The working principle of wireless signal jammer

　　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 data and sound transmission at a certain baud rate and modulation method. The mobile phone 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 to effectively receive and complete communication.

　　According to the above working principle, the mobile phone signal jammer is generally composed of power supply, electronic scanning control unit, segmented radio frequency module unit, amplifier unit, transmitting antenna unit and other parts. The scanning signal generated by the signal generator passes the inverter, 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 exhibits the phenomenon of no signal and no service system in the search network, which achieves the blocking effect.

　　The working principle of the signal jammer is to scan from the low end frequency of the forward channel to the high end at a certain speed during the working process. This scanning speed can cause garbled interference in the message signal received by the mobile phone, and 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 and achieve the purpose of shielding the mobile phone signal. The mobile phone appears to search the network, no signal, No service system, etc.

　　The interference power of the signal 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. , 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 the signal jammer is, as long as the transmission power is a fixed value, as the distance increases, the interference signal strength will gradually attenuate. Thus losing the ability to interfere. The following table shows the comparison table of distance and path attenuation. Then the output channel power of the jammer, the base station signal level, and the coverage line gain can determine the theoretical coverage radius with reference value.

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