microstrip antenna design for wlan 2.4ghz

T p o r n C n Ph n A: Khoa h c T n n, Cn n v M tr ng: 26 (2013): 97-104

97

THIT K ANTEN VI DI PHN CC TRN CHO NG DNG WLAN DI TN 2,4 GHZ V Ngc Li1 v Lng Vinh Quc Danh2 1 H v n C o n n thut n t, r n i h B o n ph H C M n

2 B mn n t Vin t n , o Cn n , r n i h c C n

Thng tin chung: N y n n: 08/01/2013 N y p n n: 19/06/2013

Title: Design of a Circularly Polarized Microstrip Antenna for 2.4 GHz WLAN Applications

T kha: Anten v d , p n trn, WLAN

Keywords: Microstrip antennas, circular polarization, WLAN

ABSTRACT This paper presents a circularly polarized microstrip antenna used for 2.4 GHz WLAN applications. The designed antenna consists of a circular patch fabricated on FR-4 substrate with a V-shaped slot carved on its surface and a circular metal plate (reflector). The antenna substrate is stacked above the reflector by a small distance. The antenna size and positions of the two feeding ports using coaxial cables are optimized to have a circularly polarized antenna with resonant frequency at 2.44 GHz, 8.43-dBi peak gain, and the isolation between the two ports below -20 dB. The simulation results show good agreement with the measurement. The proposed antenna can be used for 2.4 GHz wireless access points (APs) with 2x2 multiple-input multiple-output (MIMO) antenna systems. T T T N dun v t ny tr n y v mt nten v d p n trn o n dn WLAN d t n 2,4 GHz. Anten t t k o m mt tm m n FR-4 n trn v mt k e k n V v mt tm k m lo n trn (tm p n x ). Bn m n FR-4 t tm p n x mt k on n . t nten v v tr t 2 n vo (port) t p t n u s dn p n tr t u sn p n trn, t n s n n 2,44 GHz, l n 8,43-dB , v ly 2 n vo d 20 dB. C k t qu m p n p p v k t qu o t t . Anten n t s dn n mt nten p n kp o ess po nt (AP) d t n 2,4 GHz t n nten MIMO 2x2.

1 I I THI U Trong cc h thng thng tin khng dy,

cht lng tn hiu ph thuc rt nhiu vo h thng anten thu pht. c bit, loi anten vi di (microstrip antennas) vi c im nh gn, chi ph ch to thp, li kh cao, c s dng ph bin trong cc h thng thng tin

v tuyn hin i. Anten vi di l loi anten c xut u tin bi G. A. Deschamps vo nm 1953 [1], sau nhanh chng c pht trin, in h nh nh: ong, K. L. thit k anten planar cho h thng truyn thng khng dy [2], T. G. Abo-Elnaga, E. A. F. Abdallah, and H. El-Hennawy thit k anten phn cc trn bng rng cho b c th RFID (radio


98

frequency identification) di tn s 2,4 GHz [3], Dau-Chyrh Chang, Bing-Hao Zeng, and Ji-Chyun Liu vi thit k anten mng hiu sut cao [4]. Anten vi di c nhiu dng cu trc, c li v kiu phn cc sng khc nhau c th c thit k ty theo tng ng dng c th [5].

Bn cnh , sng in t c phn cc trn c xem l mt trong cc gii php c hiu qu lm gim nh hng ca hin tng phn x a ng multipath fading v c bit ph hp cho trng hp ngi s dng di chuyn vi trm pht sng c nh. c nhiu bi bo gii thiu cc loi anten phn cc trn c cng b trong thi gian qua, chng hn nh V. G. Kasabegoudar and K. J. Vinoy thit k anten vi di bng rng tip in ri c phn cc trn [6], S. A. Malekabadi vi anten phn cc trn s dng mt ng tip in [7]. Ni dung bi vit ny tr nh by vic thit k mt anten phn cc trn, c li cao, tip in bng cp ng trc vi 2 ng vo ng dng cho h thng WLAN di tn 2,4 GHz. Vi khe khc h nh ch V trn tm bc x bng vt liu mch in FR-4, cch ly gia 2 ng vo ca anten (S12, S21 c ci thin khong 6 dB so vi loi anten khng c khe khc ch V trn tm bc x FR-4. Ngoi ra, anten c thit k c th c s dng nh mt anten phn cc kp dual polarization trong thit b thu pht LAN vi h thng MIMO 2x2. Kt qu m phng trn my tnh cc thng s tn x S11, S22, S12, S21 c so snh vi kt qu o c thc t. li ca anten cng c kim chng thc t thng qua vic o c v so snh s dng AP vi anten c li 4 dBi. 2 THIT

Cc kch thc cng hng s in mi v k thut tip in ca anten l nhng vn quan trng trong vic thit k anten ni chung v anten vi di ni ring [8][9][1 ]. Thay i hng s in mi, iu ch nh v tr tip in cng vic tnh ton cc thng s k thut trn c s l thuyt a ra cc kch thc ban u cho vic thit k anten ch mang tnh c lng. T cc thng s ny ta s a ra cc

thng s ti u bng cch m phng anten s dng phn mm Ansys HFSS [11].

Cc thng s l thuyt ban u ca anten a trn [2] [5]:

Tn s cng hng ca

fre

r 2 8412.1 (1) Bn knh hiu dng ca tm patch c

tnh bi cng thc: 0.5

21 ln 1.77262e r

h aa a

a h (2)

Tn s cng hng ca anten GHzfr 44.2 . Mch in FR-4 vi: Hng s in mi 6.4r dy tm mch in mmh 6.1 .

1.84122e r r

a cf (3)

0.52

1 ln 1.77262

Fa

h FF hr

(4)

Vi: 98.791 10

r r

Ff (5)

Mt phn x c ng knh bng 2 . Khong cch gia mt phn x v tm

patch l 10

.

V tr t port 40r .

Vi l bc sng c tnh theo cng thc: 57

r r

cmm

f (6)

ci thin cch ly gia hai ng vo ca anten, mt khe khc h nh ch V c to trn nn tm mch in FR-4. H nh dng v kch thc ca khe khc h nh ch V c xc nh bng phng php ti u ha.


99

Qua qu tr nh hiu ch nh cc kch thc ca anten trn phn mm m phng HFSS nhm t c cc yu cu t ra, cc kch thc ti u ca anten t c nh sau: tm a phn x bng kim loi c bn knh r1 = 55 mm, bn mt a bc x FR-4 bn knh a = 28.6 mm t pha trn tm kim loi mt khong khng 2 ) h2 = 6 mm, tm mch in FR-4 c hng s in mi 6.41 , dy h1 = 1.6 mm. Mt trn nn tm mch in FR-4 khc mt khe h nh ch V v mt h nh trn ti tm c cc kch thc r2 = 3 mm, b = 10 mm,

c = 13 mm, d = 4 mm. Cu trc chi tit c th hin H nh 1 v H nh 2.

Bng k thut tip tn hiu bng cp ng trc vi 2 ng vo trn ng vung gc qua tm, cch tm mt khong r0 = 13 mm nh H nh 2. Cc kch thc ca anten c ti u t c s phi hp tr khng 5 ti cc ng vo, phn cc trn cng hng ti tn s 2,44 GHz, v cc thng s nh: li, suy hao phn x, cch ly gia hai ng vo t c nh yu cu t ra.

Hnh 1: Cu trc mt bn ca anten a trn

Hnh 2: Cu trc mt trn ca anten a trn 3 T QU PH N V O C

Anten c thit k v m phng trn phn mm Ansys HFSS. Cc thng s tn x S c o c bng my Vector Network Analyzer R&S ZBV8. T kt qu m phng v o c

c th hin qua cc h nh cho ta mt anten phn cc trn tn s cng hng ti 2,44 GHz, li nh 8,43 dBi H nh 3, H nh 4 , h s phn x S11 v S22 l 3 dB H nh 5, H nh 6 . cch ly gia hai ng vo S12 v S21 theo m

Bn mt trn

o

o

Ng vo 1

ro

ro a

r2

d

d

c

c

b b

r1

Tm phn x

Ng vo 2


100

phng so snh vi kt qu o c c tr nh by H nh 7. T s sng ng ti hai ng vo 1 v 2 l 1. 6 H nh 8a, v 8b , gc bp sng chnh ca anten l 6 0, bng thng ca anten l 200 MHz.

Ngoi ra, kim nghim thc t v li, anten c gn vo mt access point WLAN di tn 2,4 GHz, chun N c tnh nng MIMO 2x2 (vi 2 anten bc x ton hng li 4 dBi). Kt qu o c cng trung b nh ca tn hiu RF thu c mi trng c fading mnh ca anten a trn v anten ton hng ln lt l 55 dBm v 62 dBm H nh 9 , v mi trng c fading yu ca anten a trn v anten ton hng ln lt l 65 dBm v 72 dBm H nh 1 . Phn mm Netstumbler [12]

ci t trn my tnh xch tay c s dng trong cc o c ny. Kt qu m phng H nh 11 cng cho thy anten ngh, vi khe khc ch V trn tm bc x FR-4, c cch ly S12 (S21) trong di tn s 2,4 ~ 2,5 GHz c ci thin khong 6 dB so vi loi anten khng c khe ch V.

Kt qu m phng cc thng s S11, S22 ph hp vi s liu o c thc t. Kt qu o c thc nghim cng cho thy cng tn hiu LAN thu c ca anten a trn tt hn so vi trng hp s dng cp anten ton hng li 4 dBi. Nh vy, c th kt lun anten c thit k c nh hng, t s sng ng, bng thng v cch ly gia hai ng vo t yu cu t ra ban u.

Hnh 3: th bc x dng 2 ca anten

Hnh 4: th bc x dng 3 ca anten


101

Hnh 5: H s phn x S11

Hnh 6: H s phn x S22

Hnh 7: cch ly S12 (S21)

1 2 3 4 5 6 7 8-35

-30

-25

-20

-15

-10

-5

0

5

Frequency [GHz]

S11

dB

S11

simulatedMeasured

1 2 3 4 5 6 7 8-40

-35

-30

-25

-20

-15

-10

-5

0

5

Frequency [GHz]

S22

dB

S22

simulatedMeasured

1 2 3 4 5 6 7 8-35

-30

-25

-20

-15

-10

-5

0

Frequency [GHz]

S12

dB

S12

simulatedMeasured


102

(a)

(b) Hnh 8: T s sng ng VSWR ng vo 1 (a) v ng vo 2 (b)

Hnh 9: t qu o cng tn hiu WLAN trong mi trng fading mnh


103

Hnh 10: t qu o cng tn hiu WLAN trong mi trng fading yu

Hnh 11: t qu m ph ng S12 (S21) vi tm bc c v hng c he ch V 4 T LU N

Mt anten phn cc trn c thit k cho ng dng WLAN di tn 2,4 GHz. Kt qu v li, tn s cng hng, h s phn x, cch ly gia 2 ng vo thu c bng m phng s dng phn mm Ansys HFSS kh ph hp vi kt qu o c thc t. iu chng t anten c thit k t cc yu cu ra v li, v cc thng s tn x S. Anten ny c th c s dng nh mt

anten phn cc kp cho cc access point WLAN 2,4 GHz vi h thng anten MIMO 2x2.

LI CM T Tc gi chn thnh cm n cn b ph

trch Phng Th nghim Anten v Siu cao tn, Trng i hc Bch Khoa Tp. H Ch Minh, h tr trong vic o c cc thng s ca anten.

2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3-35

-30

-25

-20

-15

-10

-5

0

5

Frequency [GHz]

S12

dB

S11

Co khe chu VKhong co khe chu V


104

T I LI U THA HO 1. Deschamps, G. A., Microstrip microwave

antennas, Proceedings of Third USAF Symposium on Antennas, 1953.

2. Wong, K. L., Planar Antennas for Wireless Communications, Chap. 5, Wiley, New York, 2003.

3. T. G. Abo-Elnaga, E. A. F. Abdallah, and H. El-Hennawy, UWB Circular Polarization RFID Reader Antenna for 2.4 GHz Band, PIERS Proceedings, Xi'an, China, March 22 26, 2010.

4. Dau-Chyrh Chang, Bing-Hao Zeng, and Ji-Chyun Liu, High Performance Antenna Array with Patch Antenna Elements, PIERS Proceedings, Xi'an, China, March 22 26, 2010.

5. James, J. R. and P. S. Hall, Handbook of Microstrip Antennas, Peter Peregronic Ltd., London, 1989.

6. V. G. Kasabegoudar and K. J. Vinoy, a broadband suspended microstrip antenna for circular polarization, Progress In Electromagnetics Research, PIER 90, 353 368, 2009.

7. S. A. Malekabadi, circular polarized dielectric resonator antennas using a single probe feed, Progress In Electromagnetics Research C, Vol. 3, 81 94, 2008.

8. Wang, H., X. B. Huang, and D. G. Fang, A single layer wideband U-Slot microstrip patch antenna array, IEEE Antennas Wireless Propag. Lett., Vol. 7, 9 12, 2008.

9. Gupta, R. K. and G. Kumar, High-gain multilayered antenna for wireless applications, Microw. Opt. Technol. Lett., Vol. 5, No. 7, 1923 1929, 2008.

10. aterhouse, R. B., Design of probe-fed stack patches," IEEE Trans. Antennas Propag., Vol. 47, No. 12, 1780 1784, 1999.

11. Ansys HFSS software. URL: http://www.ansys.com/

12. Netstumbler software. URL: http://www.netstumbler.com/downloads/

microstrip antenna design for wlan 2.4ghz

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