It is a well-known fact that electromagnetic radiation can be emitted from the edges of printed circuit boards. When a current carrying via passes through two or more reference planes, an EM wave propagates radially away from the via within the cavity. It is guided by the respective planes; much like a water ripple will propagate radially away from a rain drop hitting a puddle of water. When the wave meets the PCB edge, the two reference planes form a slot antenna and will radiate noise with the potential to generate electromagnetic interference (EMI) to nearby equipment.