Antenna types fall into 3 main categories
- Omnidirectional
- Semi-directional
- Highly directional
Which will be discussed below.
Omnidirectional Antennas
Omnidirectional antennas radiate RF signal in all directions, a typical omnidirectional antenna is dipole antenna, that has a radiation pattern similar to figure 1.
Figure 1: Omnidirectional Antenna propagation pattern
Omnidirectional antenna are designed to provide coverage in all directions, the horizontal beamwidth of 360 degrees and the vertical beamwidth can range from 7 to 80 degrees, depending on antenna used.
Omnidirectional antennas are often used in following deployments
- Point to multipoint: A omnidirectional antenna is connected to a transceiver device that propagates it RF signal similar to figure 1. to multiple transceivers
- Wireless mesh deployment: provides a wireless network that allows network ingress locations where wired infrastructure is not available or possible. Wireless meshed networks provide multiple backhaul links, providing redundancy in the even one of the wireless nodes fails
- Indoor 802.11 wireless networks: wireless 802.11 access points can have internal or external omnidirectional antennas depending on the environment that they are to be used in. for example a corporate office would use access points with internal antennas for cosmetic reasons where a warehouse would have access points with external high gain antennas mounted at height to provide more coverage
Semi directional Antennas
Semi directional antennas are often used to direct signals in certain direction. i.e. down walk ways or warehouse aisles. where the signal requires a specific coverage as well they can be used in short-to-medium distance links i.e. between two buildings.
Semi directional antennas are unlike omnidirectional that propagates in all directions.
Figure 2: Semi directional Antenna propagation pattern
Common types of semi directional antennas are
- Yagi
- Patch
- Panel
- Sector
Highly directional antennas
Are to used for point-to-point communications which required a much narrower beamwidth to cover larger distances.
Figure 3. Highly directional Antenna propagation pattern
Two types of highly directional antennas
- Parabolic dish antenna
- Grid antenna
J.L. Olenewa (2014). Guide to Wireless Communication (Third Edition). Boston:CENGAGE Learning
D.A Westcoot, D.D Coleman (2014). Certified Wireless Network Administrator (Fourth Edition).Indianapolis: John Wiley & Sons, Inc.
