Because the company is going to install telecom base stations, it may be worried about using electromagnetic radiation, so I'm looking for relevant articles for your reference. Of course, I hope everyone will also strengthen exercise and enhance their immunity.
With the expansion of mobile communication network and the increase of users, the number of base stations is increasing, and the radiation of base stations has attracted more and more attention. By introducing the principle and classification of electromagnetic wave, radio wave and microwave, the electromagnetic radiation intensity of base station is verified in theory and practice, and compared with relevant standards, so as to deeply discuss the influence of base station radiation on human body.
1, Introduction
The radio sends out sweet music, the TV plays wonderful series and movies, the voices of distant relatives are heard through mobile phones, the radar shows that warships are sailing in the distance, planes are flying at high speed, and distant planets are discovered through radio telescopes ... all these depend on magical radio waves.
With the rapid development of radio communication technology, the safety of these devices and the potential harm of the interaction between electromagnetic radiation and human tissues have aroused widespread concern. However, people can't resist the flexibility and convenience brought by wireless devices. Therefore, it is necessary for us to study this problem in depth, accurately quantify these interactions, and determine whether they comply with relevant safety standards.
2, electromagnetic wave and its classification
First of all, we know that mobile phone communication relies on radio waves, including visible light waves, X-rays for physical examination and gamma rays for treatment. The only difference is wavelength. See table 1 for the electromagnetic spectrum range.
Table 1 electromagnetic spectrum range
So, what is electromagnetic wave? When the charge or current of a charged system changes with time, the electric field and magnetic field generated by the system also change with time. The changing electric field arouses a magnetic field around it, and the changing magnetic field also arouses an electric field around it. This changing electric and magnetic field will spread to the space around the system. The electromagnetic field of this movement is electromagnetic wave.
Modern people live in an electromagnetic environment. Lightning strikes, sunspot activities, the atmosphere, the universe, etc. all produce electromagnetic waves, which are natural electromagnetic waves; Artificial electromagnetic waves mainly come from radio transmitting equipment, industrial equipment and medical equipment, such as radio stations, hand-held mobile phones, helium arc welding machines, AC high-voltage transmission lines, car igniters, microwave ovens, televisions and computers. In fact, in any part of the earth, there are electromagnetic waves with different frequencies and intensities, which are invisible, intangible and inaudible, no matter day or night. However, some are what we need and some are not.
Electromagnetic waves are closely related to our lives. If we really stay away from it, it will bring great inconvenience to our lives. However, the continuous improvement of the quality of life has also prompted people to pay more and more attention to electromagnetic radiation.
3. Radio waves and electromagnetic radiation
The phenomenon that electromagnetic waves emit or leak into the air is called electromagnetic radiation, and excessive electromagnetic radiation will cause electromagnetic pollution. At present, the sources of electromagnetic radiation mainly come from the following aspects:
◆ High-frequency induction heating: high-frequency heat treatment, welding, melting, semiconductor processing, such as regional melting (purifying semiconductor) and epitaxy (making a layer of monocrystalline silicon on the substrate silicon wafer). , the frequency of use is mostly 300 kHz ~ 3 MHz.
◆ High-frequency medium heating: the heating object is poor conductor, such as sealing of plastic products, drying of wood and cotton yarn, vulcanization of rubber, etc. , the frequency is 10 MHz ~ 30 MHz.
◆ Microwave: It is mainly used for radar navigation, detection, communication, television and nuclear physics research, and its frequency is generally between 3 GHz and 300 GHz.
Life: TV, refrigerator, microwave oven, home computer, hair dryer, electric blanket, eye protection lamp and other household appliances.
◆ Signal transmitting equipment: such as TV signal towers, mobile communication base stations, paging base stations, electrified railways, high-voltage transmission lines, etc.
At present, according to "Regulations on Radio Frequency Division in People's Republic of China (PRC)", China has planned the radio services in the 9KHz ~ 1000 GHz frequency band:
◆ Long wave: the frequency is 100 kHz ~ 300 kHz, and the wavelength is 3 km ~ 1 km.
◆ Medium wave: the frequency is 300 kHz ~ 3 MHz, and the wavelength is between 1 km ~ 100 km.
◆ Short wave: the frequency is 3 MHz ~ 30 MHz, and the wavelength is between100 m ~100 m. ..
◆ ultrashort wave: the frequency is 30MHz~300MHz, and the wavelength is between10m ~1m.
◆ Microwave: frequency 300 MHz ~ 300 GHz, wavelength1m ~1mm.
◆ Mixed band: refers to the electromagnetic wave in which two or more bands of long, medium, short, ultrashort and microwave are mixed together.
Broadcasting mainly uses medium wave and short wave, and millimeter wave, centimeter wave and decimeter wave are also collectively called microwaves. 890 MHz ~ 954 MHz for GSM mobile communication and 1920 MHz ~ 2 170 MHz for 3G are decimeter waves in microwave. The daily microwave oven is generally 2450MHz, which also belongs to decimeter wave in microwave.
4, electromagnetic radiation intensity and national standards
4. 1 electromagnetic radiation intensity
More and more communication base stations are built, and the coverage of mobile phone signals is strengthened. People suspect that the electromagnetic waves emitted by communication base stations are harmful to human health. According to the concept of electromagnetic radiation, electromagnetic radiation is actually a kind of energy, and its impact on the environment mainly depends on the strength of energy. Units used to measure its strength mainly include:
◆ Power: The greater the radiation power, the higher the intensity of the radiated electric field and magnetic field, otherwise it is very small, in watts (W).
◆ Power density: refers to the high-frequency electromagnetic energy received or emitted in unit time and unit area, in watts/meter? (W/m？ ), the power density in high frequency electromagnetic radiation environmental assessment is usually MW/cm? Express delivery.
◆ Electric field intensity: a physical quantity used to express the intensity and direction of electric field in various parts of space. The electric field is strong near the charged body and weak in the distance. The unit of electric field intensity is volt/meter (V/m), and the power frequency electric field intensity near transmission lines and high-voltage electrical equipment is usually expressed by kV/m. ..
◆ Magnetic field intensity: a physical quantity used to express the magnetic field intensity and direction in various places in space, with the unit of ampere/meter (A/m).
◆ Magnetic induction intensity: It represents the magnetic flux per unit volume and area, and is used to describe the energy intensity of the magnetic field. The unit is Tesla or gauss (t or Gs).
How to measure the influence of electromagnetic radiation on human body? To what extent should electromagnetic radiation energy do harm to human body? Let's first understand the term "SAR", which means "specific absorption rate" in Chinese. SAR is defined as the electromagnetic radiation power absorbed by a unit mass organism, that is, the absorption metering rate, in W/kg.
Determination of SAR: The SAR value measurement system consists of a mannequin, measuring instruments, probes and mechanical arms. When measuring, the special test liquid is poured into the human model, and the electromagnetic characteristics of the liquid are consistent with that of the human body; Place the transmitter close to the model, set the transmitting power of the transmitter, drive the probe to move in the liquid through the mechanical arm, and automatically measure the field strength E. The SAR value can be calculated by the following formula:
SAR=E？ (δ/p)
Where e is the field strength, δ is the dielectric constant and p is the liquid density.