The shielding effectiveness(SE) for high- frequency electromagnetic waves, also referred to as the shielding effectiveness, is a characteristic value for the tightness of the shielding of shielded cables, equipment housings and shielded rooms. The higher the shielding quality, the higher the shielding factor.
The shielding of cables can also act as an antenna and receive RF radiation from outside and generate cable currents from it. The same applies in the opposite direction. The cable shield can radiate the RF signals to the outside.
The shielding effectiveness, specified in decibels( dB), is calculated from the logarithmic ratio of the field strengths of unshielded to shielded cable: `SE(dB) = 10log*(F0)/(F1)`, where F0 is the radiated field strength of the unshielded cable and F1 is that of the shielded cable. The shielding effectiveness can be increased by technical measures in the form of combined foil and braided shielding, as can the coupling resistance. In the case of braided shielding, the degree of coverage contributes to this. In addition, the shielding effectiveness increases considerably with multilayer foil and braided shielding.
High-frequency cables with double foil and braided shielding achieve shielding attenuations of 80 dB and above, and with triple foil shielding the shielding effectiveness exceeds 90 dB. Special cables with a copper tube shielding have a shielding effectiveness of over 120 dB.