Cable radiation accounts for a significant and principal issue in Electromagnetic Compatibility testing. Cable shield grounding is probably the most-overlooked--and most-easily preventable--EMI problem. Here, a common problem and solution are shown wherein the impedance of a pigtail drain wire leads to a buildup of common mode voltage on an ordinary cable. Reducing the impedance of cable shield ground reduces voltage, driving down the residual radiation.

As clock and operating frequencies climb ever higher, the presence of gaps and slots in metallic cases provide a signficant "leakage" point for high frequency radiated energy. To suppress these emissions, the gap lengths must be much less than the resonance wavelength to prevent aperture radiation. Here, this phenomena is demonstrated and resolved.
 

Conducted emissions testing is required for AC-powered (mains) connections in many EMI regulations. Here, the household appliance measurement standards mandate that emissions from broadband sources (typically motor-commutator noise) be reduced to prevent interference on power lines. The solution for this type of situation is careful design of the motor and installation of properly-selected common mode filter (here, a ferrite is used to suppress emissions to tolerable levels).
 

Magnetic fields from 60 Hz sources can cause interference with CRT and similar systems; the phenoma causes a jitter in the display which is the result of the "beating" of the 60 Hz frequency and the vertical refresh rate on the CRT. (Televisions are inherently immune to this problem because the refresh rate is exactly 60 Hz). The solution is to either select a reduced-immunity system (such as an LCD panel display, which are inherently immune) or provide shielding around the system using a highly permeable metallic shield; the shield "shunts" the field through the low-reluctance path of the mu-metal, which bypasses the electron beam in the CRT.