The working principle of the WiFi signal jammer is: within a certain frequency range, the wireless device (mobile phone, etc.) and the base station are connected by radio waves, and the data and sound are transmitted with a certain baud rate and modulation method. The mobile phone communication is to connect with the base station through the uplink frequency, and then transmit 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 need for a call, it will first be assigned to the mobile phone service channel according to the specific conditions of the near-terminal channel, so that the mobile phone can jump to the service channel for calls and data transmission. At the same time, in order to receive and complete communications effectively, a sufficient signal-to-noise ratio must be guaranteed.
According to the above principles, a 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 WiFi 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 controls the power, and the amplified frequency scanning 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 (increase the ratio of the noise signal to the device threshold), the mobile phone cannot receive the normal data sent by the base station, so it cannot connect with the base station normally, resulting in the mobile phone and the base station. Communication network separation. The mobile phone shows that the search network has no signal, no service system, etc., so as to achieve 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 WiFi signal jammers to the mobile network, it is necessary to ensure that the field strength of the signal sent by the jammer is greater than that 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 transmission power range, the interference range depends on the field strength of the interference area. No matter how powerful the WiFi jammer is, as long as the transmission power is fixed, the farther the distance is, the weaker the interference signal strength will be, thus losing the ability to interfere . Below 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 WiFi jammer, the signal level of the base station, and the gain of the shielded wire.