Shulou(Shulou.com)12/24 Report--

In the past two days, there has been a great controversy over a popular science video of bilibili technology on the Internet.

In the video, a UP master straightens the antenna in order to test the signal.

The UP master may think that after straightening the antenna, the antenna can produce directional signal radiation effect.

So, is it really the right thing to do?

In addition, many people often ask: our home Wi-Fi router, there are multiple antennas. How should these antennas be pointed in order to have a better transmission effect?

Today, Mr. Xiaozao will briefly tell you about this knowledge.

The antenna is actually very familiar to everyone. But where there is wireless technology, basically there are antennas. Its purpose is to send and receive radio waves.

More professionally, an antenna is a "converter"-transforming guided waves propagating on a transmission line into electromagnetic waves propagating in free space, or vice versa.

How does the antenna realize the conversion between guided wave and space wave?

Look at the following picture:

High school physics, two parallel wires, when there is alternating current, it will form electromagnetic wave radiation.

When the two wires are very close, the radiation is very weak (the current of the wire is in the opposite direction, and the induced electromotive force is almost offset).

When the two wires open, the radiation increases (the current of the wire is in the same direction and the induced electromotive force is in the same direction).

When the length of the wire increases to 1P4 of the wavelength, a more significant radiation effect can be formed!

With the electric field, there is a magnetic field, there is a magnetic field, there is an electric field, such a cycle, there are electromagnetic fields and electromagnetic waves.

Electromagnetism, magnetism and electricity. Let's take a look at this beautiful process.

The change of the current direction of the wire produces a changing electric field.

These two straight wires that produce an electric field are called oscillators.

What is an oscillator like in the real world?

Duang! That's it--

That's the piece of metal. Half-wave symmetrical oscillator (non-converted)

Well, in fact, the above is just a traditional form of the oscillator, it also has N kinds of transformation:

Strangely shaped vibrators you may ask: the antennas we see in real life are not like this?

The reason is simple: to be exact, the oscillator is not a complete antenna. The oscillator is the core component of the antenna, and its shape will change with the shape of the antenna.

And the shape of the antenna is too much TM.

All in all, hundreds of thousands. Sometimes, there is a radome on the outside of the antenna, covering the real vibrator inside. This will cause you to misunderstand the actual shape of the antenna.

Antennas have a variety of strange shapes, which can be roughly classified into the following categories according to their similarity:

Whip antenna

Paraboloid antenna

Yagi Antenna PS: Yagi Antenna is not Yagi. Although I am not good at math, I can count Yagi. It is called Yagi because it was invented by Japanese Hideji Yagi and Taro Uda in the 1920s. It is called "Yagi Uda Antenna", or "Yagi Antenna" for short.

As mentioned at the beginning of this article, the antenna in the video is one of the most common vertically polarized rubber rod antennas, similar to a whip antenna, but also an omni-directional antenna.

So, how does the signal of this kind of antenna spread outward?

If you take a look at its signal direction diagram, you can see:

Yes, its signal is transmitted around the vertical direction of the stick. Professionally speaking, "the axial direction is the smallest and the normal direction is the largest". As a matter of fact, the previous motion picture is already a spoiler. )

As you can see, the direction of signal propagation is perpendicular to the antenna. In other words, the signal is the weakest in the direction pointed at the top of the antenna.

So, if you want to maximize the effectiveness of this antenna, it should be placed like this:

By the same token, if you want to get better results, the router in your home should also recommend that the antenna stand upright.

If the antenna is placed sideways, it will be like this:

Pointing to the pendulum is even more wrong, and the signal is the worst.

Of course, if your router is relatively high or short, it is also possible to adjust the antenna angle appropriately.

With regard to the placement of antennas, there is some common sense to pay attention to:

The way of putting a can on the antenna, which is transmitted on the Internet, will enhance the signal. This is wrong and will not produce a greater gain.

Do not get too close between antennas, or there will be interference between them.

3 the more router antennas, the better. Different antennas have different purposes, such as 2.4GHz or 5GHz signals. The MIMO (multi-antenna transceiver) supported by your phone is limited, usually 2X2 or 4X4. It doesn't mean that your router has 100 antennas and a mobile phone can communicate with it. Now many routers have a lot of antennas, in fact, it may be just to increase the number of machines.

All right, have you all learned to waste the way the antenna is placed?

This article comes from the official account of Wechat: fresh Jujube classroom (ID:xzclasscom), author: Xiaozaojun

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