The mobile phone signal shielding device, in essence, implements electromagnetic interference on the wireless network on which the mobile phone communication depends, so that the mobile phone cannot access the network, and thus cannot receive the information transmitted by the mobile network, and cannot send out information through the network, but It has no effect on the signals generated by the phone.
The principle of mobile phone (radio communication) is as follows: In 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.
In response to the above communication principle, the mask scans from the low-end frequency of the forward channel to the high-end at a certain speed during operation. The scanning speed can form garbled interference in the message 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. Mobile phones are characterized by search networks, no signals, no service systems.
Since there are many channels in any frequency band of mobile communication, and each channel can be used as a BCH, as to which channel in a certain cell is used as: BCH, it is completely determined by the MSC according to the distribution of channels in the entire network area. . Generally, in order to prevent mutual crosstalk between channels and channels, the frequencies between channels in the same cell should be significantly different. For example, after using channel 5, do not use channels 4 and 6, adjacent. The same channel and adjacent channels cannot be used in the cell. Among the channels allocated in each cell, one channel is designated as BCH, and the remaining channels are traffic channels.
Due to the unfixed nature of the BCH, the uncertainty of the use of the shield, and the possibility that there are two or more BCHs in the adjacent area of ​​the cell, and therefore interference with the signal masker may occur in the area. All channels of the mobile communication network interfere with each other, that is, all frequency signals in several frequency bands of GSM, DCS, PHS, CDMA, SCDMA, WCDMA, TDS-CDMA should be transmitted, so as to achieve interference to all mobile phone signals, as a whole The shielding of the received signal of the mobile phone, cutting off the connection between the mobile phone and the base station.
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