Bo Co Thc Hnh Chuyn Ngnh in T Vin Thng THIT K, M PHNGV KHO ST CC THNG S K THUT CA ANTEN VI DII.MC CHGip cho sinh vin hiu c vai tr,v tr ca anten trong cc h thng truyn thng v tuyn. Sinh vin c tin hnh m phng kho st cc thng s k thut ca anten bng phn mm m phng HFSS, tnh ton thit k v ch to anten vi di hot ng di tn yu cu, s dng my phn tch mng (network analyzer) o c kho st cc thng s k thut ca mt s anten mu.II. C S L THUYTAntenlthitbquantrngkhngththiutrongmihthngtruyn thng khng dy. N l thit b chuyn i sng in t rng buc trong cc h nh hng thnh sng in t lan truyn trong khng gian t do v ngc li. Anten v ng dy dn (feeder) ng vai tr l thit b ghp gia cc mch in t v khng gian t do, feeder l b phn giao tip gia anten v mch in t. Ng vo ca feeder phi phi hp tr khng vi my pht, cn antenna pht nhn nng lng t my pht qua feeder v bc x ra khng gian. Ngoi vic phi hp tr khng yu cu i vi anten cn phi p ng v li v phng hng bc x.Hin nay, ty thuc vo mc ch s dng ca cc h thng truyn thng v tuyn ngi ta s dng rt nhiu loi anten khc nhau, nh anten parabol vi li v tnh nh hng cao thng c s dng trong truyn hnh, thng tin vi ba, thng tin v tinh... cn u cui thng s dng cc loi anten nh nh anten Yagi,anten dy,... v c bit cng vi s pht trin mnh m v cng ngh ca cc u cui di ng th anten vi di ngy cng c s dng rng ri v khng ngng ci tin p ng nhu cu ca ngi s dng.Anten vi di (hay anten mch in) c kch thc rt nh c cu to gm mt lp kim loi l mt bc x, mt lp kim loi khc gi l mt t (mn chn kim loi ), mt lp in mi gia hai lp kim loi trn v b phn tip in. Anten vi di c nhiu hnh dng nh hnh trn,hnh tam gic, hnh vung, hnh ch nht... trong , loi ph bin nht c kt cu hnh ch nht v c hng tnh, li cao ng thi d kt hp vi cc mch in t trn cngmt mch in.Gio vin hng dn: TH.S L Th Kiu Nga TH.S Nguyn Th Minh1Bo Co Thc Hnh Chuyn Ngnh in T Vin Thng Cc thng s k thut c bn ca anten- Tn s cng tc ca anten l tn s cng hng ca anten. Anten lun lm vic ch cng hng v khi cng sut bc x ca anten l ln nht.- H s nh hng ca anten theo hng cc i c nh ngha bng t s cng trng bc x ti mt v tr trn hng v cng trng bc x ca mt anten chun cng v tr tng ng (D). H s tng ch ( li) ca anten (G=e.D), trong e l hiu sut bc x ca anten;- Tr khng vo ca anten : ZA = RA + jXAKhi kt ni anten vi feeder cn ch ti iu kin phi hp tr khng,Thng thng tr khng c tnh ca feeder l R0 ph hp tr khng th ZA = R0- H s tn hao RL (dB) nh gi mc phn x ca sng ti im kt ni anten vi feeder- H s sng ng SWR nh gi mc khng phi hp tr khng gia anten v feeder.Trong :W l chiu rng mt bc x;L l chiu di mt bc x;h l b dy ca lp in mi;Wg l chiu rng ca mt phng t;Lg l chiu di ca mt phng t.III. TNHTON, MPHNGVKHOSTCCTHNGSK THUT CA ANTENAnten vi di hnh ch nht c cu to gm mt bc x, mt phng t v lp in mi gia 2 mt kim loi trn. Kch thc ca mt bc x, chiu cao v h s in mi l nhng thng s quyt nh tn s cng hng ca anten, nn chng phi c la chn v tnh ton chnh xc.Chn vt liu ch to anten l tm mch in hai mt c h s in mi v dy l: r = 4.5; h = 1.6 mm;Tnh ton kch thc ca anten vi di lm vic tn s:Gii tn GSM: f0= 1900 MHzGio vin hng dn: TH.S L Th Kiu Nga TH.S Nguyn Th Minh2Bo Co Thc Hnh Chuyn Ngnh in T Vin Thng Chiu rng ca mt bc x c tnh theo cng thc:W =2120+rfc 48(mm)c = 3x108 m/sVi c = 3x108 m/s ( c l vn tc nh sng), f0 l tn s cng hng ca anten, r l h s in mi ca lp in mi.H s in mi hiu dng reff ph thuc c vo cc kch thc (W , h) v n c xc nh theo cng thc:reff = 12r + + 12r 1/ 21 12wh 1+ 1 ]Thay s vo ta c reff 4.22 di hiu dng ca anten c xc nh theo cng thc:Leff e2o r ffcf Thay s vo ta c Leff 0.038 tng di L c tnh theo cng thc:L = eew( 0.3)( 0.264)0.412 .w( 0.258)( 0.8)r ffr ffhhh+ + + = Thay s vo ta c L 0.76(mm) di thc ca mt bc x c tnh bi cng thc:L = Leff- 2L =0.038 - 2x0.76x10-3 0.766 (mm)Kch thc ca mt phng t ( Wg v Lg ) c xc nh theo cng thc:Wg 6h + W Wg 6x1.6 + 48 58(mm) Lg 6h + L Lg 6x1.6 +36 46 (mm)3.1. Cc phng php tip in cho anten vi dia. Tip in bng cp ng trc (hnh 1)Trong phng php tip in cho anten vi di bng cp ng trc th li cp c hn tip xc vi mt bc x, v cp tip xc vi mt phng t.V tr tip in tt nht c tnh ton v xc nh c ta ( L/4, W/2)Gio vin hng dn: TH.S L Th Kiu Nga TH.S Nguyn Th Minh3Bo Co Thc Hnh Chuyn Ngnh in T Vin Thng Phng php tip in ny c cc u im l d thc hin v khng c bc x ph.b. Tip in bng ng truyn vi diTrong k thut tip in ny, mt di dn c kt ni trc tip n cnh ca mt bc x anten vi di. Di dn c thit k trn cng b mt vi mt bc x.Chiu rng ca di dn nh hn rt nhiu so vi kch thc ca mt bc x. V tr tip in c ta (L/2, 0).Kch thc ca di dn (Wf ; Lf ) c xc nh nh sau:Tr khng c tnh ca ng truyn l: Zo = 50Chiu rng ca di dn c tnh theo cng thc sau:Wf = 1 2 0.611 ln(2 1) ln( 1) 0.392rr rhB B B 1 + + ' ; 1 ] Trong : B = 03772rZ = 5.58Mi quan h gia chiu di v chiu rng: Lf /Wf= 3.96IV. HNG DN S DNG PHN MM M PHNG HFSSHFSS(Hight FrequencyStructureSimulator)lphnmmmphng trng in t theo phng php ton sng (full wave) m hnh ha bt k thit b th ng 3D no. u im ni bt ca HFSS l c dao din ngi dng ha,tch hp m phng, o ha, m hnh ha 3D v t ng ha (t ng tm li gii) trong mt mi trng d dng hc, trong li gii cho cc bi ton in t3Dthucmt cchnhanhchngvchnhxc. Ansoft HFSSsdng phng php phn t hu hn (Finite Element Method,FEM ), k thut chia li thch nghi (adaptive meshing ) v k thut ha. Ansoft HFSS c th c s dngtnhtonccthamschnghnnh: hstnhao, tnscng hng,gin hng tnh,tr khng vo...HFSS l mt h thng m phng tng tc,trong phn t mt li c bn l mt t din. iu ny cho php bn c th tm li gii cho bt k vt th 3D no. c bit i vi cc cu trc dng cong phc tp. Ansoft l cng ty tin phong s dng phng php phn t hu hn (FEM ) m phng trng in t bng cc k thut nh: phn t hu hn,chia li thch nghi...Ansoft HFSS cung cp mt giao din trc gic v d dng s dng pht trin cc thit b RF th ng.Gio vin hng dn: TH.S L Th Kiu Nga TH.S Nguyn Th Minh4Bo Co Thc Hnh Chuyn Ngnh in T Vin Thng Tm tt qu trnh m phng bng phn mm HSFF m phng mt anten bt k v c bn ta thc hin cc bc sau: Chn HFSS \ Solution Type \ Driven Terminal Chn n v: #D Modeler \Units, chn mm Da vo cc cng c trn thanh cng c v cu trc ca anten vo giao din lm vic To port cp ngunChn mt cp ngun, sau vo HFSS \ Excitation \ Assign- Nu cp ngun bng probe th chn Wave Port - Nu cp ngun bng ng vi di th chn Lumped Port Khai bo cc mt bc x ( thng khai bo cho mt phng t ): Chn mt bc x, sau vo HFSS \ Boundaries \ Assign \ Perfect E To khng gian bc x cho anten- V mt Box bao trm c anten, thng thng khong cch t ra anten n mt Box khong bc sng cng hng cn thit, sau vo:HFSS \ Boundaries \ Assign \ Radiation- Chn cc mt ca Box pha m anten c bc x- Chn HFSS \ Radiation \ nsert Far Field Setup \ Infinite Sphere- Mn hnh hin ln bng pha Far Field Radiation Sphere Setup- Nhp cc thng s mnh mun v nhn OK Khai bo tn s cng hng mong mun, s bc lp v sai s ln nht chp nhn c: HFSS \ Analysis Setup \ Add Solution Setup- Solution Frequency: nhp vo tn s cng hng mong mun- Maximum Number of Passed: s bc lp ti a ca m phng- Maximum Delta S Per Pass: sai s chp nhn c, cng nh cng chnh xc.Chng trnh m phng s chy cho n khi sai s tnh ton nh hn hoc bng delta S. Khi xem nh m phng chnh xc v c hi t ( Converged). Nu chy ht tt c cc bc lp m vn khng c sai s no nh hn delta S, chng trnh cng s t ng dng li. Khi qu trnh m phng s khng hi t v cho kt qu khng chnh xc. Mun khc phc ta phi tng gi tr delta S ln hoc l tng s bc lp ln nhn c kt qu chnh xc. Tuy nhin nu sai s tnh ra ngay nhng bc lp u tin nh hn Delta S th kt qu nhn c Gio vin hng dn: TH.S L Th Kiu Nga TH.S Nguyn Th Minh5Bo Co Thc Hnh Chuyn Ngnh in T Vin Thng cng khng ng tin. trnh hin tng ny ta phi gim Delta S tng s bc lp ca chng trnh. Thng thng nu chng trnh chy nhiu hn 5 bc lp v c hi t th s nhn c kt qu chnh xc. Khai bo vng tn s kho st ( xung quanh tn s trung tm)Vo HFSS \ Analysis Setup \ Add Sweep Sau khi thc hin tt c cng on trn, ta vo HFSS \ Validation check kim tra li thit k. Nu khng c li, vo HFSS \ Analyze v bt u chy m phng. Hin th cc kt qu m phng- vo HFSS \ Results \ V. CC THNG S M PHNG TN S 1900Ghz5.1. Thit k ng ten vi di- Khi ng chng trnh: Program => Ansoft => HFSS11 => HFSS11- Thit lp thng s: + Tool => Option => HFSS optionTi khung General tch chn nh sau:+ Tool => Options => Modeler optionsTrong khung 3D Modele options mc Operation chn Automatically cover closed polylinesTrong mc Drawing chn edit properties of new primitivesGio vin hng dn: TH.S L Th Kiu Nga TH.S Nguyn Th Minh6Bo Co Thc Hnh Chuyn Ngnh in T Vin Thng + Moderler => units => Select units: mm+ HFSS => Solution type => Chn Driven Terminal y chn gi quyt bi ton tn s lm vic f0 = 1900 MHZ- Thit k mt phng t: Draw => box ( t) + Thng s thit k lp tGio vin hng dn: TH.S L Th Kiu Nga TH.S Nguyn Th Minh7Bo Co Thc Hnh Chuyn Ngnh in T Vin Thng + Thit lp mt phng t:Edit => select => faceHFSS => Boundaries => Asign => Finite Conductivity Ok- Thit k lp in mi: Draw => box ( in mi) Thng s thit k lp in mi- Thit k mt bc x => box ( bc x)Gio vin hng dn: TH.S L Th Kiu Nga TH.S Nguyn Th Minh8Bo Co Thc Hnh Chuyn Ngnh in T Vin Thng Thng s thit k lp Mt bc x - Thit k lp line => box ( line)Thng s thit k lp Line- Thit k im cp ngun cho ng vi di v ngun ta vo Draw=>Rectangle (v hnh ch nht vung gc v tip xc mt ngoi Feed Line)Gio vin hng dn: TH.S L Th Kiu Nga TH.S Nguyn Th Minh9Bo Co Thc Hnh Chuyn Ngnh in T Vin Thng Thng s thit k lp Ngun Thit lp cp in: HFSS=>Excitations=>Asign=>Lumped Port (Nu thy Feed Line bn mc Conducting Objects c ngha c tip im, nhn Ok cp ngun)- Thit k lp khng gian: Draw => box ( khng gian) + Thng s thit k lp Khng gian Gio vin hng dn: TH.S L Th Kiu Nga TH.S Nguyn Th Minh10Bo Co Thc Hnh Chuyn Ngnh in T Vin Thng + mt bc x: Kch chn ln lt 4 mt bn v mt trn ca mt bc x ri thc hin: HFSS=> Boundaries=>Assign=> Radiation + Thit lp hng bc x: HFSS=>Radiation=>Insert Far Field Setup=>Infinte=>Ok+ Thit lp tn s lm vic: HFSS=> Analysis Setup=>Add Solution Setup y ta thit lp tn s lm vic nh chn l : 1900 MHZAdd Frequency Sweep Ta cStar: 1.5GHZ, Stop : 2.4 GHZ , cn Step Sto+ Thit lp gii hn tn s qut: HFSS=>Analysis Setup=>p l : 10 MHZSau Sweep Type chn: Fast > chn Ok To5.3. Thng s thit k ng ten cp ngun bng cp ng trc- Thng s thit k lp t (tng t nh trn)- Thng s thit k lp in mi (tng t nh trn)- Thng s thit k lp Mt bc x (tng t nh trn)- Thng s tip in trn Gio vin hng dn: TH.S L Th Kiu Nga TH.S Nguyn Th Minh11Bo Co Thc Hnh Chuyn Ngnh in T Vin Thng - Thng s tip in di- Thng s vng ngoi- Thng s thit k lp Cp ngunGio vin hng dn: TH.S L Th Kiu Nga TH.S Nguyn Th Minh12Bo Co Thc Hnh Chuyn Ngnh in T Vin Thng - Thit k lp khng gian: Draw => box ( khng gian) + Thng s thit k lp Khng gian + mt bc x: Kch chn ln lt 4 mt bn v mt trn ca mt bc x ri thc hin: HFSS=> Boundaries=>Assign=> Radiation - Thit lp cc thng sGio vin hng dn: TH.S L Th Kiu Nga TH.S Nguyn Th Minh13Bo Co Thc Hnh Chuyn Ngnh in T Vin Thng + Thit lp hng bc x: HFSS=>Radiation=>Insert Far Field Setup=>Infinte=>Ok+ Thit lp tn s lm vic: HFSS=> Analysis Setup=>Add Solution Setup y ta thit lp tn s lm vic nh chn l : 1900 MHZAdd Frequency Sweep Ta cStar: 1.5GHZ, Stop : 2.4 GHZ , cn Step Sto+ Thit lp gii hn tn s qut: HFSS=>Analysis Setup=>p l : 10 MHZSau Sweep Type chn: Fast > chn Ok ToVI . Kt qu m phng6.1. Kt qu m phng thit k ng ten vi di tn s 900Hnh m phng 3DGio vin hng dn: TH.S L Th Kiu Nga TH.S Nguyn Th Minh14Bo Co Thc Hnh Chuyn Ngnh in T Vin Thng Tn s cng hng: th smith: li:Gio vin hng dn: TH.S L Th Kiu Nga TH.S Nguyn Th Minh15Bo Co Thc Hnh Chuyn Ngnh in T Vin Thng nh gi v qu trnh v kt qu m phng:- suy hao khng ln- Kt qu m phng t c kt qu gn st vi tn s 900- Hnh dng th t vi yu cu ra- Qua nhiu ln cn chnh cho thy: vi tn s kh cao l 900 th kt qu kh chnh xc,cn tnh ton t m, chnh sa hp l mi c th t kt qu tt nht6.2. Kt qu m phng thit k ng ten cp ngun bng cp ng trc tn s 1900GhzHnh m phng 3DTn s cng hng: th smith: Gio vin hng dn: TH.S L Th Kiu Nga TH.S Nguyn Th Minh16Bo Co Thc Hnh Chuyn Ngnh in T Vin Thng th 3D Polar Plotnh gi kt qu m phng thit k ng ten cp ngun bng cp ng trc:- Tnh ton ta t phc tp v t cn sa hn so vi thit k ng ten vi di- Cho hnh dng m phng t chun t cn chnh hn- Tn s t c kh st vi tn s 1900khz- Trn kt qu ta thy suy hao vn cn kh lnVII. KT QU S DNG MY PHN TCH MANG CHO ANTEN VI DI7.1.Cung cp ngun v nhn nt khi ng cho my phn tch mng E5061A7.2. Kt ni ph kin cao tn chun MSA Port 1 ca my phn tch mng E5061 A Agilent E5061 RF Network Analyzer7.3. H s phn x ( S11):Gio vin hng dn: TH.S L Th Kiu Nga TH.S Nguyn Th Minh17Bo Co Thc Hnh Chuyn Ngnh in T Vin Thng H s suy hao im phn x S11 = -13.437dB Tn s cng hng im phn x f=970.30464MHz7.4. th Smith Chart uc hin th:Tr khng o uc trn th l =47.41 7.5. H s sng ng SWR:Ti im S11 xc nh tn f= 969.31MHzH s sng ng =1.52 Gio vin hng dn: TH.S L Th Kiu Nga TH.S Nguyn Th Minh18Bo Co Thc Hnh Chuyn Ngnh in T Vin Thng 7.6. Bng thng:Ta xc nh uc 2 im S11 v S12 trn th vi h s =9.5dB trn th y ta c tn s f1,f2 tung ng l:f1=980.352MHzf2=961.589MHzBng thng uc tnh = f1-f2=980.352-961.589 = 18.763MHz7.7. li: tnh li ta da vo cng thc:Gain=1/2 (Pr(dB)-Pt(dB)+20 log(d)+20log(f)-27.56)Trong Pr,Pt l h s dB hin th trn my:pr=-14dB Pt=-22dBd l khang cch gia 2 anten:d=15cmf la tn s dao ng ca anten:f=900MHzNh vy: Gain =1/2 ( -14-(-22))+20 log(15)+20log(950)-27.56)=23.775Gio vin hng dn: TH.S L Th Kiu Nga TH.S Nguyn Th Minh19Bo Co Thc Hnh Chuyn Ngnh in T Vin Thng VIII. SO SNH KT QU VI YU CU BIV KT LUNH s tn hao =-13.437dB