Consequently, reducing EMI at one frequency may increase it at another. When evaluating EMI fixes, it is imperative to evaluate the effect of a change at several frequencies. The size, shape, and orientation of a structure acting as an antenna can be inferred by carefully examining the patterns of its EMI signals. A dipolelike structure can be inferred as oriented horizontally. Gain additional insight by looking at patterns at progressively higher harmonics.
Several factors can make the pattern identification technique difficult to use.
When designing antennas, strong, steady signals are desirable for pattern measurements. But when it comes to EMI, weak emissions are preferred. This can be further exacerbated if the EMI fluctuates rapidly. Devices are also different from intentional antennas because they usually contain multiple random radiators or incidental antennas. Almost any conductive structure or part can act as an antenna.