The function of the mobile phone jammer is to shield the signal, and it is used in many occasions. The most frequently used occasion we come into contact with is the examination room. What is the principle of the signal jammer used in the examination room?
The working principle of mobile communication is that within a certain frequency range, wireless devices (mobile phones, etc.) communicate with the base station through radio waves, and complete the transmission of data and sound with a certain baud rate and modulation method. When the mobile phone communicates, it communicates with the base station through the uplink frequency, and then transfers the signal to the mobile service switching center to realize the call. In the standby state, the mobile phone communicates with the base station through the broadcast control channel. Once there is a call demand, it will be allocated to the mobile phone service channel according to the specific conditions of the channel near the terminal through the request, so that the mobile phone can jump to the service channel to realize the call and data transmission . At the same time, wireless communication must ensure a sufficient signal-to-noise ratio in order to receive effectively and complete the communication.
According to the above working principles, the mobile cell phone jammer is generally composed of a Power supply, an electronic scanning control unit, a segmented radio frequency module unit, an amplifier unit, and a transmitting antenna unit. After the signal generator generates the scan signal, passes through the inverter, it enters the oscillator and modulates it to the mobile communication working frequency band, and then is amplified by the Power amplifier and the voltage regulator tube controls the Power . The amplified frequency sweep signal is transmitted into the air in the form of radio waves. Because the frequency sweep signal forms garbled interference in the message signal received by the mobile phone (increasing the proportion of noise and noise signals to the device threshold), the mobile phone cannot receive the normal data sent by the base station, so that the mobile phone cannot establish a normal connection with the base station, thereby causing the mobile phone to disconnect Base station communication network. The mobile phone shows the phenomenon of no signal and no service system in the search network, which achieves the blocking effect.
The interference Power of the mobile phone jammer is fixed, and the shielding radius of the unblocked space is determined by the path attenuation and the signal level of the receiving base station. To realize interference from mobile phone signal jammers to mobile networks, it is necessary to ensure that the signal field emitted by the jammer is stronger than that of the mobile signal in the interference area. The closer the interference location is to the base station, the stronger the field strength and the smaller the effective interference area, and vice versa. , The farther the interference location is from the base station, the weaker the field strength and the larger the effective interference area.
It can be seen that within a certain transmission Power , the interference range depends on the field strength in the interference area. No matter how Powerful a mobile phone jammer is, as long as the transmission Power is a fixed value, the interference signal strength will gradually attenuate as the distance increases. Loss of interference ability. The following table shows the comparison table of distance and path attenuation. Then the signal jammer output channel Power , base station signal level, and coverage line gain can determine the theoretical coverage radius with reference value.
The installation height of the mobile phone signal jammer: 1.0-2.0 meters is the best or the installation direction on the classroom platform: directly connect the Power plug to the AC220V Power supply. When the signal jammer is used less than 300 meters away from the mobile phone tower, the shielding effect will be inversely proportional to the distance from the signal source. It is recommended that in some particularly important places, the number of mobile phone jammers should be increased when necessary to ensure the shielding effect. The transmission frequency can be changed according to the on-site environment and customer requirements
