Beyond Rabbit Ears
Antennas focus or broaden coverage in a specific direction by taking existing signal energy from the RF cabling and converting it to directed electromagnetic waves. One common misconception is that antennas increase absolute output power, but that's the role of an amplifier, not an antenna.
Of the four most popular antenna types--omnidirectional, patch, Yagi and parabolic--the latter two are almost never used to provide indoor coverage, especially for Wi-Fi. An omnidirectional antenna, also called a dipole or rubber duck antenna, is the most basic model included with almost all APs. Its coverage pattern is a doughnut shape around the antenna's vertical axis, and it's best used in the middle of buildings.
Patch antennas are square and flat, anywhere from 4 to 5 inches to a foot along one side, depending on the frequency required and amount of packaging around the array. They're used anywhere coverage must be directed, for example, at the ends of long hallways, or at the edges of building to focus coverage inward.
A new approach that's generating buzz is the use of DAS, or distributed antenna system. Rather than place APs at each location where coverage is required, radios are centralized and antennas are distributed. DAS technology has been used to provide better in-building coverage of cellular, PCS and public safety systems, but Wi-Fi is now being incorporated.
