Signal jammer, help college entrance examination, maintain fairness

  　As a college entrance examination candidate, you found a router-like device when you walked into the examination room. Don't be "excited" to be able to "Internet", it may be a "cell phone signal blocker".

　　 Today is the college entrance examination, let’s talk about communication interference
　　 Mobile Unicom Telecom's frequency range
　　 When the communication technology was still in the 2G era, "mobile phone signal jammers" could work perfectly. At that time, most operators used relatively fixed frequency bands, narrow bandwidths, and relatively easy interference.
　　 As can be seen from the above figure, 2G mainly works in the 900/1800MHz frequency band in mobile communication technology, 3G works in the 1900-2100MHz frequency band, and 4G works in the 2300-2500MHz frequency band.
　　 With the rapid advancement of communication technology, the development of 3G and 4G communication technology has caused the "signal jammer" to encounter a dilemma. The signal interference originally designed for 2G will cause the shielding to be invalid due to frequency reasons that cannot cover 3G and 4G signals.
　　 Fortunately, signal jammers are also developing, and soon there will be interference functions specifically for 3G and 4G frequency bands, which can shield these three frequency bands at the same time and space.
　　The principle of mobile phone signal jammer
　　The mobile phone signal jammer scans from the low end frequency of the forward channel to the high end at a certain speed during the working process, the transmission power is in the order of several watts, and the shielding range is adjustable, generally tens of meters. Garbled interference is formed in the signal received by the mobile phone, so that the mobile phone cannot detect normal data sent from the base station, and the mobile phone cannot establish a connection with the base station. It is manifested as the phenomenon of searching the network, mobile phone no signal, no service system, etc.
　　 Different mobile phones with different working standards have different encoding methods or different modulation methods, and their information content is different. According to Shannon's formula, their signal-to-noise ratio requirements are also different, and their sensitivity requirements are also different.
Modern communication technology uses advanced anti-interference technologies, such as frequency hopping, direct sequence spread spectrum (DSSS), etc., but the suppression of interference by frequency hopping and spread spectrum mainly depends on intermediate frequency filtering, but due to the front-end high-frequency amplifier and mixer They are all non-linear devices, which will produce intermodulation interference and noise deterioration when there is strong interference, that is, blocking of the radio frequency front end.
　　 In addition, there are many technologies for communication interference, such as broadband noise interference, noise interference in some frequency bands, multi-tone interference, frequency sweep interference, tracking interference, smart interference, and so on. The mobile phone signal jammer only needs to ensure that the communication signal is shielded in a certain small area, so it is easier to interfere as long as the frequency band can be covered.
　　 More challenges for shields
　　 Don’t think that “all the better” if the cell phone signal is blocked! I heard that someone once used the “WIFI name” to complete the transmission of the answer. It seems that the development of the shielding device cannot be relaxed for a moment, and see if it is necessary to upgrade to the 5GHz frequency band! According to reports, there are also illegal self-made radio transceiver equipment that maliciously use those frequency bands that the shielding device does not cover.
  Mastering the stick, but aiming for the yard!
　　 There are reports that the drone can be equipped with radio detection equipment to record and "decode" the signal, and it can even locate the emission source and directly capture the answering party.
　　 The technology is not good or bad, but the consequences are good or bad, such as communication, radar, and interference and anti-jamming technology!
　　 The college entrance examination is a key point in life. What we should do is to hold the correct beliefs and the right way to eliminate fluke. The development of technology must be used to benefit mankind and maintain world peace. It is not used for temporary self-interest in an improper way. Only a solid knowledge reserve can make you really worry-free.

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