Main WiFi Antenna :directional antenna & Omni-directional
The antennas can be divided into three categories according to the usage, the omnidirectional antennas issued by the main lobe horizontally, the omnidirectional antennas with the main lobe downwards, and the directional antennas. The so-called omnidirectional antennas mean that the radiation is distributed in the same shape at 360 degrees horizontally. We must select the appropriate antenna according to the environment, so that the most wireless devices can transmit wireless data at the required signal strength. In a large wireless network, choosing the right antenna and installation method can not only improve the overall coverage performance, but also reduce the number of APs to reduce costs.
Omnidirectional antenna with horizontal lobes
Can be connected to a wireless device or AP. If the AP and such an omnidirectional antenna are installed in a high place such as an outdoor 30-meter high lamp post, since the radiation shape of the antenna resembles a blisters, most of the signals are radiated horizontally, and the radiation distance is Increase, but under the antenna will cause blind spots, so the antenna of both sides of the transceiver needs to be at the same level.
In the warehouse, if the height of the bottom of the building is within ten meters, such an omnidirectional antenna can also be used. Although some of the upward energy is wasted, the main energy is horizontal radiation, so the coverage will be larger than other antennas. Below the antenna, although it is not within the width of the lobes, the side lobes with less energy are already providing good signal coverage because they are not far from the antenna.
Omnidirectional antenna with main lobe down
The radiation shape is similar to a hemisphere. The signal is emitted both outward and downward. Only a small amount of energy is emitted upwards, so that the wireless signal is evenly radiated and transmitted in the coverage area. It is most suitable for installation in some places higher than 20 meters, such as Covering wireless devices that require the same level and ground, such antennas are ideal.
This type of antenna has a smaller horizontal coverage area than an omnidirectional antenna that is issued horizontally at the main lobe, but the latter can only take into account the same level of wireless equipment.
In some warehouses with a floor of ten meters, it is not recommended to use such antennas. Because excessive energy is distributed near the bottom of the antenna, it is wasteful. We should use the omnidirectional antenna issued by the main lobe horizontally to maximize energy. Radiation in the horizontal direction to increase the coverage area.
The radiant energy is only distributed in a certain direction of the antenna. It has different gain, horizontal lobe width and vertical lobe width. It is suitable for the environment where the wireless device is in one direction of the AP. It is also used in point-to-point and point-to-point. Multi-point wireless system.
A directional antenna, as the name implies, focuses the wireless signal in a specific direction resulting in a limited coverage area. An analogy for the radiation pattern would be how a vehicle head light illuminates the road. High gain directional antennas can transmit and receive wireless signals for several miles given clear and sufficient transmit power. Applications for directional antennas include point to point wireless links connecting buildings, a back-haul data link connecting cell towers together and point to multi-point wireless links where multiple remote clients with directional antennas communicate with a single central tower with an Omni directional antenna.
Typical Directional Antenna Radiation Pattern
In the example above building A and building B are set up for a directional, point to point network using Yagi antennas.
Types of Directional AntennasIn this example both remote sites A and B have directional Wi-Fi connectivity to the base station fitted with an Omni directional antenna. This is an example of a point to multi-point set up.
Examples of directional antennas include Yagi, Parabolic Grid, Patch, and Panel antenna styles.
Omni directional antennas provide a 360° donut shaped radiation pattern to provide the widest possible signal coverage in indoor and outdoor wireless applications. An analogy for the radiation pattern would be how an un-shaded incandescent light bulb illuminates a room. A high gain Omni’s vertical radiation pattern will exhibit a flattened donut shape as shown below for the HG24215U-PRO. The typical application for Omni directional antennas include indoor office spaces, retail stores, warehouses, small office or home networks, outdoor cafés, campgrounds, RV parks and marinas. Omni-directional
Typical Omni directional Antenna Radiation Pattern (HG2415U-PRO)
The example above depicts an outdoor café that offers WiFi access to its customers. You can see the centrally located Omni antenna provides wireless signal to various laptops, tablets, and smart phones in the coverage area.
Types of Omni directional antennas
Examples of Omni directional antennas include the common "Rubber Duck" found on many WiFi access points and routers as well as the complicated antenna arrays used on cellular towers.
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MIMO antennas are mainly used in conjunction with 802.11n devices. Each transceiver component is equipped with more than one antenna (currently up to three) to increase the received signal and increase the transmission speed. Based on multi-path reflection, the signal transmitted from one point reaches another receiving point with more than one receiving antenna. Different antennas may receive direct signals and reflected signals with different degrees of different strengths and different polarities. Choose the best signal from it. In addition to the "omnidirectional antenna" issued by the main lobe horizontally, the current MIMO antenna will install three antennas in the same component, and three antennas in the directional antenna, one of which will be 90 degrees different from the other two. polarity.
The antenna is a passive body, that is, it does not need to provide power or other energy. It is not a power amplifier. It does not amplify the input wireless signal. On the contrary, due to the signal attenuation caused by the feeder and the connector, the wireless energy emitted will be compared to the input. The energy of the antenna contact is small. In fact, the antenna only acts as a directional amplifier, so that the transmission and reception energy is concentrated in a certain area of the space. Changing the energy distribution area to the required place is the sole purpose of the antenna. Some places without wireless devices, or excessive distribution of energy to a certain area are wasteful. According to the law of energy invariance, the energy is released in one direction and the energy in other areas is reduced.