2, Low frequency (LF) 30-300 KHz long wave disturbance, 10 km to 1 km wavelength, the main ground wave propagation, suitable for transoceanic communication. Intermediate frequency(MF) 0.3-3 MHz medium wave, 1 km to 100 m wavelength, ground wave combined with sky wave, used in Marine communications, amateur radio communications and mobile communications, as well as medium distance navigation.
3, this division is a popular name in the radar industry, there is no strict, unified standard. The usual division is: L-band 1~2GHz; S-band 2~4GHz; C-band 4~8GHz; X-band 8~12GHz; Ku-band 12~18GHz; K-band 18~27GHz; Ka-band 27~40GHz; Uid=' Is mobile phone wireless charger harmful '> Is mobile phone wireless charger harmful
1, no harm to mobile phones. Wireless charger using wireless charging frequency Wireless charging technology Wireless charging frequency Wireless charging frequency , By using the alternating magnetic field generated between the coils to transmit electrical energy, the inductive coupling technology will be used to connect the charging base station and the devicePrepare the bridge. 2, from the theory, wireless charging technology is safe and harmless to the human body, the resonance principle of wireless charging is magnetic field resonance, only in the same frequency resonance between the coil transmission, and other devices can not accept the band, in addition, the magnetic field used by wireless charging technology itself is harmless to the human body.
3, under normal circumstances will not harm the mobile phone, wireless charging now the working frequency is done below 1M, so the signal of the mobile phone will not have an impact. Wireless charging also has no effect on the battery life of the phone, and wired charging is basically the same, but the speed is lowerSome, but the wireless charger power conversion rate is still high, more energy saving.
1, wireless charger operating frequency, according to QI standard is 110-205kHz; The frequency of mobile phone communication is in the range of 0.8GHz to 2GHz (the communication system will vary, 1GHz=10^9Hz).
2, according to the Electromagnetic Radiation Protection Regulations, the average user of the whole body within 24 hours a day, continuously for 6 minutesRadiation absorption Radiation rate should be less than 0.02 w/kg. However, there are no specific standards for wireless charging. Experts say that while there are national standards for traditional mobile phone chargers, there should be national industry standards for emerging wireless charging devices as soon as possible. The Qi wireless charging standard uses a low frequency non-ionization frequency (110-205khz) that is harmless to the human body.
3, the test found that: using a high-sensitivity radiation tester, the radiation value of the wireless charger is between 150 and 180, although compared to the 250 to 627 in front of the computer screen or the thousands of values when making phone calls, but cumulativeThe effects may not be negligible. At the same time, when wireless chargers, mobile phones, computers and other electronic devices are used together, the radiation value will increase significantly.
4, first of all, not all wireless chargers on the market can be competent for watch charging. Many products do not clearly label the radiation value, which is somewhat worrisome. Since the radiation standard of wireless charging technology has not yet been perfected, we need to be concerned that the current regulatory requirements, such as the Electromagnetic Radiation Protection Regulations, stipulate that the electromagnetic radiation of the user in continuous contact with the wireless charger within 24 hours shall not exceed the specific absorption rate (SAR) limit of 0.02W/kg. <5, according to the "Electromagnetic radiation protection Regulations", the average specific absorption rate (SAR) of the whole body for any consecutive 6 minutes within 1 day and 24 hours should be less than 0.02W/kg. But at present, there is no standard specifically for wireless charging. He Guili, director of the Tel Laboratory of the Telecommunication Research Institute of the Ministry of Industry and Information Technology, said that the wireless charger has radiation is inevitable, but since it has been listed, it means that it must meet international standards and will not cause harm to the human body.
6, expand knowledge: According to the test of relevant institutions, the radiation amount of Apple 12 is 0.137W/ when the wireless signal is strongestm, while the standard value requires less than 0.4W/m. In the range of radiation perceived by the human body, the highest value of electromagnetic radiation energy appears in the proactive area, but it is also far below the safety standard. The impact of electromagnetic radiation on the human body varies from person to person, and it is generally believed that long-term exposure to high intensity electromagnetic radiation will have a negative impact on human health.
Frequency,Received by resonant antenna system, frequency and phase reversal. The transmitter apparently modulates its ambient field, and the receiver receives everything that satisfies the resonance condition. At the phase velocity of signal transmission, the interpretation of the resonant circuit fails. But high-frequency engineers, still using language they were familiar with, offered another explanation.
Electromagnetic induction: Simple and efficient intimate contact electromagnetic induction, just like a pair of tacit dancers, the sending end and the receiving end transfer power through the induction magnetic flux. It is known for its simple structure, high efficiency and low cost, and is especially suitable for close-range device charging. However, it also has limitations and transmission distance is subject toThe charging device must be accurately aligned, as shown in Figure 4-1.
Using the principle of electromagnetic induction charging equipment, its principle is similar to the transformer, through the transmitter and receiver end set coil, transmitter coil under the action of power to send electromagnetic signals, the receiving end coil receives electromagnetic signals and convert electromagnetic signals into current, so as to achieve the purpose of wireless charging.
Qi wireless charging system is composed of base stations and mobile devices. The base station contains one or more emitters that provide the energy to be received. The mobile device contains a receiver for useTo provide power to a load (such as a battery), the receiver will also provide information to the transmitter. An energy conversion unit in the transmitter converts electrical energy into a wireless energy signal, and an energy collection unit in the receiver converts the wireless energy signal into electrical energy.
Compatibility testing: Transmitters need to perform interoperability testing with all QI-certified receivers to ensure seamless connectivity. During the test, the receiver needs to establish communication with the transmitter in a short period of time and charge steadily for 5 minutes at a low battery level. This high-standard test undoubtedly improves the market competitiveness and user trust of Qi certified products.
1, 5GHz is a frequency in the wireless band, which refers to the wireless communication equipment operating at 5 GHZ frequency. In general, smartphones, computers, wireless routers and other devices support both 4GHz and 5GHz bands. Compared to the 4GHz band, the 5GHz band has a higher transmission rate and less interference, so it is widely used in high-speed data transmission, video streaming and online games.
2. Wi-fiThe technology is defined by IEEE 8011b/g/n and operates at 4ghz, where the 4ghz spectrum is divided into 14 overlapping and staggered 20 MHz wireless carrier channels with a center frequency of 5 MHz each. The 8011a/n has more channels in the 0ghz spectrum, and the 8011n also uses channel welding technology to merge two 20MHz carrier channels into one 40mhz channel to increase throughput.
3, the wireless router working frequency band is generally divided into 2.4 GHz and 5.0 GHz two bands. 2.4 GHz is an early noneLine routers are commonly used in the frequency band, and this situation has continued until now. Now 5GHz is also beginning to be widely used, combining with 2.4GHz to form a dual frequency. Compared with single frequency, dual frequency has higher wireless transmission rate, stronger anti-interference, stronger wireless signal, higher stability, more difficult to drop the line.
4, the wireless router working frequency band is generally divided into 4GHz and 0GHz two bands. 4GHz is the common frequency band used by early wireless routers, which has continued to the present; Now 5GHz has also begun to be widely used, and the combination with 4GHz forms a dual frequency. Compared to aloneFrequency band, dual frequency has a higher wireless transmission rate, with stronger anti-interference, wireless signal is stronger, higher stability, not easy to drop.
5, n Supports the 20MHz and 20MHZ/40MHz channels.
6, wireless router is also like other wireless products belong to the radio frequency (RF) system, need to work within a certain frequency range, in order to be able to communicate with other devices, we call this frequency range is called the working band of wireless router. However, because different products use different network standards, the working frequency bands used are not the same. Currently no lineThe server mainly complies with IEEE8011b, IEEE8011a, IEEE8011g and other network standards.