E-field emission VS. H-field emission

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bittware

Joined: 03 Apr 2004
Posts: 208
Helped: 1

31 May 2005 10:23 e-field vs h-field

Hello experts,
When I read the books about EMC, I often come cross two buzz words, they are "E-field emission" and "H-field emission". I am wondering what they are meant for. Why does E-field emission focus on 30MHz-40GHz, while H-field emission is only interested in 9KHz-30MHz range? How to measure them respectively?
Thanks for your explanation.
Best regards,
bittware

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Kral

Joined: 28 Mar 2005
Posts: 1182
Helped: 187

31 May 2005 13:47 e field and h field

An electromagnetic wave consists of two components; E, H physically at right angles to each other, and at right angle to the direction of propogation:
. E Field is the electrical component
. H Field is the magnetic component.
The relative importance of the E, H fields depends on the impedance of the receptor (victim).
If the impedance is high, the electric filed will induce a large voltage.
If the impedance is low, the magnetic field will induce a large current.
At high frequencies, the inductive reactance of the victime will likely be high, and therefore the E field will likely have more influence. It is difficult to generalize, because there are other influences, such as resonances that must be dealt with.