Meaning
The reduction in electromagnetic signal strength achieved by placing a conductive barrier between a noise source and a receiver determines the effectiveness of a shielding enclosure. Measuring RF shield attenuation ensures that a metal shield can protect sensitive RF circuits from external noise and prevent the device from radiating unwanted emissions. This metric is expressed in decibels and varies across different frequency bands.
The shielding performance is limited by the conductivity of the material and the presence of any gaps or slots in the shield.
Measurement Metric
Decibel levels of reduction indicate the ratio of the signal strength with and without the shield. Higher numbers mean better protection for the internal circuitry. The frequency of the signal is the primary variable affecting this value.
Attenuation Factor
Aperture size and the spacing of ground solder joints are the essential factors that determine the leakage through the shield at high frequencies. If a gap is larger than a fraction of the wavelength of the signal, the signal will pass through the shield easily. Engineers must design the shield with small holes for thermal ventilation and tight spacing of the ground pins.
This ensures that the shield remains effective at gigahertz frequencies where modern wireless systems operate.
Material Impact
High conductivity metals like copper or brass provide the best performance for thin shields. These materials are often plated to prevent oxidation and ensure good solderability. This maintains the shielding performance over the life of the product.
