via「Google News search」：https://www.eletimes.com/pcb-for-low-emi-dc-dc-converters-working-design

Every switch-mode power supply presents a wide-band noise source. Integrating a DC/DC converter from the car board net into an automotive control unit and still fulfilling the EMC requirements of automotive OEMs is a difficult task.
Typically, noise from the DC/DC converter and other high-speed circuits radiates via connected cables that provide an effective antenna path. To block this potential radiation path, filter circuitry is required at each cable connection point. This filtering is only effective if no H- or E-fields from the noise source couple into the filter components or cables.
In close-field environments, the amplitude of the fields falls by 1 over distance squared (1/d2). Therefore, a certain minimum distance is required between the noise source, filter components, and connector.
Unfortunately, PCB size and connector positions for the cables are usually pre-defined by mechanical constraints. Additionally, the maximum component height may be very limited in certain areas of the PCB, and two-sided assembly may not be possible. These conditions necessitate careful component placement and PCB layout—especially when working within highly regulated industries such as automotive manufacturing.


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