When it comes to antennas, everyone must be familiar.
In modern society where wireless technology is very popular, antennas are everywhere in our lives.
The most common one is, of course, the base station antenna used by our mobile communication network.
Base station antennas are essential to our lives. Without it, our mobile phone would have no signal, and we would not be able to happily shop online, chase dramas, and eat chicken.
If you observe carefully, you will find that the antennas of different devices have different shapes and sizes.
That's right! In theory, the ideal length of an antenna is usually 1/4 of the electromagnetic wave wavelength.
Therefore, we will see that the length of the analog TV rod antenna is generally 0.175 ~ 0.5 meters, and the length of the FM radio antenna is 0.675 ~ 0.85 meters.
And our mobile communication network, the operating frequency is mainly between 700M ~ 3500MHz, so the size of the antenna is much smaller.
It ’s too small to be seen (hidden in the phone)
However, the higher operating frequency and shorter wavelength of the wireless signal have led to a bad result-its anti-interference ability and diffraction ability have been significantly weakened. Especially in complex urban environments, signal quality is more likely to be affected.
Therefore, engineers need to constantly develop new technologies for improving the capacity and coverage of mobile communication systems.
Antennas, as a key link in mobile communications, naturally become the primary target for engineers to open their brains.
Next, we come to Kangkang, what kind of god operation does our base station antenna play.
In the earliest 1G era of mobile communications, almost all base stations used omnidirectional antennas. At that time, the number of users was small, and the transmission rate was relatively low.
In the 2G era, the antenna gradually evolved into a directional antenna. For example, the antenna coverage angle is 120 °, and a cell will have three sectors, which will evolve into cellular communication.
In the 3G era, smart antennas were born, and single antennas developed into multiple antennas, which is what we often say MIMO (Multiple-Input Multiple-Output, multiple input multiple output) multiple antenna technology.
MIMO increases the number of antennas, which increases the number of channels for signal transmission.
So, how to use the extra channel number?
At the beginning, the engineers thought of using it to enhance coverage.
Based on MIMO, they proposed a new transmission mode called "transmission diversity" . Simply put, it is "sending the same content through different antennas".
"Transmission diversity": scattered transmission and centralized processing
This mode can alleviate the performance degradation caused by unstable channel quality, thereby enhancing coverage.
Later, MIMO developed another mode, called "spatial multiplexing" .
Spatial multiplexing divides the data to be transmitted into several data streams, and then transmits them on different antennas, thereby improving the transmission rate of the system.
This mode is mainly used to increase cell capacity.
In practical applications, the same part of the antenna cannot be used for both transmission diversity and spatial multiplexing. Therefore, the MIMO antenna needs to be weighed in the above two modes. The result of the trade-off directly affects the utilization rate of frequency resources.
In the 5G era, the situation has changed again.
In the evolution of 4G to 5G, with the increase of frequency, the antenna size is further reduced and the number of antennas is further increased.
Vodafone equipment photographed by British enthusiasts.
It can be seen that the antenna size of 5G is more compact.
As a result, MIMO became Massive MIMO, also known as "massive MIMO". Traditional MIMO usually has 2 antennas, 4 antennas, and 8 antennas. Massive MIMO can have more than 100 antennas.
For example, the 64T64R antenna, one of the current 5G mainstream choices, that is, the 64-channel Massive MIMO antenna, is composed of 192 antenna elements.
The emergence of Massive MIMO gives the transmission mode a new way of playing.
The Massive MIMO system can control the phase and signal amplitude of the signal transmitted (or received) by each antenna unit. By adjusting multiple antenna units, a beam with directivity is generated.
In this way, the wireless signal energy can form a superposition of electromagnetic waves at the location of the mobile phone, thereby improving the received signal strength.
This technique is the legendary beamforming .
Beamforming allows the energy of the beam to be concentrated in a specified direction, which not only enhances the coverage distance, but also reduces the interference between adjacent beams, allowing more users to communicate at the same time and increasing the cell capacity.
In other words, it combines the advantages of diversity and reuse.
It is worth mentioning that the effect of beamforming depends on the number of antennas and the quality of the algorithm. The algorithm is based on the location and status information of the mobile phone to perform real-time calculations and form an ideal beam through the antenna.
In contrast, diversity and multiplexing work more loosely, and when the mobile phone information is insufficient (for example, the mobile phone moves too fast), it can still play a big role.
In addition to enhancing coverage and capacity, Massive MIMO also has a secret technique-when the number of antenna elements is sufficient, Massive MIMO can break the space limitation.
Massive MIMO antenna arrays under 16T16R can only provide 2D beamforming in the horizontal dimension. Massive MIMO antenna arrays of 32T32R and 64T64R can achieve 3D beamforming in the horizontal and vertical directions, thereby effectively enhancing the coverage of high-rise residential buildings.
This shows that Massive MIMO pushes multi-antenna technology to a higher height. Massive MIMO and beamforming, the strongest pair in history, make the antenna smarter and more powerful. It is well known as the key technology of 5G.
Behind the powerful energy of " Massive MIMO + beam forming " is a severe test of the manufacturer's software and hardware research and development capabilities.
In the process of research and development, the filtering characteristics, gain effect, and anti-interference effect of the antenna system are all issues that engineers need to consider carefully. And the more the number of antennas and the number of mobile phone terminals, the higher the complexity of the antennas, and the higher the algorithm and chip processing capabilities.
Only a powerful algorithm can make beamforming produce the ideal effect like stage chasing.
At present, only a few manufacturers have the R & D and manufacturing capabilities of high-end (64T64R and above) Massive MIMO antennas.
And Huawei is one of them. Judging from the development trend of 5G antennas announced by Huawei, the highly integrated Massive MIMO is a key 5G technology, and it has superb beam forming capability, which brings considerable performance improvement to 5G.
Well, the story about the 5G antenna will be here today. Thank you all for watching, and we will see you next time!
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Author: Jun jujube
Caricature drawing: Xiaoyang classmates
