Re-Evaluating Radiated Emissions and Exposure for Potted Transmitter Housings
Encapsulating transmitters alters dielectric loading, detuning antennas and shifting RF exposure boundaries, demanding re-evaluation of emissions and SAR compliance.
Phantom Tissue
Meaning
Simulating materials formulated to match the electrical properties of human organs allow for the standardized testing of wireless transmitters. Preparing phantom tissue requires blending water, salt, and gelling agents to achieve the target permittivity and conductivity values at specific radio frequencies. This mixture replicates the electromagnetic absorption characteristics of human heads or limbs during safety evaluations.
Material Composition
Liquid or gel-like mixtures fill the hollow anatomical shells during compliance tests. To ensure a stable phantom tissue, manufacturers add preservatives to prevent evaporation over time. This formulation must remain homogeneous to avoid measurement errors.
Electrical Matching
Calibrating the dielectric properties requires regular testing with coaxial probes and network analyzers. The phantom tissue must match the dielectric constant and conductivity of actual body tissues within a tight tolerance percentage. These parameters are highly frequency-dependent, meaning a different mixture is required for testing sub-gigahertz bands compared to high-frequency wireless networks.
Maintenance Protocol
Exposure to air and temperature variations can alter the water content of the simulation fluid. Maintaining the phantom tissue involves keeping the test environment at a constant temperature and using sealed containers when not in use. Regular verification runs confirm that the liquid properties remain within the limits defined by international testing standards.