Wireless World
If you’re like me, the only time you remember antennas exist is when whatever is attached to the antenna, like a TV or FM radio, starts looking – or sounding – fuzzy.
But with wireless LANs, the time to start thinking about antennas is before, not after, you buy, according to Leslie Reading, CTO at Galtronics Inc., a Phoenix antenna and electronics manufacturer for 23 years.
Reading is not unbiased. Galtronics just recently launched a subsidiary, Pear Wireless, that will offer a line of IEEE 802.11b (and eventually 802.11a) wireless access points. The initial products are aimed at the so-called small-office/home-office (SOHO) market, but Pear will come out with an enterprise product in 2002. And it’s exploiting its antenna expertise to deliver some intriguing features.
Antenna design can affect everything from the range of your wireless LAN, to security, to the number of access points you have to deploy.
Think of radio waves like a water-filled balloon: you press one part of it, and another part increases. Antennas do this pressing. “You want the [radio] energy to come preferentially in one specific pattern,” Reading says.
Good antenna design, the quality of the cable that connects the antenna with the radio, and reflectors can “sculpt” the direction and spread of radio waves with surprising precision.
One of the key measures of an antenna is “gain,” in decibels (dB). An antenna with 10 dB of gain is sending out a narrower signal that’s 10 times stronger than a signal simply radiating out from the antenna in all directions, Reading says.
“Here’s the surprise, you increase the power sent in one direction. If the receiver [on the other end] has an antenna with the same gain, it increases the sensitivity of the receiver by 10 times. [With two 10-dB antennas] the next effect on the overall communications increases by a factor of 100,” Reading says.
Higher gain makes an antenna more “directive” and can make it more sensitive. But manufacturers can ignore or sacrifice electrical efficiency, Reading warns. “You can direct twice the power in one direction, but if you lose half of it getting it there, you haven’t improved anything,” he says. “There are lots of ways to throw away power, but not many ways to get it back.”
Cox is editor in chief for Network World (U.S.). He can be reached at
john_cox@nww.com
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