The difference between omnidirectional and directional antennas
Antennas have different radiation or reception abilities in different directions of space, which is the directionality of antennas. According to the different directionality, there are two types of antennas: omnidirectional and directional. Below, we will mainly explain the differences and related parameters between them.
Omnidirectional antenna:
Omnidirectional antenna, which exhibits uniform radiation at 360 ° on a horizontal pattern, is commonly known as directionless. In general, the smaller the lobe width, the greater the gain. Omnidirectional antennas are generally used in communication systems for their close range, wide coverage, and low cost. The gain is generally below 9dB. The following figure shows the signal radiation diagram of an omnidirectional antenna.
The radiation range of an omnidirectional antenna is more like an apple
Directional antenna:
Directional antennas exhibit radiation within a certain angle range on a horizontal pattern, which is commonly referred to as directional. Like omnidirectional antennas, the smaller the lobe width, the greater the gain. Directional antennas are generally used in communication systems in environments with long communication distances, small coverage range, high target density, and high frequency utilization.
We can also think about the relationship between omnidirectional antennas and directional antennas in this way: omnidirectional antennas emit signals in all directions, and signals can be received in all directions, front, back, left, and right. Directional antennas are like a bowl shaped reflection surface behind the antenna, and signals can only be transmitted to the front. Signals that are directed to the back are blocked by the reflection surface and reflected to the front, enhancing the signal strength in front. The following figure shows the signal radiation diagram of the directional antenna.
The main radiation range of directional antennas is like an inverted and incomplete cone
Through the above text, we can vividly understand what omnidirectional antennas and directional antennas are. So what should we pay attention to in practical applications?
If the antenna selection needs to meet the requirements of multiple sites, and these sites are distributed in different directions of the AP, omnidirectional antennas need to be used; If concentrated in one direction, it is recommended to use directional antennas; In addition, it is necessary to consider whether the joint form of the antenna matches the AP, and whether the gain size of the antenna meets your needs;
The installation of antennas requires the addition of lightning protection equipment between outdoor antennas and wireless APs; Directional antennas should pay attention to the direction of the antenna's front facing the remote site; The antenna should be installed at the highest possible position, and the distance between the antenna and the station should be as close as possible to the line of sight (visible to the naked eye, avoiding obstacles in the middle).
·Common antenna gains: whip antenna 6-9dBi, Yagi antenna 15-17dBi for GSM base station, and parabolic directional antenna can easily achieve 24dBi.