Which of the following is a documented EMI suppression technique?

• A. Upgrading air conditioning
• B. Replacing components with plastic
• C. Limiting bandwidth
• D. Increasing transmitter power

Answer: (C)

Limiting bandwidth is a documented EMI suppression technique because narrowing the signal’s spectral width directly reduces the energy radiated outside the desired channel. With less energy spread across frequencies, there’s less potential to interfere with nearby systems and to violate emission limits. In EMI control, the goal is to minimize energy in unwanted frequencies and reduce susceptibility to or generation of interference. By restricting the bandwidth, you limit out-of-band emissions and the overall radiated power that can cause problems for other equipment. The other options don’t address EMI in a meaningful way: upgrading air conditioning doesn’t affect electromagnetic emissions, replacing components with plastic has no standard EMI benefit, and increasing transmitter power actually increases EMI rather than suppressing it.