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2. How is radio frequency energy used?
Probably the most important use of RF energy is for
telecommunications. Radio and TV broadcasting, wireless
phones, pagers, cordless phones, police and fire department
radios, point-to-point links and satellite communications all rely
on RF energy.
Other uses of RF energy include microwave ovens, radar,
industrial heaters and sealers, and medical treatments. RF
energy, especially at microwave frequencies, can heat water.
Since most food has a high water content, microwaves can
cook food quickly. Radar relies on RF energy to track cars and
airplanes as well as for military applications. Industrial heaters
and sealers use RF energy to mold plastic materials, glue wood
products, seal leather items such as shoes and pocketbooks,
and process food. Medical uses of RF energy include pacemaker
monitoring and programming.
3. How is radio frequency radiation measured?
RF waves and RF fields have both electrical and magnetic
components. It is often convenient to express the strength of
the RF field in terms of each component. For example, the unit
"volts per meter" (V/m) is used to measure the electric field
strength, and the unit "amperes per meter" (A/m) is used to
express the magnetic field strength. Another common way to
characterize an RF field is by means of the power density.
Power density is defined as power per unit area. For example,
power density can be expressed in terms of milliwatts (one
thousandth of a watt) per square centimeter (mW/cm2 or
microwatts (one millionth of a watt) per square centimeter
(µW/cm2).
The quantity used to measure how much RF energy is actually
absorbed by the body is called the Specific Absorption Rate or
SAR. The SAR is a measure of the rate of absorption of RF energy.
It is usually expressed in units of watts per kilogram (W/kg) or
milliwatts per gram (mW/g).
Section 4: Safety Guidelines and Warranty Information
4A: Safety 194
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