Chapter 19: The Antenna

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Overview

Antennae are so important to a WLAN's success that the reader should understand antenna technology. This chapter will provide a quick tutorial on antennae in a WLAN environment.

An antenna has two purposes: (1) transmitting data via radio waves, and (2) receiving data via radio waves. Metal is generally used in the construction of antennae, in particular those metals that are electrical conductors, as they will absorb radio signals that occur in the space around it. Conversely, given enough feed power, a metal object will emanate radio signals into the atmosphere. The shape and structure of the "metal" affects the behavior of the antenna.

Antennae increase the range of a WLAN. However, choosing an antenna involves many factors such as coverage area, maximum distance, and location. A detailed site survey is essential.

Providing adequate RF coverage is a primary concern when deploying a WLAN. This is where the antenna plays a vital role. When a WLAN is designed around an effective antenna solution, it's possible not only to increase the WLAN's range and corresponding coverage, but also to decrease its overall costs due to the need for fewer access points.

Ironically, the development and adoption of wireless networking for PCs was initially hampered by the fact that major PC companies were data and digital experts, but not experts in high-speed analog and antenna design. Now, of course, the technology has become popular (first in Europe and now in the U.S.), and many PCs and laptops have small PCMCIA ("PC Card") network interface cards equipped with small antennae or even hidden, built-in antennae.

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