Signal shield, why can it interfere with your cell phone signal?

At present, the main principles of signal shielding and signal jammer are to make huge noise in the frequency band used by mobile phones, which will disturb the reception and transmission of normal signals of mobile phones. This small object is not only used to prevent cheating in exams, but also used to prevent terrorist attacks politically and militarily.

In layman's terms, when the mobile phone signal shield works, it will emit frequency to interfere with the downlink signal of its base station. If the power of the shield is greater than that of the local base station signal, then the mobile phone will have no signal, and if the power of the shield is less than that of the local base station signal, the mobile phone will have a signal.

the principle of mobile phone signal shield is that within a certain frequency range, the mobile phone and the base station are connected by radio waves, and the data and sound are transmitted at a certain baud rate and modulation mode. According to the above communication principle, the shield scans from the low-end frequency to the high-end frequency of the forward channel at a certain speed during the working process.

The mobile phone signal shielding device installed in schools is mainly to prevent students from cheating during exams. When the device is turned on, the mobile phone will be unable to answer calls, send text messages and surf the Internet.

it can shield all the 2G, 3G, 4G signals, 4GWIFI signals and bluetooth signals under all three operators, namely China mobile, China Unicom and China telecom. its principle is to interfere the mobile phone to receive the frequencies sent by the base station and the wireless router through its own frequencies, so as to achieve the shielding purpose.

the car GPS signal shielding device does not shield the cell phone signal. The mobile phone screen is used to screen the signal of the mobile phone card, that is, to screen the signal of the base station, and the GPS screen is used to screen the signal of GPS positioning. Summary: Cell phone signal and GPS shielding are not in the same frequency band. So the cell phone signal will not be blocked.