Developing integrated antenna subsystems for laptop computers

IBM Journal of Research and Development, Mar/May 2003 by Liu, Duixian, Gaucher, Brian P, Flint, Ephraim B, Studwell, Thomas W, Et al

As expected, the integrated wireless system provides much better performance than the PC card version system. Performance, convenience, and mechanical strength ensure that the integrated wireless will lead the way for the WLAN in the new generations of laptops.

As mentioned in the Introduction, the 5-GHz band provides a data rate of 54 Mbps or more. Future generations of laptops will require integrated antennas for a 5-GHz band as well. A very likely scenario is a laptop supporting both 802.11b and 802.11a wireless LAN technologies. In this case, it is natural to have a dual-band antenna to cover both bands. Moving to the 5-GHz band raises the key issue of cable loss. Since the radio card is usually in the base of a laptop and the antenna is on the top of the display, the feeding cable length tends to be long, more than 50 cm in most implementations. The coaxial cable used for the integrated wireless has a very small diameter (around 1.1 mm) to allow routing through hinges, so the cable has more than 5 dB/m loss at 5 GHz. As a result, the cable loss will be more than 3 dB for the integrated wireless. A loss of 3 dB is very costly from the perspective of wireless performance. Therefore, more studies are needed for the 5-GHz wireless implementation.

Acknowledgment

This paper would not have been possible without the support and assistance of a number of people. We would like to thank the IBM Yamato ThinkPad design team for their contributions of range and performance testing as well as the production-level models used in this testing. Peter Lee of IBM Raleigh had both the foresight and tenacity to understand how important wireless communication would become, and to stick by his convictions providing the support to further this work. The authors also thank Frances K. O'Sullivan, Peter D. Hortensius, and Jeffrey W. Clark of IBM Raleigh, Arimasa Naitoh and Sohichi Yokota of IBM Yamato, Japan, and Ellen J. Yoffa, Mehmet Soyuer, and Modest M. Oprysko of IBM Yorktown for their leadership and vision in the ThinkPad antenna integration project.

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References

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