The working principle of the wifi signal jammer is: within a certain frequency range, wireless devices (mobile phones, etc.) and base stations are connected through radio waves, and data and sound are transmitted at a certain baud rate and modulation method. Mobile phone communication is connected to the base station through the uplink frequency, and then the signal is transmitted to the mobile service switch 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 first be assigned to the mobile phone business channel according to the specific conditions of the near-terminal channel through request, so that the mobile phone jumps to the business channel for calls and data transmission. At the same time, in order to effectively receive and complete communications, a sufficient signal-to-noise ratio must be ensured.
According to the above principles, wireless signal jammers are generally composed of power supply, electronic scanning control unit, segmented radio frequency module, amplification unit, transmitting antenna unit, etc. The wireless signal jammer generates a scanning signal. After passing through the inverter, the oscillator is modulated to the mobile communication operating frequency band. The power amplifier is then amplified and the voltage regulator tube controls the power. The amplified frequency sweeping 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 proportion of noise signals to the device threshold), the mobile phone cannot receive the normal data sent by the base station, and therefore cannot make a normal connection with the base station, causing the mobile phone to communicate with the base station. Communication network separation. The mobile phone shows that there is no signal in the search network, there is no service system, etc., achieving a blocking effect.
The interference power of the screen is certain, 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 cell phone signal jammer on the mobile network, it must be ensured that the field strength of the signal emitted by the jammer is greater 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 transmitting power, the interference range depends on the field strength of the interference area. No matter how powerful the shielder is, as long as the transmitting power is fixed, the farther the distance, the weaker the interference signal strength, thus losing the interference capability. Below is a comparison table of distance and path attenuation. 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, the gain of the shielding line, etc.