NGHIEN CUtJ THIET KE CHE TAO MAY THU TIN HIEU BANG T A N L
Dgng Thi Thanh Thuy vd Bach Gia Duong'
'^Khoa Vdt ly, Tnrdng Dgi hge Khoa hge Tu nhien, DHQGHN
71 —
' Trung tdm nghien ciru diin tir vd viin thdng, Trudng Dgi hge Cong nghi, DHQGHN
Tom tdt:
Viec trao doi thong tin trong qudn ly hdng khong Id mgt nhiem vu quan trgng. Boi vdy, trong hi thong nhdn biet chu quyin qudc gia, ben cgnh hi thdng phdt md hdi voi tdn sd sdng mang 1030MHz, cdn co mgt hi thdng thu de kiem tra tin hiiu md ddi tugng bay thu dugc vd xdc dinh dugc may bay nuoc nao cung nhu mgt sd thong tin ve mdy bay do. Trong bdi bdo ndy cluing toi de cap den cdc ket qud nghien ciru. thiet ke die tgo mdy thu bdng tdn L vdi do nhgy cao, bdng thong rgng vd cdc modun trong hi thdng dugc thiet ke nhd ggn thuan tiin cho cong tdc ung dung trong he thong qudn ly hdng khong.
Abstract:
Two-way secure query interrogation is a crutial task in air navigation. Therefore, except an uplink part usually operating at 1030MHz, there is also a transceiver part needed in the systeiJi which aims at determination of national identity ofaircrafis. Here the authors present recent results of a study, design and fabrication of a highly sensitive, compact and fiexibly modulated, wide band-width L transceiver for the purpose of application in air navigation.
I. G l 6 l THIEU
Bdo ve chu quyen qudc gia la mdt nhiem vy dac bidt quan trgng ddi vdi mdi qudc gia trong cd thdi chien Idn thdi binh. Viet nam Id qudc gia dang trong giai doan phdt trien, cdng nghe con rdt lac hau. Trong thdi ky md cua hdi nhap qudc te, ben canh nhirng co hdi cdn chiia dyng khdng ft nhiing riii ro. Mdt trong nhiing he thdng bdo ve an ninh qudc gia, an todn dudng khdng vd tang cudng sy phdt trien kinh te trong cd dan sy Idn quan sy la he thdng nhdn biet ma chu quyen qudc gia.
He thdng qudn ly khdng luu (Air Traffic Management ATM) co the hieu Id qudn ly sy luu thdng ciia may bay di chuyen tren khdng [1]. De ddm bdo an todn vd hieu gud cho cdc chuyen bay cdn phai cd sy dieu hdnh ciia bd phdn kiem sodt khdng luu dudi mat ddt nhd sy hd trg cua cdc thilt bj radar. Tuy nhien, dl xdc djnh tuyen dudng bay tren khdng, cdc may bay cdn phdi dya vao cac mdc tfn hieu phdt len cua cdc thiet bj dan dudng. Trudc thye trang ngay nay, khi luu lugng bay dat din mdt ngudng ndo dd, thi ha tdng ky thudt phuc vy qudn ly khdng luu hien nay se khdng dii an todn vd hieu qud de ddp iing yeu cdu cua qudn ly khdng luu. Nam 1983, td chiic hdng khdng dan dung quoc tl ICAO (Intemational Civil Aviation Organization) da tiln hdnh nghien ciiu tim gidi phdp cho vdn d l nay.
Trong he thdng nhan bidt ma xac djnh chu quyIn qudc gia, phdi kl din sy hd trg dac lyc cua thilt bj djnh vj vd tuydn (Radar). Thdng thudng thilt bj nay boat dgng d tan sd rat cao vd tfn hieu phan hdi thu dugc rdt ylu. De tdng do nhay cua thiet bj djnh vj, ddi hdi sy boat dgng rdt hieu qud ciia bd khulch dai tap dm thdp LNA ngay sau anten thu, tilp din la bd trdn tdn vd cudi cimg la xu If tin hieu nhdm phdt hien, do dac va phan loai ddi tugng.
II. TONG QUAN HE THONG
Mdt may bav dirac trans bj bd phai dap chd do S khi bay vao pham vi thdm do cua thigtbj iham dd chi do's se'nhan dugc mgi tin hieu tham do. Bd phat ddp trong he thong dieu khien cii (ATCRBS) se tra ldi vdi rhdt dinh dang tra ldi chudn, trong khi do bg phat dap che dp S se trd ldi vdi dinh dang mode S bao gdm 24 bits >dja chi.^ Sy thdm dd mdy bay dugc trang bj che dd mode S bao g6m tmdng chi thj, trudng nay cd the dugc khda lai khi bg^phat dap mode-S cap tfn hieu thdm dd mode-A/C/S all-call. Tfn hieu thdm dd mode-A/C khong bi anh huong bdi tfn hieu khda ndy vi vdy bg phdt ddp mode S se tra ldi theo mgi hudng. Neu truong dia chi cua nai din cd cac bit dlu Id 1 thi tdt ca cac bg phat dap mode S se trd ldi tfn hieu tham do nay va dua ra dja chi ciia chiing [5].
Mdt chu ky truyen phat ciia bg phat ddp dugc bdt ddu khi bg phat nhan dugc mgt tin hieu tham dd Bd phdt dap tilp nhan vd xdc dinh xem cd dugc chap nhan hay.khdng. Neu dupe chdp nhdn nd se xir ly tfn hieu tham dd dugc vd xdc ldp tfn hieu tra ldi. Chu ky truyen phatse kit thuc'khi mdt dilu kien cdn thilt cho vide chdp nhdn bj Idi hodc khi tin hieu tham dddugc chdp nhan nhung khdng yeu cau trd ldi hodc la qua trinh truyen tin hieu tra ldi da hodn thanh.
Anten
Bd khulch dai tap am thdp
Bg tao dao dgng
ngoai sai Bg khulch dai trung tan Loga
Bd trgn tan Bd tach sdng
Bg dieu khien he sd khulch dai ty dgng
theo thdi gian
Hinh 1. Sff do khoi cua he thong thu tin hifu ma nhan biet chii quyen quoc gia
He thdng thu nhdn ma dugc nid td nhu hinh 1. Anten thu: boat dgng d tin sd 1090 MHz.
Bg khulch dai tap am thdp (LNA): la mgt modul khulch dai dac biet, sir dyng trong cdc h? y6 tuyIn dl khulch dai nhirng tfn hieu rdt ylu thu dugc tir anten. Nd thudng dugc dat rat gan anten thu dk gidm thilu suy hao. Khi su dyng bg khulch dai nay d mdy thu thi dn nhieu cua nhiing tdng sau se dugc gidm bdi hd sd khuech dai cua nd. Trong khi dd, dn nhieu ciia LNA lai dugc cdng tryc tilp vao tfn hieu nhan dugc. Viec sir dung LNA Id cdn thilt de tang c6ng sudt tfn hieu mong mudn, cdn tap nhilu se dugc xir ly d nhirng tang tidp theo. Bg tao dao dgng ngoai sai: cd nhiem vy phdt ra tfn hieu cao tan. Bd ddo tan xudng: ve ban chat bg dao tan len vd xudng Id gidng nhau, chi khdc tin hieu ddu vao vd vj tri su dung. Ndu nhu bd dao tan len dugc su dung d khdi phdt thi bg ddo tdn xudng dugc chi tao dk dimg cho khdi thu. Tin hieu cao tdn RF khi qua bg nay se dugc chuyen vl tfn hieu trung t4n IF mang thdng tin. BO khulch dai yung tdn Loga: co ddi rdng va tuyIn ti'nh hda theo tfn hieu. Bd dilu khiln hS so khulch dai ty ddng theo thdi gian: nhdm cd dugc he sd khulch dai thi'ch hgp tai mgi vj tri do muc tieu, vi myc tieu khdng diing yen ma di chuyIn liic ra xa liic lai gdn. Bd tach sdng: co nhiem vy tach lay thdng tin mong mudn.
in. KET QUA THirc NGHIEM [3,4]
^ Bg khudch dai tap am thap sir dyng JFET loai SPF-3043 dugc tinh todn md phdng tren phdn mim ADS (hinh 2a) vd dugc chi tao tren mach thye tl ( hinh 2b).
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(a) So dd nguyen ly mach khuech dai tap am thap (b) Mach khuech dai tap dm thdp thye nghiem
Hlnh 2. Mach khulch dai tap am thap
O tan sd 1090 MHz khi cdng suat vdo tir -80 dBm thi ti sd giiia cdng suat tin hieu tren cdng suat tap am vao cd 1,5. Khdo sat bang mdy phan tich pho cho thay bg khulch dai tap am thdp CO he sd khuech dai tren 20 dB tren cd ddi tdn sd tir 1030 MHz den 1090 MHz. Ddi tan hoat dgng cua bd khuech dai tap am thdp tuomg ddi rdng (hinh 3a).
Tan so khao sal 1090 MHz
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Cong suat wo (dBm)
MHZ (b)He sd khulch dai
/NT^-.i , *<. ' v-11. ^ i - . * * - *v,- theo cdng suat vao d tdn sd 1090 MHz (a)Dai tan hoat dgng cua bg khuech dai tap am thap ^
Hinh 3. Cac kit qua khao sat mach khuech dai tap am thap
Khdi dao ddng tai chd hay bg td hgp tdn sd dugc thilt kl va ehl tao dya tren IC ADF4113. Tin sd chuin dua vao IC ADF4113 dugc ify tir dao dgng thach anh vdi do dri djnh cao. Vi mach ADF4113 dugc ghep ndi vdi vi dilu khiln AT89C51 cua hang ATMEL dl thay ddi tdn sd phat cua bd td hgp tan sd. Vi dilu khiln dugc lap trinh dk nhan bilt cdng tac dugc bdm, sd lieu dugc nhap tir bdn phim, hidn thj thdng bdo qua LCD vd thye hien chiic nang quan "trgng la fruyen ma dilu khiln tan sd tdi IC ADF4113 lam thay ddi tdn sd phdt cua bg td hgp tdn sd Tap hgp 4 chuyIn mach dugc sir dyng de chgn tdn sd phdt cd djnh, tuomg umg vdi 4 chuyIn mach la'4 tdn sd phdt 1030MHz, 1050MHz, 1070MHz, 1090MHz. Bk chgn tdn sd phdt ra tuy f, bg td hgp tdn sd dugc trang bj them bdn phim. Tren bdn phim cd 10 phim tuomg
ung vdi cac so tir 0-9 va 1 phim # dk thdng bdo kit thue vi?c nhap sd lieu. Qud trinh nh^p s6 lieu ciing nhu tdn sd phdt hien thdi cua bg td hgp tdn sd dugc thdng bdo qua man hinh hiln thj LCD. Sau khi nhdn ma dieu khien tan so, bg tao ddng ciia IC ADF4113 se sinh ra mgt dong dien tren chan CP (chdn 2). Ddng di?n nay qua dien trd dugc chuyIn thdnh dien dp va dugrc dua c^ua bg Igc la mach RC, tilp dd la qua klioi khuech dai sir dgng IC LF356 de chuyIn dien dp dieu khiln VCO tdi gid trj tucmg img vdi ddi tan s6 can phdt. Mach dao dgng tai cho dugc dilu chinh phdt d tan so 1036MHZ
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1(a) ICADF4113 (b)Bg tao dao ddng tai cho (c)Tin hi?u dao dgng ngoai sai Hinh 4. Bo tao dao dgng tai cho diing phuong phSp mach vdng bdm pha
Bd trdn dimg Transistor sa dd nguyen ly tren cd thi dugc chia 1dm ba khdi nhd: khoi thii nhdt la mach trdn vdi transistor Ql(2sc2353), khoi thiir hai la mdt tdng khuyech dai trung tan dOMhz, vdi transistor Q2( 2sc535), khoi thii ba gom cdc L, C dugc mdc theo kilu Igc thong ddi Chebyshev Tin hieu dao ddng ngoai quan sdt fren may phan tich phd Advantest R3765CG Network Analyzu 300KHz-3.8 GHz cho thdy dmh pho tin hieu tin sd 1030 MHz khd sac net bien do 3.09 dBm (hinh 4c).
Tilp dd chiing tdi thilt kl vd che tao bg frdn (hinh 4). Muc dich che tao mgt bg trgn hai tin sd ldi vdo Idii lugt Id : 1090 Mhz cd cdng suit phdt Id -20dBm(RF) va 1030 Mhz cd miirc cdng suit tir 0 din -5 dBm( LO), dl thu dugc ldi ra la hieu hai ldi vao cd tin sd la 60 Mhz, cdng suat Idn hom -1 OdBm.
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Hinh 4.Mach tron tan
b) Mach trdn
Tin hieu diu vdo 1090 MHz dugc trdng vdi tin hieu dao ddng tai chd 1030 MHz , tin hidu sau bd trgn qua may phan tich phd cho ra nhilu hda ba nhung tin sd 60MHz cd dinh phd cao nhit (-4.b4dB).
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Hmh 5. Tin hieu ra sau bo tron trong dai tir 0 den 300 Mhz
Nhu vay, da cd tin hieu trdn thdnh 60 MHz( Id hieu cua hai tin so loi vao). Ting khulch dai trung tin IF co he so Ichuech dai Id khoang 13dB. Hai khung LC dugc mdc theo ciu tnic Igc thong dai kilu Chebyshev dl Idm gidm dnh hudng cua cdc hdi khdng mong muon ( cd cong suat nhd hom -20 dBm).
nguon
Bg tach sdng pha dugc thilt kl bang phin niem Protel99 SE3. Mach tdch sdng pha cd ion nudi la +12v, biln thi dugc dilu chinh d tin sd cgng hudng Id 60 MHz. Ldi ra eua bd tdch sdng, chung tdi thu dugc xung thdng tin (hmh 6b), cdc thdng sd cua tin hieu thdng tin tuong ddi trung thye vdi tin hieu ban dau.
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a) So dd mach tach sdng b) Tin hieu ldi ra
Hinh 6.
Bd khulch dai trung tin vd bd dilu khiln he sd Idiulch dai ty ddng theo thdi gian, vi sy khd khdn vl linh kien thilt kl chung tdi xin dugc trinh bay trong nhiing cdng bd tiep theo.
IV. KET LUAN
Chimg ldi da che tao ihanh cdn^ cac khdi ca ban trong he thdng thu tfn hieu d bdng tan L, Viec nghien cuu hoan chinh he Ihdng sc md ra img di,ing cho khoi thu nhdn tfn hieu tra Idi trong he Ihdng nhan bilt chii quyen qudc gia
Kdt qua nghien ciiu Id mdt phan thugc de tai KC.01.12//06-10 ciia Bg Khoa bgc Viet nam va cd ddng gdp ciia dk tai cip ca sd cua D?i hge Qudc gia Hd ngi ndm 2010.
TAI LIEU THAM KHAO
[1] Nguyen Thi Xuan My- H? thdng thdng tin, dan dudng, gidm sdt phyc vu qudn ly khdng luu CNS/ATM- Tap Chf Buu Chfnh Viln thdng -27/07/2007
[2] GS.TSKH Phan Anh. Gido trinh ly thuyet vd ky thudt siiu cao tdn, Bg mdn Thdng tin vd tuydn, Khoa Dien tir Vien thdng, Trudng Dai Hge Cdng Nghe.
[3] David M.Pozar, Microwave engineering, John Wiley & Sons, Inc.
[4] W Alan Davis, Radio Frequency Circuit Design, John Wiley & Sons, Inc (2001) [5] ICAO (2001)- Air Trairfic Control Services, Flight Information Service and Alerting Services, 13 Edittion , July 2001.
