What Is an Omnidirectional Antenna?

An omnidirectional antenna, that is, 360 ° uniformly radiates on the horizontal pattern, which is usually referred to as non-directional, and appears as a beam with a certain width on the vertical pattern. Generally, the smaller the lobe width, The greater the gain. The omnidirectional antenna is generally applied to the station type of suburban districts in mobile communication systems and has a large coverage area. ^[1]

An omnidirectional antenna will transmit signals in all directions, and can receive signals from front to back, left and right. A directional antenna is like a bowl-shaped reflecting surface behind the antenna. The signal can only be transmitted to the front. The signal directed to the back is blocked and reflected by the reflecting surface Going forward, strengthens the signal strength in the front. The following figure shows the signal radiation pattern of a directional antenna. The main radiation range of a directional antenna resembles an inverted, incomplete cone. ^[2]

If multiple sites need to be met, and these sites are distributed in different directions of the AP, an omnidirectional antenna needs to be used; if concentrated in one direction, a directional antenna is recommended; it is also necessary to consider whether the antenna connector form

For outdoor antennas, lightning protection equipment needs to be added between the antenna and the wireless AP; the directional antenna should pay attention to the front of the antenna facing the far site; the antenna should be installed as high as possible, and the line of sight between the antenna and the site should be as close as possible (Visible to the naked eye, avoid obstacles in the middle).

Omnidirectional antenna array

It is difficult for general unit antennas to form omnidirectional radiation. We can consider forming them into an array so that the array antenna can form an omnidirectional pattern. In addition, the gain of a single antenna is generally limited. By forming an array, the gain can be increased to meet the requirements of the omnidirectional high gain we want to design. ^[1]

Microstrip omnidirectional antenna

Microstrip antennas have become a key technology in the field of antennas due to their simple structure, low processing costs, and light weight. Therefore, microstrip antennas with various performances are being studied, and omnidirectionality has become the development of microstrip antennas. A trend, such as the use of microstrip transmission lines for cross-feeding, can achieve the omnidirectional radiation performance of microstrip antennas. A multi-point excited linear array antenna. The antenna is formed by cascading multiple / 2 microstrip segments. The floor and conduction band of the microstrip segment are placed alternately on both sides of the dielectric substrate, and the width of the microstrip floor is Varying, the use of cross connection to achieve the purpose of phase inversion. In addition to the transmission mode in this structure, there is also a radiation mode formed by the discontinuity of the cross connection points. The wave is transmitted along the conduction band and the inner surface of the floor. The size of the radiation is controlled by the width of the floor. Limited to approximately / 4. In order to achieve good radiation efficiency of the antenna, impedance matching can also be performed. A rectangular patch is added to each conduction band, and the matching is improved by increasing the reactance component. ^[1]