FreeLists / si-list / [SI-LIST] what is the conductivity of a dielectric?

[Patrick_Carrier@xxxxxxxx]

Transmission line gurus and people who love dielectrics--

I am trying to figure out the conductivity of a dielectric.
I have an equation that gives me:
tanD = 1/(2*pi*Freq*Er*rd) where rd is the resistivity of the dielectric
I assume that 1/rd is the conductivity of the dielectric.  Is that an
erroneous assumption?
That gives me the equation:
conductivity of dielectric = 2*pi*Freq*Er*tanD

This second equation makes sense to me in that increasing your frequency
increases the dielectric conductivity, causing more "leakage" of your
transmitted energy.  However, using this equation, that would indicate that
the conductivity of a dielectric with Er=4 and tanD=0.02 would have a
conductivity approaching that of copper at 100MHz.  Now that does not make
sense.

Is there a such thing as non-frequency-dependent conductivity of a
dielectric?  How would I obtain such a number?
Is there something else I am missing?

Any guidance would be greatly appreciated.  Thanks.
--Pat




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