Electromagnetic Radiation Standards and Mitigation Techniques

Electromagnetic radiation can impact device functionality and compliance. This guide discusses key standards governing radiation levels and mitigation techniques to ensure device safety and regulatory adherence. As we know, this is the age of mobile evolution across the globe. To meet the demands of an increasing number of mobile and wireless devices, telecom operators are deploying a large number of cellular towers. These cellular towers are referred to as base stations or Node-Bs or EnodeBs depending upon the wireless standards.

These cellular mobile phone towers employ multiple antennas and transmit electromagnetic waves to serve subscribers.

Mobile and wireless standards are evolving very fast, and equipment based on emerging technologies are getting deployed across the world. The standards include WiMAX, EVDO, CDMA, WiBro, LTE, iBurst, LTE Advanced, and more. Due to the existence of multiple technologies and simultaneous transmissions from various towers, concern has arisen regarding the safety of the common public. This is because electromagnetic radiation from these cellular towers sometimes exceeds the limits prescribed by government and health organizations.

If the EM radiation is above the limit, it can cause various health-related diseases such as brain tumors, eye cancer, and damage to tissues, etc. As per surveys, people living near cellular towers are the worst affected.

The figure below depicts the zones surrounding the cellular tower, i.e., the base station.

As mentioned, there are three zones: exceedance zone, occupational zone, and compliance zone. In the exceedance zone, power density levels are higher compared to the compliance zone. In the compliance zone, the power levels are within the limit prescribed by various health agencies.

The figure also depicts EM radiation field regions around the antenna. As mentioned, there are reactive near field, radiating reactive near field, radiating Fresnel near field, and radiating far field regions. For RF exposure assessment, it is required to measure E field, H field, and SAR (Specific Absorption Rate). All these parameters depend upon the observer location (i.e., field region) and field impedance.

RF Level Set by ICNIRP

As mentioned, a high level of RF exposure to humans will result in the heating of body parts (tissues) and will have adverse effects. This is due to the fact that humans do not have heat dissipating capabilities. Especially parts such as eyes and kneecaps will be affected more.

There are two main types of radiation: ionizing and non-ionizing. We know that the Human body will have large components as water. Ionizing EM radiation breaks the chemical bonds of water, while non-ionizing EM radiation does not break the bonds. Hence, non-ionizing electromagnetic radiation is harmful to human beings. The International Commission on Non-Ionizing Radiation Protection (ICNIRP) has developed international guidelines and limits for EM radiation. The same have been mentioned in Table 1 below.

Table 1

Compliance Distance from Base Station Antenna

As mentioned, there are various zones around the base station antenna based on the RF strength of the transmitter power. This depends on compliance distance, which is calculated based on EIRP and operating frequency (or wavelength). The table below (Table 2) mentions the compliance distance from the base station antenna based on these parameters.

Table 2

Electromagnetic Radiation Mitigation Techniques

There are countries where RF exposure limits or EM radiation is monitored by government and standards agencies. In countries where it is not closely monitored and the government is generous about the radiations, it will have adverse effects on the general public.

In these countries, it is strongly desired to take action to reduce or mitigate EM radiation. Following are the techniques used for Electromagnetic radiation mitigation.

• Transmit Power directly depends on power density and the square of E/H. Hence, reduction in transmit power will result in a reduction in RF radiation level. But this leads to coverage area reduction.

• As power density at a point from the antenna depends on antenna height, if antenna height is increased, then RF field strength at the observer point will be reduced due to the increase in distance.

• It is advised to decrease Vertical Radiation Pattern (VRP) downtilt to reduce the EM radiation.

• Higher antenna gain and lower transmit power can be used in near proximity to the antenna. This results in the same EIRP. This helps greatly in limiting RF radiation.

• As VRP is the function of the elevation angle, it is basically the distribution of RF energy in the vertical plane. Optimization of VRP will result in a reduction in Electromagnetic radiation.

• HRP (Horizontal Radiation Pattern) depends on the azimuth angle. This represents the distribution of energy across the horizontal plane. A narrow horizontal beam along with low transmit power will reduce the EM radiation.

All these techniques can be applied either individually or combined for EM radiation mitigation.

Other than the mitigation techniques mentioned above, following are the basic tips for health concerns to be adopted by all mobile phone or wireless device users. This helps avoid exposure to unnecessary RF radiation.

• Minimize the usage of mobile phones and/or wireless devices.
• Do not continuously wear wireless earphone devices based on wireless technologies such as Bluetooth, Zigbee, etc.
• Do not allow children to use them more.
• Try to use them in safer zone areas far from the base station or cellular towers.

Conclusion

Adhering to radiation standards and employing mitigation techniques are vital for safe and compliant devices. These practices help reduce interference and improve performance.