Radiated emission effects from multiple via stimulation within a printed circuit board

Radiated emissions propagate from printed circuit boards (PCB) due to common-mode RF currents developed by digital components switching logic states. Transmission lines connect an output to an input pin, generally on another component, and are usually routed on different planes within a PCB, jumping layers through vias. Vias themselves may propagate an undesired RF field causing significant EMI. Research on field propagation from a single via exists. However, radiated effects from the phasing of multiple internally created common-mode current sources simultaneously have not been examined with extensive analysis. This paper investigates the phasing of 100 vias (stimulus sources) simultaneously in the Gigahertz range, emulating a real printed circuit board using today´s high-speed technology, and not a typical theoretically perfect model and single stimulus. Simulated results are presented with field propagation plots illustrating what an antenna could observe at three meters distance due to multiple field propagating sources, illustrating the complexity of the field patterns and the difficulty in determining, or measuring accurate field strength in the far field.