T Phn A: Khoa hc T  ng: 26 (2013): 97-104 97 THIT K ANTEN VI DNG DNG WLAN DI TN 2,4 GHZ c Li 1 c Danh 2 1 H thun ti hph H  2 B n t Vii hc 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     chu ph thuc rt nhi th    c bit, loi anten vi di (microstrip antennas) v  m nh g to th lc s dng 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 thit k   c ng cho b c th RFID (radio  T Phn A: Khoa hc T  ng: 26 (2013): 97-104 98 frequency identification) di tn s 2,4 GHz [3], Dau-Chyrh Chang, Bing-Hao Zeng, and Ji-Chyun Liu vi thit k anten mng hiu sut cao [4]. Anten vi d u dng c  l th c thit k  ng ng dng c th [5]. in t   mt gi u qu   gim  ng ca hi ng phn x      c bing hi s dng di chuyn vi tr       nhi   i thi     c     trong thi gian qua, chng h           Nc thit k m li cao, tin bng trc vng dng cho h thng WLAN di tn 2,4 GHz. Vi khe kh m bc x bng vt liu mch in FR-  a anten (S 12 , S 21 c ci thin khong 6 dB so vi loc ch m bc x FR-c thit k   c s d  t anten t b i h thng MIMO 2x2. Kt qu   x S 11 , S 22 , S 12 , S 21 i kt qu  c thc t  li c   c kim chng thc t   dng AP vi anten  li 4 dBi. 2                             u cho vic thit k anten ch c ng. T          tng anten s dng phn mm Ansys HFSS [11].      u ca anten  Tn s cng c a f re r  2 8412.1  (1)   u dng ca t  c c: 0.5 2 1 ln 1.7726 2 e r ha aa ah               (2) Tn s cng ca anten GHzf r 44.2 . Mch in FR-4 vi: Hng s  6.4 r   m mch 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) Vi: 9 8.791 10 rr F f    (5) Mt phn x ng  2 . Kho  a mt phn x  m  10  . V t port 4 0  r . Vi  c: 57 rr c mm f    (6)  ci thi        ca anten, mt khe kh c to n tm mch in FR- c ca khe kh nh b T Phn A: Khoa hc T  ng: 26 (2013): 97-104 99    u ch   c c   n m  ng HFSS nh c t        t  n x bng kim lo    r 1 = 55 mm, bn mc x FR-      m kim loi mt kho   2  ) h 2 = 6 mm, tm mch in FR-  ng s   6.4 1      h 1 = 1.6 mm. Mn tm mch in FR-4 khc m i c r 2 = 3 mm, b = 10 mm, c = 13 mm, d = 4 mm. Cc th hin   Bng k thut tiu bng trc vi 2  t khong r 0  c cc t  c s phi hp tr  ng ti tn s   li, suy hao phn x        c t ra.   3  c thit k n m  c c b R&S ZBV8. T kt qu c c th hi   t anten n s cng ti 2,44 GHz,  l    s phn x S 11  22     12  S 21  Bn m o o  r o r o a r 2 d d c c b b r 1 Tm phn x  T Phn A: Khoa hc T  ng: 26 (2013): 97-104 100 ph i kt qu     s ng t   0  200 MHz.  kim nghim thc t v  li, anten c g t access point WLAN di tn 2,4 GHz, chu 2x2 (vi 2 anten bc x   li 4 dBi). Kt qu  a  c   mnh cng l  u c ng l72    n mm Netstumbler [12]       c s dng      t qu  ng   ngh, vi khe khc ch m bc x FR-  ly S 12 (S 21 ) trong di tn s 2,4 ~ 2,5 GHz c ci thin khong 6 dB so vi lo  Kt qu  S 11 , S 22  hp vi s lic thc t. Kt qu c thc nghi u c c vng hp s dng cng  l    kt lun anten c thit k          u.  th bc xa anten  th bc xa anten T Phn A: Khoa hc T  ng: 26 (2013): 97-104 101  s phn x S11  s phn 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 Phn A: Khoa hc T  ng: 26 (2013): 97-104 102 (a) (b)  s ng VSWR      T Phn A: Khoa hc T  ng: 26 (2013): 97-104 103    t qu 12 (S 21 ) v 4  M    c thit k cho ng dng WLAN di tn 2,4 GHz. Kt qu v  li, tn s cng, h s phn x  c bng  ng s dng phn mm Ansys HFSS p vi kt qu c thc tu  ng t  c thit k    c ra v  l       c s d  t         WLAN 2,4 GHz vi h thng anten MIMO 2x2. LI CM T         ph         t  i h       tr trong vic  ca 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 Phn A: Khoa hc T  ng: 26 (2013): 97-104 104 O 1.   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. Wan single layer wideband U-Slot microstrip patch IEEE Antennas Wireless Propag. Lett., Vol. 7, 9  12, 2008. 9. -gain multilayered antenna for wireless Microw. Opt. Technol. Lett., Vol. 5, No. 7, 1923  1929, 2008. 10. -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 for 2.4 GHz WLAN Applications Từ khóa:  WLAN Keywords: Microstrip antennas, circular polarization, WLAN. ng: 26 (2013): 97-104 97 THIT K ANTEN VI DNG DNG WLAN DI TN 2,4 GHZ c Li 1 c Danh 2 1