Wireless antennas are the elements of a radio communications system that radiates and/or collects radiofrequency energy. It is usually connected to using a low loss coaxial cable either to a power amplifier, splitter, and filter or directly to wireless devices. For outdoor usage, wireless antennas are often attached via mounting clamps to a mast or the side of a building via mounting brackets. Wireless Antennas used indoors are typically ceiling mounted or wall mounted.
A wireless antenna also an important element of APs. The business class APs uses external wireless antennas for better results. Cisco uses different types of antennas with 802.11 APs. The type of antenna depends on deployment conditions, layout, and distance coverage. APs can use. The figure below illustrates the general type of Wireless Antennas.
Omni Directional Wi-Fi Antennas
Omnidirectional antennas cover 360-degree area and are better for an open area for example hallways, conference rooms and outside areas. This type of antenna sends out and receives signals from all directions. The Omnidirectional antennas are commonly used on Wi-Fi routers and mobile adapters that support connections from several directions. Wi-Fi devices and APs usually use basic dipole antennas of the rubber duck design. These antennas usually have again between 2 and 9 dBi.
Directional Wi-Fi Antennas
Directional antennas spot the lobs in the specific direction. The directional antenna provides better gain. Directional Wi-Fi Antenna enhances the signal strength while receiving and transmitting. The drawback of the directional antenna is that it sends and receive strong signals only in one direction and less signal strength in all other directions. Directional antennas are usually used to extend the range of a Wi-Fi network into hard-to-reach areas of buildings or in situations where 360-degree coverage not required.
Yagi antenna is used for long-distance communication. A Yagi antenna is another type of directional radio antenna that can be used for long-distance Wi-Fi networking in a specific direction. These antennas are extremely high gain used with outdoor APs to extend the gain up to 12 dBi or higher.
MIMO technology increased wireless bandwidth. The IEEE 802.11n/ac/ad standard uses MIMO technology. The MIMO technology uses several antennas to send and receive more data than possible using a single antenna. Four antennas can be used to increase throughput. All wireless routers are not the same. For example, 802.11n routers have the capacity of 150 Mbps using one Wi-Fi radio with one antenna. We can get more data using more than one radios and antennas in parallel. We can add more radio to the network in parallel. Each radio will increase the 150 Mbps data speed into the router.