Mobile phone jammer: detect + shield the existing problems
1. Mobile phone detection technology The mobile phone detection technology mainly detects when the electromagnetic wave signal emitted by the mobile phone causes the electromagnetic power in the area where the mobile phone is located to increase to a set value, thereby determining that the mobile phone is working. This technology is very advanced at first glance, and in fact it is just a very superficial understanding. When proposing this technology, the following issues were not considered: 1. Uncertainty of mobile phone transmission power The specific base station through which the mobile phone enters the network when it is working is determined by the traffic volume and dynamic deployment of surrounding base stations. When the mobile phone is used for logging in, if the nearby base station is busy, it will log in to the far idle base station to work. The transmission power of the mobile phone will be adjusted according to the link loss of the radio wave from the mobile phone to the base station. Usually the mobile phone receives the base station If the signal is strong, the transmit power is weak. 2. The distance between the mobile phone and the detector (link loss) is uncertain. The distance between the mobile phone and the detector and whether there are obstructions in the middle will affect the strength of the signal received by the detector. 3. The intensity of space electromagnetic interference is uncertain. Common lightning, fluorescent lamps, electronic equipment, etc. are all sources of interference. At the same time, the out-of-band spurs of mobile phones are very large. Although the detector is used in the SAW filter on the mobile phone, the out-of-band suppression of the filter is not enough, and it is very easy to produce cross-frequency phenomenon. When used for detection, it cannot effectively filter out other interference signals, making the detection system in chaos. 4. The sensitivity of the detector setting is uncertain. Generally, the sensitivity setting of the detector does not have a specific quantitative value. When debugging, dial the mobile phone by constantly adjusting the position, and observe whether the detector detects the arrival and adjust the sensitivity. 5. 3G signal detection is more difficult. Because 3G technology uses advanced technologies such as code division, spread spectrum and time division, and is often submerged in environmental noise, its transmission power is smaller. Especially the time division technology of mobile 3G, the mobile phone transmitting and receiving signals are in the same frequency band, separated by time, if it is in an area with strong TD signal, the detected downlink signal strength exceeds the signal strength sent by the mobile phone, it will be difficult to detect and distinguish . Therefore, the shielding system using detection technology is mainly manifested as false positives and false negatives, which are extremely serious, and cannot achieve practical purposes.
2. Mobile phone detection + shielding technology The detector controls the switch of the shielding device. When the mobile phone is detected, the shielding device is turned on immediately, hoping to achieve the purpose of immediate shielding. However, in actual operation, the reason why the shielding device cannot be activated immediately is that the shielding effect is mainly achieved by preventing the mobile phone from logging in to the network, and the base station sends the mobile phone login command to be issued intermittently. If the mobile phone has logged on to the network, especially The call is already made, and the mobile phone can still make a normal call during the period when the base station does not send the mobile phone to change the original login instruction. This phenomenon is more obvious in China Unicom's 3G and WCDMA networks. Unless the shielding power can far exceed tens or even hundreds of times that of conventional shielding equipment, the effect of interrupting mobile phone communication can be achieved immediately. Such power is not only difficult to achieve in terms of technology and cost, but its radiation is strong and even more unsafe.
3. Current application status of detection + shielding technology. This technology seems to be superior in terms of application principles, and is especially favored and respected by users in the southeast and northeast regions of my country, but in fact, no successful cases have emerged so far, and it is in the industry. It caused considerable misleading and brought no small adverse effects to the entire industry. If cavity filtering and code stream analysis are used, the above shortcomings can basically be solved, but the cost is too high and it is difficult to be accepted by users and loses market significance.
