#15 Loss tangent discrepancy...

[Anonymous]

Question: Is the "loss tangent" parameter in the
substrate definition defined in its classical sense?
For example, I used 0.018 for FR4 and that seems to
wipe out all the resonance peaks above 100 MHz or so.
Is this right? Is this "loss tangent" which you also
refer to as "rho" related to the "actual" loss tangent
by some other factor?

thanks

Loizos Vakanas, PhD
Signal Integrity Engineer
Cisco Systems, San Jose, CA
408-853-2505

[Eugene Jansen]

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Hi ,

The loss tangent parameter is used in its classical sense i.e.
what is commonly provided as a dielectric loss specification
by substrate manufacturers. The "rho" is actually a historical
reference to the parameter used in the HP Touchstone
software (now Agilent EEsof) and may cause some
confusion. Note that "rho" as used by Touchstone implied tan
(rho), which is indeed the dielectric loss tangent.

It would make it easier to investigate the issue if you could
provide us with the circuit you've used.

Cheers,
Eugene