What types of antennas are there? Detailed explanation of antenna types

祥嘉盛XJS

What types of antennas are there? Detailed explanation of antenna types [Copy link]

Since wireless networks use radio waves to transmit data signals and adopt radio frequency (RF) technology to send and receive data through the air, the role of antennas is extremely important. With the popularization of WLAN, many people are looking for antennas that can expand the coverage of wireless signals. Let's take a look at the types of antennas. Interested friends can choose the one that suits them best.

　　In most cases, the most direct way to expand the coverage of a wireless network is to replace the antenna with a high-gain one, or to install an external antenna, preferably an omnidirectional or directional antenna.

　 Directional Antenna

　　Directional antennas are usually used in point-to-point systems, and sometimes at the far end of a point-to-multipoint system. If you want to connect two different locations, it is recommended to use this type of antenna. Directional antennas mainly include: backfire antennas, flat antennas, Yagi antennas, parabolic antennas, etc.

　 Omnidirectional antenna

　　This type of antenna is usually used as the center point of a point-to-multipoint system, or in your car. The omnidirectional antenna is used as the center antenna to provide signals to other computers or devices (such as wireless printers, PDAs, etc.). You can also use 2 omnidirectional antennas to form a point-to-point system, but we usually don't recommend it because the signal is not concentrated and the effect is very poor. Common omnidirectional antennas include: vertical omnidirectional, ceiling antenna, rubber duckbill antenna, desktop antenna and mobile vertical antenna.

　 peer to peer

　　Point-to-point usually involves 2 different wireless APs, or building-to-building wireless connections. But there are exceptions, if your AP is across a river or valley, and you want to provide wireless access to multiple users, this is a point-to-multipoint approach, but use directional antennas.

　 Point-to-multipoint

　　Point-to-multipoint is usually used to share a WLAN, or to share an Internet connection with family members or neighbors. It can also be a WAP (Wireless Access Points) in a coffee shop, train station, airport, etc.

　 Signal coverage

　　The signal coverage range includes several major factors, including the output power of the wireless network card or router, the signal receiving sensitivity of the wireless network card, and the obstacles on the transmission path, such as trees, walls, etc. Since there are so many factors that affect your coverage range, it is impossible to explain it clearly here. But a common method is to choose a suitable antenna. Why do I say that? Because the output power is very small.

　　Most wireless cards have an output power of 32mw (+15dBm), which is about the same power consumption as a high-power LED. LEDs emit light and can be seen from a distance or through trees and buildings. Why is the output power so low? Because 802.11 operates at the same frequency as a microwave oven, 2.4 GHz.

　 Antennas for specific environments

　　A question we often ask is how to choose a suitable antenna for a specific environment. This is a simple and complex question, depending on the user's specific needs, that is, what you want to do. The current 802.11b (11 Mbps), 802.11g (54 Mbps) and SuperG (108 Mbps) standards provide a relatively good speed, and the signal effect mainly depends on the signal strength and noise of your wireless network card and wireless router. In other words: the greater the signal strength and the lower the noise, the better the signal.

　　There are many applications of wireless, in homes, offices, etc. Let's look at these applications.

　 family

　　Antennas for home use are the easiest to purchase and the easiest to choose and install. In most cases, you only need to use an antenna on the remote computer. We recommend that you use an antenna on the remote computer, because when you install it on the router, the signal will be extended to your neighbors and security will not be guaranteed. If you have multiple studies or a large house, you need to install an antenna on each computer so that the range and bandwidth can be improved. Every wall you need to pass through will reduce the strength of the signal. To achieve stronger signal strength and signal, we recommend installing a 5db antenna, desktop antenna, etc. on the remote PC. The best way is to test it with an antenna on the remote PC first.

　 office

　　The antennas in the office are generally required to be beautiful and aesthetically pleasing. If you want to be able to access the Internet while working anywhere in the office without using a network cable, then first you must buy a good quality wireless network card and then install the antenna on the wireless router to maximize the signal extension. It is very simple. However, if your office is divided into several different rooms or is very large, there will be some difficulties.

　 About Dual Antennas

　　Putting aside the influence of environmental factors, under the condition of a certain transmission power, dual antennas can effectively increase wireless coverage, bringing an average signal-to-noise ratio gain of about 3dB (the ratio of useful signal power to useless power). The antenna gain of wireless routers on the market is generally 2dBi, but this does not mean that two antennas are 4dBi. Dual antennas are not simply 1+1=2, but automatic coordination of two antennas, also known as antenna diversity. One antenna only receives, and the other receives and transmits. The router can continuously select the antenna with better reception to receive wireless signals, thereby achieving the ideal effect.

　 Antenna on the move

　　Why do you use wireless networks in your car? This is a very good question. In some developed countries, wireless services are now available throughout the city, and you can directly access the Internet in your car. WiMAX networks are developing in this direction, and in the near future, some major cities in China will also provide high-quality wireless access services.

　 Yagi Antenna

　　Yagi antennas were designed by two Japanese. Originally designed for radio equipment, they are now also used on 802.11 equipment. These antennas are highly directional and are usually used at the remote end of a point-to-point system or point-to-multipoint. For outdoor use, consider using a waterproof Yagi antenna, which has good signal strength and can reach several kilometers in some environments!

　 Backfire Antenna

　　The backfire antenna is a small directional antenna with a relatively high gain. This antenna looks like a round dish and is recommended for use in point-to-point or point-to-multipoint systems. The backfire antenna has a gain of 16dbi and a diameter of no more than 30cm.

　 Parabolic antenna

　　This is a real high-power antenna, much like a "dish" for receiving satellite signals, with very high gain, but it is difficult to align in the target direction. The greater the gain of the antenna, the narrower the beam and the stronger the directivity, so the more difficult it is to adjust. This type of antenna is usually used in long-distance point-to-point systems. When this type of antenna works, it concentrates power to a central point and focuses the wireless signal to a specific area, just like a turned on flashlight.

　　Issues to consider when choosing antenna gain

　　The antenna gain you need depends on the obstacles on the transmission path, the coverage range you need, and the performance of your wireless network card. These factors should be taken into consideration when choosing an antenna. For ordinary consumers, the antenna gain of wireless routers and APs currently on the market is between 2dBi, 3dBi and 5dBi, which can fully meet the needs of daily use. For users with special needs, there are 8dBi and 9dBi antennas available for users to replace.

　　About signal interference

　　Like all wireless devices, WIFI also has interference issues. Just like when you listen to the radio, sometimes you can hear some noise, which is interference. The same thing happens in WIFI systems, but it is not so obvious. The main factors that affect WIFI systems are microwave ovens, some specific lighting systems, other 802.11 devices, microwave transmission equipment, and even high-speed processors in computers can cause interference to 802.11 systems. These factors must be taken into consideration when you use wireless devices.

　　Summary: The most important things about wireless networks are speed and signal effects. The original equipment may not be able to meet our actual requirements, which requires the help of adding antennas. You can choose the most suitable one based on the actual situation.