What are the consequences of not connecting high-power wireless data transmission equipment to an antenna?

成都亿佰特

What are the consequences of not connecting high-power wireless data transmission equipment to an antenna? [Copy link]

Since the birth of wireless transmission technology, it has brought great convenience to people. At the same time, the device that is closely and inseparable from wireless devices is the antenna. Antennas play a great role in wireless devices. In the past, the radio stations that we have seen in movies are very familiar.

As shown in Figure 1.1, the power of this type of radio station is generally very large. An obvious sign is that there is a long antenna on the upper left side, which ensures the normal use of the radio equipment.

Figure 1.2 shows an early mobile phone, and you can see the shadow of the antenna in the upper right corner.

So what is the significance of the antenna for wireless devices? First of all, we have to talk about the actual function of the antenna.

The antenna mainly converts electrical signals (i.e. energy) into electromagnetic wave signals (also a form of energy) and radiates them omnidirectionally or directionally into space. This is the essential function of the antenna. Therefore, when a wireless device does not have an antenna, the electrical signal will not be able to be well converted into an electromagnetic wave signal. Without an electromagnetic wave signal, the most basic wireless communication cannot be achieved. This is one of the reasons why the signal of a wireless device will be greatly reduced without an antenna.

Since we have just said that the lack of an antenna is one of the reasons for the reduction of wireless signals, there must be other reasons. There is also an impedance matching problem. In current wireless devices, 50Ω (ohm) impedance matching is basically used. That is to say, looking from the antenna interface to the circuit board, the equivalent resistance inside the circuit board should be 50Ω (ohm). This will achieve the best impedance matching. Of course, this is also part of the wireless high-frequency circuit design. Yibite Electronics Company in Chengdu is quite good at wireless high-frequency circuit design and has special equipment to measure impedance problems. You should know that this equipment is very expensive.

We have just talked about the reasons for signal degradation, such as antenna and impedance problems. Now let’s talk about the problem of the antenna itself.

Antennas come in many forms, and each type has different performance. To put it simply, there are the following questions:

Frequency causes:

The antenna must match the wireless operating frequency. A 2400MHz frequency requires a 2400MHz antenna, and a 5.8GHz frequency requires a 5.8GHz antenna. If the antenna frequency does not match the actual wireless frequency, the signal will be poor and the transmission distance will be short. Here, a concept called standing wave ratio is introduced. Frequency mismatch will lead to an increase in the standing wave ratio.

Frequency is also determined by physical properties. Simply put, the lower the frequency, the better the diffraction, and the higher the frequency, the worse the diffraction. This can also explain why the performance of 2.4G WiFi through walls is better than that of the 5.8G WiFi signal of the same level. At the same time, the lower the frequency, the lower the amount of data that can be transmitted. This can be explained most simply by 2G, 3G and 4G mobile phones. In the 2G era, it was also around 900MHz. In the 3G era, the mobile network speed increased, and the frequency was around 2000MHz. In the 4G era, it was still around 2000MHz. It is worth mentioning that China Mobile has a TDD-LTE base station with a frequency of 2500MHz, and China is the only country in the world that has this frequency band. So it can be seen that the number of base stations in the 4G era is more and denser than that in the GSM era. Then the question is again, 4G and 3G are both at 2000MHz, why is 4G faster than 3G? This is again thanks to the antenna. MIMO technology, multiple-transmit multiple-receive technology, is only available in 4G systems. Mobile phones can now use MIMO technology with up to 4 antennas, while base stations use 8MIMO technology, which is spatial division multiple access technology. This also shows the importance of antennas to wireless devices.

Poor signal caused by environmental factors:

As we all know, wireless signals travel in a straight line, and the earth is a sphere, a circle, so it is impossible to transmit from point A in Asia to point B in America (Note: this is also one of the main reasons why when wireless communication is carried out between two places not far apart, the higher the antenna, the longer the communication distance). However, the wireless signal can still be transmitted normally in time. In addition to the reason of the relay station, there is another point that there is an ionosphere in the earth's atmosphere. When the wireless signal is transmitted, it will be reflected in the atmosphere (there are many reflections, such as space reflection, diffuse reflection, etc.). After reflection, point B can receive the signal. Since it is a reflection, according to the physical properties of the wireless frequency, the reflection effect of low frequency is definitely better than that of high frequency.

Problems with decline:

The fading problem involves the free space fading theory. Here is a free space communication distance equation. Let the transmitting power be PT, the transmitting antenna gain be GT, and the operating frequency be f. Let the receiving power be PR, the receiving antenna gain be GR, and the distance between the receiving and transmitting antennas be R. Then, when there is no environmental interference, the radio wave loss L0 during the propagation process has the following expression:

L0 (dB) = 10 Lg (PT/PR)

= 32.45 + 20 Lg f ( MHz ) + 20 Lg R ( km ) - GT (dB) - GR (dB)

According to this equation, wireless frequency, power, antenna performance and communication distance are closely related, so the birth of wireless devices is inseparable from antennas. Of course, there are fast fading and slow fading, and fast fading is definitely the most terrible. There is also a kind of fading caused by reflection, such as waveguide effect and multipath fading. The actual phenomenon is that when you are around a long river, the signal is actually not good, and in the forest, the signal is also very bad, and the leaves will cause a lot of multipath fading.

Problems with the antenna itself:

The problem with antennas is the type of antennas. There are many types of antennas, such as Yagi antennas, mushroom antennas, double diamond antennas, smart antennas, ceiling antennas, etc. There are also omnidirectional antennas, directional antennas, and high-gain antennas. The antenna lobe problem is also one of the reasons for the quality of wireless signals. There is a very common saying, "darkness under the tower", which means that there is basically no wireless signal directly below the antenna. This is inseparable from the world's electromagnetic transmission method. In the radiation direction of the antenna, there is no lobe directly below, resulting in no signal directly below.

An omnidirectional antenna is one that radiates 360 degrees around the antenna vibrator. That is to say, the signal is the worst at the upper and lower ends of the antenna vibrator. As shown in Figure 1.3 Omnidirectional antenna:

Now let's talk about directional antennas. The electromagnetic wave radiation of directional antennas is directional, which can be divided into main lobe, side lobe and back lobe. The main lobe concentrates most of the energy, while the side lobe and back lobe are only a small part of the energy, which also leads to the fate of no signal when the antenna is off duty. As shown in Figure 1.4 directional antenna:

Of course, the quality of the wireless signal is also related to the antenna interface, such as SMA port, IPX port, PCB antenna, feeder, etc. These are also one of the factors that affect the quality of the wireless signal.

There are many other reasons, which I will not go into detail here.

Having said so much, if there is an antenna, but the antenna is not good, it will lead to the consequence of being unable to communicate. So what will happen if these devices do not have antennas? To put it simply, without an antenna, there is no communication, and the device is hot. When the device is a high-power device, according to the nature of the antenna mentioned in the previous question, when a lot of energy cannot be transmitted through the antenna in time, the energy is concentrated on the board, causing the board to heat up and eventually burn the chip. Similarly, when the antenna impedance is seriously mismatched, a large amount of antenna energy is reflected into the circuit, and the parameter is reflected in the increase of the standing wave ratio, the chip heats up, and the chip is also burned.