THIẾT KẾ ANTEN VI DẢI CHO ỨNG DỤNG GNSS

7/28/2019 THIT K ANTEN VI DI CHO NG DNG GNSS

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THIT K ANTEN VI DI CHO

NG DNG GNSSNgy nay cc ng dng ca h thng GNSS (Global Navigation

Satellite System) v ang thm nhp vo i sng x hi ngy cng a

dng v phong ph. phc v cuc sng ngy mt tt hn, nhiu h thng

nh v dn ng trn th gii ra i nh: GPS (Global Positionting

System) ca M, GLONASS ca Nga v Galileo ca Chu u. Trong cc b

thu tn hiu nh v, thit b u cui anten ng vai tr quan trng, lm tng

nhy, gim mc tiu th nng lng. Trong phm vi bi bo ny s phn

tch v thit k mt anten vi di hot ng tn s 1565MHz sau:

1595MHz, phc v cho cc thit b tch hp ng dng ca GNSS trong

hin ti v tng lai.

I. Gii thiu chung v anten vi di

Nhng cu trc bc x vi di c a ra ln u tin vo nm 1953.

Tuy nhin phi gn hai mi nm sau, nhng anten thc t mi c sn

xut. K t , vic nghin cu, pht trin cc anten vi di v cc mng

anten vi di khng ngng c m rng, nhm khai thc trit nhng u

im, cng nh cch khc phc cc u nhc im ca loi anten ny.

Anten vi di vi cu hnh n gin nht bao gm mt patch pht x nm

trn mt mt ca mt lp in mi (lp ), mt kia lp in mi l mt

phng t, cht dn in l tng. Ming Patch l cht dn in, c th lbt k hnh dng no, nhng thng s dng hnh dng sao cho vic phn

tch, tnh ton thit k d dng, hiu qu. Tuy nhin vi s pht trin ca

cng ngh v s ra i ca cc chng trnh m phng thit k cho php c

th thit k patch bt k hnh dng no. Hng s in mi ca lp


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ng vai tr quan trng i vi hot ng ca anten, nh hng n tr

khng c tnh, tn s cng hng, bng thng v hiu sut ca anten.

II. Tnh ton kch thc v m phng

Anten thit k y l m hnh anten mt lp, in mi c s

dng l FR4_epoxy c hng s in mi = 4,4. Tnh ton xp x kch

thc ca anten theo cng thc sau: L = W 0,49.d = 0,49. Vi l bc

sng trong khng gian t do, d l bc sng trong cht in mi, l h s

in mi ca lp . Thng s v kch thc gn ng ca anten nh sau:

Wp = Lp = 43,91mm, L = 4,87mm, r1l = 27,09mm, w1l = 2,21mm, r2l =

10mm, w2l = 6,1mm, s dng lp in mi c = 4,4 b dy lp in mi h(h c th thay i tm c anten c ti u), kch thc lp in mi

v Ground: 90mmx104mm. Anten GNSS gm hai phn c bn: Mt bc x

(patch), ng truyn vi di tip in cho patch, cng l mch phi hp tr

khng dng b phi hp tr khng /4. Bng tn lm vic, bng thng ph

thuc vo kch thc tm patch v b dy lp in mi. Sau y s tin

hnh kho st mt vi trng hp thy c s ph thuc ny.

Hnh 1: Anten vi di


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Khi tng hoc gim b dy lp in mi trong mt gii hn cho php th

cc thng s k thut ca anten nh bng thng, t s trc (AR) thay i ng

k. Theo kt qu nh trn, m hnh anten vi h = 1,6mm v h =

3,2mm u t c S11 tt nhng bng thng li khc nhau, vi h =

1,6mm bng thng ca GPS 60MHz (3,8%), vi h = 3,2mm l ti u hn

c, tha mn c v S11, bng thng v t s trc. Vy m rng bng thng

cho anten l tng dy ca lp in mi.

Kho st anten khi thay i kch thc tm patchB dy lp in mi khng i c chn l h = 3,2mm, thng s thay i

y l kch thc tm patch, thc hin iu chnh di ca on ct vt thay i t s trc AR < 3dB. Khi thay i kch thc on ct vt ca tm

patch thu c kt qu t s trc (AR) nh hnh 4.

Hnh 4: AR khi delta_l thay i

Thay i kch thc tm patch lm thay i cc thng s k thut ca anten.

M hnh anten vi delta_l = 4,87mm c chn v cc thng s k thut tha


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mn yu cu v l ti u nht trong nhng m hnh trn.

III. Kt qu m phng v ch to anten tha mn yu cu

t ra

M hnh anten vi b dy lp in mi h = 3,2mm v delta_l = 4,87mm

chp nhn c vi yu cu t ra ca anten GNSS, di y l kt qu m

phng trn phn mm ANSYS HFSS vi thng s anten nh sau: Wp = Lp =

43,91mm, L = 4,87mm, r1l = 27,09mm, w1l = 2.21mm, r2l

= 10mm, w2l = 6,1mm, = 4,4, h = 3,2mm.


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Hnh 5: Phn b in trng

IV. Kt lun

Anten thit k nh trn tha mn yu cu ca anten GNSS, c th thy rt

n gin trong vic ch to. Cc thng s k thut ca anten c ti u t

c yu cu k thut.

Trong gii hn ca bi bo ny ch dng li vic thit k cc anten vi di

phn cc trn, tip in n dng ng truyn vi di. Mc d cc tham s

k thut t yu cu ca anten phc v cho ng dng GNSS, nhng t s

trc ca anten vn cn ln so vi yu cu t ra cho anten phn cc trn, hiu

sut s dng ca anten cha cao. ci thin cc tham s k thut anten, c

th thay i cch thc tip in, phi hp trkhng, to phn cc, s dng lp

c hng s in mi ln hn.

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THIẾT KẾ ANTEN VI DẢI CHO ỨNG DỤNG GNSS