The working principle of the wireless signal jammer is: within a certain frequency range, the wireless device (mobile phone, etc.) and the base station are connected by radio waves, and data and sound are transmitted at a certain baud rate and modulation method. Mobile phone communication connects with the base station through the uplink frequency, and then transmits the signal to the mobile service exchange to complete the call. In the standby state, the mobile phone is connected to 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 situation of the near terminal channel by asking for instructions, so that the mobile phone can jump to the service channel for call and data transmission. At the same time, in order to effectively receive and complete the communication, a sufficient signal-to-noise ratio must be guaranteed.
According to the above principles, the wifi jammer is generally composed of a power supply, an electronic scanning control unit, a segmented radio frequency module, an amplifying unit, and a transmitting antenna unit. The wireless signal jammer generates the scanning signal, after the inverter, the oscillator is modulated to the mobile communication working frequency band, and then the power is amplified by the power amplifier and the voltage regulator tube is used to control the power, and the amplified frequency sweep signal is transmitted to the air through radio waves. When the mobile phone receives the information signal, due to the garbled interference caused by the frequency sweep signal (increasing the ratio of the noise signal to the device threshold), the mobile phone cannot receive the normal data sent by the base station, and therefore cannot connect with the base station normally, resulting in the mobile phone and the base station Separation of communication network. The mobile phone shows that the search network has no signal, no service system, etc., which achieves the blocking effect.
The interference power of the screen is fixed, and the shielding radius of the shielding space is determined by the channel attenuation and the level of the received base station signal. In order to realize the interference of the mobile phone signal jammer to the mobile network, it is necessary to ensure that the field strength of the signal emitted by the jammer is stronger than the field strength of the signal in the interference area. The closer the interference point is to the base station, the stronger the field strength and the smaller the effective interference area, and vice versa. , The farther the interference point is from the base station, the smaller the effective interference area and the larger the effective interference area.
It can be seen that within a certain range of transmission power, the interference range depends on the field strength of the interference zone. No matter how powerful the jammer is, as long as the transmission power is fixed, the longer the distance, the weaker the interference signal strength, and the loss of interference capability. The following is a comparison table of distance and path attenuation. Once again, the theoretical shielding area radius with reference value can be determined by the output channel power of the shielding device, the signal level of the base station, and the shielding line gain.