People today are well aware of the fact that prolonged exposure to very high levels of radiofrequency (RF) radiation can be harmful. Therefore, many countries across the globe have developed exposure standards for the RF energy. In the US, the Federal Communications Commission (FCC) has stipulated several safety guidelines for RF exposure. Want to know how FCC handles the issue of human exposure to the RF electromagnetic fields? First,learn a few important aspects of RF radiation.
What Is Radiofrequency Exposure?
Electromagnetic radiation has two parts – electric and magnetic energy. They move together through space at the speed of light. Radio waves and microwaves emitted by transmitting antennas are collectively referred to as ‘radiofrequency’ or ‘RF’ energy or radiation. It must be noted that here the term ‘radiation’ has nothing to do with ‘radioactivity.’ The term ‘electromagnetic field’ or ‘radiofrequency field’ refers to the spaces where you can detect the presence of electromagnetic or RF energy. An ‘electromagnetic spectrum’ may consist of different forms of electromagnetic energy, which can be categorized according to their wavelengths and frequencies. The RF part of the electromagnetic spectrum consists of electromagnetic waves having frequencies in the range of about 3 kilohertz (3 kHz) to 300 gigahertz (300 GHz). Microwaves, on the other hand, have frequencies ranging from about 1 GHz to 30 GHz.
How Is Radiofrequency Radiation Measured?
An RF electromagnetic wave has both an electric and a magnetic component. The unit ‘volts per meter’ (V/m) denotes the strength of an electric field while the unit ‘amperes per meter’ (A/m) is used to express the strength of a magnetic field. ‘Power density’ is another unit which is used to measure power flow per unit area. It characterizes the total electromagnetic field. This unit is typically used when the field you want to measure is located far away from an antenna. The unit ‘Specific Absorption Rate’ (SAR) is used to measure the rate at which RF energy is actually absorbed in a body.
An Overview of FCC Guidelines for RF Exposure
The FCC authorizes and licenses devices, transmitters and facilities that generate RF radiation. FCC’s jurisdiction extends over all transmitting services in the US except those that come directly under the jurisdiction of the Federal Government.
According to FCC, radio, television, satellite-earth stations, and certain cellular, Personal Communications Service (PCS) and paging facilities are some of the highly potential sources of RF radiation.
FCC stipulates an exposure limit in terms of the Specific Absorption Rate or SAR which refers to the quantity of RF radiation that a body actually absorbs. The applicable limits depend upon the type of sources such as cellphones, broadcast transmitting antennas, and more. For example, according to FCC, the safe limit for a mobile phone user is an SAR of 1.6 watts per kg. US cellphone manufacturers must comply with this limit for all their products. It will be worthwhile to mention that FCC does not handle the electromagnetic interference issues relating to medical devices. It’s the FDA’s Center for Devices and Radiological Health (CDRH) that is tasked with developing medical device regulation.
Human exposure to RF is a pressing issue. If you want your product to comply with FCC’s RF standards, it is best to reach out to an expert who can help you to build the right shielding solution for your application.