Concurrent 2.4/5-GHz Multi-Loop MIMO Antennas with Wide 3-dB Beamwidth Radiation for Access-Point Applications
- 1. 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
- 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 (design example) Antenna performance (III) Related Multi-Antennas for wide/dual-band single radio for dual-band dual-radio (IV) Conclusion
- 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 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
- 4. 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
- 5. 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
- 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 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!
- 7. 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
- 8. 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
- 9. 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
- 10. 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
- 11. 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
- 12. 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
- 13. 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
- 14. 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
- 15. 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
- 16. 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
- 17. 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
- 18. 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
- 19. 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
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