Radiation source and characteristics of wireless communication network yzF safety regulations and electromagnetic compatibility network
Generally speaking, in wireless communication networks, base station transmission systems, satellite earth communication stations, mobile stations (mobile phones, PHS, etc.), wireless routers, and wireless APs can generate electromagnetic waves of various forms, different frequencies, and different intensities. Radiation source. yzF safety regulations and electromagnetic compatibility network
The electromagnetic radiation field can be divided into near field and far field. In general, for field sources with low voltage and high current (such as transmitting antennas, feeders, etc.), the electric field is much stronger than magnetic fields; for field sources with low voltage and large current (such as molds of some induction heating equipment), the magnetic field is higher than the electric field Much bigger. The far field is a weak field, and its electromagnetic field strength is relatively small. Therefore, for a fixed electromagnetic radiation source that can produce a certain intensity, attention should be paid to the protection of the electromagnetic field in the near field, including the protection of operators and personnel in the near field environment, and the protection of the field in the near field The protection of various electronic and electrical equipment. In the far field, the harm to people is usually small, and the main factor that should be considered at this time is the protection of the signal. yzF safety regulations and electromagnetic compatibility network
Quantitative analysis of electromagnetic radiation damage in wireless communication network yzF safety regulations and electromagnetic compatibility network
Radiation damage is divided into free radiation damage and non-free radiation damage. When a high-energy electromagnetic wave transmits energy to other substances, it may hit the electrons of atoms and molecules in the substance, filling the substance with charged ions. This effect is called "dissociation", and the damage caused by the dissipation of electromagnetic waves is called For free radiation damage, free radiation damage will seize charge with substances in the body and produce ions to destroy physiological tissues. Non-free radiation damage is divided into non-free radiation damage by thermal effects and non-free radiation damage without thermal effects. Non-free radiation damage is a medium-low energy radiation, and the generated energy does not break molecular bonds or free atoms. yzF safety regulations and electromagnetic compatibility network
The frequency band of electromagnetic waves that produce free radiation damage is 1012 ～ 1024Hz, and the frequency bands used in wireless communication networks are 150MHz, 450MHz, 800MHz, 1.9GHz, 2.4GHz, 3.5GHz and 5GHz or higher frequency bands. The frequency range of non-free damage is far below 1012Hz, so the electromagnetic radiation in the wireless communication network will not cause free radiation damage to the human body, only non-free radiation damage to the human body. yzF safety regulations and electromagnetic compatibility network
Quantitative analysis of thermal effects yzF safety regulations and electromagnetic compatibility network
The human body is an organic organism that is undergoing metabolism all the time. The heat generated by the metabolism can maintain the body temperature within the normal temperature range to ensure the normal physiological function of the human physiological system. Physiological studies have shown that the heat produced by the human metabolism is about 100W, and the surface area of ​​the human body is about 2m2. If the human body wants to maintain temperature balance, the power of the human body to radiate energy should also be 100W.
The human body's absorption of microwaves is about 50%. Therefore, when the radiated field strength is greater than 10mW / cm2, the average power absorbed by the human body is also greater than 5mW / cm2. At this time, the average heat dissipation power of the human body is less than the average power absorbed by the body. The energy returns to the body, causing damage to the human body. Therefore, the radiation power density damage specification is 8 ～ 10mW / cm2. yzF safety regulations and electromagnetic compatibility network
Single radiation field strength density and safe residence time yzF safety regulations and electromagnetic compatibility network
Because the radio frequency radiation damage of the wireless communication network has a cumulative effect, when exposed to radio frequency radiation, the human body will not be injured immediately, and it will only cause harm to the human body when it accumulates to a certain extent over time. This accumulation process is the safe residence time. According to ANSI (AmericanNaTIonalSecurityInsTItute) regulations yzF safety regulations and electromagnetic compatibility network
Among them, K1 is the specification value of the field strength density in the frequency band, and the relationship with the frequency is shown in Figure 1, which is a certain value for a certain frequency. K2 is the field measurement value of the field strength density in this frequency band. The larger the field measurement value of the field strength density, the shorter the safe residence time T; otherwise, the smaller the measurement value, the longer the safe residence time T. yzF safety regulations and electromagnetic compatibility network
Safety residence time of multiple different frequency band radiation sources yzF safety regulations and electromagnetic compatibility network
Under multiple frequency band radiation sources, the safe residence time is the sum of the safe residence time of a single radiation source. yzF safety regulations and electromagnetic compatibility network
Quantitative analysis of mobile phone radio frequency radiation yzF safety regulations and electromagnetic compatibility network
In the wireless communication network, mobile phones, PHS and laptop mobile stations are the closest radiators to users. In this article, taking mobile phones as an example to quantitatively analyze the radiation of mobile phones to the human body. yzF safety regulations and electromagnetic compatibility network
Mobile phone radiation damage electrical parameters yzF safety regulations and electromagnetic compatibility network
Suppose the radiated field strength density of the mobile phone is E (V / m), the radiated power of the mobile phone is P (W), the ratio of the radiating antenna gain is G, and the distance of the mobile phone from the head is R (m). Then E can be expressed as: yzF safety regulations and electromagnetic compatibility network
The mobile phone antenna is a single rod-shaped non-directional antenna, so its gain is 0dB, and the gain ratio is 1; R is generally 3cm. yzF safety regulations and electromagnetic compatibility network
The size of mobile phone radiation damage is measured by the size of the mobile phone's radiation power density K: Z = 377Ω, which is the spatial impedance ohm, so the larger the P, the larger the E and the greater the injury. yzF safety regulations and electromagnetic compatibility network
At the same time, in the quantitative analysis of mobile phone radiation damage, it is necessary to determine whether the radiation damage belongs to far-field radiation or near-field radiation damage. yzF safety regulations and electromagnetic compatibility network
At that time, it was far-field radiation injury; at that time, it was near-field radiation injury. When calculating near-field radiation damage, the electrostatic field and the induction field must be considered in the radiation field strength density. yzF safety regulations and electromagnetic compatibility network
1800MHz / 900MHz mobile phone radiation analysis yzF safety regulations and electromagnetic compatibility network
Using a 1800MHz mobile phone, if the mobile phone's transmission power is 0.55W, the gain ratio is 1, the distance between the mobile phone and the head is 3cm, which is far-field radiation, there is no need to consider the electrostatic field and the induction field when quantifying the radiation damage situation. Density, using 900MHz mobile phone, under the same conditions as 1800MHz mobile phone, it is near-field radiation. In the quantitative analysis, electrostatic field and induction field must be considered. The actual mobile phone radiation field strength density E2> E1, the corresponding mobile phone radiation power density K2 is also Large, the corresponding single radiation field strength density specification value found from Figure 1 is 3mW / cm2, the safe residence time is as follows. If the mobile phone is used in an environment near a wall corner or a reflector, the radiation intensity is doubled due to increased reflection, and the safety time will be reduced by half. yzF safety regulations and electromagnetic compatibility network
Quantitative analysis of base station radiation yzF safety regulations and electromagnetic compatibility network
Like the mobile phone, the radiation intensity of the base station is also related to the average output power of the transmitter PAV, the ratio of the base station antenna gain and the distance R between the person and the base station, expressed as :. When analyzing the radiation damage characteristics of the base station, the safety retention distance R is used to measure. yzF safety regulations and electromagnetic compatibility network
If the GSM900 transmitter outputs an average power of 200W, the base station antenna gain ratio is 13.7 and the safe radiation density is 4.5W / m2. yzF safety regulations and electromagnetic compatibility network
It is known that the average power output from the GSM1800 transmitter is 200W, the base station antenna gain ratio is 13.7, and the safe radiation density is 9W / m2, then the radiation intensity of the base station is as follows. yzF safety regulations and electromagnetic compatibility network
From the above analysis results, whether it is a mobile phone or a base station, the damage of the GSM900 system is greater than the damage of the GSM1800 system. yzF safety regulations and electromagnetic compatibility network
Wireless communication network electromagnetic radiation test yzF safety regulations and electromagnetic compatibility network
Taking the Radiation Environmental Supervision and Management Station of Guangxi Zhuang Autonomous Region as an example of the test process and data of a communication limited liability company's base station, the test method is as follows. yzF safety regulations and electromagnetic compatibility network
Test point selection yzF safety regulations and electromagnetic compatibility network
Along the main direction of the antenna, it is laid out from the inside to the outside at a certain interval, and the rest are laid out radially with the antenna as the center. Increase the number of monitoring points where there are more people. Monitoring items and monitoring methods yzF safety regulations and electromagnetic compatibility network
According to HJ / T10.2-1996 Radiation Environmental Protection Management Guidelines-Electromagnetic Radiation, the environmental electromagnetic radiation power density is monitored. yzF safety regulations and electromagnetic compatibility network
Monitoring conditions and monitoring instruments yzF safety regulations and electromagnetic compatibility network
Under rain-free weather conditions, select the peak period of mobile communication and monitor the mobile communication base station under normal operation. The measuring instrument adopts the electromagnetic radiation analyzer produced by Italian PMM company. yzF safety regulations and electromagnetic compatibility network
Evaluation standard yzF safety regulations and electromagnetic compatibility network
(1) "Electromagnetic Radiation Protection Regulations" (GB8702-88): Within 24 hours of a day, the average value of the field electromagnetic radiation field parameters within 6 minutes of continuous personnel should meet the requirements of Table 3. yzF safety regulations and electromagnetic compatibility network
(2) "Electromagnetic Radiation Environmental Impact Assessment Methods and Standards" (HJ / T10.3-1996): The total exposure dose of the public includes the total impact of various electromagnetic radiation on it, including the possible or already caused by the proposed facility The influence also includes the influence of the existing background electromagnetic radiation. The total exposure dose limit should not exceed the requirements of the national standard "Electromagnetic Radiation Protection Regulations" (GB8702-88). yzF safety regulations and electromagnetic compatibility network
Monitoring results and analysis yzF safety regulations and electromagnetic compatibility network
It can be seen that the environmental electromagnetic radiation power density of each monitoring point is lower than the national standard limit. yzF safety regulations and electromagnetic compatibility network
Measures to deal with electromagnetic radiation of wireless communication network yzF safety regulations and electromagnetic compatibility network
The monitoring report shows that the electromagnetic radiation in the wireless communication network is much lower than the national standard limits, so it can be used with confidence. From a protection point of view, some methods can be used to effectively reduce the radiation damage of the wireless communication network. yzF safety regulations and electromagnetic compatibility network
Strict frequency management, standardize electromagnetic radiation equipment setting yzF safety regulations and electromagnetic compatibility network
Various types of radio transmission equipment and electromagnetic radiation devices must meet the relevant national technical indicators, and must also meet the national standards for electromagnetic radiation protection regulations, to meet the requirements of public and occupational exposure standards, to minimize the impact of electromagnetic radiation on the human body. yzF safety regulations and electromagnetic compatibility network
Strictly approve yzF safety regulations and electromagnetic compatibility network of high-power short-wavelength radio stations
The shorter the wavelength of electromagnetic radiation, the greater the electromagnetic wave power absorbed by the human body and the longer the time that the electromagnetic wave is irradiated, the greater the influence of electromagnetic waves on the human body. Therefore, we should fundamentally pay attention to the problem of high-power, short-wavelength electromagnetic wave radiation equipment and the time of being irradiated by electromagnetic waves.
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