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2008 IEEE AP-S-Internal Wideband Monopole Antenna For MIMO Access-Point Applications
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2008 IEEE AP-S-Internal Wideband Monopole Antenna For MIMO Access-Point Applications


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A three-antenna MIMO system capable of generating a wide operating bandwidth of 2400-5850 MHz for access-point applications is introduced. The proposed design is based on a bent metal-plate monopole …

A three-antenna MIMO system capable of generating a wide operating bandwidth of 2400-5850 MHz for access-point applications is introduced. The proposed design is based on a bent metal-plate monopole antenna with a compact size of 20 × 20 × 14 mm3. The three antennas are equally spaced along the perimeter of a circular ground and all generate a wide bandwidth of larger than 4 GHz. With the antenna short-circuiting facing the center of the ground, not only the overall antenna size is reduced but also good isolation of less than -20 dB can easily be obtained. Calculated envelope correlation is also less than 0.002 across the operating band.

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  • 1. 2008 IEEE AP-S International Symposium Internal Wideband Monopole Antenna for MIMO Access- Point Applications *Saou-Wen Su, Ph.D. Network Access Strategic Business Unit Lite-On Technology Corp., Taipei, Taiwan *E-mail: July 9, 2007
  • 2. Outlines (I) Introduction Conventional wideband antennas Conventional MIMO antennas MIMO technology and antenna design consideration (II) Design Considerations & Results Constructed prototype Antenna performance (III) Application Examples Antenna on desktop chassis Remote AP antenna (IV) Conclusion 2
  • 3. Conventional Wideband Antennas 1 Wideband planar monopole antenna antenna perpendicular to a large ground plane impedance matching controlled by shaping antenna geometry and/or adjusting antenna structure around feeding MOTL, vol 42, pp 463-466, IEEE AP, vol 53, pp 1626-1629, Sep 2004 Apr 2005 3
  • 4. Conventional Wideband Antennas 2 Wideband planar monopole antenna in various shapes and sizes 4
  • 5. Conventional MIMO Antennas 1 Height incl. antenna and enclosure at least > 80 mm Antenna type: dipole, monopole, collinear antenna D-link wireless N series Invax MIMO antenna 5 M.gear MIMO antenna
  • 6. Conventional MIMO Antennas 2 for 802.11b/g 3Com wireless 11n adapter for 802.11b/g/a Despite internal antennas, only single or dual-band Airgain MaxBeam smart antenna operation can be obtained 6
  • 7. 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 7 antenna platform design rules for MIMO wireless architectures, Intel
  • 8. 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) 8
  • 9. Design Consideration 1- Three-antenna MIMO system equally spaced along the perimeter of a circular ground MIMO system comprises: three bent, metal-plate monopole antennas and a circular ground; Flat plate onto a base of size 20 x 20 x 14 mm3 9 US/TW/CN patent pending
  • 10. Design Consideration 2- Proposed low-profile, wideband antenna Antenna mainly comprises: a shorted monopole antenna and a supporting metal plate; Antenna height about 11% wavelength of lower-edge operating frequency at 2.4 GHz prior art IEE Microwave AP, vol 153, pp 456-460, Oct 2006 10
  • 11. Design Consideration 3- S parameters and envelope correlation 10-dB RL BW easily covers entire band of 2400~5850 MHz; S21 remains < -20 dB S11: reflection coefficient S21: isolation Band 1: 2400-2690 MHz Band 2: 3400-3800 MHz Band 3: 5150-5850 MHz 11 MOTL, vol 48, pp 832-834, May 2006
  • 12. Design Consideration 4- Envelope correlation 1987 from far-field antenna radiation pattern 2003 from S parameters 2005 commonly cited! 12 correct form for 3 antenna!!
  • 13. Design Consideration 5- Measured 3-D radiation patterns Measured radiation patterns at 2.5, 3.6, and 5.5 GHz Peak gain levels about 2.4, 2.5, and 3.6 dBi over Bands 1, 2, and 3; Measured radiation efficiency > 73% 13
  • 14. Applications Examples 1.2- Antenna on desktop chassis antenna carrier three MIMO three MIMO antennas antennas strain relief on chassis antenna location US/TW/CN patent pending 14
  • 15. Applications Examples 2.2- Remote AP antenna antenna fed by long coaxial cable for flexibility in arrangement low profile low profile 20 mm only 20 mm only circular ground constructed prototype antenna 15 US/TW/CN patent pending old hat!
  • 16. Applications Examples 3.2- Indoor AP antenna 16
  • 17. Conclusion Proposed antenna has a low profile (14 mm) and is easy to construct by stamping a metal plate Wide BW covers entire 2.4/5-GHz WLAN and 2.5/3.5/5-GHz WiMAX bands with low isolation (< -20 dB) More designs of MIMO antennas embedded in wireless AP, desktop, and notebooks are in progress 17