Meaning
Unintentional electromagnetic fields emitted from an electronic device enclosure or interface cables outside the allocated channel bandwidth define unwanted radiation characteristics. Measuring spurious radiated emissions requires far-field testing inside anechoic chambers to quantify energy levels generated by internal clocks and high-speed buses. Scope applies across the entire electromagnetic spectrum up to multiple harmonics of the highest operating frequency.
Unwanted Energy
Switching power supplies, high-speed digital lines, and non-linear semiconductor junctions generate harmonic frequencies that radiate through structural openings. Inadequate grounding paths allow common-mode currents to flow onto external interconnect cables, forming effective radiating antennas. Shielding enclosures attenuate these fields before reaching the surrounding environment.
Enclosure Leakage
Seams, display apertures, and connector cutouts in metal housings create slots that allow internal radio frequency energy to escape. Conductive gaskets and ground springs maintain continuous electrical contact across structural enclosure joints to minimize leakage. Cable shielding integrity dictates total radiation performance during high-frequency system operation.
Far-Field Measurement
Regulatory compliance requires rotating the device through three hundred sixty degrees inside a calibrated semi-anechoic test chamber. Receiving antennas capture radiated field strength across horizontal and vertical polarizations at standardized distances. Measured field values must remain below strict regulatory limits to prevent interference to radio communication services.
