng
pht trin cc dipole n gin, cc anten vng v cc anten c thanh phnx n gin.
1897 Alexader Popov (Nga) thit lp tuyn anten tht u tin vikhong cch 3 dm.
1901 Marconi thc hin thng tin v tuyn xuyn i ty dng (tn s
60KHz).
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1916 ln u tin ting ni c truyn i bng v tuyn (iu bin).
1920 cc h thng c th t c n tn s 1MHz, do kch thcanten c gim nh.
1930 cc ngun pht dao ng c th t n tn s hng GHz (Klistron,magnetron).
1934 h thng v tuyn thng mi u tin gia Php v Anh c thitlp (1,8GHz).
1940-1945 nhm phc v th chin th 2 nhiu pht minh trong vic phttrin Rada, cc anten phn x, cc anten thu knh.
1945- nay: k nguyn ca anten hin i, vi nhiu cng ngh v k thut
mi p ng cho Mng li thng tin v tuyn c tnh ton cu v tc cao, bng thng rng : (GPS, Wireless, GSM, CDMA, UWB, WiMax,MIMO).
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II. CC LOI ANTEN
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Anten dy (thanh):
Dipole Anten vng : trn, vung
Anten Helix
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Anten khe
Anten dng loa kn hnh chp
Anten dng loa kn hnh nn (cone)
ng dn sng vi u cui h
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Anten vi di (patch - microstrip antennas):
Anten vi di vung, kch thch bng ng truyn vi di
Anten vi di trn, kch thch bng cp ng trc
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Anten phn x
Mt phn x parabol vi ngunkch thch t pha trc
2 Mt phn x parabol vi ngun
kch thch t pha sau
Mt phn x phng
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Anten thu knh
H s khc x n>1
H s khc x n
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H thng bc x (array antenna)
Anten Yagi Mng cc khe bc x
Mng anten vi di Mng cc khe trn ng dn sng
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Hnh minh ha mt s anten
Anten dipole na bc
sng (/2=5mm)f=29,9GHz
Cng in trng o ti mt cu cch anten 100m
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Anten YagiVi chn t kch
thch l= /2=5mmf=29,9GHz
Cng trng in o ti mt cu cch anten 100m
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Anten Helix
D=4mm, f=1GHz
Cng in trng o ti mt cu cch anten 100m
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III. MT S H THC GII TCH VETOR
332211... iAiAiAA
Vector:
r
H to cu:
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M
ri
i
i
H to cu:
Ta im M xc nh bi: ),,( rM
Cc vector n v:
iiiiiiiii rrr
,,
321 ,, uuru
.sin .cos ,
.sin .sin ,
.cos
x r
y r
z r
Cc h s Larmor (metric):
sin.,,1 321 rhrhh
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Vector dch chuyn:
idridridrdl r
..sin....
2 2 2
. .sin .dl dr r d r d
Vi phn din tch:
idrdrdS
idrdrdS
idrdrdS rr
)..)((
)..sin.)((
)..sin.)(.(
Vi phn th tch:
).sin.)(.)(( drdrdrdV
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Mt s h thc vector
Tch v hng 2 vector: 332211 .... BABABABA
Tch vector:
321
321
321
BBB
AAA
iii
BA
Gradient: (tc ng ln v hng):
3
33
2
22
1
11
.1.1.1. iuf
hi
uf
hi
uf
hffgrad
Divergence:
)()()(
1.
321
3
213
2
132
1321
Ahhu
Ahhu
Ahhuhhh
AAdiv
0
.
lim S
V
AdS
divAV
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Ton t Laplace:
Tc ng ln v hng: 2. . f f f div grad f
Tc ng ln vector: AAA
)..(
Curl:
332211
321
332211
321
1
AhAhAh
uuu
ihihih
hhhAArotAcurl
0
.
. lim ln
S
Adl
curlA iS
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IV.BC X IN T
T nhng vng c in tch hay dng in bin thin c th bc x sngin t lan truyn trong khng gian. Cc vng c in tch hay dng in
bin thin gi l ngun bc x. Chng ta ch xt trng in t bin thin iu ho vi tn s . Cc i
lng ca trng c biu din bng cc bin phc.
Thng thng, xc nh trng bc x, chng ta phi gii phng trnhsng tm th vector A . Cc vector in trng v t trng c suy ra
t th vector nay.
Phng trnh sng: 2 A k A J
2
k v
Vi:
1v
Nghim phng trnh ny:'
1 ( ').( ) '
4
jkR
V
J r e A r dv
R
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V
'
1 ( ').( ) '
4
jkR
V
J r e A r dv
R
'
',1
( , ) '4
V
R J r t
v A r t dv
R
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1,
',1
( , ) .4
i
i N i
R J r t
v A r t v
R
1 'J r
2 'J r
3 'J r1'r 2 'r
3'r
r
M
y
x
z
1R
2R
3R
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C
'
1 ( ').( ) '
4
jkR
C
I r e A r dl
R
Nu ngun l dng in phn b di trn mt on cong C, vi dngin th nghim tr thnh:)'(rI
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Bc x in t ca nguyn t anten thng
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'
1 .'.
4
jkR
z
C
I e A dl i
R
. .
'
. .
1 .'.
4
.. . .
4 .
j k r
z
C
j k r z z z
I e A dl i
r
l Ie i A i
r
iAiAA rr
.. . .
. .
..cos . .cos
4 .
..sin . .sin
4 .
j k r
r z
j k r
z
l I A A e
r
l I A A e
r
H A rotA iHH
.
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Cng sut bc x:
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Mt s nhn xt:
1) T biu thc: virr itPtP
.)()( 0)( tPr
Nh vy min xa nng lng in t lun lun
truyn t ngun ra khng gian chung quanhtheo hng vector .ri
2) T biu thc:
2
. . . .. . . . .sinsin . .
4 . 2. .
j k r j k r I l k j j I l H e e
k r r
Hzer
klIjE C
rkj..sin.
.4
... ..2
Suy ra : cc vector E, H cng pha, vunggc vi nhau v vung gc vi
phng truyn ri
3) Bin ca E, H t l nghch vi khong cch r. Cn mt cng sut bc x t l nghch vi bnh phng khong cch r.
sin lI
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Suy ra Cc mt ng pha E, H l cc mt cu c bn knh r=const
5) T biu thc:2
2
3
..
lIzP mCbx
Cng sut bc x t l nghch vi bnh phng bc sng (tc t l thun vibnh phng tn s f. Cng sut bc x cng ln khi tn s cng cao.
4) T biu thc: )2
..cos(.2
sin..)(
rkt
r
lItH m )(.)( tHztE C
6) T biu thc:
2
. . . .. . . . .sinsin . .
4 . 2. .
j k r j k r I l k j j I l H e e
k r r
Hzer
klIj
E Crkj
..sin..4
... ..2
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Cc nhn xt 1, 2, 3, 4 c rt ra i vi nguyn t anten thng , nhng cth chng minh rng chng cng ng vi ngun bc x phn b bt k.