WIFI Antenna Basic Knowledge
WIFI Antenna Basic Knowledge
Wireless wireless router single antenna, dual antenna, three antenna and other multi-antenna pair wireless signal
Whether the influence of signal intensity and scope has been enhanced
Use facts to debunk the myth of double antenna gain
Dual antennas can only reduce blind spots in the coverage area
Look at the summary first:
The difference in performance mainly comes from the chip rather than the brand
However, the performance gap of products using the same chip is not big at all, so it is an important link to understand the chipset of the product before buying. Of course, it does not mean to give up the concept of brand, each brand still has different control of product quality, which will also cause great differences in products (mainly reflected in product quality)
At this stage, 802.11N wireless routers have greatly surpassed 54M
It took several years from 54M to 11N, but we saw the advantages of 11N and hope in this Hengping review. The actual test shows that the overall performance of 11N products is much higher than 54M, with a qualitative leap in speed and coverage.
The number of antennas has nothing to do with speed
Although this evaluation is divided into two groups, dual-antenna and multi-antenna, the test results show that the speed is only
In terms of the above, there is not much difference between dual antennas and three antennas. (The antenna principle has been introduced, and our actual situation is
Consistent. Of course the comparison is based on the same type of chips, different types of chips are not comparable) But
There is indeed a difference in coverage, so users who want to buy do not always need to be obsessed with multiple antennas.
To start, dual antennas are sufficient for general environments.
New features will improve people’s habit of using wireless networks
For example, new features such as WPS fast encryption will improve people’s habit of using wireless networks.
Pressing the two keys on the terminal and router will automatically connect and encrypt, refuse to enter cumbersome passwords, and enter
This step lowers the threshold of wireless networks and makes it easier for users to use.
802.11N is the backbone of building a digital home
In addition to changing people’s habits, the transmission rate of 802.11N can fully cope with high-definition
The smooth transmission of movies, and the legendary digital home can also be played by the 802.11N network to support the whole
Two platforms: wireless playback of high-definition media files, wireless control of home appliances, and various terminals wirelessly, allowing your
Stay away from wiring troubles.
The current products are monotonous, and more personalized products are needed.
But then again, everything needs to be developed. Now 11N can be regarded as just released.
Tao, so there are still many things that can be improved. For example, in addition to providing wireless Internet access, the products tested this time
There are fewer additional functions to make IT products more individualized. This is a development direction that makes the invisible wireless
Can be colorful.
802. 11N Hengping first wave is over, more low-priced products will follow
The evaluation lasted for 1 month, and several new products appeared during the test, but they did not catch up.
This Hengping review is very regrettable, but we still have opportunities, because the low-price 11N era is coming soon.
Each brand will have more and more excellent products released, please continue to pay attention to the bubble network wireless channel, more refined
The color will come one after another.....
Data 1: 802.11g 802.11n coverage comparison
● 11g coverage
Compared with the current mainstream 11g, the 802.11n standard also claims to have a great improvement in coverage.
Rise. For example, Intel said, "The new wireless technology is better than the 802.11g network that is now commonly used in receiving signals.
The enclosure has been doubled", and most large network equipment manufacturers also stated in their promotional materials that "802.11n technology can
To cover the signal to a longer range", what about the actual situation? Most 802.11g claims
The transmission distance is up to 100 meters indoors and 400 meters outdoors (varies depending on the environment), and a few use
Line extension transmission technology products, it claims that the wireless transmission distance of its 802.11g products is the normal 11b, 11g production
The transmission range is extended to 4-9 times, the transmission distance can be up to 200 meters indoors, and the longest outdoors.
The distance can be up to 830 meters (depending on the environment). The coverage performance of the enhanced 54Mbps wireless router has also increased significantly
Strong Of course, this is the same as the nominal speed of wireless products, except for the maximum theoretical coverage and transmission distance.
Most of them are obtained by testing in a relatively ideal environment. The wireless signal will be interfered by many factors,
For example, various obstacles, many objects will partially or completely absorb wireless signals, or reflect them and diffract them.
We, such as metal and water, human body, etc. tend to absorb and reflect wireless signals, air, wood and glass
Although it tends to let the signals pass, it also weakens them. Other WLAN equipment, Bluetooth, microwave equipment (such as
Microwave ovens), battery phones, 2.4GHz cordless phones and copiers, etc. will affect the transmission of wireless signals.
Even including weather, the maximum transmission distance of wireless signals in sunny and cloudy days differs greatly. So various measured tables
Obviously, the actual transmission distance of ordinary 802.11g products is generally the farthest indoors is about 30 meters, and the farthest outdoors is 100.
Around meters (different depending on the environment).
● 11n coverage
What’s interesting is that although major network vendors claim that 802.11n technology can cover the signal
A farther range, but limited to the immaturity of the current standard, they have been "cautious" and have not given the actual coverage of 802.11n.
Cover distance. It’s just a general view that "3 send and 3 receive MIMO architecture is better than the common 2 send and 3 receive or single send and single receive.
The structure can provide better wireless transmission performance and stability; the application of SST technology can improve the medium and long distance and interference
Wireless transmission performance in large environments; CCA technology can automatically avoid channel interference and make full use of channel bundling advantages
Potential" and so on.
Is there any qualitative improvement in the coverage and transmission distance of 802.11n?
The current evaluation shows that compared with 11g products, 802.11n has the same coverage and transmission distance.
There is no major improvement (at least the current draft product is so), through the application of multiple antennas and various new technologies,
The more breakthrough of 802.11n is to increase the stability of signal transmission within the actual coverage distance and reduce the interconnection of products.
Blind spots that may appear at the time. However, the reinforced concrete walls that 11g products are difficult to penetrate are the same for 11n products
It is the sky, which is determined by the characteristics of the wireless signal, and cannot be changed by the product.
Data 2: Antenna and signal analysis of dual-antenna wireless routers and wireless APs
When it comes to wireless products, many people pay more attention to the signals of wireless products.
Theoretically, there is a range of 100 meters to 300 meters in the environment, and 35 meters to 100 meters in the office environment.
Cover range.
In fact, the theory is a bit different from reality. The wireless range of an AP cannot be determined uniformly.
The same product has different ranges. Everyone knows that wireless APs have antennas. The main purpose is to greatly enhance the signal.
To increase the transmission distance, we can often see that many products have an ap with an antenna and two antennas.
The ap of the line, many people wonder in the city, whether the ap of one antenna has a wide signal range or two antennas
The transmission signal range is wide? Is the transmission signal range of the AP of two antennas necessarily wider than that of one antenna? With this
For some questions, we conducted a focused discussion on this aspect.
Factors affecting the coverage of the signal
The signal coverage range of a wireless AP is related to many factors, in addition to environmental factors, there are
The parameters of ap itself are related. The transmission power of ap and the transmission power of antenna are the two dominant factors.
Externally, it is related to the encoding of signal processing by general ap.
The transmit power of the AP frankly affects the signal coverage, this is also the high-priced AP and the low-priced AP
The difference between the transmission power and the price will be higher. Manufacturers need to improve the efficiency of the AP, mainly in the AP
For the research and development of technology, we can look at this simple formula below: the power amplifier input is real
Signal level (db) = equipment output power (db)-cable attenuation (db)-connector attenuation (1db), from this
It can be seen from the formula that the actual signal level of the power amplifier input is related to the frank connection of the equipment output. For example:
The output is 64mw (180dbm), the attenuation of the 40m lmr400 cable is 8.8db, and the power amplifier inputs a real signal
For: 18dbm-8.8db-1db=8.2dbm≈32mw
On the other hand, the transmission power of the antenna also affects the signal coverage range of the antenna classification standards.
It can be roughly divided into omnidirectional antennas and directional antennas. For the same network segment, directional antennas are generally used.
For different network segments, omnidirectional antennas must be used. Generally speaking, most of the APs currently use dual antennas.
Line preset, it can be said that the newer AP uses dual antenna presets, and the previous APs use one
The root antenna preset is more appropriate.
AP analysis with two antennas
The dual antenna AP can improve the effective coverage, and the professional access point city provides two high-frequency plugs.
The two antennas of the same type are respectively connected to the two antennas. The distance between the installation positions of the two antennas is not strict, and it is more than one meter.
But when transmitting a signal, the wireless component will only pass through one of the plugs (main plug), but when receiving a signal,
The wireless component will select the higher signal noise ratio between the two antennas.
The received signal is based on multiple reflections. Two antennas separated by more than one meter will have different received signal-to-noise ratios.
When the wireless client computer transmits the wireless signal to the access point, in a complex use environment, a
By default, the antenna will receive a direct signal and a reflected signal at the same time. If these two signals show a certain degree of
"Reverse phase", the final received signal will attenuate the signal-to-noise ratio due to energy cancellation. At the same time, dual
The antenna is preset, because the antenna on one side is more than one meter away from the antenna on the other side, it receives direct and reflected signals
There may be a certain degree of "in-phase", so that the final received signal has a better signal-to-noise ratio.
Setting will bring an average signal-to-noise ratio gain of about 3db, thereby increasing the effective coverage.
In general, the gain value of the simple dipole antenna used on the ap is about 2.2dbi, but the two antennas are not
It will get a total gain of 4.4dbi, but it can or may support dual-antenna automatic selection (antenna
diversity) to improve the performance of the wlan network through a special technique.
Data 3: The relationship between transmit power and gain
Data 4: Hengping 802.11N wireless routing in 2008
To summarize the advantages of 802.11N, these keywords are: dual-frequency, MIMO, WPS, faster,
farther.
Dual frequency:
Everyone knows that data transmission requires channels, and 2.4Ghz only has three independent channels 1, 6, 11,
The previous 54M products only occupy one channel, while the 802.11N products will occupy one channel for faster wireless speed.
Two, so that the originally rare channel is even more tense. It’s a good technology, but it’s not complete. There will be no
There should be more and more wire signal fights, so if it is combined with 5Ghz, there will be more space.
This should be the most important issue currently facing wireless products.
MIMO:
Multiple Input Multiple Output, literally can be understood as wireless network through
Multiple antennas can send and receive synchronously, so the data transmission rate can be increased; in fact, the principle is that the network data passes more
After re-cutting, multiple antennas are used for synchronous transmission, so the receiving end will also have multiple antenna connections at the same time.
Receive, then use DSP to recalculate, according to the time difference, recombine the separated data, and then send
A correct and fast data flow.
Because the transmitted information is divided and transmitted, the flow of a single data is reduced and the transmission can be expanded.
Therefore, MIMO technology can not only increase the transmission speed of the wireless network, but also increase the coverage.
WPS:
The full name is WiFi Protected Setup, which is an optional certification item provided by the Wi-Fi Alliance
It is mainly used to simplify the settings and security configuration in the wireless LAN environment. This batch of products comes with this
Features. (Some are called AOSS and some are called QSS, but the functions are the same.) For novice users,
WPS escapes complicated encryption settings and brings more convenience to users. This feature will be available in the future
Widely used, wireless routers and wireless network cards will join this system, and future wireless connections will become ten
The points are simple.
Faster and farther:
I just said that due to the addition of MIMO, dual-frequency and other technologies, it has great speed and coverage.
Promote. The wireless standard transmission speed of 54M products is 3MB/s, this batch of 802.11N can surpass
10MB/s, it's not even faster. And through our actual test, there is indeed a lot of coverage
Growing up, 54M can really retire.
The story of two antennas and three antennas
Although I just introduced MIMO in general, regarding the difference between the 2 and 3 antennas of the wireless router,
I would like to explain in detail. In general, the 2 antenna products are mainly 1T2R MIMO or 2T2R MIMO
Two architectures, 3 antenna products are mainly 2T3R MIMO or 3T3R MIMO two MIMO architectures.
2T2R (2 sends and 2 receives) is the current standard MIMO technology of 2 Streams, with two data streams
It is transmitted through 2 antennas, and the receiving part is also 2 antennas.
The sending part of 2T3R (2 sending 3 receiving) is the same as 2T2R, but the receiving part adds 1 channel to receive.
More effective signals can be received in a farther and noisier environment, and more effective signals can be received in 3 channels.
Select the best deal in the number. Currently, most of the 11N products with 3 antennas use this 2T3R MIMO architecture.
The receiving part of 3T3R (3 sending and 3 receiving) is the same as 2T3R. At the same time, the sending part also adds 1 channel to send.
Send and send redundant signals to enhance signal reliability. (For example, TP-LINK’s 3-antenna products are 3T3R
MIMO architecture. )
In addition, there are some multi-antenna products, their principles are the same, we can analogize.
This reminds consumers not to blindly worship multi-antenna, they are no different from 2 antennas in terms of speed, (after
The speed test of the surface has proved that it can solve more dead spots in theory, but this depends on the environment.
Moreover, the 2 antennas in the current ordinary home environment are enough, so you don’t need to spend more money to choose multiple antennas.
My hobby.
Comparison test item 2: wireless transmission speed
Wireless transmission speed is an important performance indicator of wireless routers.
As the server side, connect to the wireless router, through Chariot to have Centrino 2 wireless module 5350
Notebook client to send data (with reverse transmission, notebook to
