PCB EMI Causes


By attaching antennas to a printed circuit board we can analyze the physics of unwanted radiation

Modeling Biconical Antennas


The biconical antenna can be modeled using simple and inexpensive software tools

Davis EMC patent


Jeffrey Davis’ innovative design for a device driver lowers emissions without compromising performance

PCB EMC and traces


As a signal trace is moved towards the edges of a return plane, the inductance of the return plane rises

EMC and Lost Flux


Flux from a signal conductor can loop around a return conductor inducing a voltage along it

Shielding and EMC


A plane wave impinging on a metal shield with an aperture emerges as a point source

Anechoic Chambers


The pyramidal absorbers can be modeled as a sandwich of planes with varying resistivity

Radiation from small wire


A map of vector potential from a small wire element

EMC and common mode currents


A return plane can develop a voltage along its length causing attached cables to radiate

EMC and slot on PCB


A slot cut across a solid return plane can cause havoc because of its affect on return inductance

EMC lost flux and shield


“Lost Flux," --the flux created by the center conductor that leaks around a shield -- causes the shield to radiate

EMC unbalanced currents


Common mode currents are created when balanced geometries meet unbalanced ones”

Maxwells Equations divergence


Divergence -- the flux flowing into and out of a small volume element -- is a key concept in field theory

Field propagation small volume


A small change in an electric field over distance creates a changing magnetic field at right angles to it

EMC lost flux and PCB


Varying signal and return geometries radiate differently due to varying amounts of "lost flux"

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