FreeLists / si-list / [SI-LIST] Re: Question on EMI radiated power

["Andrew Ingraham" <a.ingraham@xxxxxxxx>]

> In short, the answer is no.

Maybe it's just me ... but I would have worded it differently:  that the
answer to Doug's question is essentially yes, but that (like so many things
in RF) it is a frequency-dependent resistance.  At any one frequency, you
could come up with a resistance in the circuit that represents the transfer
of energy from the circuit into EMI rather than heat.  I don't know how
useful it would be to determine this radiation resistance, even at a single
frequency, unless the EMI is large.  So, conceptually yes, but in practice
maybe not that useful.

But ... Is there such a thing as a complex radiation impedance?  If it has
an imaginary component, what does it represent?  Radiation resistance is a
circuit stand-in for the energy (power) that gets radiated from the
radiating element.  An imaginary component doesn't pass any net (average)
power.  While it makes sense to have imaginary components of the circuit's
impedance due to the structure of the physical device, standing waves, etc.,
I don't see this as a component of the radiation impedance, which ought to
be pure real, shouldn't it?  Radiation implies energy radiated outwards,
which means power loss from the circuit.

Regards,
Andy


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