Commission to Assess the Threat to the United States from Electromagnetic Pulse (EMP) Attack

EMP Commission (pdf file at link) ^ | EMP Commission

[dhs12345]

Agreed. Compliance testing at an OATS.

I saw one OTAS that tested for EMP. It was in a huge facility (so that you could park a fighter jet, etc. in it and test it immunity).

Commercial electronics is vulnerable but the design has improved in recent years. I have seen the evolution. Lastly, the physical geometries of the electronics have gotten smaller which would mean that it would require higher and higher frequencies to affect its operation. Higher frequencies can be easier to control. So maybe there is an inherent immunity?

Good EMC design (as you probably know) is not a simple thing.

[dhs12345]

Probably in the form of a massive aurora borealis. Interesting the interaction of the earth's magnetic field too with all of the charged particles from the blast which would induce massive currents on the ground. The light show would be impressive, though.

[RFEngineer]

The physical geometries of the electronics does help, but if you connect it to anything conductive (power supply cord) you negate the advantage of a smaller geometry.

The other thing is that as microprocessors evolve, they also have reduced geometry in the semiconductor substrate. This reduced geometry between semiconductor junctions requires less energy to arc across the gap (meaning the EMP has to couple less energy into a processor to disrupt, damage, or destroy it.

[dhs12345]

Actually, they are the same. Acronyms aside.

Noise is noise. Blasting anything with a broadband noise source like is produced in a nuke (15hz up to 400MHz from one website)) will find its vulnerabilities. Its susceptibilities.

BTW, this is roughly the frequency range for emissions compliance testing. Susceptibility testing is now done but is still limited (or was limited). Good news is that engineers are doing a better job of designing systems.

[dhs12345]

But at a higher frequency? Smaller wavelength?

Also, the other side — skin effect which can increase the current density?

My experience with higher frequencies is that they tend to not propagate well through an enclosure or system. So by the time the energy hits the circuit in question, it is greatly attenuated. Then again, I could be wrong.

On the other hand, engineers are not designing for susceptibility at higher frequencies. Only enough to pass the regulatory requirements (with some margin). But as a general rule, good “RF design” will offer some immunity.

[RFEngineer]

generally, for EMC purposes, higher frequencies (radiated) penetrate into an enclosure better than lower frequencies.

lower frequencies conduct better than higher frequencies into enclosures.

However, higher frequencies couple into cables of typical dimensions better than lower frequencies.

You’re right. Good RF design comes into play for EMP tolerance.

[dhs12345]

Ya, but what about skin effect (conducted)? So there is a natural “impedance” to all RF currents and it gets worse with higher frequencies. That is why the noise current flow can get weird and why ground planes are a good thing.

Also, not all of the electronics in an enclosure are small geometries. Probably only the digital stuff like the processors and chip sets and memory buses but the power circuitry and IO circuitry is probably larger geometries.

Anyway, it would be an interesting study to determine who susceptible our electronics is to broadband emissions.