There are many kinds of cell phone signal jammers on the market today, and most of them are realized by wide-band white noise power suppression. During its use, there are many types of shielding devices that more or less interfere with the surrounding mobile phone base stations. This kind of interference is mainly aimed at the interference of the uplink signal of the base station, and the method to solve this interference problem is actually not difficult. It only needs to add the time division duplex synchronization technology of the signal base station to the interference signal of some specific frequency bands. Then, in which frequency bands does the mobile phone signal shielding system need to add base station time division duplex synchronization technology to avoid interfering with the base station?

The frequency band targeted by the base station time division duplex synchronization technology mentioned here refers to the mobile phone frequency band using time division duplex, and the other frequency bands adopt frequency division duplex mode, which strictly distinguishes the range of uplink frequency band and downlink frequency band. Taking the frequency band of GSM900 as an example, the uplink frequency range of GSM900 is 885-915MHz. In this frequency range, only data transmission of uplink signals is performed. The downlink frequency range of GSM900 is 930-960MHz. In this frequency range, only the data transmission of the downlink signal is carried out. The two frequency bands do not overlap each other, and data communication is carried out in its own way. Let's take the time division duplex frequency band as an example, such as the TD-SCDMA frequency band, the frequency range is 2010-2025MHz, and the overall bandwidth is 15MHz, but because of the time division duplex technology, their uplink data and downlink data are all in this 15MHz The transmission is performed in the bandwidth, but it is divided by time, that is, it is dedicated to uplink data in a period of time, and dedicated to downlink data in the next period of time.

We use base station time-division duplex synchronization technology for signal jammers, that is, time synchronization for time-division duplex frequency bands, so that the signal shielding module for time-division duplex can process downlink at the mobile phone base station after clock synchronization When the signal is transmitted, an interference signal is emitted. On the contrary, when the base station processes uplink data, the corresponding frequency band of the mobile phone signal shielding system stops working.

We sort out and count the time division duplex frequency bands used by various operators at present. Now there are mainly 5 frequency bands using time division duplex technology, namely China Mobile's 1885-1915MHz, 2010-2025 MHz G, 2515- 2675 MHz, 2300MHz for indoor micro base station signal amplification, and 3.5GHz for China Telecom and China Unicom.

Based on the above analysis, we only need to install the time division duplex synchronization technology of the signal base station in all the five frequency bands in the mobile phone signal shielding system, and then we can completely avoid interfering with the uplink signal of the mobile phone base station.