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Concurrent 2.4/5-GHz Multi-Loop MIMO Antennas with Wide 3-dB Beamwidth Radiation for Access-Point Applications
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Concurrent 2.4/5-GHz Multi-Loop MIMO Antennas with Wide 3-dB Beamwidth Radiation for Access-Point Applications

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A high-gain, wide-beamwidth, six-loop-antenna MIMO system suited for wireless access points in the concurrent WLAN 2.4 and 5 GHz bands is presented. The antenna system mainly comprises an antenna ...

A high-gain, wide-beamwidth, six-loop-antenna MIMO system suited for wireless access points in the concurrent WLAN 2.4 and 5 GHz bands is presented. The antenna system mainly comprises an antenna ground plane and single-band loop antennas, among which the three antennas are designated for 2.4 and 5 GHz operation respectively. The antennas are set in a sequential, rotating arrangement on the ground plane with an equal inclination angle of 60° to form a symmetrical structure, and the 2.4 and 5 GHz loops are facing each other one by one. The experimental results show that good port isolation can be obtained between antenna ports. High-gain, directional radiation patterns with wide 3-dB beamwidth in elevation planes are also observed. Details of a design prototype are described and discussed in the paper.

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Concurrent 2.4/5-GHz Multi-Loop MIMO Antennas with Wide 3-dB Beamwidth Radiation for Access-Point Applications Concurrent 2.4/5-GHz Multi-Loop MIMO Antennas with Wide 3-dB Beamwidth Radiation for Access-Point Applications Presentation Transcript

  • Concurrent 2.4/5-GHz Multi-Loop MIMO Antennas with Wide 3-dB Beamwidth Radiation for Access-Point Applications * Saou-Wen Su, Ph.D. Network Access Strategic Business Unit Lite-On Technology Corp., Taipei, Taiwan *E-mail: stephen.su@liteon.com
  • 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 (design example)
      • Antenna performance
    • (III) Related Multi-Antennas
      • for wide/dual-band single radio
      • for dual-band dual-radio
    • (IV) Conclusion
  • 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
    antenna platform design rules for MIMO wireless architectures, Intel Z 12 : induced voltage on ant.1 by driving current on ant. 2 http://www.eetasia.com/ART_8800432129_499488_TA_3d8cb44b.HTM
  • MIMO Antenna Design Consideration
    • Isolation (e.g. S 21 , S 12 )
      • 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
      • 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
      •  e < 0.3 ( Intel and Dell spec.)
      • can be derived directly from S parameters
    • 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)
    MOTL, vol. 47,Nov. 2005 integration of cellular and WLAN antennas EL, vol. 39, May 2003
  • MIMO AP/Router on the Market More and more antennas required From dual-radio to concurrent dual-band D-link wireless N series U4EA Fusion 50 HiveAP 300 series
  • 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
    2.4 GHz 5 GHz Diplexer Dual-Band Antenna 2.4 GHz 5 GHz Two-Antenna System single feed to/from antenna two feeds to/from two antennas comparable in size!
  • Concurrent Dual-Band Antennas 1 US patent no. 6535170 B2, Mar. 2003/Sony Corp. single-feed, dual-band antenna: achieve concurrent operation by adding extra diplexer component two-antenna system is self-diplexered
  • Concurrent Dual-Band Antennas 2 US/TW/CN patent pending swivel-type AP antenna coaxial cable is arranged to first go through monopole ground and then center of dipole ground MOTL, vol 51, May 2009 bottom end two coaxial cables in two-antenna system can affect mutual coupling between antennas
  • Concurrent Dual-Band Antennas 3
    • Two-antenna element comprises:
    • one 2.4 GHz monopole
    • one 5 GHz PIFA and
    • a common ground
    US/TW/CN patent pending TWO antennas excited by two separate feeds with a common ground MOTL, vol 50, Jun 2008
    • Different orientation of the AP can affect its communications coverage
    • on-table or table-stand AP: omnidirectional radiation in horizontal planes
    • ceiling-mount AP: conical radiation in elevation planes
    • wall-mount AP: broadside radiation
    AP Radiation-Pattern Concern omnidirectional broadside conical ceiling mount table stand wall mount
  • Design Consideration 1- Six-loop-antenna system US/TW/CN patent pending
    • Multi-antenna system:
    • a dodecagonal antenna/system ground
    • three 2.4 GHz loops and three 5 GHz loops
    • 6 loops are equally spaced along the perimeter with the inclination angle 60 degrees
  • Design Consideration 2- Design example US/TW/CN patent pending MADE of a 0.4-mm-thick alloy plate with only one set of mold for tooling; the ground can be circular as long as 6 loops are set thereon symmetrically
  • Design Consideration 2- Detailed dimensions
    • Two one-wavelength loops:
    • 2.4 GHz loop formed by a central loop with two tuning portions on the sides for tuning the center frequency without largely increasing the horizontal length
    • d 1 or d 2 affect both operating frequencies and impedance matching
    • g 1 or g 2 mainly influences operating frequencies
  • Experimental Results 1- Reflection coefficients and isolation reflection isolation
    • reflection coefficient < –10 dB for both bands
    • 2.4 GHz loop shows one 1.5-wavelength loop mode at about 4 GHz
    • 5 GHz antenna has a broadband 0.5-wavelength loop mode from 2.6 to 3.4 GHz
    isolation below –15 and –25 dB over the 2.4 and 5 GHz bands; good isolation below –25 dB (even < –35 dB for 5 GHz loops) between two identical antennas
  • Experimental Results 2- Measured far-filed, 2-D radiation patterns Radiation patterns at 2442 and 5490 MHz
    • directional patterns
    • wide 3-dB beamwidth in the x-z planes
    • high axial gain around the +z axis in the y-z planes with less backward radiation below the x-y planes
  • Experimental Results 3- Measured far-filed, 3-D radiation patterns
    • 3-D radiation patterns at 2442 and 5490 MHz for loops 1 and 6; wide beamwidth covering a quadrant in elevation planes; the ground behaves like a reflector for the 1.0-wavelength loops due to the suppression of surface currents on the ground
  • Related Designs 1- Dual-band single-radio antennas MOTL, vol 50, May 2008 IEEE AP, to appear in 2010 BW: 2400-5850 MHz (10 dB RL); isolation < – 20 dB 2.4 and 5 GHz bands (10 dB RL); isolation < –15 and –20 dB over the 2.4 and 5 GHz bands
  • Related Designs 2- Dual-band dual-radio antennas very-low-profile < 6 mm; isolation < – 15 and – 20 dB over the 2.4 and 5 GHz bands for high-gain, short-circuited AP antennas; isolation < – 25 dB MOTL, vol 51, Nov 2009
  • Conclusion
    • Proposed 6-loop-antenna system is of one-piece flat plate structure
    • Concurrent 2.4 & 5-GHz WLAN bands with low isolation (< –15 dB)
    • Compared to single-feed AP antennas using diplexers, proposed design loses no extra gain
    • Many multi-antenna designs for wireless APs are in progress
  • NA SBU ODM/OEM Product Line advanced consumer-electronics devices digital photo frame internet radio MP3/PMP Bluetooth headset/car hands free kit digital TV tuners DVB-T/WLAN combo TV dongle WLAN/Bluetooth/WiMAX modules AP/router full/half-size PCIe communications USB form factor WiMAX network hub BT dongle/PCMCIA antennas USB hub half-size mini-card
  • Lite-On Global Headquarters THANK YOU FOR YOUR ATTENTION!