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Common mobile phone signal jammers on the market have operating frequencies of: 869~894MHz; 825~960MHz; 1805~1880MHz and 1900~1990MHz, etc. The applicable frequency bands are CDMA800, GSM900, DCS1800, and PCS1900. It can control a range of about 40 meters in diameter, using a DC-DC converter input voltage and 5V output voltage. After turning on the signal jammer, garbled interference is formed in the message signal received by the mobile phone. The mobile phone cannot detect the normal data sent from the base station, so that the mobile phone cannot establish a connection with the base station. Mobile phones show symptoms such as searching the network, no signal, and no service system. The signal sending and receiving functions of mobile phones within the specified range are invalid, and outgoing and incoming calls cannot be made, thus achieving the purpose of mandatory ban.

signal jammer

Principles of mobile communication
The working principle of mobile phones is as follows: within a certain frequency range, mobile phones and base stations are connected through radio waves, and data and sound transmission are completed with a certain baud rate and modulation method.

Principle of mobile phone signal jammer (shielding device)
According to the communication principle, the jammer scans from the low-end frequency of the forward channel to the high-end at a certain speed during operation. This scanning speed can cause garbled interference in the message signals received by the mobile phone. The mobile phone cannot detect normal data sent from the base station, making it impossible for the mobile phone to establish a connection with the base station. Mobile phones show symptoms such as searching the network, no signal, and no service system.

Basic functions of signal jammer
1. After the slow start function is powered on, the working power supply rises from zero to stable within 4 seconds.

2. After the shielding function is activated, mobile phones within the range will be blocked within 35 seconds.

Application scope of signal jammer
Various examination rooms, conference rooms, gas stations, oil depots, churches, hospitals, courts, military sites, libraries, theaters and other places.

Mobile phone detection technology mainly detects when the electromagnetic wave signal emitted by the mobile phone when it is working causes the electromagnetic power in the area where the mobile phone is to increase to a set value, thereby determining that a mobile phone is working. This technology sounds very advanced at first, but in fact it is just a very superficial understanding. When this technology was proposed, the following issues were not considered:

signal jammer

1. Uncertainty of mobile phone transmit power

The specific base station through which a mobile phone enters the network when working is determined by the traffic volume and dynamic deployment of surrounding base stations. When the mobile phone is logged in and used, if the nearby base station is busy, it will log in to the idle base station farther away. The transmit power of the mobile phone will be adjusted accordingly according to the link loss of the mobile phone to the base station radio wave. Usually, the mobile phone receives the signal from the base station. The stronger the signal, the weaker the transmit power.

2. The distance between the mobile phone and the detector (link loss) is uncertain

The distance between the mobile phone and the detector and whether there are any obstacles in the middle will affect the strength of the signal received by the detector.

3. The intensity of space electromagnetic interference is uncertain

Common lightning, fluorescent lamps, electronic equipment, etc. are all sources of interference. At the same time, when mobile phones are working, there is a lot of out-of-band stray noise. Although the surface acoustic filter used in the detector is used on mobile phones, the filter has insufficient out-of-band suppression and is prone to cross-frequency phenomena. When used for detection, it cannot effectively filter out other interference signals, causing the detection system to be in chaos.

4. Detector setting sensitivity is uncertain

Generally, the sensitivity setting of a detector does not have a specific quantitative value. During debugging, adjust the sensitivity by constantly adjusting the position and dialing the mobile phone to observe whether the detector detects it.

 
In order to ensure the leading level of 5G network, the 2.6GHz frequency band is given priority to adopt the 100MHz networking solution design, which coincides with the operating frequency of the deployed TD-LTE system in the D1/D2 frequency band. In areas where TD-LTE frequency bands have not been cleared in the D1/D2 frequency band, 5G will encounter serious technical problems with LTE co-channel interference. In addition, according to the summary of 5G interference technology examples, 5G in the 2.6GHz frequency band will also encounter interference technology from the multi-channel microwave distribution system (MMDS) of the radio and television network, interference technology from video surveillance network transmission equipment, and pseudo base stations. Jamming technology and jammer jamming technology, etc. Therefore, studying and identifying 5G interference problems is of great practical significance to promote 5G interference technology to solve problems and ensure customer experience and business process understanding. signal jammer

1. LTE co-channel interference

In areas where TD-LTE in the D1/D2 frequency band has not been cleared, under long-term load conditions in TD-LTE residential areas, terminal equipment will cause increased co-channel interference in the same covered 5G residential areas, seriously affecting the characteristics of 5G Internet. The strength of LTE co-channel interference is closely related to factors such as the size of the covered area, the wireless network environment, and the traffic volume of LTE adjacent areas.

The main characteristics of LTE co-channel interference are that the 163~273PRB noise floor used in the D1/D2 frequency band increases significantly in the time domain, and the wave pattern characteristics show characteristics that are relatively highly related to the production scheduling optimization algorithm; in the frequency domain, the 24h interference immunity The pressure intensity fluctuates significantly with the freight volume and the trend analysis is basically consistent, showing significant frequency domain uncertainty.

2. MMDS interference

The multi-channel microwave distribution system (MMDS) uses microwave heating frequency to transmit at one point and receive at more points to transmit television, audio broadcast programs and data signals to the front or directly of each cable digital television public antenna television system. Microwave heating system software assigned to individual customers. According to the MMDS transmission configuration in my country, MMDS operating in the 2500-2700MHz frequency range will cause serious interference to the 5G system deployed in the 2.6GHz frequency band. The interference is characterized by several regular continuous 8MHz networks. Bandwidth Rectangular Box Interference Technology Wave Pattern.

In recent years, car and property theft incidents have occurred frequently in downtown areas. Through layers of radio waves, a car jammer simply modified from a micro-power radio transmitter interferes with the car owner’s ability to lock the door.signal jammer

At about 7:30 in the morning on July 17, 2015, Chen Qing (pseudonym) drove her child to Beijing Daxing 11 Jianhua Kindergarten.

Chen Qing recalled that it was raining heavily that day, so she parked the car and pressed the lock and hurriedly escorted her child into the kindergarten.

About 7 minutes later, Chen Qing returned and found her wallet stolen from the car. “I obviously got out of the car and pressed the lock!” In panic, she immediately called the police.

Chen Qing usually has the habit of opening the door to confirm whether the car is locked after parking the car. Because it rained that day, she ignored the details of locking the car.

After reporting the crime, the police reminded that Chen Qing was most likely to have encountered a thief who used a car jammer to commit theft. The theft suspect turned on the jammer not far from the vehicle, causing the door to fail to lock. When the owner left carelessly, he entered the vehicle to commit theft.

Chen Qing’s case is not an isolated case.

On the morning of February 23 this year, the police in Haidian District, Beijing captured two suspects, Guo Mouzhen and Guo Moufeng, who were suspected of using car jammers and other items to commit theft. In the suspect car, the police seized a large number of crime tools such as car jammers and screwdrivers, as well as suspected stolen items such as a laptop and a handbag.

The suspects Guo Mouzhen and Guo Moufeng confessed that when committing crimes, they chose to attack unattended high-end cars on the roadside, or used jammers to interfere with the owner’s locking of the car, or used screwdrivers and other tools to break the car glass, and then stole property. Since December last year, they have committed more than ten crimes in Haidian and Changping, stealing a total of more than 30,000 yuan in cash, several mobile phones, handbags, laptops and other items.

On May 9, 2016, the Beijing Haidian District Court tried a three-person gang that specifically used jammers to interfere with car owners locking their cars and then steal property in the car.

The defendant described that when committing the crime, the three of them held jammers and waited for the opportunity to stand on the opposite side of the road when a car stopped. At the same time, they turned on the jammer to release the “jamming signal.” After the car owner left, several people came forward to see if there was anyone left in the car. Once there is valuable property in the car, they open the door and steal it. Using this method, property has been stolen from many luxury cars such as Porsche, Audi, and BMW.

According to data from the China Judgment Document Network, since January 26, 2014, courts in various districts of Beijing have heard 26 cases involving the use of car jammers to commit theft.

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