On Mon, 4 Nov 2002, raines wrote:
> >Antenna System Is Said to Expand Wireless Internet Use > >By JOHN MARKOFF Hrm, Markoff. N.B. > >AN FRANCISCO, Nov. 3 � A start-up company plans to announce new antenna > >technology on Monday that it says can expand the limits of a popular > >wireless Internet format, providing access to hundreds or even thousands > >of portable computer users at distances of more than 2,000 feet within > >buildings and about four miles outdoors. Hrm. Well, I'd like to see a practicle application of this. > >The Vivato technology, which stems from 1950's research for so-called > >phased-array antennas for military applications, makes it possible to > >electronically steer numerous radio beams from a single point. Focusing > >the beams increases their signal strength, and using large numbers of them > >greatly increases the antenna's traffic capacity. Phased arrays are nothing new, though not exactly common. We use this technology on our antenna (http://www.aerialix.com) The problem with all this beam-focusing is it ends up like trying to read with a laser pointer: If you hit the right spot, it works well but if you stray off a degree, it doesn't work at all. And while it might be possible to have the pinpoint signal follow a single user, it would become quite complicated and unpredictable to follow a number of them, even if you knew exactly where they were. Now the electronic steering -- I have several ideas on how to do this, but don't want to go too deep into antenna tech here. Instead of trying to find a one-size-fits-all solution, it would be better to find the right antenna for the job. Mesh networks, point-to-point applications, infrastructured networks, have different requirements. Geography and user behavior also play an important part. Also important is quality construction -- better conductors make better antennas, and the physical form of the antenna can be quite important for maximum performance. Deformation due to imprecise machining or damage in use caused by thin, fragile materials can be of great concern. This will be even more important as we move up in frequency from 802.11b to 802.11a. I could go on and on, about polarization, impedance matching, angles of radiation, etc. but until there's a forum for WLAN antennas, I'll just pipe down. Bob Keyes -- general wireless list, a bawug thing <http://www.bawug.org/> [un]subscribe: http://lists.bawug.org/mailman/listinfo/wireless
