Shielding Effectiveness Testing 9KHz to 18GHz

Posted: Monday, August 4th, 2014 at 12:00 AM

R-Box Testing is capable of testing shielding effectiveness from 9KHz to 18 GHz



Employing the latest technologies.




Radio frequency shielding was the first fully developed EMF shielding application, and is widely used in many different forms. Two broad categories of utilization are recognized: (1) protection of sensitive equipment (or people) from high intensity electromagnetic fields, and (2) prevention of signal escape from secure facilities where secret or classified information is processed. The primary design considerations are the frequencies to be shielded and the required attenuation, or degree of shielding effectiveness. Types of material utilized range from conductive coatings and fabrics to a fully welded steel enclosure. Modular EMF shielding systems with proven performance characteristics are also available.

It is important to realize that a shield can be completely effective against one type of field and not at all effective against another. For instance, a well performing RF shield of copper foil or screen would be minimally effective against power frequency magnetic fields. Likewise, a power frequency magnetic shield could provide excellent reduction of 60 Hz fields, but offer little reduction of radio frequency fields. The same is true for different RF frequencies. A simple large-mesh screen shield would work well for lower frequencies, but would be ineffective for microwaves. Nevertheless, it is possible to create a shield that would be concurrently effective against most forms of EMF, although it would be impractical for all but the most demanding, high-end applications.

So how do you know if your RF shield is doing it’s job? You have to test.


SHEILDING Effectiveness

1) The relative capability of a shield to screen out undesirable electric and magnetic fields and plane waves. The measurement is the ratio of the signal received without the shield to the signal received inside the shield.

2) A measure of the reduction or attenuation in electromagnetic field strength at a point in space caused by the insertion of a shield between the source and that point. Usually stated in dB

3) The factor that expresses the attenuation caused by scattering, e.g., of radiant or acoustic energy, during its passage through a medium. Note: The scattering coefficient is usually expressed in units of reciprocal distance.

4) Measure of a given material’s ability to block interference. Expressed in dB.

5) The insertion loss when the shield is placed between the transmitting antenna and the receiving antenna. (IEEE 299-1991)

Radio Frequency:

1) Electromagnetic energy from the lower part of the KHz (kilohertz) band to the upper end of the GHz (gigahertz) range.

2) any of the electromagnetic wave frequencies that lie in a range extending from below 3 kilohertz to about 300 gigahertz and that include the frequencies used in radio and television transmission

"Shielding is a mechanical fix for an electrical issue."