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2009 EuCAP-Hybrid of Monopole and Dipole Antennas for Concurrent WLAN AP


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A novel hybrid of a 2.4-GHz monopole antenna and a 5-GHz dipole antenna is presented to provide concurrent 2.4 and 5 GHz band operation for access- point applications. The two antennas are arranged in a collinear structure and printed on a compact dielectric substrate with dimensions 12 mm × 60 mm. The monopole antenna has a meandered radiating strip and is short-circuited to a small ground plane through a shorting strip. The dipole antenna includes two sub-dipoles at the opposite side of a narrow ground plane and fed by a simple T-junction microstrip-line network. The two antennas are closely set with a distance of 1 mm only, yet good port isolation (S21) well below –20 dB can be obtained. With a low profile, the proposed design can easily fit into the casing of some standard access points and allow the 2.4 and 5 GHz band signals to be simultaneously received or transmitted with no external diplexer required. Good omnidirectional radiation has been observed too.

Published in: Technology

2009 EuCAP-Hybrid of Monopole and Dipole Antennas for Concurrent WLAN AP

  1. 1. 3rd European Conference on Antennas and Propagation Hybrid of Monopole and Dipole Antennas for Concurrent 2.4- and 5-GHz WLAN Access Point *Saou-Wen Su, Ph.D. Network Access Strategic Business Unit Lite-On Technology Corp., Taipei, Taiwan *E-mail: Mar 24, 2009
  2. 2. Outlines (I) Introduction MIMO technology and antenna design consideration MIMO AP/router on the market Concurrent vs. dual-band operation; concurrent dual-band antennas (II) Design Consideration & Results Constructed prototype Antenna performance (III) Application Examples Antenna integrated with APs Remote AP antennas (IV) Conclusion 2
  3. 3. MIMO Technology use multiple antennas to increase data throughput signals transmitted in the same radio channel at the same time multiple wireless data capacity w/o extra frequency spectrum multidimensional signals: each of multiple signals is transmitted from a different radio and antenna Closely spaced antennas give rise to mutual coupling Effects of mutual coupling change in driving point impedance of each antenna less efficient power transfer change in radiation pattern constructive and destructive interference Z12: induced voltage on ant.1 by driving current on ant. 2 3 antenna platform design rules for MIMO wireless architectures, Intel
  4. 4. MIMO Antenna Design Consideration Isolation (e.g. S21, S12) larger antenna separation results in less mutual coupling (better isolation) for two antennas at the same frequency, the separation is empirically chosen about 0.5 wavelength of the antenna operating frequency for isolation < -15dB arrangement of antennas and positions of antenna short-circuiting can largely affect isolation integration of cellular and WLAN antennas MOTL, vol. 47,Nov. 2005 with design techniques, we can locate antennas in the vicinity while maintaining small isolation level Envelope correlation numerically/experimentally obtained from far-field radiation pattern of the antenna ρe < 0.3 (Intel and Dell spec.) can be derived directly from S parameters EL, vol. 39, May 2003 Radiation pattern (polarization) Other issues coaxial-cable loss (attenuation) (dB/m): @2.4 GHz ~ 2.7 dB; @5.2 GHz ~ 4.1 dB cable routing (1.13mm, manufacturing) and length (power) 4
  5. 5. MIMO AP/Router on the Market more d a nd uire M ore as req e nn ant HiveAP 300 series D-link wireless N series io to d l-rad l-ban dua dua From rrent u conc U4EA Fusion 50 5
  6. 6. Concurrent vs. Dual-Band Operation for efficient spectrum usage, concurrent operation is demanded conventional dual-band antenna has one RF port external diplexer between the antenna and two modules is needed for concurrent operation/additional insertion loss single feed to/from antenna 2.4 GHz Dual-Band Diplexer Antenna 5 GHz comparable in size! 2.4 GHz Two-Antenna System 5 GHz two feeds to/from two antennas 6
  7. 7. Concurrent Dual-Band Antennas 1 single-feed, dual-band antenna: achieve concurrent operation by adding extra diplexer component two-antenna system is self-diplexered US patent no. 6535170 B2, Mar. 2003/Sony Corp. 7
  8. 8. Concurrent Dual-Band Antennas 2 also refer to 2-in-1 antenna system two-dual-band dipoles set in collinear structure; single-band operation for each dipole antenna for concurrent operation TW patent no. M274658, Sep. 2005/JOYMAX 8
  9. 9. Concurrent Dual-Band Antennas 3 two antennas excited by two separate feeds with a common ground Two-antenna element comprises: one 2.4 GHz monopole one 5 GHz PIFA and a common ground 9 US/TW/CN patent pending
  10. 10. Design Consideration 1- Two-antenna MIMO system MIMO system: 2.4G monopole and 5G dipole collinear structure substrate: 12 mm x 60 mm 1 mm small gap between antennas 10 US/TW/CN patent pending
  11. 11. Design Consideration 2- Applications in swivel-type AP swivel-type access point two coaxial cables in two- antenna system can affect mutual coupling between antennas coaxial cable is arranged to first go through monopole ground and then center of dipole ground bottom end 11 US/TW/CN patent pending
  12. 12. Design Consideration 3- Detailed dimensions 2.4G monopole: small ground: 12 × 15.5 mm2 S-shaped radiating strip meandered shorting strip: better impedance matching; 5G dipole: two back-to-back sub-dipoles T-junction microstrip-line network 12
  13. 13. Experimental Results 1- Reflection coefficients and isolation measured measured 10-dB RL BW covers 2.4 and 5 GHz bands; S21 remains < -20 dB when no gap between two antennas, S21 deteriorate by about 10 dB simulated simulated 13
  14. 14. Experimental Results 2- Measured far-filed radiation patterns Radiation patterns at 2442 and 5490 MHz Omnidirectional radiation in horizontal plane; 2.4G monopole radiates dipole-like radiation 14
  15. 15. Applications Examples 1- Antenna integrated with APs single-feed dual- band antenna paddle antenna 3 concurrent dual-band antennas inside 15 Linksys WRT300N Router
  16. 16. Applications Examples 2- Remote AP antennas antenna fed by long coaxial cable for flexible deployment rubber duck antennas proposed antennas Invax MIMO antenna M.gear MIMO antenna replace 3 single-feed, rubber duck antennas by 3 concurrent dual-band Buffalo WZR-AG300NH antenna systems: 3 6 MIMO antennas 16
  17. 17. Conclusion Proposed two-antenna system is compact and easy to fabricate on PCB Concurrent 2.4 & 5-GHz WLAN bands with low isolation (< -20 dB) Compared to single-feed AP antennas using diplexers, proposed design loses no extra gain More multi-antenna designs for wireless APs are in progress 17
  18. 18. NA SBU ODM/OEM Product Line advanced consumer-electronics devices WLAN/Bluetooth/WiMAX modules USB form factor full/half-size PCIe MP3/PMP WiMAX communications digital photo frame network hub BT dongle/PCMCIA internet radio USB hub antennas AP/router digital TV tuners Bluetooth headset/car hands free kit TV dongle half-size mini-card 18 DVB-T/WLAN combo
  19. 19. Lite-On Global Headquarters THANK YOU FOR YOUR ATTENTION! 19