EMI Shield

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Calmont Wire and Cable produces electromagnetic interference (EMI Shield) and electromagnetic pulse (EMP) resistant cable to provide effective shielding for sensitive conductors and power wiring exposed to a wide frequency range, interference environment and internal cross coupling. EMI shielding has superior attenuation that is effective from the kHz to GHz frequency range. Calmont’s EMI shielding assures that your electrical and electronic systems meet specifications relating to electromagnetic interference. EMP resistant cable

Calmont applies two shields of differing magnetic properties for EMI Shield and EMP cable. A high and low permeable alloy material is used for each layer of the cable for maximum deflection, and two twisted pairs and two twisted triads each are double shielded over the core.

Calmont's experience and expertise as a leader in the development of versatile EMI shielding and EMP resistant products will help solve your interference challenges in applications such as

Computers
Audiovisuals
Gaming
Cellular Phones
Automotive
Aerospace
Construction
Logistics
EMI

As shown in Fig. 1, the input signal is interference-free until it comes in contact with the power line magnetic field (or other magnetic field), which then causes a distorted signal in the equipment.

Figure 1: Effect of Magnetic Field on Signal Cable

Figure 2: Shielding Frequency

EMI Shielding Frequency

Fig. 2 illustrates that copper has very little shielding effect at low frequencies. Calmont's EMI shielding outer braid provides moderate shielding at low frequencies and good shielding at high frequencies. The inner braid provides excellent shielding at low frequencies. The result is a shielding combination effective throughout a broad frequency range.

Electromagnetic frequency shielding provides protection for the input signal susceptible to magnetic field induction and electrical fields until the signal is safely within the desired electrical or electronic equipment, as illustrated in Fig. 3.

Figure 3: Effects of Magnetic Field on
Signal Cable with EMI Shield

Magnetic Field on Signal Cable with EMI Shield

Figure 4: EMI Shield Application

EMI Shield Diagram

As illustrated in Fig. 4, a cable whose conductors are to be protected from an external source of EMI has an outer low permeability shield braided over a high permeability shield. The incident radiation of external EMI strikes the outside surface of the outer shield (the first boundary reflection loss area) where some of the radiation is reflected. The radiation then penetrates the material, where it is absorbed.

The second reflection loss occurs at the inside surface of the outer EMI Shield (the second boundary reflection loss area). If the radiation is strong enough, it will proceed through the outer shield to the outside surface of the inner shield (the third boundary reflection loss area) where more of the reduced radiation is reflected. The radiation proceeds to the fourth boundary reflection loss area (the inside surface of the inner shield), where some of the radiation is absorbed into the inner shield material.

To prevent electromagnetic interference from signals present in wires, the EMI Shield’s inner layer should be of low permeability braid and the outer layer of high permeability braid.

EMI Shields can also be configured with low permeability inside and high permeability outside shields. The low permeability shield should always be closest to the source of interference.