[SI-LIST] Re: Quasi Static Assumptions

Merrick,

I believe Young gives just a guideline. For you to know exactly when a 
quasi-static tool 
(that assumes negligible longitudinal EM field components) is not good enough, 
you need 
to look at the error in the "tangible" parameters of your interest.

For example, if you use a quasi-static tool to extract a model of a realistic 
interconnect (microstrip line, stripline, via, coaxial line, etc.), you may 
wish to look 
at how the characteristic impedance and attenuation provided by the 
quasi-static model 
compare with those parameters provided by a fullwave model, for the frequencies 
and 
interconnect lengths of your interest. You may be surprised to see how the two 
models 
compare.

From my experience, I can tell you (also in a general sense) fullwave 
interconnect 
models are indispensable for frequencies above 5GHz, especially on lossy 
substrates, and 
long transmission lines. Below 5GHz, the error is within the general error 
level of 
everything else in typical printed circuit board systems.

Regards.

Hassan.

On Jul 31, "Moeller, Merrick" <mmoeller@xxxxxxxxxxxxxxx> wrote:
> 
> When does a Quasi Static 3D simulation tool become obsolete? B. Young's
> book describle the limitation by maximum circuit dimension d < wavelength/10 
> or d < 
wavelength/30.
> With wavelength of interest being calulated from the standard digital 
> frequency of
> interst equation f = .35/Tr, and the maximum circuit dimension or effective 
> electrical 
length
> to be, SQRT(Er)*Mechanical Length, Is this a correct approximation? Why the 
> large 
range of wavelength ratios?
> Are there tell tale signs that the Quasi Static assumption has broken down?
> Thanks,
> Merrick
> 

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