Internal EMC problems caused by parasitic resonances

Parasitic coupling among components and circuits on the PCB of a high-frequency analog or digital device can distort transfer characteristics, cause errors in data transfer and processing, and jeopardize the stability of active components. Particularly strong coupling can occur due to parasitic resonances of various structures, including power-distribution conductors, coils, reactively terminated transmission lines, improperly grounded coaxial lines and other conductors mounted above the PCB, enclosures, etc. Such resonances must be predicted while designing the device, which is not a simple task. Their influence can be reduced to a tolerable level by increasing the resonant frequencies and by dampening the resonances by introducing losses.