[SI-LIST] Dielectric loss modeling

Hi, Gurus,

One topic confused me for a long time, I look forward somebody here 
can help me to clarify. To model the dielectric loss for trace, it 
is used to express the conductance as

G(f) = G0 + freq * Gd

where G0 is in terms of leakage current loss at DC and Gd is 
dielectric loss. As I know, Gd is expressed as

Gd = 2* pi * (tan delta) * C

where (tan delta) is loss tangent. and (tan delta) is defined as 
conductivity / (2* pi * freq * epsilon). As a result,

G(f) = G0 + freq * (2*pi*(conductivity)/(2 * pi*freq*epsilon))*C
G(f) = G0 + (conductivity/epsilon) * C

My questions are

(1) Ideally, G0 is equal to (conductivity/epsilon) * C, as well as G
(f) is frequency independent variable! Is it right? 

(2) Base on the definition, loss tangent is proportial to 1/freq. 
However, we typically treated loss tangent as a constant versus 
frequency. If loss tangent is a constant, it means conductivity is 
proportion to frequency if we assumed epsilon is stable versus 
frequency. Is it true regarding a constant loss tangent or a linear 
frequency dependent conductivity? Or, both of them is wrong.

(3) We verify the extracted RLGC file against Hspice in v. 2004.09. 
We found the Gd is exactly the half of above equation for Microstrip 
line in inhomogeneous medium. The rsults for Stripline agree with 
the above equation. It seems Gd for Microstrip line is the average 
value of dielectric and free space area. It is reasonable? Does 
anyone verify the same issue before?

Best regards,

Sogo Hsu, Ph. D.

Simulation center/Foxconn




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