1 mobile amplifier

The so-called mobile amplifier does not mean that the equipment can improve the communication effect in the original place, and the cell phone signal can not improve the quality of the signal by enlarging the signal alone. The signal quality is largely removed from the signal to noise ratio, and the signal to noise ratio is not possible to be improved by simple amplification, because the noise signal is amplified as well as the useful signal is amplified.

When the signal is bad, the mobile phone users tend to take the mobile phone according to the signal on the mobile phone to find the signal everywhere. This is a very effective way, but it is very inconvenient, because the better location of the signal is not necessarily the place where the mobile phone users can stay. So, choose a high gain antenna, set up where the signal is as good as possible, then connect the antenna with a radio frequency coaxial cable to the place where the mobile phone users often stay and connect to the cell phone, so that it is possible to use a cell phone in a place without a signal.

There are two ways to improve the quality of the signal. One is to improve the energy of the signal that the antenna can pick up in the air as much as possible. The other is the secondary one, which is as much as possible to reduce the noise of the system. Reducing the system noise to a secondary position is because it is very difficult to reduce system noise and is very unrealistic. Therefore, the most effective way to improve the signal quality is to increase the output of the antenna. However, the output of the antenna depends on the intensity of the signal field. As long as the location of the mobile antenna is determined, the effect of any method to improve the quality of the signal is very limited.

The above methods must be very effective, but there are many inconveniences. One is that it is hard for people to accept the use of a cable for mobile phones, and the other is that many mobile phones have no external antenna socket. Even if there is a socket, it is not necessarily able to buy a matching plug, so it is necessary to solve the problem of wireless connection between the high gain antenna and the mobile phone in order to make use of the higher quality signals received by the high gain antenna.

If a high gain antenna can be installed at a very near strong signal, such as the basement of a large city, there is little signal inside, and a strong signal can be found outside the outside, so that the following diagram can be used to solve the problem.

The high gain antenna is set to the outside strong signal, and a few meters long radio frequency coaxial cable is introduced into the non signal room. A small antenna is connected to a small antenna at the terminal and the cell phone is close to the small antenna, so it can communicate reliably in the non signal room.

However, the above is only a more extreme situation, more occasions are not such a good condition, often need to find a strong signal outside ten meters outside the twenty meters, at this time, using this simple method can not work. Because in the 900MHz band, the loss of the cable is relatively large, and the signal transmission between the small antenna and the mobile phone also has a small decline, so the high gain antenna and the mobile phone can not be effectively transmitted between the mobile phone, of course, it is impossible to communicate. The solution is to insert an amplifier in the transmission channel to compensate for the transmission loss.

It has been proved that the insertion of a 20 decibels amplifier, even if it is a 20-30 meter long cable, is still very effective. As long as the position signal installed by the high gain antenna is strong enough and the mobile phone is 1-2 meters away from the small antenna, the signal can be displayed. However, such devices can not communicate, because mobile communication relies on two transmission channels, one is an uplink channel, is used to speak and respond to base station instructions, and the other is a downlink channel for receiving base station instructions and answering the phone. These two channels are indispensable if only the downlink channel shown in the previous picture is only a downlink channel, Although the related instructions sent by the base station can be well received, no upstream channel is unable to respond, the system will not connect the communication link, the whole communication can not be realized. Therefore, we must add a transmission channel in the device shown above, so that communication can be realized.

Do not expect to use two outdoor antennas, two indoor antennas and two amplifiers to work on the above picture system, but in fact it will not work. Because the two amplifiers have 20 dB gain, and two amplifiers are equivalent to the first and end connection between the 10-30 meter radio frequency coaxial cable and the coupling between the two antennas, the total gain of the two amplifiers is more than fifty times more than the transmission loss between the invisible channels. It is inevitable to be self excited and impossible to work. Therefore, the amplifier must have a good frequency selection characteristic, that is, the uplink signal amplifier only allows the uplink signal to pass through, and the downlink signal amplifier only allows the downlink signal to pass, so that the system can work steadily.

In practice, two outdoor high gain antennas are very inconvenient to install as the structure shown in the diagram, so the regular signal amplifier should be the structure shown in the lower figure. A high gain outdoor antenna is both the receiving antenna of the downlink signal and the transmitting antenna of the uplink signal.

In a word, the main function of the system is to move a good signal from one place to the required position. The function of the signal amplifier is to make up for the transmission loss between the high gain outdoor antenna set up in the strong signal and the mobile phone in the weak (no) signal. Do not expect to install this system in indoor weak signal area to improve signal quality.