[Laptrinh.vn]-Ly Thuyet Anten

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Mc lcTrangLI NI U . 3TM TT NI DUNG 5CC T VIT TT S DNG TRONG LUN VN . 6CHNG 1 L THUYT ANTEN 71.1Khi nim v anten .... 71.2H phng trnh Maxwell . 71.3Qu trnh vt l ca s bc x sng in t .. 71.4Cc thng s c bn ca anten .. 81.4.1Tr khng vo ca anten . 101.4.2Hiu sut ca anten . 101.4.3H s hng tnh v h s tng ch .. 111.4.4 th phng hng v gc bc x ca anten 111.4.5Cng sut bc x ng hng tng ng 121.4.6Tnh phn cc ca anten .. 131.4.7Di tn ca anten . 131.5Cc h thng anten . 14CHNG 2ANTEN MCH DI ..................................................................... 162.1Cu to v nguyn l hot ng ca anten mch di . 162.1.1Cu to . 162.1.2Nguyn l hot ng ca anten mch di 212.2Tnh phn cc ca anten mch di . 222.3Bng thng ca anten mch di . 242.4Phng php phn tch v thit k anten mch di ... 242.5Nhc im ca anten mch di v xu hng pht trin .. 26CHNG 3TNG QUAN METAMATERIAL . 273.1nh ngha metamaterial ... 273.2c im ca metamaterial ... 273.2.1iu kin entropy 333.2.2o ngc hiu ng Doppler .. 333.2.3o ngc hin tng khc x ... 3413.2.4nh hng n cc h s Fresnel ... 373.2.5o ngc hiu ng Goos-Hanchen .. 383.2.6o ngc s hi t v phn k trong thu knh li v lm .. 403.3Hng pht trin ca Metamaterial . 413.3.1Nhng vt liu nhn to thc s .. 413.3.2Thu knh v cc thit b quang c chit sut m .................................... 423.3.3Thit b bo v anten v b mt chn la tn s ....................................44 3.3.4MTMs linh hot .. .443.4L thuyt anten metamaterial ...... 44 3.4.1Cu trc CRLH TLs l tng ...... 453.4.1.1Nhng c tnh c bn ca TL .. 453.4.1.2Cng hng cn bng v khng cn bng 513.4.1.3Thit k mng LC . 533.4.1.4Xy dng m hnh CRLH 1D ... 56 3.4.2L thuyt anten bc sng v hn trn cu trc chu k . 57CHNG 4THIT K ANTEN METAMATERIAL ... 61 4.1Thit k anten metamaterial 614.2Thc nghim v o c ... 70KT LUN CHUNG . 74 TI LIU THAM KHO .. 75

2LI NI UThng tin xut hin t rt lu t khi con ngi bit dng la, ting ng m thanh, cc k hiu tng hnh lin lc trao i. Tri qua qu trnh pht trin, nhu cu thng tin lin lc ca con ngi cng i hi ph hp vi thc t l nhanh, chnh xc v xa trong khi nu vn gi cch thc lin lc t xa xa th khng th p ng c v kh nng hn ch v s ri ro. Chnh t nhu cu thi thc con ngi phi tm ra cch thc lin lc mi v n nm 1837 Samuel Morse pht minh ra m hiu truyn tin da trn cch thc ng m dng in gy nn ting (tich te). Vi pht minh ny n lm gim i nhiu ri ro ca thng tin tuy nhin n vn b hn ch bi khong cch xa v cho n nm 1894 Maxwell a ra l thuyt v mt dng vt cht mi c th lan truyn c i xa v ngay c trong chn khng l sng in t th thng tin c th khc phc c hn ch bi khong cch a l. iu ny c thc t hobi Maconi, ng thnh cng trong vic truyn tn hiu Morse bng sng v tuyn qua i Ty Dng vo nm 1902. S kin ny m ra mt k nguyn mi v thng tin lin lc, to tin cho nhiu ng dng trong vin thng sau ny.ng gp vo thng tin lin lc th khng th khng k ti vai tr ca anten mt thit b dng truyn t v thu nhn tn hiu. Anten cng xut hin t lu c th ni n cng c cng nin i vi thng tin lin lc mi. Anten dn tr nn ph bin t khi xut hin nhng chic radio u tin hay nhng chic ti vi n hnh tt c u s dng n n. Lc anten c cu to rt n gin ch l nhng chic anten n cc sau dn l h thng anten Yagi c ng dng rt nhiu v ph bin. p ng nhu cu thng tin lin lc ngy cng pht trin th cng ngh anten cng phi pht trin theo in hnh l nhng ng dng truyn i xa nh thng tin v tinh th anten phi thit k sao cho truyn c tn hiu i xa m khng tn nhiu cng sut pht, c th s dng anten parabol thu pht v vi loi anten ny n c li cao v nh hng ln. Ngoi ra khng th khng ni n xu hng ca thi i mi l nh gn, a ng dng. y l nhng iu tt yu v anten cng vy n cng phi nh gn p ng c yu cu trn, chnh v vy m t nhng 3nm 70 m cng ngh anten mch di c nghin cu v pht trin. c im ni bt ca anten loi ny l nh gn, d ch to, c nh hng tng i cao, v c bit l d dng tch hp vi h thng x l tn hiu. Nhng c tnh trn gip antnen mch di c quan tm nhiu hn trong cng ngh tng lai v hin ti n c s dng rt rng ri nh trong cng ngh di ng, mng WLAN, anten thng minh v h thng tch hp siu cao tn. Tuy nhin anten mch di cng c nhng nhc im l : Bng thng hp, mt s anten vi di c li thp Suy hao in tr ln trn cu trc cung cp ca mng anten C bc x tha t ng truyn v cc mi ni Hiu sut nng lng c th s dng c thp ci thin c nhng nhc im trn c rt nhiu cch thc nh h thng anten mng (Array antenna) tng li cho anten, ngoi ra c th iu khin c bp sng. Ngoi ra cn c nhng ci thin v vt cht cho anten mt trong nhng ci thin l metamaterial v n c nhng c tnh khc bit so vi cc vt liu thng thng nh c ,< 0 v c mode cng hng sng ngc Nhng c tnh s c ln lt gii thiu trong lun vnEm xin chn thnh cm n thy Phan Anh inh hng cho em lm lun vn ny, em cm n thy Thm c Phng v bn b c nhng gp v ng vin em su sc. V c bit em rt chn thnh cm n Thc s Trn Th Thu Qunh tn tnh ch bo, hng dn cho em hon thnh lun vn tt nghip .4TM TT NI DUNGNi dung ca kho lun chia lm 4 chng:Chng 1: L thuyt anten. Trong chng ny gii thiu mt nt rt khi qut th no l h thng anten. Tip n l gii thiu cc thng s c bn ca anten trong l thuyt cng nh trong thc t. V cui cng l mt ci nhn chung v h thng anten hin ang c s dng trong nhiu lnh vc.Chng 2: Anten mch di. Trong chng ny gii thiu nhng iu c bn v anten mch di nh lch s ra i, cu to v nguyn l hot ng. Tip n l cc phng php phn tch v cng thc tnh ton cho anten mch di. Cui cng l hng i mi trong tng lai cho loi anten ny.Chng 3: Tng quan Metamaterial. y chnh l phn trng tm ca lun vn cp n vn rt mi trn th gii l cng ngh vt liu nhn to c , < 0. Tip n lun vn tp trung vo cc hin tng xy ra i vi loi vt liu ny c khcg sovi cc vt liuthngthng. Saucnglnhngngdngca metamaterial trong c anten metamaterial. Chng 4: Thit k anten metamaterial. Trong chng ny phn tch kh r nhng thng s khi thit k v ch ra nhng li im ca anten metamaterial. Cui cng l kt qu thc nghim v nhng li kt lun khi qut. 5CC T VIT TT S DNG TRONG LUN VNCRLHComposite Right Left HandedFDTDFinite Difference Time Domain LH Left-Handed MTMs MeTaMaterials PLH Pure Left HandedPRHPure Right HandedRH Right-HandedTLsTransmission LinesWLAN Wireless Local Area Network6Thit b iu chMy phtH thng cung cp tn hiu H thng bc x Anten phtThit b x lMy thuH thng cm th bc xH thng gia cng tn hiuAnten thuChng 1L THUYT ANTEN1.1 Khi nim v anten Anten l thit b dng bc x sng in t hoc thu nhn sng t khng gian bn ngoi.Vi s pht trin ca k thut trong lnh vc thng tin, rada iu khin v.v..cng i hi anten khng ch n thun lm nhim v bc x hay thu sng in t m cn tham gia vo qu trnh gia cng tn hiu.Trong trng hp tng qut, anten cn c hiu l mt t hp bao gm nhiu h thng, trong ch yu nht l h thng bc x hoc cm th sng bao gm cc phn t anten (dng thu hoc pht), h thng cung cp tn hiu m bo vic phn phi nng lng cho cc phn t bc x vi cc yu cu khc nhau (trng hp anten pht), hoc h thng gia cng tn hiu (trng hp anten thu). [1]

Hnh 1.1H thng anten thu v pht[1] 1.2 H phng trnh Maxwell L thuyt anten c xy dng trn c s nhng phng trnh c bn ca in ng lc hc: cc phng trnh Maxwell. Trong phn ny ta coi cc qu trnh in t l cc qu trnh bin i iu ho theo thi gian, ngha l c th biu din qui lut sin, cos di dng phc t ie ) cos( ) Re( t E e E Et i (1.1b) hoc ) sin( ) Im( t E e E Et i (1.1b)7Cc phng trnh Maxwell dng vi phn c vit di dng:

epJ E i H rot + (1.2a)

H i E rot (1.2b)

eE div (1.2c) 0 H div(1.2d) El bin phc ca vecto cng in trng (V/m)Hl bin phc ca vecto cng t trng (A/m) ,_

ip1 (1.3) (h s in thm phc ca mi trng) h s in thm tuyt i ca mi trng (F/m) h s t thm ca mi trng (H/m) in dn xut ca mi trng(Si/m) eJl bin phc ca vecto mt dng in ( 2mA) e l mt khi ca in tch.(3mC)Bit rng ngun to ra trng in t l dng in v in tch. Nhng trong mt s trng hp, d dng gii mt s bi ton ca in ng lc hc, ngi ta a thm vo h phng trnh Maxwell cc i lng dng t v t tch. Khi nim dng t v t tch ch l tng trng ch chng khng c trong t nhin.Kt hp vi nguyn l i ln, h phng trnh Maxwell tng qut c vit nh sau: epJ E i H rot + (1.4a)mJ H i E rot (1.4b)8mE div (1.4c)eH div (1.4d)Gii h phng trnh Maxwell ta c nghim l E,H. Trong phng trnh nghim n cho chng ta bit ngun gc sinh ra E,H v cch thc lan truyn.1.3 Qu trnh vt l ca s bc x sng in tV nguyn l, bt k h thng in t no c kh nng to ra in trng hoc t trng bin thin u c bc x sng in t, tuy nhin trong thc t s bc x ch xy ra trong nhng iu kin nht nh. v d ta xt mt mch dao ng thng s tp trung LC, c kch thc rt nh so vi bc sng. Nu t vo mch mt sc in ng bin i th trong khng gian ca t in s pht sinh in trng bin thin, cn trong khng gian ca cun cm s pht sinh t trng bin thin. Nhng in t trng ny khng bc x ra ngoi m b rng buc vi cc phn t ca mch. Nng lng in trng b gii hn trong khong khng gian ca t in, cn nng lng t trng ch nm trong mt th tch nh trong lng cun cm. Nu m rng kch thc ca t in th dng dch s lan to ra cng nhiu v to ra intrng binthinvibin ln hntrong khong khng gianbn ngoi.in trng bin thin ny truyn vi vn tc nh sng. Khi t ti khong cch kh xa so vi ngun chng s thot khi s rng buc vi ngun, ngha l cc ng sc in s khng cn rng buc vi in tch ca 2 m t na m chng phi t khp kn trong khng gian hay l hnh thnh mt in trng xoy. Theo qui lut ca in trng bin thin th in trng xoy s to ra mt t trng bin i t trng bin i li tip tc to ra in trng xoy hnh thnh qu trnh sng in t.Phn nng lng in t thot ra khi ngun v truyn i trong khng gian t do c gi l nng lng bc x (nng lng hu cng). Phn nng lng in t rng buc vi ngun gi l nng lng v cng.[1]1.4 Cc thng s c bn ca anten Trong thc t k thut mt anten bt k c cc thng s v in c bn sau y [3]: -Tr khng vo -Hiu sut -H s nh hng v tng ch. - th phng hng.9 -Cng sut bc x ng hng tng ng. -Tnh phn cc -Di tn ca anten.1.4.1Tr khng vo ca antenTr khng vo ca anten ZA bao gm c phn thc v phn khng l t s gia in p UA t vo anten v dng in IA trong anten. A AAAAjX RIUZ + (1.5)Tr khng vo ca anten ngoi ra cn ph thuc vo kch thc hnh hc ca anten v trong mt s trng hp cn ph thuc vo vt t gn anten.Thnh phn thc ca tr khng vo RA c xc nh bi cng sut t vo anten PA v dng in hiu dng ti u vo anten IAe

AeAAIPR (1.6)Thnh phn khng ca tr khng vo ca anten c xc nh bi c tnh phn b dng in v in p dc theo anten (i vi anten dy) v trong mt s trng hp c th c th tnh ton theo cc biu thc ca ng dy truyn sng. Hu ht cc anten ch hot ng trong mt di tn nht nh v vy c th truyn nng lng vi hiu sut cao t my pht n anten cn phi hp tr khng gia u ra my pht v u vo ca anten.1.4.2Hiu sut ca antenAnten c xem nh l thit b chuyn i nng lng, do mt thng s quan trng c trng ca n l hiu sut. Hiu sut ca anten A chnh l t s gia cng sut bc x Pbx v cng sut my pht a vo anten Pvohay PA

AbxAPP (1.7)Hiu sut ca anten c trng cho mc tn hao cng sut trong anten. i vi anten c tn hao th Pbx < Pvo do A < 1. Gi cng sut tn hao l Pth th bx AP P P + (1.8)i lng cng sut bc x v cng sut tn hao c xc nh bi gi tr in tr bc x Rbx v Rthvy ta c: ( )th bx Ae A Ae AR R I R I P + 2 2. (1.9)10T biu thc (1.7) ta vit li thnh: th bxbxth bxbxAR RRP PP++ (1.10)1.4.3H s hng tnh v h s tng ch Nh bit anten c rt nhiu loi v so snh gia cc anten vi nhau ngi ta a vo thng s h s hng tnh (h s nh hng) v h s tng ch (h s khuch i hoc li). Cc h s ny cho php nh gi phng hng v hiu qu bc x ca anten ti mt im xa no ca trn c s so snh vi anten l tng (hoc anten chun)Anten l tng l anten c hiu sut A = 1, v nng lng bc x ng u theo mi hng. Anten l tng c xem nh mt ngun bc x v hng hoc l mt chn t i xng na bc sng. HsnhhngcaantenD( , )lslnphi tngcngsut bcxkhi chuyn t anten c hng tnh sang anten v hng (anten chun) sao cho vn gi nguyn gi tr cng trng ti im thu ng vi hng ( , ) no ) 0 () , () 0 () , () , (21 121 11 1EEPPDbxbx (1.11) Trong :D(1 1, ) l h s nh hng ca anten c hng ng vi phng (1 1, );Pbx (1 1, ) v Pbx (0) l cng sut bc x ca anten c hng tnh ng vi hng (1 1, ) v cng sut bc x ca anten v hng ti cng im xt.E(1 1, ), E(0) l cng trng tng ng ca chng.iu ny c ngha l phi tng ln D(1 1, ) ln cng sut bc x Pbx(0) ca anten v hng c c trng bc x ti im thu xem xt bng gi tr E(1 1, ).H s tng ch ca anten G( , ) chnh l s ln cn thit phi tng cng sut da vo h thng anten khi chuyn t mt anten c hng sang mt anten v hng sao cho vn gia nguyn cng trng ti im thu theo hng xc nh ( , ). ) , ( ) , ( D GA (1.12)H s tng ch l mt khi nim y hn, n c trng cho anten c c tnh bc x v hiu sut ca anten. T (1.12) c th thy h s tng ch lun nh hn h s nh hng. Nu ta bit tng ch ca anten trong di tn xc nh ta c th tnh c Pbxtheo cng thc sau:11A A bxG P P . (1.13)121.4.4 th phng hng v gc bc x ca anten Mi anten u c tnh phng hng ngha l mt hng no anten pht hoc thu l tt nht v cng c th hng anten pht hoc thu xu hn hoc khng bc x, khng thu c sng in t. V vy vn l phi xc nh c tnh hng tnh ca anten. Hng tnh ca anten ngoi thng s v h s nh hng nh phn tch trn cn c c trng bi th phng hng ca anten. th phng hng l mt ng cong biu th quan h ph thuc gi tr tng i ca cng in trng hoc cng sut bc x ti nhng im c khong cch bng nhau v c biu th trong h to gc hoc to cc tng ng vi cc phng ca im xem xt.

Hnh 1.2 th phng hng trong to cc [6]

Hnh 1.3 th phng hng trong to gc [6]13Dng th phng hng c gi tr trng theo phng cc i bng mt nh vy c gi l th phng hng chun ho. N cho php so snh th phng hng ca cc anten khc nhau. Trong khng gian, th phng hng ca anten c dang hnh khi, nhng trong thc t ch cn xem xt chng trong mt phng ngang (gc ) v mt phng ng gc ( ).Trng bc x bin i t gi tr cc i n gi tr b, c th bng khng theo s bin i ca cc gc theo phng hng khc nhau. nh gi dng ca th phng hng ngi ta a vo khi nim rng ca th phng hng hay cn gi l gc bc x. Gc bc x c xc nh bi gc nm gia hai bn knh vector c gi tr bng 0.5 cng sut cc i, cng v vy m gc bc x cn c gi l gc m na cng sut.1.4.5Cng sut bc x ng hng tng ngTrong mt s h thng truyn tin v tuyn v d nh thng tin v tinh, cng sut bc x ca my pht v anten pht c c trng bi tham s cng sut bc x ng hng tng ng. K hiu l EIRPT TG P EIRP (W)Trong PTl cng sut u ra ca my pht a vo anten v GT l h s tng ch ca h thng anten c hng tnhH s tng ch GT ca anten ni ln vic tp trung cng sut bc x ca my pht cung cp cho anten vo bp sng hp ca anten. Cng sut bc x ng hng l cng sut uc bc x vi anten v hng, trong trng hp ny c th xem GT = 1. Nu nh anten c bp sng cng hp th gi tr EIRP ca n cng ln.1.4.6 Tnh phn cc ca antenTrong trng hp tng qut, trn ng truyn lan ca sng, cc vectorH E ,c bin v pha bin i. Theo quy c, s phn cc ca sng c nh gi v xem xt theo s bin i ca vector in trng. C th l, hnh chiu ca im u mt (im cc i) ca vector in trng trong mt chu k ln mt phng vung gc vi phng truyn lan ca sng s xc nh dng phn cc ca sng.Nu hnh chiu c dng elip th phn cc l elip; nu hnh chiu l hnh trn th phn cc l trn v nu l dng ng thng th l phn cc thng. Trong trng hp tng qut th dng elip l dng tng qut cn phn cc thng v trn ch l trng hp ring.Tu vo ng dng m ngi ta chn dng phn cc. V d truyn lan hoc thu sng mt t thng s dng anten phn cc thng ng bi v tn hao thnh phn thng ng ca in trng trong mt t b hn nhiu so vi thnh phn nm ngang. Hoc pht v thu sng phn x t tng in ly thng s dng anten phn cc ngang bi v tn hao thnh phn ngang ca in trng b hn nhiu so vi thnh phn ng.141.4.7Di tn ca antenDi tn ca anten l khong tn s m trong cc thng s tnh ton ca anten nhn cc gi tr trong gii hn cho php. Gii hn c quy nh l mc na cng sut. Ngha l cc tn s lch vi tn s chun foca anten th vic lch chun lm gim cng sut bc x khng qu 50%. Cc tn s trong di tn ca anten thng gi l tn s cng tc.Thng di tn c phn lm 4 nhm- Anten di tn hp (anten tiu chun): % 100 0 v > 0). C th c 3 cu tr li Khng c s khc bit bi v nguyn l ng lc hc khng thay i nu v cng i du. Hng s in mi v t thm cng gi tr m l khng th bi v n i nghch vi cc nguyn tc c bn.28 Hng s in mi v t thm cng gi tr m l c th nhng nguyn l ng lc hc ca nhng vt liu ny s khc vi cc vt liu c ( > 0 v > 0)C th thy cu tr li th ba l ng. p dng phng trnh Maxwell :

tDcH rottBcE rot 11 (3.2) Ta c phng trnh sau: [ ][ ] EcH kHcE k (3.3)T cc phng trnh (3.2) v (3.3) c th thy k H E , , c xc nh theo quy tc bn tay phi i vi vt liu c ( > 0 v > 0) nhng cng c th xc nh c theo quy tc bn tay tri vi vt liu c( < 0 v < 0). Vi l do ny m c th gi nhng vt liu mi ny l left-handed materials. Ngoi ra cng c tn gi khc cho loi vt liu ny l backward wave din t rng sng s truyn ngc vi hng ca nng lng in t trng. Cn vt liu thng thng l right-handed media. ngn gn ta k hiu metamaterials l MTMs, left-handed l LH v vt liu thng thng l RHNh rng vecto Pointing lun c xc nh theo quy tc bn tay phi vi H E,H E S (3.4)V hng ca vecto vn tc pha p vtrng vi hng vecto sngk. Nhng trong khi hng ca vecto vn tc nhm g vcng hng vi vecto Pointings. V vy m vecto vn tc pha v vecto vn tc nhm l ngc hng nhau khi hng s in mi v t thm l cng m ( < 0 v < 0). Ngc li khi m vt liu no c vn tc pha v vn tc nhm l ngc pha nhau th ta ni vt liu c c tnh l c < 0 v < 0.

a) b)Hnh 3.1 a) biu din chiu ca vecto Pointing S v vecto song k ca vt liu 29thng thng. b) biu din chiu ca vecto Pointing S v vecto song k ca loi vt liu mi. c)Hnh 3.1c)m t hng ca vecto Pointing S v vecto song k trong c 2 vt liu [5]S khng cng hng ca vecto vn tc pha v vecto vn tc nhm c mt s nh hng n hin tng vt l vn thng gp. Vn ny s c ni r phn sau, sau y ch l mt trong nhng nh hng c bn nht ca n ch ra rng chit sut cng c th l mt s m.Nh bit thng thng mt tia sng n gp b phn cch gia 2 mi trng khc nhau tia sng s b khc x theo ng 1-4 nh trn hnh v:

Hnh 3.2Cc tia sng kh d khi i qua b phn cch [5]30Tuy nhin khi vn tc pha v vn tc nhm khng cng hng th iu l lng xy ra l tia s b lch i theo hng 1-3. V vy nu mun gi nguyn cng thc v hin tung khc x (nh lut Snellius): n sinsin(3.5)Th n < 0 v sin < 0. M theo cng thc ta cn = do cn phi iu chnh li cch vit nh sau

t n

Du + khi vt liu l thng thng c > 0 v >0 v du - khi vt liu c < 0 v < 0. Hay c th vit li cho gn l

s n (3.6)vi s l hm dus =1 khi l vt liu RHs = -1 khi l vt liu LHT y ta s c cc cp du ca ( ,) to thnh bn min trong h to ca , Hnh 3.3 H to (, )[5] Nhn vo h trn c th thy rng trong min I ( > 0 v >0) y chnh l vt liu thng thng. 31 Trong min th II ( < 0 v >0) c bit n nh l vt liu plasma. Vt liu ny c th lm t mt h dy kim loi c sp xp tun hon khi tn s hot ng nh hn tn s plasma v c kch thch bi sng c vecto in trng dc theo trc z. Hnh 3.4aM hnh vt liu plasma in [5] ) (1 1 ) (2 222 2222 +++ + pe pe pejjr (3.7) Vi

appcpeln222 a l bn knh ca si dy

20appe 0 ) Re( )] , max( [ (RH thng di) (3.56c)Ngc li, trong trng hp cn bng th khe h b ng li ( sh se )v tr khng c tnh khng ph thuc vo tn s 51 R L cZ Z Z (3.57)iu ny c ngha l iu kin cn bng cho php phi hp mi di tn By gi s xt xem iu g xy ra vi hng s truyn sng

R L RRLRRL R RLCLCLC C L' '2'''''' ' '

,_

+ (3.58)V vy RLL'''2 iu ny dn nLR'' (3.59)Cui cng ta thu c L R' '0 (3.60)iu ny ch ra rng tn s cao nht ca khe h trong CRLH TL khng cn bng tr thnh tn s tn s ca khe ng trong CRLH TL cn bng. Chnh v vy o cn c gi l tn s chuyn trng thi (transition frequency) Trong (3.59) ch ra rng hng s truyn sng trong CRLH TL cn bng n gin nh l tng cc hng s truyn sng ca PRH TL v PLH TL V chit sut n c tnh nh sau:

,_

2''1LRc n(3.61)Chit sut l m khi m < o, dng khi > ov n = 0 khi = o . o l tn s chuyn trng thi p ng vn tc pha v hn L RRpv' ''22 v bc sng v hn / ' ' /2L RgDi y l bng tng kt cc loi TL:52 PRHPLHCRLH3.4.1.3Thit k mng LC Cu trc CRLH TL l khng thc s c trong t nhin tuy nhin nhng vn c th coi l ng nht hiu dng hot ng di tn gii hn th c th thit k di dng cu trc mng LC cu thang.[5]Hnh 3.18Cu trc CRLH TL dng bc thang chu k Cu trc mng ny bao gm cc tng cell n v LC do n ging vi dng cu thang. Mi cell n v bao gm c tr khng Z c to nn bi in cm RL ni tip vi in dung LC v dn np Y c to bi in cm LLsong song vi in dung RC53 Hnh 3.19a) Cu trc cell n v ca CRLH TL cha cn bngb) Cu trc cell n v ca CRLH TL cn bngCh rng s dch pha l do cc cell n v gy nn (). iu ny nn hiu l m hnh vi phn hnh 3.14 c quan h vi chiu di vt l z, m hnh 3.18 v 3.19 l khng c th nguyn v kch thc ca chng c th c m t ch trong iu kin chiu di in (electrical length) ca chng = || (rad). Nu chiu di n v ca cell n v l p chng ta c th vit li cc thng s ca u vo cng vi z 11]1

,_

) (1p C pLjpZLp (3.62a) 1]1

,_

) (1p L pCjpYLR(3.62b)So snh cng thc (3.40) vi(4.62) thy rng nu 0 z p th cc thng s u vo tr thnh ' / Z p Z , ' / Y p Y iu ny c ngha l mng LC trong hnh 3.19 tng ng vi m hnh 3.14. M hnh 3.14 biu din ch mt phn chiu di z ca TL v chiu di thc t s l tng cc chiu di mi phn lp liN ln do L = N z. V vy m N tng cell n v LC hnh 3.18 tng ng vi CRLH TL l tng c chiu di L vi iu kin p 0. Tuy nhin trn thc t nu p < g /4 th mng LC c th coi l TL l tng trong di tn gii hn. 54Hnh 3.20S tng ng gia mng cu thang chu k vi TL l tng [5] Bng tng ktnhng c tnh ca mng LC khi di in rt nh || f0) ngha l anten ny h tr sng ngc0 < (backward wave) v sng thun0 > (forward wave).By gi s xt n trng hp khng c thnh phn LChay l Inductor Loaded TL (g = 0). Vi cu hnh anten loi ny th tn s bc sng v hn cng khng thay i c chng th b dch i mt t so vi thit k, cn mode cng hng khc ch c mode cng hng dng (khng h tr sng nghch) khc so vi cu hnh anten CRLH TL l c c mode cng hng m ln dng.66 Hnh4.10Anten Inductor- Loader TL4 cell. Hnh 4.11H s S11(dB) ca anten Inductor-Loader TL4 cell.67C th thy tn s f0b dch tn cht t tuy nhin n vn l tn s bc sng v hn. Cn cc mode cng hng khc u l mode cng hng dng ( f > f0) khng c mode cng hng m. Hnh 4.12Vector in trng ca anten Inductor-loader TL 4 cell ti f0 V nh vy t cc kt qu trn c th thy tn s bc sng v hn khng ph thuc vo cng hng ni tip n ch ph thuc vo cng hng song song.i vi anten mch di thng thng nh bit th tn s cng hng ph thuc cht ch vo kch thc ca anten v d nh anten mch di hnh ch nht ta c th thy qua cng thc (2.5),(2.7) v (2.9). V vy khi thay i kch thc tn s cng hng s thay i. Qua y ta c th thy anten metamaterial khc phc c nhc im ny. Nu ta cn thit k di tn khc th ch cn thay i cc thng s sau y: - Din tch ca cell. Nu tng din tch ca cell th theo (4.2) s lm tng RCv theo (4.1) th s lm gim tn s cng hng song song. - Bn knh ca si trc. Nu tng bn knh theo (4.2) s lm tng LLv theo (4.1) th s lm gim tn s cng hng song song.- Hng s in mi. Nu gim hng s in mi s lm gim RCvo theo (4.1) s lm tng tn s cng hng song song ngoi ra n cn lm tng c bng thng na. thy r hn ta s thit k anten vi cc thng s nh trn nhng vi gim hng s in mi xung cn l r= 4.2. Khi tn s cng hng f0 s tng c th thy qua kt qu68Hnh 4.13H s S11 (dB) ca anten metamaterial 4 cell ( r= 4.2)T th thy tn s f0 tng ln 2.04 GHz.Tng bn knh si trc ln r = 0.5mm. Theo (4.2) tnh ra LL = 0.45 nH. V t (4.1) tnh ra f0 = 2.1 GHz. Nh vy tn s f0 tng ln so vi trc. Di y l kt qu c m phng. 69 Hnh 4.14H s S11 ca anten 4 cell vi r = 0.5mmC th thy rng tn s c lch i cht so vi tnh ton f0 = 2.16 GHz v c tng ln so vi ban u4.2Thc nghim v o cTrong phn thc nghim ta s thit k 2 cell vi cc kch thc trong phn 4.1. Kt qu thc nghim nh sau:Hnh nh anten metamaterial 2 cell Ta thu c 3 nh cng hng ging nh m phng tuy nhin tn s khng ging nh thit k do cc nguyn nhn sau: -Vt liu khng ging so vi thit k (khng bng 4.4)70- Via khng va l khoan dn n in cm thay i.- dy vt liu khng chnh xc l 1.6mm3 nh cng hng l 1.767GHz 11S = -22.659 dB 3.518 GHz11S = -18.8 dB 3.667 GHz11S = -19.14 dB Kt qu o 11S vi nh cng hng th nht71 Kt qu o11S vi nh cng hng th 272 Kt qu o 11S vi nh cng hng th 373KT LUN CHUNGBng cch thay i hn v cht liu m Metamaterial khc phc c nhng hn ch ca cng ngh trc y nh siu thu knh lm bng vt liu metamaterial c phn gii cao hn thu knh thng thng nn n c kh nng theo di c cc t bo ung th V lnh vc anten n gp phn ci thin c di tn hp ca anten mch di bng cch n c th hot ng c nhiu di tn hn v c bit l c kh nng tng gainmkhnglmthayitnshotngiunyantenmchdithngthng khng lm c. Tht vy nh bit th anten mch di c tn s hot ng ph thuc cht ch vo kch thc vt l v vy khi tng kch thc ln tng gain th s lm dch tn s hot ng. Trong phn lun vn phn tch v thit k s dng phn mm Ansoft HFSS v 10 v ch r c nhng li im trn.Ngoi nhng c tnh c bn trn metamaterial c th lm b chia m mi cng ra u c pha l nh nhau bng cu trc CRLH. Vi cch thc ta c th thit k v ch to kh n gin m khng cn phi iu chnh g nhiu.Trong qu trnh thc hin lm lun vn mc d em c gng ht sc nhng khng trnh khi nhng sai st. Em rt mong nhn c nhng li nhn xt qu bu ca cc thy c.Mt ln na em chn thnh cm n thy Phan Anh, thy Thm c Phng, v bn b c nhng ng gp v ng vin su sc. c bit em mun gi li cm n n thc s Trn Th Thu Qunh tn tnh gip v hng dn em trong sut thi gian lm kho lun tt nghip.TI LIU THAM KHO74TI LIU TING VIT[1] Phan Anh, L thuyt v k thut anten, NXB Khoa hc v K thut, 2007 [2] Nguyn Chng nh, Bi Hu Ph, S dng phng php FDTD kho stanten vi di, Tp ch bu chnh vin thng, 2008[3] Thi Hng Nh, Trng in t truyn sng v anten, NXB Khoa hc v k thut H Ni, [4] V nh Thnh, Nguyn Thanh Tm, Trn Minh T, Thit k v th nghim anten vi di, Tp ch bu chnh vin thng.TI LIU TING ANH[5] Christophe Caloz, Tatsuo Itoh, Electromagnetic metamaterial: Transmission line theory and microwave applications, John Wiley & Son, INC, 2005[6] Constantine A. Balanis, Antenna theory analysis and design 2nd , John Wiley & Son, INC.[7] Ramesh Garg, Prakash Bhartia, Inder Bahl, Apisak Ittipiboon, Microstrip Antenna design handbook, Artech House, Boston London[8] Anthony Lai, Kevin M. K. H. Leong, Tatsuo Itoh, Infinte wavelength resonantantennas with monopolar radiation pattern based on Periodic structures,IEEE Transactions on antennas and propagation, vol .55, No.3, March 2007[9] David M. Pozar, Microwave engineering 2nd , John Wiley & Son, INC.[10] Adrien Tennent, High performance front end gps module, University of Victoria, P.O.Box 3055, STN CSC[11] Lei Zhu, A brief intro to metamaterial,IEEE Potentials, 2004[12] Microstrip Inductor Calculator, http://www.daycounter.com/Calculators/Microstrip-Inductor-Calculator.phtml [13] Microstrip line calculator, http://emtalk.com/mscalc.php75