What Is a Cell Phone Amplifier?

The mobile phone signal amplifier (professional name: repeater) is composed of antennas, RF duplexers, low noise amplifiers, mixers, ESC attenuators, filters, power amplifiers and other components or modules. The basic principle of its work is: Use the forward antenna (donor antenna) to receive the downlink signal of the base station into the repeater, amplify the useful signal through a low noise amplifier, suppress the noise signal in the signal, and improve the signal-to-noise ratio (S / N ); Then down-converted to IF signal, filtered by filter, IF amplified, and then frequency-shifted up-converted to RF, amplified by power amplifier, and transmitted to the mobile station by a backward antenna (retransmit antenna); meanwhile using a backward antenna The mobile station receives the uplink signal from the mobile station and processes it through the uplink amplification link along the opposite path: that is, it transmits to the base station through the low-noise amplifier, down-converter, filter, mid-amp, up-converter, and power amplifier. Thus, two-way communication between the base station and the mobile station is achieved. ^[1]

Cell phone signal amplifier

The mobile phone signal amplifier (professional name: repeater) is composed of antennas, RF duplexers, low noise amplifiers, mixers, ESC attenuators, filters, power amplifiers and other components or modules. The basic principle of its work is: Use the forward antenna (donor antenna) to receive the downlink signal of the base station into the repeater, amplify the useful signal through a low-noise amplifier, suppress the noise signal in the signal, and improve the signal-to-noise ratio (S / N ); Then down-converted to IF signal, filtered by filter, IF amplified, and then frequency-shifted up-converted to RF, amplified by power amplifier, and transmitted to the mobile station by a backward antenna (retransmit antenna); meanwhile using a backward antenna The mobile station receives the uplink signal from the mobile station and processes it through the uplink amplification link along the opposite path: that is, it transmits to the base station through the low-noise amplifier, down-converter, filter, mid-amp, up-converter, and power amplifier. Thus, two-way communication between the base station and the mobile station is achieved. ^[1]

Chinese name: Cell phone signal amplifier
Foreign name: Repeater, Cell phone signal booster

professional title: Repeater
Standard impedance: 50
Common connectors: N connector, SMA connector

Brief introduction of mobile phone signal amplifier

Mobile phone signal amplifier (mobile phone signal booster, micro repeater, mobile phone signal companion, mobile phone signal access device, mobile phone signal importer), due to the rapid development of China's mobile communications industry, mobile communications users have continued to increase, and even cellular The planning is getting smaller and smaller, and the base station position is getting lower and lower. On the other hand, with the development of urban construction, high-rise buildings are constantly emerging. Based on the shadow effect of wireless transmission, mobile communication will be formed behind or in the middle of these high-rise buildings. Signal dead zone. In addition, during the construction of a cellular mobile communication base station, because of the need to avoid interference from neighboring cells, the main lobe of the antenna radiation field pattern has a large downtilt, so that the middle and upper parts of high-rise buildings generally cannot effectively receive signals. In addition, due to the shielding effect of buildings and other electromagnetic waves, mobile communication signals cannot be normally received in some closed large buildings such as tunnels, subways, underground shopping malls, entertainment cities, parking lots, and hotels and office buildings. ^[2]

Mobile phone signal amplifier is a product specially designed to solve the dead zone of mobile phone signal. Because mobile phone signals rely on the transmission of electromagnetic waves to establish communication links, due to building blockages, in some tall buildings, basements and other places, some shopping malls, restaurants, karaoke saunas and other entertainment venues, underground civil air defense works, subway stations, etc. In many places, cell phone signals cannot be reached and cell phones cannot be used. The mobile phone signal amplifier can solve these problems well. As long as a mobile phone signal amplifier system is installed in a specific place, the mobile phone signal in the entire range can be used well, which brings great convenience to the staff or guests inside. . ^[2]

Cell phone signal amplifier selection precautions

Due to the large land area and scattered population in China, communication resources are relatively scarce. Therefore, it is very difficult to fundamentally solve such problems, after all, China Mobile has limited official base station resources. However, with the continuous development of science and technology, mobile phone signal amplifiers have become a more mature and effective solution. However, there are many reasons for the poor signal at home and the inability to make phone calls. The phenomenon is the same in different situations, but the reasons are different, and it is not a one-size-fits-all solution.

Cell phone signal amplifier bottom cell signal difference

Outdoor streets have better signals, and indoor signals are worse. This is the most common situation, mainly caused by the surrounding buildings blocking the signal of the base station.

Mobile phone signal amplifier signal difference between rural and suburban areas

There is a weak signal outdoors, and there is basically no signal indoors. The difference in signal is due to the lack of dense base stations in rural and suburban areas, and some places are far away from the base station, resulting in weak signals.

Mobile phone signal amplifier large plant, villa signal difference

Outdoor streets have better signals, and indoors have basically no signals. The poor signal is due to the fact that the reinforced concrete in the rooms of villas and workshops is difficult to pass through mobile phone signals around 900Mhz and is blocked ^[2] .

Mobile phone signal amplifier high-level signal difference

The reason for the poor signal of the mobile phone at the high-level is different from the above points. In fact, the signal of the mobile phone at the high-level is not bad, so why can't I make a call? Mainly because the upper layer can receive signals from several nearby base stations, but because there is no blocking, the signal strength is similar, so the mobile phone will frequently switch between several base stations, which is the so-called "ping-pong effect"; ^[1] In addition, the mobile phone may also receive signals from non-adjacent base stations. Because the mobile phone can only switch between adjacent base stations, it will cause the mobile phone to receive a signal from a base station with a better signal. But because they are not adjacent, they cannot switch over, causing the so-called "island effect". According to reports, the ping-pong effect and the island effect are difficult problems in mobile communications, and the solution is different from the above situation ^[2]

Application of mobile phone signal amplifier

Mobile Phone Signal Amplifier Application Overview

According to the characteristics of mobile phone signal amplifier series products and the requirements of mobile communication networks, different locations

Physical environment and application occasions, system solutions are different, which requires careful analysis and different treatment. For wireless repeaters, signal isolation is particularly important. Mobile phone signal amplifiers receive signals from space, which inevitably requires that the space signals be as pure as possible. In dense areas of base stations, the difficulty of separating signals from different base stations or sectors will increase greatly, which will easily increase the interference of mobile phone signal amplifiers to base stations. Therefore, in areas where base stations are dense, it is recommended to use cable signal introduction methods, such as optical fiber repeaters. In places where fiber repeaters are not available, wireless repeaters can only be used, but their donor antennas must have sufficient directional selectivity. For various regions and application sites, due to the differences in base station density and user traffic, the following repeater application principles are recommended: ^[2]

Urban area

Due to the large number of users and the large number of base stations, there is generally no large-scale signal dead zone. The mobile phone signal amplifier is only used to solve the blindness in a small area and the signal coverage in the building. In the case where fiber-to-the-building has not yet become widespread, wireless repeaters are required. With the increase of buildings, the number of repeaters required will also increase, and a base station will be configured with multiple repeaters. However, the introduction of repeaters will inevitably cause interference to the base station. The interference will increase with the increase in the number of repeaters, especially the introduction of high-power repeaters, which will significantly increase system interference. Therefore, low-power (under 1W) repeaters should be used in dense urban areas. ^[2]

Cell phone signal amplifier city edge

In the early days of CDMA network construction, due to the small number of base stations, high-power wireless or fiber-optic repeaters can be used. In urban fringe areas, the problem of signal coverage is mainly solved. In areas where fiber has been laid, it is best to use a fiber optic repeater with an output power of 10W. When there are no fiber resources, wireless repeaters can be used for extended coverage. The donor antenna with good directivity is used to extract a relatively pure source signal, and the output power is 5W / 10W, which is equivalent to the output of the base station, and achieves a good coverage effect rate. ^[2]

Mobile phone signal amplifier suburb, country

Suburban and rural areas mainly solve the problem of coverage. It is best to use high-power fiber optic repeater (10W / 20W) to expand the coverage area in the area where fiber is laid. For areas that do not have fiber resources but can receive base station signals, wireless repeaters can be used to solve the coverage problem. In special cases, frequency shift repeaters can also be used to increase the coverage distance ^[2]

Comparison of mobile phone signal amplifier with base station

Cell phone signal amplifier coverage area

With the same coverage area, the use of mobile phone signal amplifiers has lower investment and is more economical.

Mobile signal amplifier coverage flexibility

A base station is basically a circular coverage, and multiple mobile phone signal amplifiers can be organized into a variety of coverage forms. For example, the "one" line can cover road sections of dozens to tens of kilometers. It can also be organized into "L", "N" and "M" coverage, which is especially suitable for mountainous networks.

Investment Benefits of Mobile Phone Signal Amplifiers

In the initial stage of networking, due to fewer users and poor investment benefits, some mobile phone signal amplifiers can be used instead of base stations. After the development of users, they are now replaced with base stations, and the replaced mobile phone signal amplifiers are further placed in more marginal areas, so that they are developed step by step.

Mobile phone signal amplifier builds network quickly

Since civil construction and transmission circuit construction are not required, network construction is fast.

Mobile phone signal amplifier installation precautions

Mobile signal amplifier installation instructions

1. Selection: Choose different models according to different areas and building structures.

2. Distribution of antennas: Directional Yagi antennas are used outdoors, and the direction of the antennas can be directed to the transmitting base station of the mobile company as far as possible to achieve the best receiving effect. Omnidirectional antennas can be used indoors, and the installation height is 2-3 meters (the installation of the antenna The quantity and location are related to the indoor area and the structure of the room). An indoor unobstructed range of 300 square meters requires only 1 antenna, a range of 300-500 square meters requires 2 antennas, and a range of 500-800 square meters requires 3 antennas.

3. Signal amplifier installation: Generally, it should be installed more than 2 meters above the ground. The shortest distance wiring method (the longer the line, the larger the signal attenuation) should be used to achieve the best results.

4. The use of wires: The standard for the feeder radio and television (ie, cable television) of the signal booster is 75, but the mobile phone signal amplifier is the communication industry, and 50 is the standard, and the incorrect impedance will worsen the system indicators. The thickness of the wire is determined according to the actual situation on the site. The longer the wire, the thicker the wire must be used to reduce the attenuation of the signal.

Using 75 wire to make the host and wire mismatch will increase the standing wave and cause more interference problems. Therefore, the choice of wire should be differentiated according to the industry.

Mobile phone signal amplifier considerations

The signal from the indoor antenna cannot be received by the outdoor antenna during installation, and it will generate self-excitation. Generally, two antennas are separated by 8 meters to avoid self-excitation. ^[2]

Mobile phone signal amplifier installation diagram (10 photos)

Mobile phone signal amplifier

In general, the requirements for mobile phone signal amplifiers should mainly be based on the technical requirements of the base station.

Mobile phone signal amplifier working frequency band

China Mobile: 885-909,930-954Mhz

China Unicom: 909-915,954-960Mhz

China Telecom: 825-835,870-880Mhz

Mobile phone signal amplifier output power, gain, automatic gain control

This is a set of interrelated indicators that should be considered comprehensively.

Generally, the maximum output power should be divided into several levels for users to choose from when illustrated in the atlas that does not exceed the maximum limit specified by the Radio Administration Bureau of the Ministry of Information Industry. The downlink mainly considers coverage, and the uplink ensures satisfactory reception by the base station. Therefore, the downlink is generally greater than the uplink.

Gain is to amplify the received signal to the rated output power. Considering the difference in signal strength at the repeater installation site, the gain should be adjustable. The maximum gain can be calculated by amplifying the signal level received by the repeater to the maximum output power.

In order to ensure stable output power and avoid output nonlinearity, an automatic gain control (AGC) with 20dB seems necessary ^[1] .

Regarding tolerance, rated output power, and rated gain, only one is required. It is generally appropriate to specify the gain tolerance. Because the test is to adjust the gain to the maximum, change the input level so that the output reaches the rated value. In this case, of course, there is no need to specify a tolerance for the rated power, and at this time, the input level is also different due to different gains.

Mobile phone signal amplifier bandwidth, in-band fluctuations

This is a set of interrelated indicators, especially bandwidth and in-band fluctuations.

Generally, the bandwidth refers to the -3dB bandwidth, and the in-band fluctuation refers to the unevenness in the band. If the in-band fluctuation is required to be smaller than 3dB, the -3dB bandwidth must be wider than the bandwidth allocated to it, so that it will inevitably occupy other channels. Therefore, the maximum in-band fluctuation is only 3dBp-p.

Cellphone signal amplifier out-of- band rejection

Out-of-band rejection is primarily a requirement on the shape of the filter. In order not to interfere with others, the shape of the filter is expected to be as close to a rectangle as possible. It is usually measured by the ratio of -60 (or -40) dB bandwidth to -3 dB bandwidth (some people call it the form factor of the filter).

Note: Mobile phone signal enhancers sold online often use dielectric filters with poor out-of-band rejection. Generally, IF sound table filters are used to achieve band rejection requirements.

Cellphone signal amplifier intermodulation and spurious emissions

Harmonics, intermodulation, and spurs are all unwanted unwanted signals, and the same requirements can be raised. ^[2]

For GSM mobile phone signal enhancer, it is suitable according to YD / T 883-1999 and ETS 300 609 requirements. For CDMA mobile phone signal enhancer, only YD / T 1047-2000 is required.

Phone signal amplifier waveform quality

CDMA base stations have requirements on waveform quality (Rho). After the mobile phone signal enhancer transmits CDMA signals, this indicator may deteriorate.

Cell phone signal amplifier transmission delay

After the signal passes through the repeater, transmission delay may occur.

The transmission delay of the broadband repeater is relatively small, generally around 1 s; the transmission delay of the frequency selective and frequency-shifted mobile phone signal enhancer is relatively large, which may reach 5 s and 10 s, respectively.

Noise figure of mobile phone signal amplifier

This is a characterization of the repeater sensitivity. Based on the technical level around 2010, the noise figure is about 4-6dB.

Mobile phone signal amplifier voltage standing wave ratio

In order to ensure effective power transmission, a voltage standing wave ratio requirement is required. According to the amount of power reflected and the actual level, it is feasible to require less than 1.4 to 1.5.

Mobile Signal Amplifier

Does the mobile phone signal amplifier have radiation?

If high-power equipment, such as a host of 5W (37dBm) or more, may also have greater radiation. The output power of the mobile phone signal booster is generally within 200mW (23dBm). After reaching the antenna, it is generally within 5mW (7dBm). After installing other mobile phone signal boosters, the indoor signal is generally around -50dBm to -75dBm. Good outdoor signals are generally around -40dBm to -75dBm. When a mobile phone talks, a GSM mobile phone talks in a weak signal environment, and the worst radiated power can reach 1W (30dBm). After the amplifier signal is installed, the radiated power of the mobile phone call is about 10mW (10dBm). It can also be said that when a small power amplifier is installed in a poor signal environment, the mobile phone reduces radiation when talking.

Does the mobile phone signal amplifier interfere with the base station?

There is interference. Generally, the interference of good quality host within 100mW is almost negligible. The greater the power, the greater the interference.

Is it legal to install a mobile phone signal amplifier yourself?

illegal. Because of the regulations: the product requires a model approval certificate, etc., the installer needs the installation certificate, and the user needs the use certificate. All the certificates are almost impossible for civilian use. It is a pain in the mobile phone signal amplifier industry that the society needs but is not legal.

How to distinguish mobile phone signal amplifier

1. Look at the workmanship and choose the brand. If you use more, you can open the internal comparison.

2. There are many inferior mobile phone signal amplifiers on the Internet, mainly because some circuits for optimizing signals are omitted, such as automatic gain control, etc. Generally, there are less than 80 devices, and the mainframe with complete circuits generally has more than 200 devices.

3. Inferior mobile phone signal amplifier, the interference to the base station is very serious after a large number of installations. Of course, good quality also has interference, but the same power interference is several times dozens of times smaller.

Why does the mobile phone signal amplifier install the mobile phone signal to make the call unavailable?

The mobile phone signal amplifier is a simple device developed by China Mobile China Unicom's intermediate frequency. If the indoor China Unicom China Mobile has no signal or is weak, there should be no problem in using this device. If one of the signals is full and the other signal is not, interference will occur in this case, so it is not recommended.