What Is RF Source Characterization?
How Is an RF Source Described Before Exposure Is Assessed?
RF source characterization establishes the operating conditions and emission characteristics of a radio-frequency source. It is the first assessment activity in the progression from source emissions to external exposure, RF dosimetry, and biological-effects assessment.
Frequency, occupied bandwidth, spectrum, modulation, pulse structure, duty cycle, and intermittency describe how an emission is distributed in frequency and time. These characteristics help identify the applicable exposure limits, averaging intervals, and measurement equipment.
Power must be stated with its meaning and reference point. Rated, maximum, carrier, average, peak, and peak envelope power describe different aspects of operation. They are not interchangeable, and none alone is a measure of a person's exposure.
The antenna and feed system determine how power is distributed in space. Relevant characteristics include feeder loss, gain, radiation pattern, beam direction, beamwidth, polarization, and effective radiated power or effective isotropic radiated power.
The operating state also matters. Traffic loading, pulse repetition, scanning or rotation, adaptive power control, and simultaneous transmissions can change the emission. Characterization may describe credible maximum conditions, representative operation, or both, provided the basis is clear.
For a source used close to or against the body, free-space data may be insufficient. The body or another nearby object can alter the antenna current and radiation pattern, so the source, separation, orientation, accessories, and intended operating configuration must be characterized together.
Source characterization supplies inputs to exposure assessment; it does not itself establish exposure or compliance. A defensible record identifies the source configuration, operating modes, assumptions, data provenance, and uncertainty so that the subsequent assessment can be reproduced.
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