T Phn A: Khoa hc T ng: 26 (2013): 97-104 97 THIT K ANTEN VI DNG DNG WLAN DI TN 2,4 GHZ c Li 1 c Danh 2 1 H thun ti hph H 2 B n t Vii hc C Thông tin chung: 08/01/2013 19/06/2013 Title: Design of a Circularly Polarized Microstrip Antenna for 2.4 GHz WLAN Applications Từ khóa: 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. - -4 - 2x2. 1 th chu ph thuc rt nhi th c bit, loi anten vi di (microstrip antennas) v m nh g to th lc s dng ph bi th n hi i. Anten vi d i anten xu i G. A. Deschamps c -Elnaga, E. A. F. Abdallah, and H. El-Hennawy thit k c ng cho b c th RFID (radio T Phn A: Khoa hc T ng: 26 (2013): 97-104 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 d u dng c l th c thit k ng ng dng c th [5]. in t mt gi u qu gim ng ca hi ng phn x c bing hi s dng di chuyn vi tr nhi i thi c trong thi gian qua, chng h Nc thit k m li cao, tin bng trc vng dng cho h thng WLAN di tn 2,4 GHz. Vi khe kh m bc x bng vt liu mch in FR- a anten (S 12 , S 21 c ci thin khong 6 dB so vi loc ch m bc x FR-c thit k c s d t anten t b i h thng MIMO 2x2. Kt qu x S 11 , S 22 , S 12 , S 21 i kt qu c thc t li c c kim chng thc t dng AP vi anten li 4 dBi. 2 u cho vic thit k anten ch c ng. T tng anten s dng phn mm Ansys HFSS [11]. u ca anten Tn s cng c a f re r 2 8412.1 (1) u dng ca t c c: 0.5 2 1 ln 1.7726 2 e r ha aa ah (2) Tn s cng ca anten GHzf r 44.2 . Mch in FR-4 vi: Hng s 6.4 r m mch in mmh 6.1 . 1.8412 2 e rr ac f (3) 0.5 2 1 ln 1.7726 2 F a hF Fh r (4) Vi: 9 8.791 10 rr F f (5) Mt phn x ng 2 . Kho a mt phn x m 10 . V t port 4 0 r . Vi c: 57 rr c mm f (6) ci thi ca anten, mt khe kh c to n tm mch in FR- c ca khe kh nh b T Phn A: Khoa hc T ng: 26 (2013): 97-104 99 u ch c c n m ng HFSS nh c t t n x bng kim lo r 1 = 55 mm, bn mc x FR- m kim loi mt kho 2 ) h 2 = 6 mm, tm mch in FR- ng s 6.4 1 h 1 = 1.6 mm. Mn tm mch in FR-4 khc m i c r 2 = 3 mm, b = 10 mm, c = 13 mm, d = 4 mm. Cc th hin Bng k thut tiu bng trc vi 2 t khong r 0 c cc t c s phi hp tr ng ti tn s li, suy hao phn x c t ra. 3 c thit k n m c c b R&S ZBV8. T kt qu c c th hi t anten n s cng ti 2,44 GHz, l s phn x S 11 22 12 S 21 Bn m o o r o r o a r 2 d d c c b b r 1 Tm phn x T Phn A: Khoa hc T ng: 26 (2013): 97-104 100 ph i kt qu s ng t 0 200 MHz. kim nghim thc t v li, anten c g t access point WLAN di tn 2,4 GHz, chu 2x2 (vi 2 anten bc x li 4 dBi). Kt qu a c mnh cng l u c ng l72 n mm Netstumbler [12] c s dng t qu ng ngh, vi khe khc ch m bc x FR- ly S 12 (S 21 ) trong di tn s 2,4 ~ 2,5 GHz c ci thin khong 6 dB so vi lo Kt qu S 11 , S 22 hp vi s lic thc t. Kt qu c thc nghi u c c vng hp s dng cng l kt lun anten c thit k u. th bc xa anten th bc xa anten T Phn A: Khoa hc T ng: 26 (2013): 97-104 101 s phn x S11 s phn x S 22 1 2 3 4 5 6 7 8 -35 -30 -25 -20 -15 -10 -5 0 5 Frequency [GHz] S11 dB S 11 simulated Measured 1 2 3 4 5 6 7 8 -40 -35 -30 -25 -20 -15 -10 -5 0 5 Frequency [GHz] S22 dB S 22 simulated Measured 1 2 3 4 5 6 7 8 -35 -30 -25 -20 -15 -10 -5 0 Frequency [GHz] S12 dB S 12 simulated Measured T Phn A: Khoa hc T ng: 26 (2013): 97-104 102 (a) (b) s ng VSWR T Phn A: Khoa hc T ng: 26 (2013): 97-104 103 t qu 12 (S 21 ) v 4 M c thit k cho ng dng WLAN di tn 2,4 GHz. Kt qu v li, tn s cng, h s phn x c bng ng s dng phn mm Ansys HFSS p vi kt qu c thc tu ng t c thit k c ra v l c s d t WLAN 2,4 GHz vi h thng anten MIMO 2x2. LI CM T ph t i h tr trong vic 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 S 11 Co khe chu V Khong co khe chu V T Phn A: Khoa hc T ng: 26 (2013): 97-104 104 O 1. 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